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The Project Gutenberg eBook of Fossil plants, Vol. 1
This eBook is for the use of anyone anywhere in the United States and
most other parts of the world at no cost and with almost no restrictions
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Title: Fossil plants, Vol. 1
[A text-book] for students of botany and geology
Author: A. C. Seward
Release date: May 10, 2022 [eBook #68043]
Most recently updated: October 18, 2024
Language: English
Original publication: United Kingdom: Cambridge University Press,
1898
Other information and formats: www.gutenberg.org/ebooks/68043
Credits: Peter Becker, Robert Tonsing and the Online Distributed
Proofreading Team at https://www.pgdp.net (This file was
produced from images generously made available by The
Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK FOSSIL
PLANTS, VOL. 1 ***
This eBook is for the use of anyone anywhere in the United States and
most other parts of the world at no cost and with almost no restrictions
whatsoever. You may copy it, give it away or re-use it under the terms
of the Project Gutenberg License included with this eBook or online at
www.gutenberg.org. If you are not located in the United States, you
will have to check the laws of the country where you are located
before using this eBook.
Title: Fossil plants, Vol. 1
[A text-book] for students of botany and geology
Author: A. C. Seward
Release date: May 10, 2022 [eBook #68043]
Most recently updated: October 18, 2024
Language: English
Original publication: United Kingdom: Cambridge University Press,
1898
Other information and formats: www.gutenberg.org/ebooks/68043
Credits: Peter Becker, Robert Tonsing and the Online Distributed
Proofreading Team at https://www.pgdp.net (This file was
produced from images generously made available by The
Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK FOSSIL
PLANTS, VOL. 1 ***
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Page 5
Cambridge Natural Science Manuals.
Biological Series.
General Editor:—Arthur E. Shipley, M.A.
FELLOW AND TUTOR OF CHRIST’S COLLEGE, CAMBRIDGE.
FOSSIL PLANTS.
Biological Series.
General Editor:—Arthur E. Shipley, M.A.
FELLOW AND TUTOR OF CHRIST’S COLLEGE, CAMBRIDGE.
FOSSIL PLANTS.
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London: C. J. CLAY and SONS,
CAMBRIDGE UNIVERSITY PRESS WAREHOUSE,
AVE MARIA LANE,
AND
H. K. LEWIS,
136, GOWER STREET, W.C.
Glasgow: 263, ARGYLE STREET.
Leipzig: F. A. BROCKHAUS.
New York: THE MACMILLAN COMPANY.
Bombay: E. SEYMOUR HALE.
CAMBRIDGE UNIVERSITY PRESS WAREHOUSE,
AVE MARIA LANE,
AND
H. K. LEWIS,
136, GOWER STREET, W.C.
Glasgow: 263, ARGYLE STREET.
Leipzig: F. A. BROCKHAUS.
New York: THE MACMILLAN COMPANY.
Bombay: E. SEYMOUR HALE.
Page 8
Tree Stumps in a Carboniferous Forest. Victoria Park, Glasgow.
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F OS S IL P L A N T S
FOR STUDENTS OF BOTANY AND GEOLOGY
BY
A. C. SEWARD, M.A., F.G.S.
ST JOHN’S COLLEGE, CAMBRIDGE,
LECTURER IN BOTANY IN THE UNIVERSITY OF CAMBRIDGE.
WITH ILLUSTRATIONS.
VOL. I.
CAMBRIDGE:
AT THE UNIVERSITY PRESS.
1898
[All Rights reserved.]
FOR STUDENTS OF BOTANY AND GEOLOGY
BY
A. C. SEWARD, M.A., F.G.S.
ST JOHN’S COLLEGE, CAMBRIDGE,
LECTURER IN BOTANY IN THE UNIVERSITY OF CAMBRIDGE.
WITH ILLUSTRATIONS.
VOL. I.
CAMBRIDGE:
AT THE UNIVERSITY PRESS.
1898
[All Rights reserved.]
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Page 12
Cambridge:
PRINTED BY J. AND C. F. CLAY,
AT THE UNIVERSITY PRESS.
PRINTED BY J. AND C. F. CLAY,
AT THE UNIVERSITY PRESS.
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PREFACE.
IN acceding to Mr Shipley’s request to write a book on Fossil Plants for the
Cambridge Natural History Series, I am well aware that I have undertaken a
work which was considered too serious a task by one who has been called a
“founder of modern Palaeobotany.” I owe more than I am able to express to
the friendship and guidance of the late Professor Williamson; and that I
have attempted a work to which he consistently refused to commit himself,
requires a word of explanation. My excuse must be that I have endeavoured
to write a book which may render more accessible to students some of the
important facts of Palaeobotany, and suggest lines of investigation in a
subject which Williamson had so thoroughly at heart.
The subject of Palaeobotany does not readily lend itself to adequate
treatment in a work intended for both geological and botanical students. The
Botanist and Geologist are not always acquainted with each other’s subject
in a sufficient degree to appreciate the significance of Palaeobotany in its
several points of contact with Geology and recent Botany. I have
endeavoured to bear in mind the possibility that the following pages may be
read by both non-geological and non-botanical students. It needs but a
slight acquaintance with Geology for a Botanist to estimate the value of the
most important applications of Palaeobotany; on the other hand, the bearing
of fossil plants on the problems of phylogeny and descent cannot be
adequately understood without a fairly intimate knowledge of recent
Botany.
The student of elementary geology is not as a rule required to concern
himself with vegetable palaeontology, beyond a general acquaintance with
such facts as are to be found in geological text-books. The advanced student
will necessarily find in these pages much with which he is already familiar;
but this is to some extent unavoidable in a book which is written with the
dual object of appealing to Botanists and Geologists. While considering
those who may wish to extend their botanical or geological knowledge by
an acquaintance with Palaeobotany, my aim has been to keep in view the
IN acceding to Mr Shipley’s request to write a book on Fossil Plants for the
Cambridge Natural History Series, I am well aware that I have undertaken a
work which was considered too serious a task by one who has been called a
“founder of modern Palaeobotany.” I owe more than I am able to express to
the friendship and guidance of the late Professor Williamson; and that I
have attempted a work to which he consistently refused to commit himself,
requires a word of explanation. My excuse must be that I have endeavoured
to write a book which may render more accessible to students some of the
important facts of Palaeobotany, and suggest lines of investigation in a
subject which Williamson had so thoroughly at heart.
The subject of Palaeobotany does not readily lend itself to adequate
treatment in a work intended for both geological and botanical students. The
Botanist and Geologist are not always acquainted with each other’s subject
in a sufficient degree to appreciate the significance of Palaeobotany in its
several points of contact with Geology and recent Botany. I have
endeavoured to bear in mind the possibility that the following pages may be
read by both non-geological and non-botanical students. It needs but a
slight acquaintance with Geology for a Botanist to estimate the value of the
most important applications of Palaeobotany; on the other hand, the bearing
of fossil plants on the problems of phylogeny and descent cannot be
adequately understood without a fairly intimate knowledge of recent
Botany.
The student of elementary geology is not as a rule required to concern
himself with vegetable palaeontology, beyond a general acquaintance with
such facts as are to be found in geological text-books. The advanced student
will necessarily find in these pages much with which he is already familiar;
but this is to some extent unavoidable in a book which is written with the
dual object of appealing to Botanists and Geologists. While considering
those who may wish to extend their botanical or geological knowledge by
an acquaintance with Palaeobotany, my aim has been to keep in view the
Page 15
requirements of the student who may be induced to approach the subject
from the standpoint of an original investigator. As a possible assistance to
those undertaking research in this promising field of work, I have given
more references than may seem appropriate to an introductory treatise, and
there are certain questions dealt with in greater detail than an elementary
treatment of the subject requires. In several instances references are given
in the text or in footnotes to specimens of Coal-Measure plants in the
Williamson cabinet of microscopic sections. Now that this invaluable
collection of slides has been acquired by the Trustees of the British
Museum, the student of Palaeobotany has the opportunity of investigating
for himself the histology of Palaeozoic plants.
My plan has been to deal in some detail with certain selected types, and
to refer briefly to such others as should be studied by anyone desirous of
pursuing the subject more thoroughly, rather than to cover a wide range or
to attempt to make the list of types complete. Of late years there has been a
much wider interest evinced by Botanists in the study of fossil plants, and
this is in great measure due to the valuable and able work of Graf zu Solms-
Laubach. His Einleitung in die Palaeophytologie must long remain a
constant book of reference for those engaged in palaeobotanical work.
While referring to authors who have advanced the study of petrified plants
of the Coal period, one should not forget the valuable services that have
been rendered by such men as Butterworth, Binns, Wilde, Earnshaw,
Spencer, Nield, Lomax and Hemingway, by whose skill the specimens
described by Williamson and others were first obtained and prepared for
microscopical examination.
I am indebted to many friends, both British and Continental, for help of
various kinds. I would in the first place express my thanks to Professor T.
McKenny Hughes for having originally persuaded me to begin the study of
recent and fossil plants. I am indebted to Prof. Nathorst of Stockholm, Dr
Hartz of Copenhagen, Prof. Zeiller, Dr Renault and Prof. Munier-Chalmas
of Paris, Prof. Bertrand of Lille, Prof. Stenzel and the late Prof. Roemer of
Breslau, Dr Sterzel of Chemnitz, the late Prof. Weiss of Berlin, the late Dr
Stur of Vienna, and other continental workers, as well as to Mr Knowlton of
Washington, for facilities afforded me in the examination of fossil plant
collections. My thanks are due to the members of the Geological and
Botanical departments of the British Museum; also to Mr E. T. Newton of
from the standpoint of an original investigator. As a possible assistance to
those undertaking research in this promising field of work, I have given
more references than may seem appropriate to an introductory treatise, and
there are certain questions dealt with in greater detail than an elementary
treatment of the subject requires. In several instances references are given
in the text or in footnotes to specimens of Coal-Measure plants in the
Williamson cabinet of microscopic sections. Now that this invaluable
collection of slides has been acquired by the Trustees of the British
Museum, the student of Palaeobotany has the opportunity of investigating
for himself the histology of Palaeozoic plants.
My plan has been to deal in some detail with certain selected types, and
to refer briefly to such others as should be studied by anyone desirous of
pursuing the subject more thoroughly, rather than to cover a wide range or
to attempt to make the list of types complete. Of late years there has been a
much wider interest evinced by Botanists in the study of fossil plants, and
this is in great measure due to the valuable and able work of Graf zu Solms-
Laubach. His Einleitung in die Palaeophytologie must long remain a
constant book of reference for those engaged in palaeobotanical work.
While referring to authors who have advanced the study of petrified plants
of the Coal period, one should not forget the valuable services that have
been rendered by such men as Butterworth, Binns, Wilde, Earnshaw,
Spencer, Nield, Lomax and Hemingway, by whose skill the specimens
described by Williamson and others were first obtained and prepared for
microscopical examination.
I am indebted to many friends, both British and Continental, for help of
various kinds. I would in the first place express my thanks to Professor T.
McKenny Hughes for having originally persuaded me to begin the study of
recent and fossil plants. I am indebted to Prof. Nathorst of Stockholm, Dr
Hartz of Copenhagen, Prof. Zeiller, Dr Renault and Prof. Munier-Chalmas
of Paris, Prof. Bertrand of Lille, Prof. Stenzel and the late Prof. Roemer of
Breslau, Dr Sterzel of Chemnitz, the late Prof. Weiss of Berlin, the late Dr
Stur of Vienna, and other continental workers, as well as to Mr Knowlton of
Washington, for facilities afforded me in the examination of fossil plant
collections. My thanks are due to the members of the Geological and
Botanical departments of the British Museum; also to Mr E. T. Newton of
Page 16
the Geological Survey, and to those in charge of various provincial
museums, for their never-failing kindness in offering me every assistance in
the investigation of fossil plants under their charge. Prof. Marshall Ward has
given me the benefit of his criticism on the section dealing with Fungi; and
my friend Mr Alfred Harker has rendered me a similar service as regards
the chapter on Geological History. I am especially grateful to my colleague,
Mr Francis Darwin, for having read through the whole of the proofs of this
volume. To Mr Shipley, as Editor, I am under a debt of obligation for
suggestions and help in various forms. I would also express my sense of the
unfailing courtesy and skill of the staff of the University Press.
My friend Mr Kidston of Stirling has always generously responded to my
requests for the loan of specimens from his private collection. Prof. Bayley
Balfour of Edinburgh, Mr Wethered of Cheltenham and others have assisted
me in a similar manner. I would also express my gratitude to Dr Hoyle of
Manchester, Mr Platnauer of York, and Mr Rowntree of Scarborough for the
loan of specimens.
To Dr Henry Woodward of the British Museum I am indebted for the
loan of the woodblocks made use of in figs. 10, 47, 60, 66, and 101, and to
Messrs Macmillan for the process-block of fig. 25.
For the photographs reproduced in figs. 15, 34, 68, 102 and 103 I owe an
acknowledgment to Mr Edwin Wilson of Cambridge, and to my friend Mr
C. A. Barber for the micro-photograph made use of in fig. 40.
In conclusion I wish more particularly to thank my wife, who has drawn
by far the greater number of the illustrations, and has in many other ways
assisted me in the preparation of this Volume.
In Volume II the Systematic treatment of Plants will be concluded, and
the last chapters will be devoted to such subjects as geological floras, plants
as rock-builders, fossil plants and evolution, and other general questions
connected with Palaeobotany.
A. C. SEWARD.
Botanical Laboratory, Cambridge.
March, 1898.
museums, for their never-failing kindness in offering me every assistance in
the investigation of fossil plants under their charge. Prof. Marshall Ward has
given me the benefit of his criticism on the section dealing with Fungi; and
my friend Mr Alfred Harker has rendered me a similar service as regards
the chapter on Geological History. I am especially grateful to my colleague,
Mr Francis Darwin, for having read through the whole of the proofs of this
volume. To Mr Shipley, as Editor, I am under a debt of obligation for
suggestions and help in various forms. I would also express my sense of the
unfailing courtesy and skill of the staff of the University Press.
My friend Mr Kidston of Stirling has always generously responded to my
requests for the loan of specimens from his private collection. Prof. Bayley
Balfour of Edinburgh, Mr Wethered of Cheltenham and others have assisted
me in a similar manner. I would also express my gratitude to Dr Hoyle of
Manchester, Mr Platnauer of York, and Mr Rowntree of Scarborough for the
loan of specimens.
To Dr Henry Woodward of the British Museum I am indebted for the
loan of the woodblocks made use of in figs. 10, 47, 60, 66, and 101, and to
Messrs Macmillan for the process-block of fig. 25.
For the photographs reproduced in figs. 15, 34, 68, 102 and 103 I owe an
acknowledgment to Mr Edwin Wilson of Cambridge, and to my friend Mr
C. A. Barber for the micro-photograph made use of in fig. 40.
In conclusion I wish more particularly to thank my wife, who has drawn
by far the greater number of the illustrations, and has in many other ways
assisted me in the preparation of this Volume.
In Volume II the Systematic treatment of Plants will be concluded, and
the last chapters will be devoted to such subjects as geological floras, plants
as rock-builders, fossil plants and evolution, and other general questions
connected with Palaeobotany.
A. C. SEWARD.
Botanical Laboratory, Cambridge.
March, 1898.
Page 17
Page 18
TABLE OF CONTENTS.
———————
PART I. GENERAL.
CHAPTER I.
HISTORICAL SKETCH. Pp. 1–11.
Fossil plants and the Flood. Sternberg and Brongniart. The internal structure of fossil plants. English
Palaeobotanists. Difficulties of identification.
CHAPTER II.
RELATION OF PALAEOBOTANY TO BOTANY AND GEOLOGY. Pp. 12–21.
Neglect of fossils by Botanists. Fossil plants and distribution. Fossil plants and climate. Fossil plants
and phylogeny.
CHAPTER III.
GEOLOGICAL HISTORY. Pp. 22–53.
Rock-building. Calcareous rocks. Geological sections. Inversion of strata. Table of Strata:
I. Archaean, 34–36. II. Cambrian, 36–37. III. Ordovician, 37–38. IV. Silurian, 38. V. Devonian,
39. VI. Carboniferous, 39–45. VII. Permian, 45–47. VIII. Trias., 47–48. IX. Jurassic, 48–49. X.
Cretaceous, 50–51. XI. Tertiary, 51–53. Geological Evolution.
CHAPTER IV.
THE PRESERVATION OF PLANTS AS FOSSILS. Pp. 54–92.
Old surface-soils. Fossil wood. Conditions of fossilisation. Drifting of trees. Meaning of the term
‘Fossil.’ Incrustations. Casts of trees. Fossil casts. Plants and coal. Fossils in half-relief. Petrified
trees. Petrified wood. Preservation of tissues. Coal-balls. Fossil nuclei. Fossil plants in volcanic
ash. Conditions of preservation.
CHAPTER V.
———————
PART I. GENERAL.
CHAPTER I.
HISTORICAL SKETCH. Pp. 1–11.
Fossil plants and the Flood. Sternberg and Brongniart. The internal structure of fossil plants. English
Palaeobotanists. Difficulties of identification.
CHAPTER II.
RELATION OF PALAEOBOTANY TO BOTANY AND GEOLOGY. Pp. 12–21.
Neglect of fossils by Botanists. Fossil plants and distribution. Fossil plants and climate. Fossil plants
and phylogeny.
CHAPTER III.
GEOLOGICAL HISTORY. Pp. 22–53.
Rock-building. Calcareous rocks. Geological sections. Inversion of strata. Table of Strata:
I. Archaean, 34–36. II. Cambrian, 36–37. III. Ordovician, 37–38. IV. Silurian, 38. V. Devonian,
39. VI. Carboniferous, 39–45. VII. Permian, 45–47. VIII. Trias., 47–48. IX. Jurassic, 48–49. X.
Cretaceous, 50–51. XI. Tertiary, 51–53. Geological Evolution.
CHAPTER IV.
THE PRESERVATION OF PLANTS AS FOSSILS. Pp. 54–92.
Old surface-soils. Fossil wood. Conditions of fossilisation. Drifting of trees. Meaning of the term
‘Fossil.’ Incrustations. Casts of trees. Fossil casts. Plants and coal. Fossils in half-relief. Petrified
trees. Petrified wood. Preservation of tissues. Coal-balls. Fossil nuclei. Fossil plants in volcanic
ash. Conditions of preservation.
CHAPTER V.
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DIFFICULTIES AND SOURCES OF ERROR IN THE DETERMINATION OF FOSSIL
PLANTS. Pp. 93–109.
External resemblance. Venation characters. Decorticated stems. Imperfect casts. Mineral deposits
simulating plants. Traces of wood-borers in petrified tissue. Photography and illustration.
CHAPTER VI.
NOMENCLATURE. Pp. 110–115.
Rules for nomenclature. The rule of priority. Terminology and convenience.
———————
PART II. SYSTEMATIC.
CHAPTER VII.
THALLOPHYTA. Pp. 116–228.
PAGE
I. PERIDINIALES 117–118
II. COCCOSPHERES AND RHABDOSPHERES 118–121
III. SCHIZOPHYTA 121–138
A. SCHIZOPHYCEAE (Cyanophyceae) 122–132
Girvanella 124–126. Borings in shells 127–129. Zonatrichites 129–130.
B. SCHIZOMYCETES (Bacteria) 132–138
Bacillus Permicus 135–136. B. Tieghemi and Micrococcus Guignardi 136.
Fossil Bacteria 137–138.
IV. ALGAE 138–205
Scarcity of fossil algae. Fossils simulating Algae. Recognition of fossil algae.
Algites &c.
A. DIATOMACEAE 150–156
Recent Diatoms. Fossil Diatoms. Bactryllium &c.
B. CHLOROPHYCEAE 156–178
a. Siphoneae 157–177
α. Caulerpaceae 157–159
β. Codiaceae 159–164
Codium 159–160. Sphaerocodium 160. Penicillus 161. Ovulites 161–
164. Halimeda 164.
γ. Dasycladaceae 164–177
PLANTS. Pp. 93–109.
External resemblance. Venation characters. Decorticated stems. Imperfect casts. Mineral deposits
simulating plants. Traces of wood-borers in petrified tissue. Photography and illustration.
CHAPTER VI.
NOMENCLATURE. Pp. 110–115.
Rules for nomenclature. The rule of priority. Terminology and convenience.
———————
PART II. SYSTEMATIC.
CHAPTER VII.
THALLOPHYTA. Pp. 116–228.
PAGE
I. PERIDINIALES 117–118
II. COCCOSPHERES AND RHABDOSPHERES 118–121
III. SCHIZOPHYTA 121–138
A. SCHIZOPHYCEAE (Cyanophyceae) 122–132
Girvanella 124–126. Borings in shells 127–129. Zonatrichites 129–130.
B. SCHIZOMYCETES (Bacteria) 132–138
Bacillus Permicus 135–136. B. Tieghemi and Micrococcus Guignardi 136.
Fossil Bacteria 137–138.
IV. ALGAE 138–205
Scarcity of fossil algae. Fossils simulating Algae. Recognition of fossil algae.
Algites &c.
A. DIATOMACEAE 150–156
Recent Diatoms. Fossil Diatoms. Bactryllium &c.
B. CHLOROPHYCEAE 156–178
a. Siphoneae 157–177
α. Caulerpaceae 157–159
β. Codiaceae 159–164
Codium 159–160. Sphaerocodium 160. Penicillus 161. Ovulites 161–
164. Halimeda 164.
γ. Dasycladaceae 164–177
Page 20
Acetabularia 165–166. Acicularia 166–169. Cymopolia 169–171.
Vermiporella 172–173. Sycidium 173. Diplopora 174–175.
Gyroporella 175. Dactylopora, Palaeozoic and Mesozoic Siphoneae
175–177.
b. Confervoideae 177–178
C. INCERTAE SEDIS 178–183
Boghead ‘Coal.’ Reinschia 180–181. Pila 181–182.
D. RHODOPHYCEAE 183–190
Corallinaceae 183–190
Lithothamnion 185–189. Solenopora 189–190.
E. PHAEOPHYCEAE 191–202
Nematophycus 192–202
Pachytheca 202–204
Algites 204–205
V. MYXOMYCETES (MYCETOZOA) 205–206
Myxomycetes Mangini 206.
VI. FUNGI 207–222
Ascomycetes. Basidiomycetes.
Pathology of fossil tissues. Oochytrium Lepidodendri 216–217.
Peronosporites antiquarius 217–220. Cladosporites bipartitus 220.
Haplographites cateniger 220. Zygosporites 220–221. Polyporus
vaporarius 221.
VII. CHAROPHYTA 222–228
Chareae 223–228
Chara 225–228. C. Bleicheri 226. C. Knowltoni 226–227. C. Wrighti 227.
CHAPTER VIII.
BRYOPHYTA. Pp. 229–241.
I. HEPATICAE 230–236
Marchantites 233–235. M. Sezannensis 234–235.
II. MUSCI 236–241
Muscites 238–241. M. polytrichaceus 239–240. Palaeozoic Mosses.
Muscites ferrugineus 241.
CHAPTER IX.
PTERIDOPHYTA (VASCULAR CRYPTOGRAMS). Pp. 242–294.
I. EQUISETALES (Recent) 244–254
Equisetaceae 244–254
Equisetum 246–254.
Vermiporella 172–173. Sycidium 173. Diplopora 174–175.
Gyroporella 175. Dactylopora, Palaeozoic and Mesozoic Siphoneae
175–177.
b. Confervoideae 177–178
C. INCERTAE SEDIS 178–183
Boghead ‘Coal.’ Reinschia 180–181. Pila 181–182.
D. RHODOPHYCEAE 183–190
Corallinaceae 183–190
Lithothamnion 185–189. Solenopora 189–190.
E. PHAEOPHYCEAE 191–202
Nematophycus 192–202
Pachytheca 202–204
Algites 204–205
V. MYXOMYCETES (MYCETOZOA) 205–206
Myxomycetes Mangini 206.
VI. FUNGI 207–222
Ascomycetes. Basidiomycetes.
Pathology of fossil tissues. Oochytrium Lepidodendri 216–217.
Peronosporites antiquarius 217–220. Cladosporites bipartitus 220.
Haplographites cateniger 220. Zygosporites 220–221. Polyporus
vaporarius 221.
VII. CHAROPHYTA 222–228
Chareae 223–228
Chara 225–228. C. Bleicheri 226. C. Knowltoni 226–227. C. Wrighti 227.
CHAPTER VIII.
BRYOPHYTA. Pp. 229–241.
I. HEPATICAE 230–236
Marchantites 233–235. M. Sezannensis 234–235.
II. MUSCI 236–241
Muscites 238–241. M. polytrichaceus 239–240. Palaeozoic Mosses.
Muscites ferrugineus 241.
CHAPTER IX.
PTERIDOPHYTA (VASCULAR CRYPTOGRAMS). Pp. 242–294.
I. EQUISETALES (Recent) 244–254
Equisetaceae 244–254
Equisetum 246–254.
Page 21
II. FOSSIL EQUISETALES 254–294
A. EQUISETITES 257–281
Equisetites Hemingwayi 263–264. E. spatulatus 264–266. E. zeaeformis
266. E. arenaceus 268–269. E. columnaris 269–270. E. Beani 270–
275. E. lateralis 275–279. E. Burchardti 279–280.
B. PHYLLOTHECA 281–291
Phyllotheca deliquescens 283–284. P. Brongniarti 286–287. P. indica and
P. australis 287–289.
C. SCHIZONEURA 291–294
S. gondwanensis 292–293.
CHAPTER X.
EQUISETALES (continued). Pp. 295–388.
D. CALAMITES 295–383
I. Historical sketch 295–302
II. Description of the anatomy of Calamites 302–364
a. Stems 304–329
Arthropitys, Arthrodendron, and Calamodendron.
b. Leaves 329–342
α. Calamocladus (Asterophyllites) 332–336. C. equisetiformis 335–336.
β. Annularia 336–342. A. stellata 338–340. A. sphenophylloides 341–
342.
c. Roots 342–349
d. Cones 349–365
Calamostachys Binneyana 351–355. C. Casheana 355–357.
Palaeostachya vera 358–360. Calamostachys, Palaeostachya and
Macrostachya 361–364.
III. Pith-casts of Calamites 365–380
Calamitina 367–374. Calamites (Calamitina) Göpperti 372–374.
Stylocalamites 374–376. C. (Stylocalamites) Suckowi 374–376.
Eucalamites 376–379. C. (Eucalamites) cruciatus 378–379.
IV. Conclusion 381–383
E. ARCHAEOCALAMITES 383–388
A. scrobiculatus 386–387.
CHAPTER XI.
SPHENOPHYLLALES. Pp. 389–414.
I. SPHENOPHYLLUM 389–414
A. The anatomy of Sphenophyllum 392–406
A. EQUISETITES 257–281
Equisetites Hemingwayi 263–264. E. spatulatus 264–266. E. zeaeformis
266. E. arenaceus 268–269. E. columnaris 269–270. E. Beani 270–
275. E. lateralis 275–279. E. Burchardti 279–280.
B. PHYLLOTHECA 281–291
Phyllotheca deliquescens 283–284. P. Brongniarti 286–287. P. indica and
P. australis 287–289.
C. SCHIZONEURA 291–294
S. gondwanensis 292–293.
CHAPTER X.
EQUISETALES (continued). Pp. 295–388.
D. CALAMITES 295–383
I. Historical sketch 295–302
II. Description of the anatomy of Calamites 302–364
a. Stems 304–329
Arthropitys, Arthrodendron, and Calamodendron.
b. Leaves 329–342
α. Calamocladus (Asterophyllites) 332–336. C. equisetiformis 335–336.
β. Annularia 336–342. A. stellata 338–340. A. sphenophylloides 341–
342.
c. Roots 342–349
d. Cones 349–365
Calamostachys Binneyana 351–355. C. Casheana 355–357.
Palaeostachya vera 358–360. Calamostachys, Palaeostachya and
Macrostachya 361–364.
III. Pith-casts of Calamites 365–380
Calamitina 367–374. Calamites (Calamitina) Göpperti 372–374.
Stylocalamites 374–376. C. (Stylocalamites) Suckowi 374–376.
Eucalamites 376–379. C. (Eucalamites) cruciatus 378–379.
IV. Conclusion 381–383
E. ARCHAEOCALAMITES 383–388
A. scrobiculatus 386–387.
CHAPTER XI.
SPHENOPHYLLALES. Pp. 389–414.
I. SPHENOPHYLLUM 389–414
A. The anatomy of Sphenophyllum 392–406
Page 22
a. Stems 392–398
Sphenophyllum insigne and S. plurifoliatum 397–398.
b. Roots 399
c. Leaves 399
d. Cones 401–406
Sphenophyllostachys Dawsoni 402–405. S. Römeri 405–406.
B. Types of vegetative Branches of Sphenophyllum 407–412
Sphenophyllum emarginatum 407–408. S. trichomatosum 408–409. S.
Thoni 410–411. S. speciosum 411–412.
C. Affinities, Range and Habit of Sphenophyllum 412–414
Sphenophyllum insigne and S. plurifoliatum 397–398.
b. Roots 399
c. Leaves 399
d. Cones 401–406
Sphenophyllostachys Dawsoni 402–405. S. Römeri 405–406.
B. Types of vegetative Branches of Sphenophyllum 407–412
Sphenophyllum emarginatum 407–408. S. trichomatosum 408–409. S.
Thoni 410–411. S. speciosum 411–412.
C. Affinities, Range and Habit of Sphenophyllum 412–414
Page 23
Page 24
LIST OF ILLUSTRATIONS.
Frontispiece. Tree Stumps in a Carboniferous Forest. Drawn from a photograph. (M. Seward.)
Page 57.
FIG. PAGE
1. Lepidodendron. (M. S.) 10
2. Geological section 29
3. Table of strata 32
4. Geological section (coal seam) 44
5. Neuropteris Scheuchzeri Hoffm. (M. S.) 45
6. Submerged Forest at Leasowe. (M. S.) 59
7. Ammonite on coniferous wood. (M. S.) 61
8. Coniferous wood in flint. (M. S.) 62
9. Bored fossil wood. (M. S.) 62
10. Section of an old pool filled up with a mass of Chara. (From block lent by Dr
Woodward) 69
11. Equisetites columnaris Brongn. (M. S.) 72
12. Stigmaria ficoides Brongn. (M. S.) 73
13. Cordaites etc. in coal. (M. S.) 76
14. Crystallisation in petrified tissues 81
15. Lepidodendron. (From a photograph by Mr Edwin Wilson of a specimen lent by Mr
Kidston) 82
16. Cast of a fossil cell. (M. S.) 84
17. Calcareous nodule from the Coal-Measures 85
18. Lepidodendron from Arran. (M. S.) 89
19. Trigonocarpon seeds in a block of sandstone. (M. S.) 91
20. Restio, Equisetum, Casuarina and Ephedra. (M. S.) 95
21. Polygonum equisetiforme Sibth. and Sm. (M. S.) 96
22. Kaulfussia æsculifolia Blume. (M. S.) 97
23. A branched Lepidodendroid stem (Knorria mirabilis Ren. and Zeill.). (M. S.) 102
24. Partially disorganised petrified tissue 107
25. Coccospheres and Rhabdospheres. (Lent by Messrs Macmillan) 119
26. Girvanella problematica Eth. and Nich. (M. S.) 124
27. Fish-scale and shell perforated by a boring organism. (M. S.) 128
28. Bacillus Tieghemi Ren. and Micrococcus Guignardi Ren. (M. S.) 135
29. Laminaria sp. 140
Frontispiece. Tree Stumps in a Carboniferous Forest. Drawn from a photograph. (M. Seward.)
Page 57.
FIG. PAGE
1. Lepidodendron. (M. S.) 10
2. Geological section 29
3. Table of strata 32
4. Geological section (coal seam) 44
5. Neuropteris Scheuchzeri Hoffm. (M. S.) 45
6. Submerged Forest at Leasowe. (M. S.) 59
7. Ammonite on coniferous wood. (M. S.) 61
8. Coniferous wood in flint. (M. S.) 62
9. Bored fossil wood. (M. S.) 62
10. Section of an old pool filled up with a mass of Chara. (From block lent by Dr
Woodward) 69
11. Equisetites columnaris Brongn. (M. S.) 72
12. Stigmaria ficoides Brongn. (M. S.) 73
13. Cordaites etc. in coal. (M. S.) 76
14. Crystallisation in petrified tissues 81
15. Lepidodendron. (From a photograph by Mr Edwin Wilson of a specimen lent by Mr
Kidston) 82
16. Cast of a fossil cell. (M. S.) 84
17. Calcareous nodule from the Coal-Measures 85
18. Lepidodendron from Arran. (M. S.) 89
19. Trigonocarpon seeds in a block of sandstone. (M. S.) 91
20. Restio, Equisetum, Casuarina and Ephedra. (M. S.) 95
21. Polygonum equisetiforme Sibth. and Sm. (M. S.) 96
22. Kaulfussia æsculifolia Blume. (M. S.) 97
23. A branched Lepidodendroid stem (Knorria mirabilis Ren. and Zeill.). (M. S.) 102
24. Partially disorganised petrified tissue 107
25. Coccospheres and Rhabdospheres. (Lent by Messrs Macmillan) 119
26. Girvanella problematica Eth. and Nich. (M. S.) 124
27. Fish-scale and shell perforated by a boring organism. (M. S.) 128
28. Bacillus Tieghemi Ren. and Micrococcus Guignardi Ren. (M. S.) 135
29. Laminaria sp. 140
Page 25
FIG. PAGE
30. Rill-mark; trail of a seaweed; tracks of a Polychaet. (M. S.) 143
31. Chondrites verisimilis Salt. (M. S.) 146
32. Lithothamnion mamillosum Gümb.; Sycidium melo Sandb.; Bactryllium deplanatum
Heer; Calcareous pebble from a lake in Michigan. (M. S.) 155
33. Cymopolia barbata (L.); Acicularia Andrussowi Solms; Acicularia sp.; A. Schencki
(Möb.); A. Mediterranea Lamx.; Ovulites margaritula Lamx.; Penicillus pyramidalis
(Lamx.) (M. S.) 162
34. Acetabularia mediterranea Lamx. (Photograph by Mr Edwin Wilson) 165
35. Diplopora; Gyroporella; Penicillus; Ovulites margaritula Lam.; Confervites
chantransioides (Born.) 174
36. Torbanite; Pila bibractensis and Reinschia australis 180
37. Lithothamnion sp.; L. suganum Roth.; Sphaerocodium Bornemanni Roth. 186
38. Solenopora compacta (Billings). (M. S.) 189
39. Nematophycus Logani (Daws.) 196
40. Nematophycus Storriei Barb. (Photograph by Mr C. A. Barber) 199
41. Cells of Cycadeoidea gigantea Sew., Osmundites Dowkeri Carr and Memecylon with
vacuolated contents; Peronosporites antiquarius Smith; Zygosporites 214
42. Tracheids of coniferous wood attacked by Trametes radiciperda Hart and Agaricus
melleus Vahl. 215
43. Oochytrium Lepidodendri Ren.; Polyporus vaporarius Fr. var. succinea; Cladosporites
bipartitus Fel.; Haplographites cateniger Fel. (M. S.) 217
44. Cells of fossil plants with fungal hyphae 219
45. Chara Knowltoni Sew.; Chara foetida A. Br. (A and B, Mr Highley; C–E, M. S.) 224
46. Chara Bleicheri Sap.; Chara? sp.; C. Wrighti Forbes. (M. S.) 226
47. Chara Knowltoni Sew. (From block lent by Dr Woodward) 227
48. Tristichia hypnoides Spreng.; Podocarpus cupressina Br. and Ben.; Selaginella Oregana
Eat. (M. S.) 231
49. Marchantites erectus (Leck.) (M. S.) 233
50. Marchantites Sezannensis Sap. (M. S.) 235
51. Muscites polytrichaceus Ren. and Zeill. (M. S.) 239
52. Equisetum maximum Lam.; E. arvense L. 246
53. Equisetum palustre L. (M. S.) 247
54. Plan of the vascular bundles in an Equisetum stem; E. arvense L. 250
55. Equisetum variegatum Schl.; E. maximum Lam. 252
56. Calamitean leaf-sheath. (M. S.) 260
57. Equisetites Hemingwayi Kidst. (Mr Highley) 262
58. Equisetites spatulatus Zeill.; E. zeaeformis (Schloth.); Equisetites lateralis Phill.;
Equisetites columnaris Brongn.; Equisetum trachyodon A. Br. (M. S.) 265
59. Equisetites platyodon Brongn. (M. S.) 267
60. Equisetites Beani (Bunb.). (From a block lent by Dr Woodward) 271
61. Equisetites Beani (Bunb.). (M. S.) 272
30. Rill-mark; trail of a seaweed; tracks of a Polychaet. (M. S.) 143
31. Chondrites verisimilis Salt. (M. S.) 146
32. Lithothamnion mamillosum Gümb.; Sycidium melo Sandb.; Bactryllium deplanatum
Heer; Calcareous pebble from a lake in Michigan. (M. S.) 155
33. Cymopolia barbata (L.); Acicularia Andrussowi Solms; Acicularia sp.; A. Schencki
(Möb.); A. Mediterranea Lamx.; Ovulites margaritula Lamx.; Penicillus pyramidalis
(Lamx.) (M. S.) 162
34. Acetabularia mediterranea Lamx. (Photograph by Mr Edwin Wilson) 165
35. Diplopora; Gyroporella; Penicillus; Ovulites margaritula Lam.; Confervites
chantransioides (Born.) 174
36. Torbanite; Pila bibractensis and Reinschia australis 180
37. Lithothamnion sp.; L. suganum Roth.; Sphaerocodium Bornemanni Roth. 186
38. Solenopora compacta (Billings). (M. S.) 189
39. Nematophycus Logani (Daws.) 196
40. Nematophycus Storriei Barb. (Photograph by Mr C. A. Barber) 199
41. Cells of Cycadeoidea gigantea Sew., Osmundites Dowkeri Carr and Memecylon with
vacuolated contents; Peronosporites antiquarius Smith; Zygosporites 214
42. Tracheids of coniferous wood attacked by Trametes radiciperda Hart and Agaricus
melleus Vahl. 215
43. Oochytrium Lepidodendri Ren.; Polyporus vaporarius Fr. var. succinea; Cladosporites
bipartitus Fel.; Haplographites cateniger Fel. (M. S.) 217
44. Cells of fossil plants with fungal hyphae 219
45. Chara Knowltoni Sew.; Chara foetida A. Br. (A and B, Mr Highley; C–E, M. S.) 224
46. Chara Bleicheri Sap.; Chara? sp.; C. Wrighti Forbes. (M. S.) 226
47. Chara Knowltoni Sew. (From block lent by Dr Woodward) 227
48. Tristichia hypnoides Spreng.; Podocarpus cupressina Br. and Ben.; Selaginella Oregana
Eat. (M. S.) 231
49. Marchantites erectus (Leck.) (M. S.) 233
50. Marchantites Sezannensis Sap. (M. S.) 235
51. Muscites polytrichaceus Ren. and Zeill. (M. S.) 239
52. Equisetum maximum Lam.; E. arvense L. 246
53. Equisetum palustre L. (M. S.) 247
54. Plan of the vascular bundles in an Equisetum stem; E. arvense L. 250
55. Equisetum variegatum Schl.; E. maximum Lam. 252
56. Calamitean leaf-sheath. (M. S.) 260
57. Equisetites Hemingwayi Kidst. (Mr Highley) 262
58. Equisetites spatulatus Zeill.; E. zeaeformis (Schloth.); Equisetites lateralis Phill.;
Equisetites columnaris Brongn.; Equisetum trachyodon A. Br. (M. S.) 265
59. Equisetites platyodon Brongn. (M. S.) 267
60. Equisetites Beani (Bunb.). (From a block lent by Dr Woodward) 271
61. Equisetites Beani (Bunb.). (M. S.) 272
Page 26
FIG. PAGE
62. E. Beani (Bunb.). (M. S.) 274
63. E. lateralis Phill. (M. S.) 275
64. E. lateralis Phill. (M. S.) 278
65. E. Burchardti Dunk. (M. S.) 279
66. E. Yokoyamae Sew. (From a block lent by Dr Woodward) 280
67. Phyllotheca? sp. (From a photograph by Mr Edwin Wilson) 285
68. Phyllotheca Brongniarti Zigno; P. indica Bunb.; Calamocladus frondosus Grand’Eury.
(M. S.) 287
69. Schizoneura gondwanensis Feist. (M. S.) 293
70. Transverse section of a Calamite stem. (M. S.) 299
71. Transverse section of a young Calamite stem 305
72. Longitudinal and transverse sections of Calamites 308
73. Transverse section of a Calamite stem 310
74. Transverse section of Calamites (Arthropitys) sp. 312
75. Longitudinal section (tangential) of Calamites (Arthropitys) sp. 313
76. Longitudinal section (tangential) of Calamites (Arthropitys) sp. 314
77. Portion of a Calamite stem; partially restored. (M. S.) 316
78. Transverse and longitudinal (radial) sections of a thick Calamite stem. (Mr Highley) 318
79. 319
80. Transverse section of a Calamite showing callus wood 320
81. Longitudinal section of a young Calamite 321
82. Pith-casts of Calamites (Stylocalamites) sp. (M. S.) 323
83. Calamites (Arthrodendron) sp. Transverse and longitudinal sections 327
84. Transverse section of Calamites (Calamodendron) intermedius Ren. 328
85. Leaves of a Calamite. (M. S.) 330
86. Transverse section of a Calamite leaf 331
87. Calamocladus equisetiformis (Schloth.) (Miss G. M. Woodward) 334
88. Annularia stellata (Schloth.) (M. S.) 339
89. Annularia sphenophylloides Zenk. (M. S.) 340
90. Pith-cast of a Calamite, with roots. (M. S.) 343
91. Transverse sections of Calamite roots 345
92. Root given off from a Calamite stem 347
93. Calamostachys sp. (M. S.) 350
94. C. Binneyana (Carr.). (Mr Highley) 352
95. C. Binneyana (Carr.) 354
96. C. Casheana Will. 356
97. Palaeostachya pedunculata Will. (M. S.) 357
98. P. vera sp. nov. 359
99. Calamites (Calamitina) Göpp. (Ett.) (M. S.) 368
62. E. Beani (Bunb.). (M. S.) 274
63. E. lateralis Phill. (M. S.) 275
64. E. lateralis Phill. (M. S.) 278
65. E. Burchardti Dunk. (M. S.) 279
66. E. Yokoyamae Sew. (From a block lent by Dr Woodward) 280
67. Phyllotheca? sp. (From a photograph by Mr Edwin Wilson) 285
68. Phyllotheca Brongniarti Zigno; P. indica Bunb.; Calamocladus frondosus Grand’Eury.
(M. S.) 287
69. Schizoneura gondwanensis Feist. (M. S.) 293
70. Transverse section of a Calamite stem. (M. S.) 299
71. Transverse section of a young Calamite stem 305
72. Longitudinal and transverse sections of Calamites 308
73. Transverse section of a Calamite stem 310
74. Transverse section of Calamites (Arthropitys) sp. 312
75. Longitudinal section (tangential) of Calamites (Arthropitys) sp. 313
76. Longitudinal section (tangential) of Calamites (Arthropitys) sp. 314
77. Portion of a Calamite stem; partially restored. (M. S.) 316
78. Transverse and longitudinal (radial) sections of a thick Calamite stem. (Mr Highley) 318
79. 319
80. Transverse section of a Calamite showing callus wood 320
81. Longitudinal section of a young Calamite 321
82. Pith-casts of Calamites (Stylocalamites) sp. (M. S.) 323
83. Calamites (Arthrodendron) sp. Transverse and longitudinal sections 327
84. Transverse section of Calamites (Calamodendron) intermedius Ren. 328
85. Leaves of a Calamite. (M. S.) 330
86. Transverse section of a Calamite leaf 331
87. Calamocladus equisetiformis (Schloth.) (Miss G. M. Woodward) 334
88. Annularia stellata (Schloth.) (M. S.) 339
89. Annularia sphenophylloides Zenk. (M. S.) 340
90. Pith-cast of a Calamite, with roots. (M. S.) 343
91. Transverse sections of Calamite roots 345
92. Root given off from a Calamite stem 347
93. Calamostachys sp. (M. S.) 350
94. C. Binneyana (Carr.). (Mr Highley) 352
95. C. Binneyana (Carr.) 354
96. C. Casheana Will. 356
97. Palaeostachya pedunculata Will. (M. S.) 357
98. P. vera sp. nov. 359
99. Calamites (Calamitina) Göpp. (Ett.) (M. S.) 368
Page 27
FIG. PAGE
100. Calamites (Calamitina) approximatus Brongn. From a photograph by Mr Kidston 370
101. Calamites (Calamitina) sp. (From a block lent by Dr Woodward) 373
102. Calamites (Eucalamites) cruciatus Sternb. (From a photograph by Mr Edwin Wilson) 377
103. Archaeocalamites scrobiculatus (Schloth.). (From a photograph by Mr Edwin Wilson) 385
104. Diagrammatic longitudinal section of Sphenophyllum 393
105. Transverse and longitudinal sections of Sphenophyllum insigne (Will.) and S.
plurifoliatum Will. and Scott 394
106. Sphenophyllum plurifoliatum Will. and Scott. (From a photograph by Mr Highley) 398
107. Sphenophyllum strobilus, stem and root 400
108. Diagrammatic longitudinal section of a Sphenophyllum strobilus. (M. S.) 402
109. Sphenophyllum emarginatum (Brongn.) (M. S.) 407
110. Sphenophyllum Thoni Mahr.; S. trichomatosum Stur. (M. S.) 410
111. Sphenophyllum speciosum (Royle). (M. S.) 411
Note. The references in the footnotes require a word of explanation. The
titles of the works referred to will be found in the Bibliography at the end of
the volume. In this list the authors’ names are arranged alphabetically and
the papers of each author are in chronological order. The numbers in
brackets after the author’s name in the footnotes, and before his name in the
bibliographical list, refer to the year of publication. Except in cases where
the works were published prior to 1800, the first two figures are omitted:
thus Ward (84) refers to a paper published by L. F. Ward in 1884. This
system was suggested by Dr H. H. Field in the Biologisches Centralblatt,
vol. xiii. 1893, p. 753. (Ueber die Art der Abfassung
naturwissenschaftlicher Litteraturverzeichnisse.)
100. Calamites (Calamitina) approximatus Brongn. From a photograph by Mr Kidston 370
101. Calamites (Calamitina) sp. (From a block lent by Dr Woodward) 373
102. Calamites (Eucalamites) cruciatus Sternb. (From a photograph by Mr Edwin Wilson) 377
103. Archaeocalamites scrobiculatus (Schloth.). (From a photograph by Mr Edwin Wilson) 385
104. Diagrammatic longitudinal section of Sphenophyllum 393
105. Transverse and longitudinal sections of Sphenophyllum insigne (Will.) and S.
plurifoliatum Will. and Scott 394
106. Sphenophyllum plurifoliatum Will. and Scott. (From a photograph by Mr Highley) 398
107. Sphenophyllum strobilus, stem and root 400
108. Diagrammatic longitudinal section of a Sphenophyllum strobilus. (M. S.) 402
109. Sphenophyllum emarginatum (Brongn.) (M. S.) 407
110. Sphenophyllum Thoni Mahr.; S. trichomatosum Stur. (M. S.) 410
111. Sphenophyllum speciosum (Royle). (M. S.) 411
Note. The references in the footnotes require a word of explanation. The
titles of the works referred to will be found in the Bibliography at the end of
the volume. In this list the authors’ names are arranged alphabetically and
the papers of each author are in chronological order. The numbers in
brackets after the author’s name in the footnotes, and before his name in the
bibliographical list, refer to the year of publication. Except in cases where
the works were published prior to 1800, the first two figures are omitted:
thus Ward (84) refers to a paper published by L. F. Ward in 1884. This
system was suggested by Dr H. H. Field in the Biologisches Centralblatt,
vol. xiii. 1893, p. 753. (Ueber die Art der Abfassung
naturwissenschaftlicher Litteraturverzeichnisse.)
Page 28
Page 29
PART I. GENERAL.
Page 30
CHAPTER I.
HISTORICAL SKETCH.
“But particular care ought to be had not to consult or take relations from any but those who
appear to have been both long conversant in these affairs, and likewise persons of Sobriety,
Faithfulness and Discretion, to avoid the being misled and imposed upon either by falsehood, or
the ignorance, credulity, and fancifulness, that some of these people are but too obnoxious unto.”
John Woodward, 1728.
The scientific study of fossil plants dates from a comparatively recent
period, and palaeobotany has only attained a real importance in the eyes of
botanists and geologists during the last few decades of the present century.
It would be out of place, in a short treatise like the present, to attempt a
detailed historical sketch, or to give an adequate account of the gradual rise
and development of this modern science. An excellent Sketch of
Palaeobotany has recently been drawn up by Prof. Lester Ward[1], of the
United States Geological Survey, and an earlier historical retrospect may be
found in the introduction to an important work by an eminent German
palaeobotanist, the late Prof. Göppert[2]. In the well-known work by
Parkinson on The Organic Remains of a Former World[3] there is much
interesting information as to the early history of our knowledge of fossil
plants, as well as a good exposition of the views held at the beginning of
this century.
FOSSIL PLANTS AND THE FLOOD.
As a means of bringing into relief the modern development of the science
of fossil plants, we may briefly pass in review some of the earlier writers,
who have concerned themselves in a greater or less degree with a
descriptive or speculative treatment of the records of a past vegetation. In
the early part of the present century, and still more in the eighteenth century,
the occurrence of fossil plants and animals in the earth’s crust formed the
subject of animated, not to say acrimonious, discussion. The result was that
many striking and ingenious theories were formulated as to the exact
manner of formation of fossil remains, and the part played by the waters of
the deluge in depositing fossiliferous strata. The earlier views on fossil
vegetables are naturally bound up with the gradual evolution of geological
science. It is from Italy that we seem to have the first glimmering of
HISTORICAL SKETCH.
“But particular care ought to be had not to consult or take relations from any but those who
appear to have been both long conversant in these affairs, and likewise persons of Sobriety,
Faithfulness and Discretion, to avoid the being misled and imposed upon either by falsehood, or
the ignorance, credulity, and fancifulness, that some of these people are but too obnoxious unto.”
John Woodward, 1728.
The scientific study of fossil plants dates from a comparatively recent
period, and palaeobotany has only attained a real importance in the eyes of
botanists and geologists during the last few decades of the present century.
It would be out of place, in a short treatise like the present, to attempt a
detailed historical sketch, or to give an adequate account of the gradual rise
and development of this modern science. An excellent Sketch of
Palaeobotany has recently been drawn up by Prof. Lester Ward[1], of the
United States Geological Survey, and an earlier historical retrospect may be
found in the introduction to an important work by an eminent German
palaeobotanist, the late Prof. Göppert[2]. In the well-known work by
Parkinson on The Organic Remains of a Former World[3] there is much
interesting information as to the early history of our knowledge of fossil
plants, as well as a good exposition of the views held at the beginning of
this century.
FOSSIL PLANTS AND THE FLOOD.
As a means of bringing into relief the modern development of the science
of fossil plants, we may briefly pass in review some of the earlier writers,
who have concerned themselves in a greater or less degree with a
descriptive or speculative treatment of the records of a past vegetation. In
the early part of the present century, and still more in the eighteenth century,
the occurrence of fossil plants and animals in the earth’s crust formed the
subject of animated, not to say acrimonious, discussion. The result was that
many striking and ingenious theories were formulated as to the exact
manner of formation of fossil remains, and the part played by the waters of
the deluge in depositing fossiliferous strata. The earlier views on fossil
vegetables are naturally bound up with the gradual evolution of geological
science. It is from Italy that we seem to have the first glimmering of
Page 31
scientific views; but we are led to forget this early development of more
than three hundred years ago, when we turn to the writings of English and
other authors of the eighteenth century. “Under these white banks by the
roadside,” as a writer on Verona has expressed it, “was born, like a poor
Italian gipsy, the modern science of geology.” Early in the sixteenth century
the genius of Leonardo da Vinci[4] compelled him to adopt a reasonable
explanation of the occurrence of fossil shells in rocks far above the present
sea-level. Another Italian writer, Fracastaro, whose attention was directed to
this matter by the discovery of numerous shells brought to light by
excavations at Verona, expressed his belief in the organic nature of the
remains, and went so far as to call in question the Mosaic deluge as a
satisfactory explanation of the deposition of fossil-bearing strata.
The partial recognition by some observers of the true nature of fossils
marks the starting point of more rational views. The admission that fossils
were not mere sports of nature, or the result of some wonderful ‘vis
lapidifica,’ was naturally followed by numerous speculations as to the
manner in which the remains of animals and plants came to be embedded in
rocks above the sea-level. For a long time, the ‘universal flood’ was held
responsible by nearly all writers for the existence of fossils in ancient
sediments. Dr John Woodward, in his Essay toward a Natural History of the
Earth, propounded the somewhat revolutionary theory, that “the whole
terrestrial globe was taken all to pieces and dissolved at the Deluge, the
particles of stone, marble, and all solid fossils dissevered, taken up into the
water, and there sustained together with sea-shells and other animal and
vegetable bodies: and that the present earth consists, and was formed out of
that promiscuous mass of sand, earth, shells, and the rest falling down
again, and subsiding from the water[5].” In common with other writers, he
endeavoured to fix the exact date of the flood by means of fossil plants.
Speaking of some hazel-nuts, which were found in a Cheshire moss pit, he
draws attention to their unripened condition, and adds: “The deluge came
forth at the end of May, when nuts are not ripe.” As additional evidence, he
cites the occurrence of “Pine cones in their vernal state,” and of some Coal-
Measure fossils which he compares with Virginian Maize, “tender, young,
vernal, and not ripened[6].” Woodward (1665–1728) was Professor of Physic
in Gresham College; he bequeathed his geological collections to the
University of Cambridge, and founded the Chair which bears his name.
than three hundred years ago, when we turn to the writings of English and
other authors of the eighteenth century. “Under these white banks by the
roadside,” as a writer on Verona has expressed it, “was born, like a poor
Italian gipsy, the modern science of geology.” Early in the sixteenth century
the genius of Leonardo da Vinci[4] compelled him to adopt a reasonable
explanation of the occurrence of fossil shells in rocks far above the present
sea-level. Another Italian writer, Fracastaro, whose attention was directed to
this matter by the discovery of numerous shells brought to light by
excavations at Verona, expressed his belief in the organic nature of the
remains, and went so far as to call in question the Mosaic deluge as a
satisfactory explanation of the deposition of fossil-bearing strata.
The partial recognition by some observers of the true nature of fossils
marks the starting point of more rational views. The admission that fossils
were not mere sports of nature, or the result of some wonderful ‘vis
lapidifica,’ was naturally followed by numerous speculations as to the
manner in which the remains of animals and plants came to be embedded in
rocks above the sea-level. For a long time, the ‘universal flood’ was held
responsible by nearly all writers for the existence of fossils in ancient
sediments. Dr John Woodward, in his Essay toward a Natural History of the
Earth, propounded the somewhat revolutionary theory, that “the whole
terrestrial globe was taken all to pieces and dissolved at the Deluge, the
particles of stone, marble, and all solid fossils dissevered, taken up into the
water, and there sustained together with sea-shells and other animal and
vegetable bodies: and that the present earth consists, and was formed out of
that promiscuous mass of sand, earth, shells, and the rest falling down
again, and subsiding from the water[5].” In common with other writers, he
endeavoured to fix the exact date of the flood by means of fossil plants.
Speaking of some hazel-nuts, which were found in a Cheshire moss pit, he
draws attention to their unripened condition, and adds: “The deluge came
forth at the end of May, when nuts are not ripe.” As additional evidence, he
cites the occurrence of “Pine cones in their vernal state,” and of some Coal-
Measure fossils which he compares with Virginian Maize, “tender, young,
vernal, and not ripened[6].” Woodward (1665–1728) was Professor of Physic
in Gresham College; he bequeathed his geological collections to the
University of Cambridge, and founded the Chair which bears his name.
Page 32
Another writer, Mendes da Costa, in a paper in the Philosophical
Transactions for 1758, speaks of the impressions of “ferns and reed-like
plants” in the coal-beds, and describes some fossils (Sigillaria and
Stigmaria) as probably unknown forms of plant life[7].
Here we have the suggestion that in former ages there were plants which
differed from those of the present age. Discussing the nature of some cones
(Lepidostrobi) from the ironstone of Coalbrookdale in Shropshire, he
concludes: “I firmly believe these bodies to be of vegetable origin, buried in
the strata of the Earth at the time of the universal deluge recorded by
Moses.” Scheuchzer of Zurich, the author of one of the earliest works on
fossil plants and a “great apostle of the Flood Theory,” figures and
describes a specimen as an ear of corn, and refers to its size and general
appearance as pointing to the month of May as the time of the deluge[8].
Another English writer, Dr Parsons, in giving an account of the well-known
‘fossil fruits and other bodies found in the island of Sheppey,’ is disposed to
dissent from Woodward’s views as to the time of the flood. He suggests that
the fact of the Sheppey fruits being found in a perfectly ripe condition,
points to the autumn as the more probable time for the occurrence of the
deluge[9].
In looking through the works of the older writers, and occasionally in the
pages of latter-day contributors, we frequently find curiously shaped stones,
mineral markings on rock surfaces, or certain fossil animals, described as
fossil plants. In Plot’s Natural History of Oxfordshire, published in 1705, a
peculiarly shaped stone, probably a flint, is spoken of as one of the ‘Fungi
lethales non esculenti[10]’; and again a piece of coral[11] is compared with a
‘Bryony root broken off transversely.’ On the other hand, that we may not
undervalue the painstaking and laborious efforts of those who helped to lay
the foundations of modern science, we may note that such authors as
Scheuchzer and Woodward were not misled by the moss-like or dendritic
markings of oxide of manganese on the surface of rocks, which are not
infrequently seen to-day in the cabinets of amateurs as specimens of fossil
plants.
The oldest figures of fossil plants from English rocks which are drawn
with any degree of accuracy are those of Coal-Measure ferns and other
plants in an important work by Edward Lhwyd published at Oxford in
1760[12].
Transactions for 1758, speaks of the impressions of “ferns and reed-like
plants” in the coal-beds, and describes some fossils (Sigillaria and
Stigmaria) as probably unknown forms of plant life[7].
Here we have the suggestion that in former ages there were plants which
differed from those of the present age. Discussing the nature of some cones
(Lepidostrobi) from the ironstone of Coalbrookdale in Shropshire, he
concludes: “I firmly believe these bodies to be of vegetable origin, buried in
the strata of the Earth at the time of the universal deluge recorded by
Moses.” Scheuchzer of Zurich, the author of one of the earliest works on
fossil plants and a “great apostle of the Flood Theory,” figures and
describes a specimen as an ear of corn, and refers to its size and general
appearance as pointing to the month of May as the time of the deluge[8].
Another English writer, Dr Parsons, in giving an account of the well-known
‘fossil fruits and other bodies found in the island of Sheppey,’ is disposed to
dissent from Woodward’s views as to the time of the flood. He suggests that
the fact of the Sheppey fruits being found in a perfectly ripe condition,
points to the autumn as the more probable time for the occurrence of the
deluge[9].
In looking through the works of the older writers, and occasionally in the
pages of latter-day contributors, we frequently find curiously shaped stones,
mineral markings on rock surfaces, or certain fossil animals, described as
fossil plants. In Plot’s Natural History of Oxfordshire, published in 1705, a
peculiarly shaped stone, probably a flint, is spoken of as one of the ‘Fungi
lethales non esculenti[10]’; and again a piece of coral[11] is compared with a
‘Bryony root broken off transversely.’ On the other hand, that we may not
undervalue the painstaking and laborious efforts of those who helped to lay
the foundations of modern science, we may note that such authors as
Scheuchzer and Woodward were not misled by the moss-like or dendritic
markings of oxide of manganese on the surface of rocks, which are not
infrequently seen to-day in the cabinets of amateurs as specimens of fossil
plants.
The oldest figures of fossil plants from English rocks which are drawn
with any degree of accuracy are those of Coal-Measure ferns and other
plants in an important work by Edward Lhwyd published at Oxford in
1760[12].
Page 33
Passing beyond these prescientific speculations, brief reference may be
made to some of the more eminent pioneers of palaeobotany. The
Englishman Artis[13] deserves mention for the quality rather than the
quantity of his contributions to Palaeozoic botany; and among American
authors Steinhauer’s[14] name must hold a prominent place in the list of
those who helped to found this branch of palaeontology. Among German
writers, Schlotheim stands out prominently as one who first published a
work on fossil plants which still remains an important book of reference.
Writing in 1804, he draws attention to the neglect of fossils from a scientific
standpoint; they are simply looked upon, he says, as “unimpeachable
documents of the flood[15].” His book contains excellent figures of many
Coal-Measure plants, and we find in its pages occasional comparisons of
fossil species with recent plants of tropical latitudes. Among the earlier
authors whose writings soon become familiar to the student of fossil plants,
reference must be made to Graf Sternberg, who was born three years before
Schlotheim, but whose work came out some years later than that of the
latter. His great contribution to Fossil Botany entitled Versuch einer
geognostisch-botanischen Darstellung der Flora der Vorwelt, was
published in several parts between the years 1820 and 1838; it was drawn
up with the help of the botanist Presl, and included a valuable contribution
by Corda[16]. In addition to descriptions and numerous figures of plants from
several geological horizons, this important work includes discussions on the
formation of coal, with observations on the climates of past ages.
STERNBERG AND BRONGNIART.
Sternberg endeavoured to apply to fossil plants the same methods of
treatment as those made use of in the case of recent species. About the same
time as Sternberg’s earlier parts were published, Adolphe Brongniart[17] of
Paris began to enrich palaeobotanical science by those splendid researches
which have won for him the title of the “Father of palaeobotany.” In
Brongniart’s Prodrome, and Histoire des végétaux fossiles, and later in his
Tableau des genres de végétaux fossiles, we have not merely careful
descriptions and a systematic arrangement of the known species of fossil
plants, but a masterly scientific treatise on palaeobotany in its various
aspects, which has to a large extent formed the model for the best
subsequent works on similar lines. From the same author, at a later date,
there is at least one contribution to fossil plant literature which must receive
made to some of the more eminent pioneers of palaeobotany. The
Englishman Artis[13] deserves mention for the quality rather than the
quantity of his contributions to Palaeozoic botany; and among American
authors Steinhauer’s[14] name must hold a prominent place in the list of
those who helped to found this branch of palaeontology. Among German
writers, Schlotheim stands out prominently as one who first published a
work on fossil plants which still remains an important book of reference.
Writing in 1804, he draws attention to the neglect of fossils from a scientific
standpoint; they are simply looked upon, he says, as “unimpeachable
documents of the flood[15].” His book contains excellent figures of many
Coal-Measure plants, and we find in its pages occasional comparisons of
fossil species with recent plants of tropical latitudes. Among the earlier
authors whose writings soon become familiar to the student of fossil plants,
reference must be made to Graf Sternberg, who was born three years before
Schlotheim, but whose work came out some years later than that of the
latter. His great contribution to Fossil Botany entitled Versuch einer
geognostisch-botanischen Darstellung der Flora der Vorwelt, was
published in several parts between the years 1820 and 1838; it was drawn
up with the help of the botanist Presl, and included a valuable contribution
by Corda[16]. In addition to descriptions and numerous figures of plants from
several geological horizons, this important work includes discussions on the
formation of coal, with observations on the climates of past ages.
STERNBERG AND BRONGNIART.
Sternberg endeavoured to apply to fossil plants the same methods of
treatment as those made use of in the case of recent species. About the same
time as Sternberg’s earlier parts were published, Adolphe Brongniart[17] of
Paris began to enrich palaeobotanical science by those splendid researches
which have won for him the title of the “Father of palaeobotany.” In
Brongniart’s Prodrome, and Histoire des végétaux fossiles, and later in his
Tableau des genres de végétaux fossiles, we have not merely careful
descriptions and a systematic arrangement of the known species of fossil
plants, but a masterly scientific treatise on palaeobotany in its various
aspects, which has to a large extent formed the model for the best
subsequent works on similar lines. From the same author, at a later date,
there is at least one contribution to fossil plant literature which must receive
Page 34
a passing notice even in this short sketch. In 1839 he published an
exhaustive account of the minute structure of one of the well-known
Palaeozoic genera, Sigillaria; this is not only one of the best of the earliest
monographs on the histology of fossil species, but it is one of the few
existing accounts of the internal structure of this common type[18]. The
fragment of a Sigillarian stem which formed the subject of Brongniart’s
memoir is in the Natural History Museum in the Jardin des Plantes, Paris. It
affords a striking example of the perfection of preservation as well as of the
great beauty of the silicified specimens from Autun, in Central France.
Brongniart was not only a remarkably gifted investigator, whose labours
extend over a period connecting the older and more crude methods of
descriptive treatment with the modern development of microscopic
analysis, but he possessed the power of inspiring a younger generation with
a determination to keep up the high standard of the palaeobotanical
achievements of the French School. In some cases, indeed, his disciples
have allowed a natural reverence for the Master to warp their scientific
judgement, where our more complete knowledge has naturally led to the
correction of some of Brongniart’s conclusions. Without attempting to
follow the history of the science to more recent times, the names of Heer,
Lesquereux, Zigno, Massalongo, Saporta and Ettingshausen should be
included among those who rendered signal service to the science of fossil
plants. The two Swiss writers, Heer[19] and Lesquereux[20], contributed
numerous books and papers on palaeobotanical subjects, the former being
especially well known in connection with the fossil floras of Switzerland
and of Arctic lands, and the latter for his valuable writings on the fossil
plants of his adopted country, North America. Zigno[21] and Massalongo[22]
performed like services for Italy, and the Marquis of Saporta’s name will
always hold an honourable and prominent position in the list of the pioneers
of scientific palaeobotany; his work on the Tertiary and Mesozoic floras of
France being specially noteworthy among the able investigations which we
owe to his ability and enthusiasm[23]. In Baron Ettingshausen[24] we have
another representative of those students of ancient vegetation who have
done so much towards establishing the science of fossil plants on a
philosophical basis.
As in other fields of Natural Science, so also in a marked degree in fossil
botany, a new stimulus was given to scientific inquiry by the application of
the microscope to palaeobotanical investigation. In 1828 Sprengel
exhaustive account of the minute structure of one of the well-known
Palaeozoic genera, Sigillaria; this is not only one of the best of the earliest
monographs on the histology of fossil species, but it is one of the few
existing accounts of the internal structure of this common type[18]. The
fragment of a Sigillarian stem which formed the subject of Brongniart’s
memoir is in the Natural History Museum in the Jardin des Plantes, Paris. It
affords a striking example of the perfection of preservation as well as of the
great beauty of the silicified specimens from Autun, in Central France.
Brongniart was not only a remarkably gifted investigator, whose labours
extend over a period connecting the older and more crude methods of
descriptive treatment with the modern development of microscopic
analysis, but he possessed the power of inspiring a younger generation with
a determination to keep up the high standard of the palaeobotanical
achievements of the French School. In some cases, indeed, his disciples
have allowed a natural reverence for the Master to warp their scientific
judgement, where our more complete knowledge has naturally led to the
correction of some of Brongniart’s conclusions. Without attempting to
follow the history of the science to more recent times, the names of Heer,
Lesquereux, Zigno, Massalongo, Saporta and Ettingshausen should be
included among those who rendered signal service to the science of fossil
plants. The two Swiss writers, Heer[19] and Lesquereux[20], contributed
numerous books and papers on palaeobotanical subjects, the former being
especially well known in connection with the fossil floras of Switzerland
and of Arctic lands, and the latter for his valuable writings on the fossil
plants of his adopted country, North America. Zigno[21] and Massalongo[22]
performed like services for Italy, and the Marquis of Saporta’s name will
always hold an honourable and prominent position in the list of the pioneers
of scientific palaeobotany; his work on the Tertiary and Mesozoic floras of
France being specially noteworthy among the able investigations which we
owe to his ability and enthusiasm[23]. In Baron Ettingshausen[24] we have
another representative of those students of ancient vegetation who have
done so much towards establishing the science of fossil plants on a
philosophical basis.
As in other fields of Natural Science, so also in a marked degree in fossil
botany, a new stimulus was given to scientific inquiry by the application of
the microscope to palaeobotanical investigation. In 1828 Sprengel
Page 35
published a work entitled Commentatio de Psarolithis, ligni fossilis
genere[25]; in which he dealt in some detail with the well-known silicified
fern-stems of Palaeozoic age, from Saxony, basing his descriptions on the
characteristics of anatomical structure revealed by microscopic
examination.
THE INTERNAL STRUCTURE OF FOSSIL PLANTS.
In 1833 Henry Witham of Lartington brought out a work on The Internal
Structure of Fossil Vegetables[26]; this book, following the much smaller and
less important work by Sprengel, at once established palaeobotany on a
firmer scientific basis, and formed the starting point for those more accurate
methods of research, which have yielded such astonishing results in the
hands of modern workers. In the introduction Witham writes, “My principal
object in presenting this work to the public, is to impress upon geologists
the advantage of attending more particularly to the intimate organization of
fossil plants; and should I succeed in directing their efforts towards the
elucidation of this obscure subject, I shall feel a degree of satisfaction
which will amply repay my labour[27].”
On another page he writes as follows,—“From investigations made by
the most active and experienced botanical geologists, we find reason to
conclude that the first appearance of an extensive vegetation occurred in the
Carboniferous series; and from a recent examination of the mountain-
limestone groups and coal-fields of Scotland, and the north of England, we
learn that these early vegetable productions, so far from being simple in
their structure, as had been supposed, are as complicated as the
phanerogamic plants of the present day. This discovery necessarily tends to
destroy the once favourite idea, that, from the oldest to the most recent
strata, there has been a progressive development of vegetable and animal
forms, from the simplest to the most complex[28].” Since Witham’s day we
have learnt much as to the morphology of Palaeozoic plants, and can well
understand the opinions to which he thus gives expression.
It would be difficult to overrate the immense importance of this
publication from the point of view of modern palaeobotany.
The art of making transparent sections of the tissues of fossil plants
seems to have been first employed by Sanderson, a lapidary, and it was
afterwards considerably improved by Nicol[29]. This most important advance
genere[25]; in which he dealt in some detail with the well-known silicified
fern-stems of Palaeozoic age, from Saxony, basing his descriptions on the
characteristics of anatomical structure revealed by microscopic
examination.
THE INTERNAL STRUCTURE OF FOSSIL PLANTS.
In 1833 Henry Witham of Lartington brought out a work on The Internal
Structure of Fossil Vegetables[26]; this book, following the much smaller and
less important work by Sprengel, at once established palaeobotany on a
firmer scientific basis, and formed the starting point for those more accurate
methods of research, which have yielded such astonishing results in the
hands of modern workers. In the introduction Witham writes, “My principal
object in presenting this work to the public, is to impress upon geologists
the advantage of attending more particularly to the intimate organization of
fossil plants; and should I succeed in directing their efforts towards the
elucidation of this obscure subject, I shall feel a degree of satisfaction
which will amply repay my labour[27].”
On another page he writes as follows,—“From investigations made by
the most active and experienced botanical geologists, we find reason to
conclude that the first appearance of an extensive vegetation occurred in the
Carboniferous series; and from a recent examination of the mountain-
limestone groups and coal-fields of Scotland, and the north of England, we
learn that these early vegetable productions, so far from being simple in
their structure, as had been supposed, are as complicated as the
phanerogamic plants of the present day. This discovery necessarily tends to
destroy the once favourite idea, that, from the oldest to the most recent
strata, there has been a progressive development of vegetable and animal
forms, from the simplest to the most complex[28].” Since Witham’s day we
have learnt much as to the morphology of Palaeozoic plants, and can well
understand the opinions to which he thus gives expression.
It would be difficult to overrate the immense importance of this
publication from the point of view of modern palaeobotany.
The art of making transparent sections of the tissues of fossil plants
seems to have been first employed by Sanderson, a lapidary, and it was
afterwards considerably improved by Nicol[29]. This most important advance
Page 36
in methods of examination gave a new impetus to the subject, but it is
somewhat remarkable that the possibilities of the microscopical
investigation of fossil plants have been but very imperfectly realised by
botanical workers until quite recent years. As regards such a flora as that of
the Coal-Measures, we can endorse the opinion expressed at the beginning
of the century in reference to the study of recent mosses—“Ohne das
Göttergeschenk des zusammengesetzten Mikroskops ist auf diesem Felde
durchaus keine Ernte[30].” A useful summary of the history of the study of
internal structure is given by Knowlton in a memoir published in 1889[31].
Not long after Witham’s book was issued there appeared a work of
exceptional merit by Corda[32], in which numerous Palaeozoic plants are
figured and fully described, mainly from the standpoint of internal
structure. This author lays special stress on the importance of studying the
microscopical structure of fossil plants.
ENGLISH PALAEOBOTANISTS.
Without pausing to enumerate the contributions of such well-known
continental authors as Göppert, Cotta, Schimper, Stenzel, Schenk and a host
of others, we may glance for a moment at the services rendered by English
investigators to the study of palaeobotanical histology. Unfortunately we
cannot always extend our examination of fossil plants beyond the characters
of external form and surface markings; but in a few districts there are
preserved remnants of ancient floras in which fragments of stems, roots,
leaves and other structures have been petrified in such a manner as to retain
with wonderful completeness the minute structure of their internal tissues.
During the deposition of the coal seams in parts of Yorkshire and
Lancashire the conditions of fossilisation were exceptionally favourable,
and thus English investigators have been fortunately placed for conducting
researches on the minute anatomy of the Coal-Measure plants. The late Mr
Binney of Manchester did excellent service by his work on the internal
structure of some of the trees of the Coal Period forests. In his introductory
remarks to a monograph on the genus Calamites, after speaking of the
desirability of describing our English specimens, he goes on to say, “When
this is done, we are likely to possess a literature on our Carboniferous
fossils worthy of the first coal-producing country[33].” The continuation and
extension of Binney’s work in the hands of Carruthers, Williamson, and
others, whose botanical qualifications enabled them to produce work of
somewhat remarkable that the possibilities of the microscopical
investigation of fossil plants have been but very imperfectly realised by
botanical workers until quite recent years. As regards such a flora as that of
the Coal-Measures, we can endorse the opinion expressed at the beginning
of the century in reference to the study of recent mosses—“Ohne das
Göttergeschenk des zusammengesetzten Mikroskops ist auf diesem Felde
durchaus keine Ernte[30].” A useful summary of the history of the study of
internal structure is given by Knowlton in a memoir published in 1889[31].
Not long after Witham’s book was issued there appeared a work of
exceptional merit by Corda[32], in which numerous Palaeozoic plants are
figured and fully described, mainly from the standpoint of internal
structure. This author lays special stress on the importance of studying the
microscopical structure of fossil plants.
ENGLISH PALAEOBOTANISTS.
Without pausing to enumerate the contributions of such well-known
continental authors as Göppert, Cotta, Schimper, Stenzel, Schenk and a host
of others, we may glance for a moment at the services rendered by English
investigators to the study of palaeobotanical histology. Unfortunately we
cannot always extend our examination of fossil plants beyond the characters
of external form and surface markings; but in a few districts there are
preserved remnants of ancient floras in which fragments of stems, roots,
leaves and other structures have been petrified in such a manner as to retain
with wonderful completeness the minute structure of their internal tissues.
During the deposition of the coal seams in parts of Yorkshire and
Lancashire the conditions of fossilisation were exceptionally favourable,
and thus English investigators have been fortunately placed for conducting
researches on the minute anatomy of the Coal-Measure plants. The late Mr
Binney of Manchester did excellent service by his work on the internal
structure of some of the trees of the Coal Period forests. In his introductory
remarks to a monograph on the genus Calamites, after speaking of the
desirability of describing our English specimens, he goes on to say, “When
this is done, we are likely to possess a literature on our Carboniferous
fossils worthy of the first coal-producing country[33].” The continuation and
extension of Binney’s work in the hands of Carruthers, Williamson, and
others, whose botanical qualifications enabled them to produce work of
Page 37
greater scientific value, has gone far towards the fulfilment of Binney’s
prophecy.
DIFFICULTIES OF IDENTIFICATION.
In dealing with the structure of Palaeozoic plants, we shall be under
constant obligation to the splendid series of memoirs from the pen of Prof.
Williamson[34]. As the writer of a sympathetic obituary notice has well said:
“In his fifty-fifth year he began the great series of memoirs which mark the
culminating point of his scientific activity, and which will assure to him, for
all time, in conjunction with Brongniart, the honourable title of a founder of
modern Palaeobotany[35].” If we look back through a few decades, and
peruse the pages of Lindley and Hutton’s classic work[36] on the Fossil flora
of Great Britain, a book which is indispensable to fossil botanists, and read
the description of such a genus as Sigillaria or Stigmaria; or if we extend
our retrospect to an earlier period and read Woodward’s description of an
unusually good specimen of a Lepidodendron, and finally take stock of our
present knowledge of such plants, we realise what enormous progress has
been made in palaeobotanical studies. Lindley and Hutton, in the preface to
the first volume of the Flora, claim to have demonstrated that both
Sigillaria and Stigmaria were plants with “the highest degree of
organization, such as Cactaeae, or Euphorbiaceae, or even Asclepiadeae”;
Woodward describes his Lepidodendron (Fig. 1) as “an ironstone, black and
flat, and wrought over one surface very finely, with a strange cancellated
work[37].” Thanks largely to the work of Binney, Carruthers, Hooker,
Williamson, and to the labours of continental botanists, we are at present
almost as familiar with Lepidodendron and several other Coal-Measure
genera as with the structure of a recent forest tree. While emphasizing the
value of the microscopic methods of investigation, we are not disposed to
take such a hopeless view of the possibilities of the determination of fossil
forms, in which no internal structure is preserved, as some writers have
expressed. The preservation of minute structure is to be greatly desired from
the point of view of the modern palaeobotanist, but he must recognise the
necessity of making such use as he can of the numberless examples of
plants of all ages, which occur only in the form of structureless casts or
impressions.
prophecy.
DIFFICULTIES OF IDENTIFICATION.
In dealing with the structure of Palaeozoic plants, we shall be under
constant obligation to the splendid series of memoirs from the pen of Prof.
Williamson[34]. As the writer of a sympathetic obituary notice has well said:
“In his fifty-fifth year he began the great series of memoirs which mark the
culminating point of his scientific activity, and which will assure to him, for
all time, in conjunction with Brongniart, the honourable title of a founder of
modern Palaeobotany[35].” If we look back through a few decades, and
peruse the pages of Lindley and Hutton’s classic work[36] on the Fossil flora
of Great Britain, a book which is indispensable to fossil botanists, and read
the description of such a genus as Sigillaria or Stigmaria; or if we extend
our retrospect to an earlier period and read Woodward’s description of an
unusually good specimen of a Lepidodendron, and finally take stock of our
present knowledge of such plants, we realise what enormous progress has
been made in palaeobotanical studies. Lindley and Hutton, in the preface to
the first volume of the Flora, claim to have demonstrated that both
Sigillaria and Stigmaria were plants with “the highest degree of
organization, such as Cactaeae, or Euphorbiaceae, or even Asclepiadeae”;
Woodward describes his Lepidodendron (Fig. 1) as “an ironstone, black and
flat, and wrought over one surface very finely, with a strange cancellated
work[37].” Thanks largely to the work of Binney, Carruthers, Hooker,
Williamson, and to the labours of continental botanists, we are at present
almost as familiar with Lepidodendron and several other Coal-Measure
genera as with the structure of a recent forest tree. While emphasizing the
value of the microscopic methods of investigation, we are not disposed to
take such a hopeless view of the possibilities of the determination of fossil
forms, in which no internal structure is preserved, as some writers have
expressed. The preservation of minute structure is to be greatly desired from
the point of view of the modern palaeobotanist, but he must recognise the
necessity of making such use as he can of the numberless examples of
plants of all ages, which occur only in the form of structureless casts or
impressions.
Page 38
Fig. 1. Four leaf-cushions of a Lepidodendron. Drawn from a specimen in the Woodward
Collection, Cambridge. (Nat. size.)
In looking through the writings of the earlier authors we cannot help
noticing their anxiety to match all fossil plants with living species; but by
degrees it was discovered that fossils are frequently the fragmentary
samples of extinct types, which can be studied only under very
unfavourable conditions. In the absence of those characters on which the
student of living plants relies as guides to classification, it is usually
impossible to arrive at any trustworthy conclusions as to precise botanical
affinity. Brongniart and other authors recognised this fact, and instituted
several convenient generic terms of a purely artificial and provisional
nature, which are still in general use. The dangers and risks of error which
necessarily attend our attempts to determine small and imperfect fragments
of extinct species of plants, will be briefly touched on in another place.
Collection, Cambridge. (Nat. size.)
In looking through the writings of the earlier authors we cannot help
noticing their anxiety to match all fossil plants with living species; but by
degrees it was discovered that fossils are frequently the fragmentary
samples of extinct types, which can be studied only under very
unfavourable conditions. In the absence of those characters on which the
student of living plants relies as guides to classification, it is usually
impossible to arrive at any trustworthy conclusions as to precise botanical
affinity. Brongniart and other authors recognised this fact, and instituted
several convenient generic terms of a purely artificial and provisional
nature, which are still in general use. The dangers and risks of error which
necessarily attend our attempts to determine small and imperfect fragments
of extinct species of plants, will be briefly touched on in another place.
Page 39
Page 40
CHAPTER II.
RELATION OF PALAEOBOTANY TO BOTANY AND GEOLOGY.
“La recherche du plan de la création, voilà le but vers lequel nos efforts peuvent tendre
aujourd’hui.” Gaudry, 1883.
Since the greater refinements and thoroughness of scientific methods and
the enormous and ever-increasing mass of literature have inevitably led to
extreme specialisation, it is more than ever important to look beyond the
immediate limits of one’s own subject, and to note its points of contact with
other lines of research. A palaeobotanist is primarily concerned with the
determination and description of fossil plants, but he must at the same time
constantly keep in view the bearing of his work on wider questions of
botanical or geological importance. From the nature of the case, we have in
due measure to adapt the methods of work to the particular conditions
before us. It is impossible to follow in the case of all fossil species precisely
the same treatment as with the more complete and perfect recent plants; but
it is of the utmost importance for a student of palaeobotany, by adhering to
the methods of recent botany, to preserve as far as he is able the continuity
of the past and present floras. Palaeontological work has often been
undertaken by men who are pure geologists, and whose knowledge of
zoology or botany is of the most superficial character, with the result that
biologists have not been able to avail themselves, to any considerable
extent, of the records of extinct forms of life. They find the literature is
often characterised by a special palaeontological phraseology, and by
particular methods of treatment, which are unknown to the student of living
plants and animals. From this and other causes a purely artificial division
has been made between the science of the organic world of to-day and that
of the past.
NEGLECT OF FOSSILS BY BOTANISTS.
Fossils are naturally regarded by a stratigraphical geologist as records
which enable him to determine the relative age of fossil-bearing rocks. For
RELATION OF PALAEOBOTANY TO BOTANY AND GEOLOGY.
“La recherche du plan de la création, voilà le but vers lequel nos efforts peuvent tendre
aujourd’hui.” Gaudry, 1883.
Since the greater refinements and thoroughness of scientific methods and
the enormous and ever-increasing mass of literature have inevitably led to
extreme specialisation, it is more than ever important to look beyond the
immediate limits of one’s own subject, and to note its points of contact with
other lines of research. A palaeobotanist is primarily concerned with the
determination and description of fossil plants, but he must at the same time
constantly keep in view the bearing of his work on wider questions of
botanical or geological importance. From the nature of the case, we have in
due measure to adapt the methods of work to the particular conditions
before us. It is impossible to follow in the case of all fossil species precisely
the same treatment as with the more complete and perfect recent plants; but
it is of the utmost importance for a student of palaeobotany, by adhering to
the methods of recent botany, to preserve as far as he is able the continuity
of the past and present floras. Palaeontological work has often been
undertaken by men who are pure geologists, and whose knowledge of
zoology or botany is of the most superficial character, with the result that
biologists have not been able to avail themselves, to any considerable
extent, of the records of extinct forms of life. They find the literature is
often characterised by a special palaeontological phraseology, and by
particular methods of treatment, which are unknown to the student of living
plants and animals. From this and other causes a purely artificial division
has been made between the science of the organic world of to-day and that
of the past.
NEGLECT OF FOSSILS BY BOTANISTS.
Fossils are naturally regarded by a stratigraphical geologist as records
which enable him to determine the relative age of fossil-bearing rocks. For
Page 41
such a purpose it is superfluous to inquire into the questions of biological
interest which centre round the relics of ancient floras. Primarily concerned,
therefore, with fixing the age of strata, it is easy to understand how
geologists have been content with a special kind of palaeontology which is
out of touch with the methods of systematic zoology or botany. On the other
hand, the botanist whose observations and researches have not extended
beyond the limits of existing plants, sees in the vast majority of fossil forms
merely imperfect specimens, which it is impossible to determine with any
degree of scientific accuracy. He prefers to wait for perfect material; or in
other words, he decides that fossils must be regarded as outside the range of
taxonomic botany. It would seem, then, that the unsatisfactory treatment or
comparative neglect of fossil plants, has been in a large measure due to the
narrowness of view which too often characterises palaeobotanical literature.
This has at once repelled those who have made a slight effort to recognise
the subject, and has resulted in a one-sided and, from a biological
standpoint, unscientific treatment of this branch of science. It must be
admitted that palaeobotanists have frequently brought the subject into
disrepute by their over-anxiety to institute specific names for fragments
which it is quite impossible to identify. This over-eagerness to determine
imperfect specimens, and the practice of drawing conclusions as to
botanical affinity without any trustworthy evidence, have naturally given
rise to considerable scepticism as to the value of palaeobotanical records.
Another point, which will be dealt with at greater length in a later chapter,
is that geologists have usually shown a distinct prejudice against fossil
plants as indices of geological age; this again, is no doubt to a large extent
the result of imperfect and inaccurate methods of description, and of the
neglect of and consequent imperfect acquaintance with fossil plants as
compared with fossil animals.
The student of fossil plants should endeavour to keep before him the fact
that the chief object of his work is to deal with the available material in the
most natural and scientific manner; and by adopting the methods of modern
botany, he should always aim to follow such lines as may best preserve the
continuity of past and present types of plants. Descriptions of floras of past
ages and lists of fossil species, should be so compiled that they may serve
the same purpose to a stratigraphical geologist, who is practically a
geographer of former periods of the Earth’s history, as the accounts of
existing floras to students of present day physiography. The effect of
interest which centre round the relics of ancient floras. Primarily concerned,
therefore, with fixing the age of strata, it is easy to understand how
geologists have been content with a special kind of palaeontology which is
out of touch with the methods of systematic zoology or botany. On the other
hand, the botanist whose observations and researches have not extended
beyond the limits of existing plants, sees in the vast majority of fossil forms
merely imperfect specimens, which it is impossible to determine with any
degree of scientific accuracy. He prefers to wait for perfect material; or in
other words, he decides that fossils must be regarded as outside the range of
taxonomic botany. It would seem, then, that the unsatisfactory treatment or
comparative neglect of fossil plants, has been in a large measure due to the
narrowness of view which too often characterises palaeobotanical literature.
This has at once repelled those who have made a slight effort to recognise
the subject, and has resulted in a one-sided and, from a biological
standpoint, unscientific treatment of this branch of science. It must be
admitted that palaeobotanists have frequently brought the subject into
disrepute by their over-anxiety to institute specific names for fragments
which it is quite impossible to identify. This over-eagerness to determine
imperfect specimens, and the practice of drawing conclusions as to
botanical affinity without any trustworthy evidence, have naturally given
rise to considerable scepticism as to the value of palaeobotanical records.
Another point, which will be dealt with at greater length in a later chapter,
is that geologists have usually shown a distinct prejudice against fossil
plants as indices of geological age; this again, is no doubt to a large extent
the result of imperfect and inaccurate methods of description, and of the
neglect of and consequent imperfect acquaintance with fossil plants as
compared with fossil animals.
The student of fossil plants should endeavour to keep before him the fact
that the chief object of his work is to deal with the available material in the
most natural and scientific manner; and by adopting the methods of modern
botany, he should always aim to follow such lines as may best preserve the
continuity of past and present types of plants. Descriptions of floras of past
ages and lists of fossil species, should be so compiled that they may serve
the same purpose to a stratigraphical geologist, who is practically a
geographer of former periods of the Earth’s history, as the accounts of
existing floras to students of present day physiography. The effect of
Page 42
carrying out researches on some such lines as these, should be to render
available to both botanists and geologists the results of the specialist’s
work.
In some cases, palaeobotanical investigations may be of the utmost
service to botanical science, and of little or no value to geology. The
discovery of a completely preserved gametophyte of Lepidodendron or
Calamites, or of a petrified Moss plant in Palaeozoic rocks would appeal to
most botanists as a matter of primary importance, but for the stratigraphical
geologist such discoveries would possess but little value. On the other hand
the discovery of some characteristic species of Coal-Measure plants from a
deep boring through Mesozoic or Tertiary strata might be a matter of special
geological importance, but to the botanist it would be of no scientific value.
In very many instances, however, if the palaeobotanist follows such lines as
have been briefly suggested, the results of his labours should be at once
useful and readily accessible to botanists and geologists. As Humboldt has
said in speaking of Palaeontology, “the analytical study of primitive animal
and vegetable life has taken a double direction; the one is purely
morphological, and embraces especially the natural history and physiology
of organisms, filling up the chasms in the series of still living species by the
fossil structures of the primitive world. The second is more specially
geognostic, considering fossil remains in their relations to the superposition
and relative age of the sedimentary formations[38].”
FOSSIL PLANTS AND DISTRIBUTION.
To turn for a moment to some of the most obvious connections between
palaeobotany and the wider sciences of botany and geology. The records of
fossil species must occupy a prominent position in the data by which we
may hope to solve some at least of the problems of plant evolution. From
the point of view of distribution, palaeobotany is of considerable value, not
only to the student of geographical botany, but to the geologist, who
endeavours to map out the positions of ancient continents with the help of
palaeontological evidence. The present distribution of plants and animals
represents but one chapter in the history of life on the Earth; and to
understand or appreciate the facts which it records, we have to look back
through such pages as have been deciphered in the earlier chapters of the
volume. The distribution of fossil plants lies at the foundation of the
principles of the present grouping of floras on the Earth’s surface. Those
available to both botanists and geologists the results of the specialist’s
work.
In some cases, palaeobotanical investigations may be of the utmost
service to botanical science, and of little or no value to geology. The
discovery of a completely preserved gametophyte of Lepidodendron or
Calamites, or of a petrified Moss plant in Palaeozoic rocks would appeal to
most botanists as a matter of primary importance, but for the stratigraphical
geologist such discoveries would possess but little value. On the other hand
the discovery of some characteristic species of Coal-Measure plants from a
deep boring through Mesozoic or Tertiary strata might be a matter of special
geological importance, but to the botanist it would be of no scientific value.
In very many instances, however, if the palaeobotanist follows such lines as
have been briefly suggested, the results of his labours should be at once
useful and readily accessible to botanists and geologists. As Humboldt has
said in speaking of Palaeontology, “the analytical study of primitive animal
and vegetable life has taken a double direction; the one is purely
morphological, and embraces especially the natural history and physiology
of organisms, filling up the chasms in the series of still living species by the
fossil structures of the primitive world. The second is more specially
geognostic, considering fossil remains in their relations to the superposition
and relative age of the sedimentary formations[38].”
FOSSIL PLANTS AND DISTRIBUTION.
To turn for a moment to some of the most obvious connections between
palaeobotany and the wider sciences of botany and geology. The records of
fossil species must occupy a prominent position in the data by which we
may hope to solve some at least of the problems of plant evolution. From
the point of view of distribution, palaeobotany is of considerable value, not
only to the student of geographical botany, but to the geologist, who
endeavours to map out the positions of ancient continents with the help of
palaeontological evidence. The present distribution of plants and animals
represents but one chapter in the history of life on the Earth; and to
understand or appreciate the facts which it records, we have to look back
through such pages as have been deciphered in the earlier chapters of the
volume. The distribution of fossil plants lies at the foundation of the
principles of the present grouping of floras on the Earth’s surface. Those
Page 43
who have confined their study of distribution to the plant geography of the
present age, must supplement their investigations by reference to the work
of palaeobotanical writers. If the lists of plant species drawn up by
specialists in fossil botany, have been prepared with a due sense of the
important conclusions which botanists may draw from them from the
standpoint of distribution, they will be readily accepted as sound links in the
chain of evidence. Unfortunately, however, if many of the lists of ancient
floras were made use of in such investigations, the conclusions arrived at
would frequently be of little value on account of the untrustworthy
determinations of many of the species. In the case of particular genera the
study of the distribution of the former species both in time and space, that is
geologically and geographically, points to rational explanations of, or gives
added significance to, the facts of present day distribution. That isolated
conifer, Ginkgo biloba L. now restricted to Japan and China, was in former
times abundant in Europe and in other parts of the world. It is clearly an
exceedingly ancient type, isolated not only in geographical distribution but
in botanical affinities, which has reached the last stage in its natural life.
The Mammoth trees of California (Sequoia sempervirens Endl., and S.
gigantea Lindl. and Gord.) afford other examples of a parallel case. The
Tulip tree of North America and China and other allied forms are fairly
common in the Tertiary plant beds of Europe, but the living representatives
are now exclusively North American. Such differences in distribution as are
illustrated by these dicotyledonous forest trees in Tertiary times and at the
present day, have been clearly explained with the help of the geological
record. Forbes, Darwin, Asa Gray[39] and others have been able to explain
many apparent anomalies in the distribution of existing plants, and to
reconcile the differences between the past and present distribution of many
genera by taking account of the effect on plant life of the glacial period. As
the ice gradually crept down from the polar regions and spread over the
northern parts of Europe, many plants were driven further south in search of
the necessary warmth. In the American continent such migration was
rendered possible by the southern land extension; in Europe on the other
hand the southerly retreat was cut off by impassable barriers, and the
extinction of several genera was the natural result.
The comparatively abundant information which we possess as to the past
vegetation of polar regions and the value of such knowledge to geologists
and botanists alike is in striking contrast to the absence of similar data as
present age, must supplement their investigations by reference to the work
of palaeobotanical writers. If the lists of plant species drawn up by
specialists in fossil botany, have been prepared with a due sense of the
important conclusions which botanists may draw from them from the
standpoint of distribution, they will be readily accepted as sound links in the
chain of evidence. Unfortunately, however, if many of the lists of ancient
floras were made use of in such investigations, the conclusions arrived at
would frequently be of little value on account of the untrustworthy
determinations of many of the species. In the case of particular genera the
study of the distribution of the former species both in time and space, that is
geologically and geographically, points to rational explanations of, or gives
added significance to, the facts of present day distribution. That isolated
conifer, Ginkgo biloba L. now restricted to Japan and China, was in former
times abundant in Europe and in other parts of the world. It is clearly an
exceedingly ancient type, isolated not only in geographical distribution but
in botanical affinities, which has reached the last stage in its natural life.
The Mammoth trees of California (Sequoia sempervirens Endl., and S.
gigantea Lindl. and Gord.) afford other examples of a parallel case. The
Tulip tree of North America and China and other allied forms are fairly
common in the Tertiary plant beds of Europe, but the living representatives
are now exclusively North American. Such differences in distribution as are
illustrated by these dicotyledonous forest trees in Tertiary times and at the
present day, have been clearly explained with the help of the geological
record. Forbes, Darwin, Asa Gray[39] and others have been able to explain
many apparent anomalies in the distribution of existing plants, and to
reconcile the differences between the past and present distribution of many
genera by taking account of the effect on plant life of the glacial period. As
the ice gradually crept down from the polar regions and spread over the
northern parts of Europe, many plants were driven further south in search of
the necessary warmth. In the American continent such migration was
rendered possible by the southern land extension; in Europe on the other
hand the southerly retreat was cut off by impassable barriers, and the
extinction of several genera was the natural result.
The comparatively abundant information which we possess as to the past
vegetation of polar regions and the value of such knowledge to geologists
and botanists alike is in striking contrast to the absence of similar data as
Page 44
regards Antarctic fossils. Darwin in an exceedingly interesting letter to
Hooker à propos of a forthcoming British Association address, referring to
this subject writes as follows:—
“The extreme importance of the Arctic fossil plants is self-evident. Take
the opportunity of groaning over our ignorance of the Lignite plants of
Kerguelen Land, or any Antarctic land. It might do good[40].”
In working out any collection of fossil plants, it would be well, therefore,
to bear in mind that our aim should be rather to reproduce an accurate
fragment of botanical history, than to perform feats of determination with
hopelessly inadequate specimens. Had this principle been generally
followed, the number of fossil plant species would be enormously reduced,
but the value of the records would be considerably raised.
FOSSIL PLANTS AND CLIMATE.
Our knowledge of plant anatomy, and of those laws of growth which
govern certain classes of plants to-day and in past time, has been very
materially widened and extended by the facts revealed to us by the detailed
study of Coal-Measure species. The modern science of Plant Biology,
refounded by Charles Darwin, has thrown considerable light on the laws of
plant life, and it enables us to correlate structural characteristics with
physiological conditions of growth. Applying the knowledge gained from
living plants to the study of such extinct types as permit of close
microscopic examination, we may obtain a glimpse into the secrets of the
botanical binomics of Palaeozoic times. The wider questions of climatic
conditions depend very largely upon the evidence of fossil botany for a
rational solution. As an instance of the best authenticated and most striking
alternation in climatic conditions in comparatively recent times, we may
cite the glacial period or Ice-Age. The existence of Arctic conditions has
been proved by purely geological evidence, but it receives additional
confirmation, and derives a wider importance from the testimony of fossil
plants. In rocks deposited before the spread of ice from high northern
latitudes, we find indubitable proofs of a widely distributed subtropical
flora in Central and Northern Europe. Passing from these rocks to more
recent beds there are found indications of a fall in temperature, and such
northern plants as the dwarf Birch, the Arctic Willow and others reveal the
southern extension of Arctic cold to our own latitudes.
Hooker à propos of a forthcoming British Association address, referring to
this subject writes as follows:—
“The extreme importance of the Arctic fossil plants is self-evident. Take
the opportunity of groaning over our ignorance of the Lignite plants of
Kerguelen Land, or any Antarctic land. It might do good[40].”
In working out any collection of fossil plants, it would be well, therefore,
to bear in mind that our aim should be rather to reproduce an accurate
fragment of botanical history, than to perform feats of determination with
hopelessly inadequate specimens. Had this principle been generally
followed, the number of fossil plant species would be enormously reduced,
but the value of the records would be considerably raised.
FOSSIL PLANTS AND CLIMATE.
Our knowledge of plant anatomy, and of those laws of growth which
govern certain classes of plants to-day and in past time, has been very
materially widened and extended by the facts revealed to us by the detailed
study of Coal-Measure species. The modern science of Plant Biology,
refounded by Charles Darwin, has thrown considerable light on the laws of
plant life, and it enables us to correlate structural characteristics with
physiological conditions of growth. Applying the knowledge gained from
living plants to the study of such extinct types as permit of close
microscopic examination, we may obtain a glimpse into the secrets of the
botanical binomics of Palaeozoic times. The wider questions of climatic
conditions depend very largely upon the evidence of fossil botany for a
rational solution. As an instance of the best authenticated and most striking
alternation in climatic conditions in comparatively recent times, we may
cite the glacial period or Ice-Age. The existence of Arctic conditions has
been proved by purely geological evidence, but it receives additional
confirmation, and derives a wider importance from the testimony of fossil
plants. In rocks deposited before the spread of ice from high northern
latitudes, we find indubitable proofs of a widely distributed subtropical
flora in Central and Northern Europe. Passing from these rocks to more
recent beds there are found indications of a fall in temperature, and such
northern plants as the dwarf Birch, the Arctic Willow and others reveal the
southern extension of Arctic cold to our own latitudes.
Page 45
The distribution of plants in time, that is the range of classes, families,
genera and species of plants through the series of strata which make up the
crust of the earth, is a matter of primary importance from a botanical as well
as from a geological point of view.
Among the earlier writers, Brongniart recognised the marked differences
between the earlier and later floras, and attempted to correlate the periods of
maximum development of certain classes of plants with definite epochs of
geological history. He gives the following classification in which are
represented the general outlines of plant development from Palaeozoic to
Tertiary times[41].
1. Carboniferous epoch
I. Reign of Acrogens
2. Permian epoch.
3. Triassic epoch.
II. Reign of Gymnosperms
4. Jurassic epoch (including the Wealden).
5. Cretaceous epoch.
III. Reign of Angiosperms
6. Tertiary epoch.
Since Brongniart’s time this method of classification has been extended
to many of the smaller subdivisions of the geological epochs, and species of
fossil plants are often of the greatest value in questions of correlation. In
recent years the systematic treatment of Coal-Measure and other plants in
the hands of various Continental and English writers has clearly
demonstrated their capabilities for the purpose of subdividing a series of
strata into stages and zones[42]. The more complete becomes our knowledge
of any flora, the greater possibility there is of making use of the plants as
indices of geological age[43].
FOSSIL PLANTS AND PHYLOGENY.
Not only is it possible to derive valuable aid in the correlation of strata
from the facts of plant distribution, but we may often follow the various
stages in the history of a particular genus as we trace the records of its
occurrence through the geologic series. In studying the march of plant life
through past ages, the botanist may sometimes follow the progress of a
genus from its first appearance, through the time of maximum development,
to its decline or extinction. In the Palaeozoic forests there was perhaps no
genera and species of plants through the series of strata which make up the
crust of the earth, is a matter of primary importance from a botanical as well
as from a geological point of view.
Among the earlier writers, Brongniart recognised the marked differences
between the earlier and later floras, and attempted to correlate the periods of
maximum development of certain classes of plants with definite epochs of
geological history. He gives the following classification in which are
represented the general outlines of plant development from Palaeozoic to
Tertiary times[41].
1. Carboniferous epoch
I. Reign of Acrogens
2. Permian epoch.
3. Triassic epoch.
II. Reign of Gymnosperms
4. Jurassic epoch (including the Wealden).
5. Cretaceous epoch.
III. Reign of Angiosperms
6. Tertiary epoch.
Since Brongniart’s time this method of classification has been extended
to many of the smaller subdivisions of the geological epochs, and species of
fossil plants are often of the greatest value in questions of correlation. In
recent years the systematic treatment of Coal-Measure and other plants in
the hands of various Continental and English writers has clearly
demonstrated their capabilities for the purpose of subdividing a series of
strata into stages and zones[42]. The more complete becomes our knowledge
of any flora, the greater possibility there is of making use of the plants as
indices of geological age[43].
FOSSIL PLANTS AND PHYLOGENY.
Not only is it possible to derive valuable aid in the correlation of strata
from the facts of plant distribution, but we may often follow the various
stages in the history of a particular genus as we trace the records of its
occurrence through the geologic series. In studying the march of plant life
through past ages, the botanist may sometimes follow the progress of a
genus from its first appearance, through the time of maximum development,
to its decline or extinction. In the Palaeozoic forests there was perhaps no
Page 46
more conspicuous or common tree than the genus long known under the
name of Calamites. This plant attained a height of fifty or a hundred feet,
with a proportionate girth, and increased in thickness in a manner precisely
similar to that in which our forest trees grow in diameter. The exceptionally
favourable conditions under which specimens of calamitean plants have
been preserved, have enabled us to become almost as familiar with the
minute structure of their stems and roots, as well as with their spore-
producing organs, as with those of a living species. In short, it is thoroughly
established that Calamites agrees in most essential respects with our well
known Equisetum, and must be included in the same order, or at least sub-
class, as the recent genus of Equisetaceae. As we ascend the geologic series
from the Coal-Measures, a marked numerical decline of Calamites is
obvious in the Permian period, and in the red sandstones of the Vosges,
which belong to the same series of rocks as the Triassic strata of the
Cheshire plain, the true Calamites is replaced by a large Equisetum
apparently identical in external appearance and habit of growth with the
species living to-day. In the more recent strata the Horse-tails are still
represented, but the size of the Tertiary species agrees more closely with the
comparatively small forms which have such a wide geographical
distribution at the present time. Thus we are able to trace out the history of a
recent genus of Vascular Cryptogams, and to follow a particular type of
organisation from the time of its maximum development, through its
gradual transition to those structural characters which are represented in the
living descendants of the arborescent Calamites of the coal-period forests.
The pages of such a history are frequently imperfect and occasionally
missing, but others, again, are written in characters as clear as those which
we decipher by a microscopical examination of the tissues of a recent plant.
As one of the most striking instances in which the microscopic study of
fossil plants has shown the way to a satisfactory solution of the problems of
development, we may mention such extinct genera as Lyginodendron,
Myeloxylon and others. Each of these genera will be dealt with at some
length in the systematic part of the book, and we shall afterwards discuss
the importance of such types, from the point of view of plant evolution.
The botanist who would trace out the phylogeny of any existing class or
family, makes it his chief aim to discover points of contact between the
name of Calamites. This plant attained a height of fifty or a hundred feet,
with a proportionate girth, and increased in thickness in a manner precisely
similar to that in which our forest trees grow in diameter. The exceptionally
favourable conditions under which specimens of calamitean plants have
been preserved, have enabled us to become almost as familiar with the
minute structure of their stems and roots, as well as with their spore-
producing organs, as with those of a living species. In short, it is thoroughly
established that Calamites agrees in most essential respects with our well
known Equisetum, and must be included in the same order, or at least sub-
class, as the recent genus of Equisetaceae. As we ascend the geologic series
from the Coal-Measures, a marked numerical decline of Calamites is
obvious in the Permian period, and in the red sandstones of the Vosges,
which belong to the same series of rocks as the Triassic strata of the
Cheshire plain, the true Calamites is replaced by a large Equisetum
apparently identical in external appearance and habit of growth with the
species living to-day. In the more recent strata the Horse-tails are still
represented, but the size of the Tertiary species agrees more closely with the
comparatively small forms which have such a wide geographical
distribution at the present time. Thus we are able to trace out the history of a
recent genus of Vascular Cryptogams, and to follow a particular type of
organisation from the time of its maximum development, through its
gradual transition to those structural characters which are represented in the
living descendants of the arborescent Calamites of the coal-period forests.
The pages of such a history are frequently imperfect and occasionally
missing, but others, again, are written in characters as clear as those which
we decipher by a microscopical examination of the tissues of a recent plant.
As one of the most striking instances in which the microscopic study of
fossil plants has shown the way to a satisfactory solution of the problems of
development, we may mention such extinct genera as Lyginodendron,
Myeloxylon and others. Each of these genera will be dealt with at some
length in the systematic part of the book, and we shall afterwards discuss
the importance of such types, from the point of view of plant evolution.
The botanist who would trace out the phylogeny of any existing class or
family, makes it his chief aim to discover points of contact between the
Page 47
particular type of structure which he is investigating, and that of other more
or less closely related classes or families.
Confining himself to recent forms, he may discover, here and there,
certain anatomical or embryological facts, which suggest promising lines of
inquiry in the quest after such affinities as point to a common descent.
Without recourse to the evidence afforded by the plants of past ages, we
must always admit that our existing classification of the vegetable kingdom
is an expression of real gaps which separate the several classes of plants
from one another. On the other hand our recently acquired and more
accurate knowledge of such genera as have been alluded to, has made us
acquainted with types of plant structure which enable us to fill in some of
the lacunae in our existing classification. In certain instances we find
merged in a single species morphological characteristics which, in the case
of recent plants, are regarded as distinctive features of different
subdivisions. It has been clearly demonstrated that in Lyginodendron, we
have anatomical peculiarities typical of recent cycads, combined with
structural characteristics always associated with existing ferns. In rare
cases, it happens that the remarkably perfect fossilisation of the tissues of
fossil plants, enables us not only to give a complete description of the
histology of extinct forms, but also to speak with confidence as to some of
those physiological processes which governed their life.
GEOLOGICAL HISTORY.
So far, palaeobotany has been considered in its bearings on the study of
recent plants. From a geological point of view the records of ancient floras
have scarcely less importance. In recent years, facts have been brought to
light, which show that plants have played a more conspicuous part than has
usually been supposed as agents of rock-building. As tests of geologic age,
there are good grounds for believing that the inferiority of plants to animals
is more apparent than real. This question, however, must be discussed at
greater length in a later chapter.
Enough has been said to show the many-sided nature of the science of
Fossil Plants, and the wide range of the problems which the geologist or
botanist may reasonably expect to solve, by means of trustworthy data
afforded by scientific palaeobotanical methods.
or less closely related classes or families.
Confining himself to recent forms, he may discover, here and there,
certain anatomical or embryological facts, which suggest promising lines of
inquiry in the quest after such affinities as point to a common descent.
Without recourse to the evidence afforded by the plants of past ages, we
must always admit that our existing classification of the vegetable kingdom
is an expression of real gaps which separate the several classes of plants
from one another. On the other hand our recently acquired and more
accurate knowledge of such genera as have been alluded to, has made us
acquainted with types of plant structure which enable us to fill in some of
the lacunae in our existing classification. In certain instances we find
merged in a single species morphological characteristics which, in the case
of recent plants, are regarded as distinctive features of different
subdivisions. It has been clearly demonstrated that in Lyginodendron, we
have anatomical peculiarities typical of recent cycads, combined with
structural characteristics always associated with existing ferns. In rare
cases, it happens that the remarkably perfect fossilisation of the tissues of
fossil plants, enables us not only to give a complete description of the
histology of extinct forms, but also to speak with confidence as to some of
those physiological processes which governed their life.
GEOLOGICAL HISTORY.
So far, palaeobotany has been considered in its bearings on the study of
recent plants. From a geological point of view the records of ancient floras
have scarcely less importance. In recent years, facts have been brought to
light, which show that plants have played a more conspicuous part than has
usually been supposed as agents of rock-building. As tests of geologic age,
there are good grounds for believing that the inferiority of plants to animals
is more apparent than real. This question, however, must be discussed at
greater length in a later chapter.
Enough has been said to show the many-sided nature of the science of
Fossil Plants, and the wide range of the problems which the geologist or
botanist may reasonably expect to solve, by means of trustworthy data
afforded by scientific palaeobotanical methods.
Page 48
Page 49
CHAPTER III.
GEOLOGICAL HISTORY.
“But how can we question dumb rocks whose speech is not clear[44]?”
In attempting to sketch in briefest outline the geological history of the
Earth, the most important object to keep in view is that of reproducing as
far as possible the broad features of the successive stages in the building of
the Earth’s crust. It is obviously impossible to go into any details of
description, or to closely follow the evolution of the present continents; at
most, we can only refer to such facts as may serve as an introduction of the
elements of stratigraphical geology to non-geological readers. For a fuller
treatment of the subject reference must be made to special treatises on
geology.
For the sake of convenience, it is customary in stratigraphical geology as
also in biology, to make use of our imperfect knowledge as an aid to
classification. If we possessed complete records of the Earth’s history, we
should have an unbroken sequence, not merely of the various forms of life
that ever existed, but of the different kinds of rocks formed in the
successive ages of past time. As gaps exist in the chain of life, so also do we
find considerable breaks in the sequence of strata which have been formed
since the beginning of geologic time. The danger as well as the convenience
of artificial classification must be kept in view. This has been well
expressed by Freeman, in speaking of architectural styles,—“Our minds,”
he says, “are more used to definite periods; they neglect or forget transitions
which do indeed exist[45].” The idea of definite classification is liable to
narrow our view of uniformity and the natural sequence of events.
ROCK-BUILDING.
Composing that part of the earth which is accessible to us,—or as it is
generally called the earth’s crust,—there are rocks of various kinds, of
which some have been formed by igneous agency, either as lavas or beds of
ashes, or in the form of molten magmas which gradually cooled and became
GEOLOGICAL HISTORY.
“But how can we question dumb rocks whose speech is not clear[44]?”
In attempting to sketch in briefest outline the geological history of the
Earth, the most important object to keep in view is that of reproducing as
far as possible the broad features of the successive stages in the building of
the Earth’s crust. It is obviously impossible to go into any details of
description, or to closely follow the evolution of the present continents; at
most, we can only refer to such facts as may serve as an introduction of the
elements of stratigraphical geology to non-geological readers. For a fuller
treatment of the subject reference must be made to special treatises on
geology.
For the sake of convenience, it is customary in stratigraphical geology as
also in biology, to make use of our imperfect knowledge as an aid to
classification. If we possessed complete records of the Earth’s history, we
should have an unbroken sequence, not merely of the various forms of life
that ever existed, but of the different kinds of rocks formed in the
successive ages of past time. As gaps exist in the chain of life, so also do we
find considerable breaks in the sequence of strata which have been formed
since the beginning of geologic time. The danger as well as the convenience
of artificial classification must be kept in view. This has been well
expressed by Freeman, in speaking of architectural styles,—“Our minds,”
he says, “are more used to definite periods; they neglect or forget transitions
which do indeed exist[45].” The idea of definite classification is liable to
narrow our view of uniformity and the natural sequence of events.
ROCK-BUILDING.
Composing that part of the earth which is accessible to us,—or as it is
generally called the earth’s crust,—there are rocks of various kinds, of
which some have been formed by igneous agency, either as lavas or beds of
ashes, or in the form of molten magmas which gradually cooled and became
Page 50
crystalline below a mass of superincumbent strata. With these rocks we
need not concern ourselves.
A large portion of the earth’s crust consists of such materials as
sandstones, limestones, shales, and similar strata which have been formed
in precisely the same manner as deposits are being accumulated at the
present day. The whole surface of the earth is continually exposed to the
action of destructive agencies, and suffers perpetual decay; it is the products
of this ceaseless wear and tear that form the building materials of new
deposits.
The operation of water in its various forms, of wind, changes of
temperature, and other agents of destruction cannot be fully dealt with in
this short summary.
A river flowing to the sea or emptying itself into an inland lake, carries
its burden of gravel, sand, and mud, and sooner or later, as the rate of flow
slackens, it deposits the materials in the river-bed or on the floor of the sea
or lake.
Fragments of rock, chipped off by wedges of ice, or detached in other
ways from the parent mass, find their way to the mountain streams, and if
not too heavy are conveyed to the main river, where the larger pieces come
to rest as more or less rounded pebbles. Such water-worn rocks accumulate
in the quieter reaches of a swiftly flowing river, or are thrown down at the
head of the river’s delta. If such a deposit of loose water-worn material
became cemented together either by the consolidating action of some
solution percolating through the general mass, or by the pressure of
overlying deposits, there would be formed a hard rock made up of rounded
fragments of various kinds of strata derived from different sources. Such a
rock is known as a Conglomerate. The same kind of rock may be formed
equally well by the action of the sea; an old sea-beach with the pebbles
embedded in a cementing matrix affords a typical example of a coarse
conglomerate. Plant remains are occasionally met with in conglomerates,
but usually in a fragmentary condition.
From a conglomerate composed of large water-worn pebbles, to a fine
homogeneous sandstone there are numerous intermediate stages. A body of
water, with a velocity too small to carry along pebbles of rock in suspension
or to roll them along the bed of the channel, is still able to transport the
need not concern ourselves.
A large portion of the earth’s crust consists of such materials as
sandstones, limestones, shales, and similar strata which have been formed
in precisely the same manner as deposits are being accumulated at the
present day. The whole surface of the earth is continually exposed to the
action of destructive agencies, and suffers perpetual decay; it is the products
of this ceaseless wear and tear that form the building materials of new
deposits.
The operation of water in its various forms, of wind, changes of
temperature, and other agents of destruction cannot be fully dealt with in
this short summary.
A river flowing to the sea or emptying itself into an inland lake, carries
its burden of gravel, sand, and mud, and sooner or later, as the rate of flow
slackens, it deposits the materials in the river-bed or on the floor of the sea
or lake.
Fragments of rock, chipped off by wedges of ice, or detached in other
ways from the parent mass, find their way to the mountain streams, and if
not too heavy are conveyed to the main river, where the larger pieces come
to rest as more or less rounded pebbles. Such water-worn rocks accumulate
in the quieter reaches of a swiftly flowing river, or are thrown down at the
head of the river’s delta. If such a deposit of loose water-worn material
became cemented together either by the consolidating action of some
solution percolating through the general mass, or by the pressure of
overlying deposits, there would be formed a hard rock made up of rounded
fragments of various kinds of strata derived from different sources. Such a
rock is known as a Conglomerate. The same kind of rock may be formed
equally well by the action of the sea; an old sea-beach with the pebbles
embedded in a cementing matrix affords a typical example of a coarse
conglomerate. Plant remains are occasionally met with in conglomerates,
but usually in a fragmentary condition.
From a conglomerate composed of large water-worn pebbles, to a fine
homogeneous sandstone there are numerous intermediate stages. A body of
water, with a velocity too small to carry along pebbles of rock in suspension
or to roll them along the bed of the channel, is still able to transport the
Page 51
finer fragments or grains of sand, but as a further decrease in the velocity
occurs, these are eventually deposited as beds of coarse or fine sand. The
stretches of sand on a gradually shelving sea shore, or the deposits of the
same material in a river’s delta, have been formed by the gradual wearing
away and disintegration of various rocks, the detritus of which has been
spread out in more or less regular beds on the floor of a lake or sea. Such
accumulations of fine detrital material, if compacted or cemented together,
become typical Sandstones.
In tracing beds of sandstone across a tract of country, it is frequently
found that the character of the strata gradually alters; mud or clay becomes
associated with the sandy deposit, until finally the sandstone is replaced by
beds of dark coloured shale. Similarly the sandy detritus on the ocean floor,
or in an inland lake, when followed further and further from the source
from which the materials were derived, passes by degrees into argillaceous
sand, and finally into sheets of dark clay or mud. The hardened beds of clay
or fine grained mud become transformed into Shales. As a general rule,
then, shales are rocks which have been laid down in places further from the
land, or at a greater distance from the source of origin of the detrital
material, than sandstones or conglomerates. The conglomerates, or old
shingle beaches, usually occur in somewhat irregular patches, marking old
shore-lines or the head of a river delta. Coarse sandstones, or grits, may
occur in the form of regularly bedded strata stretching over a wide area; and
shales or clays may be followed through a considerable extent of country.
The finer material composing the clays and shales has been held longer in
suspension and deposited in deeper water in widespread and fairly
horizontal layers.
In some districts sandstones occur in which the individual grains show a
well marked rounding of the angles, and in which fossils are extremely rare
or entirely absent. The close resemblance of such deposits to modern desert
sands suggests a similar method of formation; and there can be no doubt
that in some instances there have been preserved the wind-worn desert
sands of former ages. Aeolian or wind-formed accumulations, although by
no means common, are of sufficient importance to be mentioned as
illustrating a certain type of rock.
CALCAREOUS ROCKS.
occurs, these are eventually deposited as beds of coarse or fine sand. The
stretches of sand on a gradually shelving sea shore, or the deposits of the
same material in a river’s delta, have been formed by the gradual wearing
away and disintegration of various rocks, the detritus of which has been
spread out in more or less regular beds on the floor of a lake or sea. Such
accumulations of fine detrital material, if compacted or cemented together,
become typical Sandstones.
In tracing beds of sandstone across a tract of country, it is frequently
found that the character of the strata gradually alters; mud or clay becomes
associated with the sandy deposit, until finally the sandstone is replaced by
beds of dark coloured shale. Similarly the sandy detritus on the ocean floor,
or in an inland lake, when followed further and further from the source
from which the materials were derived, passes by degrees into argillaceous
sand, and finally into sheets of dark clay or mud. The hardened beds of clay
or fine grained mud become transformed into Shales. As a general rule,
then, shales are rocks which have been laid down in places further from the
land, or at a greater distance from the source of origin of the detrital
material, than sandstones or conglomerates. The conglomerates, or old
shingle beaches, usually occur in somewhat irregular patches, marking old
shore-lines or the head of a river delta. Coarse sandstones, or grits, may
occur in the form of regularly bedded strata stretching over a wide area; and
shales or clays may be followed through a considerable extent of country.
The finer material composing the clays and shales has been held longer in
suspension and deposited in deeper water in widespread and fairly
horizontal layers.
In some districts sandstones occur in which the individual grains show a
well marked rounding of the angles, and in which fossils are extremely rare
or entirely absent. The close resemblance of such deposits to modern desert
sands suggests a similar method of formation; and there can be no doubt
that in some instances there have been preserved the wind-worn desert
sands of former ages. Aeolian or wind-formed accumulations, although by
no means common, are of sufficient importance to be mentioned as
illustrating a certain type of rock.
CALCAREOUS ROCKS.
Page 52
The thick masses of limestone which form so prominent a feature in parts
of England and Ireland, have been formed in a manner different from that to
which sandstones and shales owe their origin. On the floor of a clear sea,
too far from land to receive any water-borne sediment, there is usually in
process of formation a mass of calcareous material, which in a later age
may rise above the surface of the water as chalk or limestone. Those
organisms living in the sea, which are enclosed either wholly or in part by
calcareous shells, are agents of limestone-building; their shells constantly
accumulating on the floor of the sea give rise in course of time to a thick
mass of sediment, composed in great part of carbonate of lime. Some of the
shells in such a deposit may retain their original form, the calcareous body
may on the other hand be broken up into minute fragments which are still
recognisable with the help of a microscope, or the shells and other hard
parts may be dissolved or disintegrated beyond recognition, leaving nothing
in the calcareous sediment to indicate its method of formation.
Not a few limestones consist in part of fossil corals, and owe their origin
to colonies of coral polyps which built up reefs or banks of coral in the
ancient seas.
In the white cliffs of Dover, Flamborough Head and other places, we
have a somewhat different form of calcareous rock, which in part consists
of millions of minute shells of Foraminifera, in part of broken fragments of
larger shells of extinct molluscs, and to some extent of the remains of
siliceous sponges. As a general rule, limestones and chalk rocks are ancient
sediments, formed in clear and comparatively deep water, composed in the
main of carbonate of lime, in some cases with a certain amount of carbonate
of magnesium, and occasionally with a considerable admixture of silica.
In such rocks land-plants must necessarily be rare. There are, however,
limestones which wholly or in part owe their formation to masses of
calcareous algae, which grew in the form of submarine banks or on coral
reefs. Occasionally the remains of these algae are clearly preserved, but
frequently all signs of plant structure have been completely obliterated.
Again, there occur limestone rocks formed by chemical means, and in a
manner similar to that in which beds of travertine are now being
accumulated.
of England and Ireland, have been formed in a manner different from that to
which sandstones and shales owe their origin. On the floor of a clear sea,
too far from land to receive any water-borne sediment, there is usually in
process of formation a mass of calcareous material, which in a later age
may rise above the surface of the water as chalk or limestone. Those
organisms living in the sea, which are enclosed either wholly or in part by
calcareous shells, are agents of limestone-building; their shells constantly
accumulating on the floor of the sea give rise in course of time to a thick
mass of sediment, composed in great part of carbonate of lime. Some of the
shells in such a deposit may retain their original form, the calcareous body
may on the other hand be broken up into minute fragments which are still
recognisable with the help of a microscope, or the shells and other hard
parts may be dissolved or disintegrated beyond recognition, leaving nothing
in the calcareous sediment to indicate its method of formation.
Not a few limestones consist in part of fossil corals, and owe their origin
to colonies of coral polyps which built up reefs or banks of coral in the
ancient seas.
In the white cliffs of Dover, Flamborough Head and other places, we
have a somewhat different form of calcareous rock, which in part consists
of millions of minute shells of Foraminifera, in part of broken fragments of
larger shells of extinct molluscs, and to some extent of the remains of
siliceous sponges. As a general rule, limestones and chalk rocks are ancient
sediments, formed in clear and comparatively deep water, composed in the
main of carbonate of lime, in some cases with a certain amount of carbonate
of magnesium, and occasionally with a considerable admixture of silica.
In such rocks land-plants must necessarily be rare. There are, however,
limestones which wholly or in part owe their formation to masses of
calcareous algae, which grew in the form of submarine banks or on coral
reefs. Occasionally the remains of these algae are clearly preserved, but
frequently all signs of plant structure have been completely obliterated.
Again, there occur limestone rocks formed by chemical means, and in a
manner similar to that in which beds of travertine are now being
accumulated.
Page 53
Granites, basalts, volcanic lavas, tuffs, and other igneous rocks need not
claim our attention, except in such cases as permit of plant remains being
found in association with these materials. Showers of ashes blown from a
volcano, may fall on the surface of a lake or sea and become mixed with
sand and mud of subaerial origin. Streams of lava occasionally flow into
water, or they may be poured from submarine vents, and so spread out on
the ocean bed with strata of sand or clay.
Passing from the nature and mode of origin of the sedimentary strata to
the manner of their arrangement in the Earth’s crust, we must endeavour to
sketch in the merest outline the methods of stratigraphical geology. The
surface of the Earth in some places stands out in the form of bare masses of
rock, roughly hewn or finely carved by Nature’s tools of frost, rain or
running water; in other places we have gently undulating ground with beds
of rock exposed to view here and there, but for the most part covered with
loose material such as gravel, sands, boulder clay and surface soil.
GEOLOGICAL SECTIONS.
In the flat lands of the fen districts, the peat beds and low-lying salt
marshes form the surface features, and are the connecting links between the
rock-building now in progress and the deposits of an earlier age. If we
could remove all these surface accumulations of sand, gravel, peat and
surface soil, and take a bird’s eye view of the bare surface of the rocky
skeleton of the earth’s crust, we should have spread before us the outlines of
a geological map. In some places fairly horizontal beds of rock stretching
over a wide extent of country, in another the upturned edges of almost
vertical strata form the surface features; or, again, irregular bosses of
crystalline igneous rock occur here and there as patches in the midst of
bedded sedimentary or volcanic strata. A map showing the boundaries and
distribution of the rocks as seen at the surface, tells us comparatively little
as to the relative positions of the different rocks below ground, or of the
relative ages of the several strata. If we supplement this superficial view by
an inspection of the position of the strata as shown on the walls of a deep
trench cut across the country, we at once gain very important information as
to the relative position of the beds below the earth’s surface. The face of a
quarry, the side of a river bed or a railway cutting, afford horizontal
sections or profiles which show whether certain strata lie above or below
others, whether a series of rocks consists of parallel and regularly stratified
claim our attention, except in such cases as permit of plant remains being
found in association with these materials. Showers of ashes blown from a
volcano, may fall on the surface of a lake or sea and become mixed with
sand and mud of subaerial origin. Streams of lava occasionally flow into
water, or they may be poured from submarine vents, and so spread out on
the ocean bed with strata of sand or clay.
Passing from the nature and mode of origin of the sedimentary strata to
the manner of their arrangement in the Earth’s crust, we must endeavour to
sketch in the merest outline the methods of stratigraphical geology. The
surface of the Earth in some places stands out in the form of bare masses of
rock, roughly hewn or finely carved by Nature’s tools of frost, rain or
running water; in other places we have gently undulating ground with beds
of rock exposed to view here and there, but for the most part covered with
loose material such as gravel, sands, boulder clay and surface soil.
GEOLOGICAL SECTIONS.
In the flat lands of the fen districts, the peat beds and low-lying salt
marshes form the surface features, and are the connecting links between the
rock-building now in progress and the deposits of an earlier age. If we
could remove all these surface accumulations of sand, gravel, peat and
surface soil, and take a bird’s eye view of the bare surface of the rocky
skeleton of the earth’s crust, we should have spread before us the outlines of
a geological map. In some places fairly horizontal beds of rock stretching
over a wide extent of country, in another the upturned edges of almost
vertical strata form the surface features; or, again, irregular bosses of
crystalline igneous rock occur here and there as patches in the midst of
bedded sedimentary or volcanic strata. A map showing the boundaries and
distribution of the rocks as seen at the surface, tells us comparatively little
as to the relative positions of the different rocks below ground, or of the
relative ages of the several strata. If we supplement this superficial view by
an inspection of the position of the strata as shown on the walls of a deep
trench cut across the country, we at once gain very important information as
to the relative position of the beds below the earth’s surface. The face of a
quarry, the side of a river bed or a railway cutting, afford horizontal
sections or profiles which show whether certain strata lie above or below
others, whether a series of rocks consists of parallel and regularly stratified
Page 54
beds, or whether the succession of the strata is interfered with by a greater
or less divergence from a parallel arrangement. If, for example, a section
shows comparatively horizontal strata lying across the worn down edges of
a series of vertical sedimentary rocks, we may fairly assume that some such
changes as the following have taken place in that particular area.
The underlying beds were originally laid down as more or less horizontal
deposits; these were gradually hardened and compacted, then elevated
above sea-level by a folding of the earth’s crust; the crests of the folds were
afterwards worn down by denudation, and the eroded surface finally
subsided below sea-level and formed the floor on which newer deposits
were built up. Such breaks in the continuity of stratified deposits are known
as unconformities; in the interval of time which they represent great
changes took place of which the records are either entirely lost, or have to
be sought elsewhere.
In certain more exceptional cases, it is possible to obtain what is
technically known as a vertical section; for example if a deep boring is
sunk through a series of rocks, and the core of the boring examined, we
have as it were a sample of the earth’s crust which may often teach us
valuable lessons which cannot be learnt from maps or horizontal sections.
INVERSION OF STRATA.
It is obvious, that in a given series of beds, which are either horizontal or
more or less obliquely inclined, the underlying strata were the first formed,
and the upper beds were laid down afterwards. If, however, we trusted
solely to the order of superposition in estimating relative age, our
conclusions would sometimes be very far from the truth. Recent geological
investigations have brought to light facts well nigh incredible as to the
magnitude and extent of rock-foldings. In regions of great earth-
movements, the crust has been broken along certain lines, and great masses
of strata have been thrust for miles along the tops of newer rocks. Thus it
may be brought about that the natural sequence of a set of beds has been
entirely altered, and older rocks have come to overlie sediments of a later
geological age. Facts such as these clearly illustrate the difficulties of
correct geological interpretation.
In the horizontal section (Fig. 2), from the summit of Büzistock on the
left to Saasterg on the right, we have a striking case of intense rock-folding
or less divergence from a parallel arrangement. If, for example, a section
shows comparatively horizontal strata lying across the worn down edges of
a series of vertical sedimentary rocks, we may fairly assume that some such
changes as the following have taken place in that particular area.
The underlying beds were originally laid down as more or less horizontal
deposits; these were gradually hardened and compacted, then elevated
above sea-level by a folding of the earth’s crust; the crests of the folds were
afterwards worn down by denudation, and the eroded surface finally
subsided below sea-level and formed the floor on which newer deposits
were built up. Such breaks in the continuity of stratified deposits are known
as unconformities; in the interval of time which they represent great
changes took place of which the records are either entirely lost, or have to
be sought elsewhere.
In certain more exceptional cases, it is possible to obtain what is
technically known as a vertical section; for example if a deep boring is
sunk through a series of rocks, and the core of the boring examined, we
have as it were a sample of the earth’s crust which may often teach us
valuable lessons which cannot be learnt from maps or horizontal sections.
INVERSION OF STRATA.
It is obvious, that in a given series of beds, which are either horizontal or
more or less obliquely inclined, the underlying strata were the first formed,
and the upper beds were laid down afterwards. If, however, we trusted
solely to the order of superposition in estimating relative age, our
conclusions would sometimes be very far from the truth. Recent geological
investigations have brought to light facts well nigh incredible as to the
magnitude and extent of rock-foldings. In regions of great earth-
movements, the crust has been broken along certain lines, and great masses
of strata have been thrust for miles along the tops of newer rocks. Thus it
may be brought about that the natural sequence of a set of beds has been
entirely altered, and older rocks have come to overlie sediments of a later
geological age. Facts such as these clearly illustrate the difficulties of
correct geological interpretation.
In the horizontal section (Fig. 2), from the summit of Büzistock on the
left to Saasterg on the right, we have a striking case of intense rock-folding
Page 55
and dislocation[46]. Prof. Heim[47] of Geneva has given numerous
illustrations of the almost incredible positions assumed in the Swiss
Mountains by vast thicknesses of rocks, and in the accompanying section
taken from a recent work by Rothpletz we have a compact example of the
possibilities of earth-movements as an agent of rock-folding. The section
illustrates very clearly an exception to the rule that the order of
superposition of a set of beds indicates the relative age of the strata. The
horizontal line at the base is drawn at a height of 1650 metres above sea-
level, and the summit of Büzistock reaches a height of 2340 m. The
youngest rocks seen in the diagram are the Eocene beds e, at the base and as
small isolated patches on the right-hand end of the section; the main mass
of material composing the higher ground has been bodily thrust over the
Eocene rocks, and in this process some of the beds, b and c, have been
folded repeatedly on themselves. Similar instances of the overthrusting of a
considerable thickness of strata have been described in the North-west
Highlands of Scotland[48] and elsewhere in the British Isles. It is important
therefore to draw attention to cases of extreme folding, as such phenomena
are by no means exceptional in many parts of the world.
Fig. 2. Section from Büzistock to Saasterg. [After Rothpletz, (94) Pl. ii. fig. 2.]
a = Sernifit or Verrucano (Permian).
b = Röthidolomit etc. (Permian).
c = Dogger (Jurassic).
d = Malm (Jurassic).
e = Eocene.
The order of superposition of strata has afforded the key to our
knowledge of the succession of life in geologic time, and the refinements of
the stratigraphical correlation of sedimentary rocks are based on the
comparison of their fossil contents. By a careful examination of the relics of
fossil organisms obtained from rocks of all ages and countries, it has been
found possible to restore in broken outline the past history of the Earth. By
illustrations of the almost incredible positions assumed in the Swiss
Mountains by vast thicknesses of rocks, and in the accompanying section
taken from a recent work by Rothpletz we have a compact example of the
possibilities of earth-movements as an agent of rock-folding. The section
illustrates very clearly an exception to the rule that the order of
superposition of a set of beds indicates the relative age of the strata. The
horizontal line at the base is drawn at a height of 1650 metres above sea-
level, and the summit of Büzistock reaches a height of 2340 m. The
youngest rocks seen in the diagram are the Eocene beds e, at the base and as
small isolated patches on the right-hand end of the section; the main mass
of material composing the higher ground has been bodily thrust over the
Eocene rocks, and in this process some of the beds, b and c, have been
folded repeatedly on themselves. Similar instances of the overthrusting of a
considerable thickness of strata have been described in the North-west
Highlands of Scotland[48] and elsewhere in the British Isles. It is important
therefore to draw attention to cases of extreme folding, as such phenomena
are by no means exceptional in many parts of the world.
Fig. 2. Section from Büzistock to Saasterg. [After Rothpletz, (94) Pl. ii. fig. 2.]
a = Sernifit or Verrucano (Permian).
b = Röthidolomit etc. (Permian).
c = Dogger (Jurassic).
d = Malm (Jurassic).
e = Eocene.
The order of superposition of strata has afforded the key to our
knowledge of the succession of life in geologic time, and the refinements of
the stratigraphical correlation of sedimentary rocks are based on the
comparison of their fossil contents. By a careful examination of the relics of
fossil organisms obtained from rocks of all ages and countries, it has been
found possible to restore in broken outline the past history of the Earth. By
Page 56
means, then, of stratigraphical and palaeontological evidence, a
classification of the various rocks has been established, the lines of division
being drawn in such places as represent gaps in the fossil records, or
striking and widespread unconformities between different series of deposits.
It is only in a few regions that we find rocks which can reasonably be
regarded as the foundation stones of the Earth. As the globe gradually
cooled, and its molten mass became skinned over with a solid crust,
crystalline rocks must have been produced before the dawn of life, and
before water could remain in a liquid form on the rocky surface. As soon as
the temperature became sufficiently low, running water and rain began the
work of denudation and rock disintegration which has been ceaselessly
carried on ever since. In this continual breaking down and building up of
the Earth’s surface, it would be no wonder if but few remnants were left of
the first formed sediments of the earliest age.
The action of heat, pressure and chemical change accompanying rock-
foldings and crust-wrinklings, often so far alters sedimentary deposits, that
their original form is entirely lost, and sandstone, shales and limestones
become metamorphosed into crystalline quartzites, slates and marbles.
The operation of metamorphism is therefore another serious difficulty in
the way of recognising the oldest rocks. The earliest animals and plants
which have been discovered are not such as we should expect to find as
examples of the first products of organic life. Below the oldest known
fossiliferous rocks, there must have been thousands of feet of sedimentary
material, which has either been altered beyond recognition, or from some
cause or other does not form part of our present geological record.
As a general introduction to geological chronology, a short summary may
be given of the different formations or groups of strata, to which certain
names have been assigned to serve as convenient designations for
succeeding epochs in the world’s evolution. The following table (Fig. 3, pp.
32, 33) represents the geological series in a convenient form; the most
characteristic rocks of each period are indicated by the usual conventional
shading, and the most important breaks or lacunae in the records are shown
by gaps and uneven lines. The relative thickness of the rocks of each period
is approximately shown; but the vertical extent of the oldest or Archaean
rocks as shown in Fig. 3 represents what is without doubt but a fraction of
classification of the various rocks has been established, the lines of division
being drawn in such places as represent gaps in the fossil records, or
striking and widespread unconformities between different series of deposits.
It is only in a few regions that we find rocks which can reasonably be
regarded as the foundation stones of the Earth. As the globe gradually
cooled, and its molten mass became skinned over with a solid crust,
crystalline rocks must have been produced before the dawn of life, and
before water could remain in a liquid form on the rocky surface. As soon as
the temperature became sufficiently low, running water and rain began the
work of denudation and rock disintegration which has been ceaselessly
carried on ever since. In this continual breaking down and building up of
the Earth’s surface, it would be no wonder if but few remnants were left of
the first formed sediments of the earliest age.
The action of heat, pressure and chemical change accompanying rock-
foldings and crust-wrinklings, often so far alters sedimentary deposits, that
their original form is entirely lost, and sandstone, shales and limestones
become metamorphosed into crystalline quartzites, slates and marbles.
The operation of metamorphism is therefore another serious difficulty in
the way of recognising the oldest rocks. The earliest animals and plants
which have been discovered are not such as we should expect to find as
examples of the first products of organic life. Below the oldest known
fossiliferous rocks, there must have been thousands of feet of sedimentary
material, which has either been altered beyond recognition, or from some
cause or other does not form part of our present geological record.
As a general introduction to geological chronology, a short summary may
be given of the different formations or groups of strata, to which certain
names have been assigned to serve as convenient designations for
succeeding epochs in the world’s evolution. The following table (Fig. 3, pp.
32, 33) represents the geological series in a convenient form; the most
characteristic rocks of each period are indicated by the usual conventional
shading, and the most important breaks or lacunae in the records are shown
by gaps and uneven lines. The relative thickness of the rocks of each period
is approximately shown; but the vertical extent of the oldest or Archaean
rocks as shown in Fig. 3 represents what is without doubt but a fraction of
Page 57
their proportional thickness. This table is taken, with certain alterations,
from a paper by Prof. T. McKenny Hughes in the Cambridge Philosophical
Proceedings for 1879. Speaking of the graphic method of showing the
geological series, the author of the paper says, “It is convenient to have a
table of the known strata, and although we cannot arrange all the rocks of
the world in parallel columns, and say that ABC of one area are exactly
synchronous with A′B′C′ of another, still if we take any one country and
establish a grouping for it, we find so many horizons at which equivalent
formations can be identified in distant places, that we generally make an
approximation to homotaxis as Huxley called it. The most convenient
grouping is obviously to bracket together locally continuous deposits, i.e.
all the sediment which was formed from the time when the land went down
and accumulation began, to the time when the sea bottom was raised and
the work of destruction began. In the accompanying table I have given the
rocks of Great Britain classified on this system, and bearing in mind that
waste in one place must be represented by deposit elsewhere, I have
represented the periods of degradation by intervals estimated where
possible by the amount of denudation known to have taken place between
the periods of deposition in the same district[49].”
from a paper by Prof. T. McKenny Hughes in the Cambridge Philosophical
Proceedings for 1879. Speaking of the graphic method of showing the
geological series, the author of the paper says, “It is convenient to have a
table of the known strata, and although we cannot arrange all the rocks of
the world in parallel columns, and say that ABC of one area are exactly
synchronous with A′B′C′ of another, still if we take any one country and
establish a grouping for it, we find so many horizons at which equivalent
formations can be identified in distant places, that we generally make an
approximation to homotaxis as Huxley called it. The most convenient
grouping is obviously to bracket together locally continuous deposits, i.e.
all the sediment which was formed from the time when the land went down
and accumulation began, to the time when the sea bottom was raised and
the work of destruction began. In the accompanying table I have given the
rocks of Great Britain classified on this system, and bearing in mind that
waste in one place must be represented by deposit elsewhere, I have
represented the periods of degradation by intervals estimated where
possible by the amount of denudation known to have taken place between
the periods of deposition in the same district[49].”
Page 58
TABLE OF STRATA.
Page 59
Page 60
Fig. 3.
I. Archaean.
“Men can do nothing without the make-believe of a beginning.”
George Eliot.
There is perhaps no problem at once so difficult and so full of interest to
the student of the Earth’s history, as the interpretation of the fragmentary
records of the opening stages in geological and organic evolution. In tracing
I. Archaean.
“Men can do nothing without the make-believe of a beginning.”
George Eliot.
There is perhaps no problem at once so difficult and so full of interest to
the student of the Earth’s history, as the interpretation of the fragmentary
records of the opening stages in geological and organic evolution. In tracing
Page 61
the growth and development of the human race, it becomes increasingly
difficult to discover and decipher written documents as we penetrate farther
back towards the beginning of the historical period; the records are usually
incomplete and fragmentary, or rendered illegible by the superposed
writings of a later date. So in the records of the rocks, as we pass beyond
the oldest strata in which clearly preserved fossils are met with, we come to
older rocks which afford either no data as to the period in which they were
formed, or like the palimpsest, with its original characters almost
obliterated by a late MS., the older portions of the Earth’s crust have been
used and re-used in the rock-building of later ages. In the first place, it is
exceedingly difficult to determine with any certainty what rocks may be
regarded as trustworthy fragments of a primaeval land. Throughout the
geological eras the Earth’s surface has been subjected to foldings and
wrinklings, volcanic activity has been almost unceasing, and there is
abundant evidence to show how the original characters of both igneous and
sedimentary rocks may be entirely effaced by the operation of chemical and
physical forces. It was formerly held that coarsely crystalline rocks such as
granite are the oldest portions of the crust, but modern geology has
conclusively proved that many of the so-called fundamental masses of rock
are merely piles of ancient sediments which have been subjected to the
repeated operation of powerful physical and chemical forces, and have
undergone a complete rearrangement of their substance. As the result of
more detailed investigations, many regions formerly supposed to consist of
the foundation stones of the Earth’s crust, are now known to have been
centres of volcanic disturbance and widespread metamorphism, and to be
made up of post-archaean rocks.
THE OLDEST ROCKS.
The first formed rocks no doubt became at once the prey of denudation
and disintegration, and on their surface would be accumulated the products
of their own destruction: newer strata would entirely cover up portions of
the original land, to be in their turn succeeded by still later deposits. There
is reason to believe that in the remotest ages of the Earth’s history, the
forces of denudation and igneous activity were more potent than in later
times, and thus the oldest rocks could hardly retain their original structure
through the long ages of geologic time. The earliest representatives of
organic life were doubtless of such a perishable nature that their remains
difficult to discover and decipher written documents as we penetrate farther
back towards the beginning of the historical period; the records are usually
incomplete and fragmentary, or rendered illegible by the superposed
writings of a later date. So in the records of the rocks, as we pass beyond
the oldest strata in which clearly preserved fossils are met with, we come to
older rocks which afford either no data as to the period in which they were
formed, or like the palimpsest, with its original characters almost
obliterated by a late MS., the older portions of the Earth’s crust have been
used and re-used in the rock-building of later ages. In the first place, it is
exceedingly difficult to determine with any certainty what rocks may be
regarded as trustworthy fragments of a primaeval land. Throughout the
geological eras the Earth’s surface has been subjected to foldings and
wrinklings, volcanic activity has been almost unceasing, and there is
abundant evidence to show how the original characters of both igneous and
sedimentary rocks may be entirely effaced by the operation of chemical and
physical forces. It was formerly held that coarsely crystalline rocks such as
granite are the oldest portions of the crust, but modern geology has
conclusively proved that many of the so-called fundamental masses of rock
are merely piles of ancient sediments which have been subjected to the
repeated operation of powerful physical and chemical forces, and have
undergone a complete rearrangement of their substance. As the result of
more detailed investigations, many regions formerly supposed to consist of
the foundation stones of the Earth’s crust, are now known to have been
centres of volcanic disturbance and widespread metamorphism, and to be
made up of post-archaean rocks.
THE OLDEST ROCKS.
The first formed rocks no doubt became at once the prey of denudation
and disintegration, and on their surface would be accumulated the products
of their own destruction: newer strata would entirely cover up portions of
the original land, to be in their turn succeeded by still later deposits. There
is reason to believe that in the remotest ages of the Earth’s history, the
forces of denudation and igneous activity were more potent than in later
times, and thus the oldest rocks could hardly retain their original structure
through the long ages of geologic time. The earliest representatives of
organic life were doubtless of such a perishable nature that their remains
Page 62
could not be preserved in a fossil state even under the most favourable
conditions. Such organisms, whether plants or animals, as possessed any
resistant tissues or hard skeletons might be preserved in the oldest rocks,
but as these strata became involved in earth-foldings or were penetrated by
injections of igneous eruptions, the relics of life would be entirely
destroyed. It is, in short, practically hopeless to look for any fragments of
the primitive crust except such as have undergone very considerable
metamorphism, and equally futile to search for any recognisable remains of
primitive life.
In many parts of the world vast thicknesses of rock occur below the
oldest known fossiliferous strata; these consist largely of laminated
crystalline masses composed of quartz, felspar, and other minerals, having
in fact the same composition as granite, but differing in the regular
arrangement of the constituent parts. To such rocks the terms gneiss and
schist have been applied. Rocks of this kind are by no means always of
Archaean age, but many of the earliest known rocks consist of gneisses of
various kinds, associated with altered lavas, metamorphosed ashes, breccias
and other products of volcanic activity; with these there may be limestones,
shales, sandstones, and other strata more or less closely resembling
sedimentary deposits. Such a succession of gneissic rocks has been
described as occupying a wide area in the basin of the St Lawrence river,
and to these enormously thick and widespread masses a late Director of the
Canadian Geological Survey applied the term Laurentian. These Laurentian
rocks, with similar strata in Scandinavia, the north-west Highlands of
Scotland, in certain parts of such mountain ranges as the Alps, Pyrenees,
Carpathians, Himalayas, Andes, Atlas, &c., have been classed together as
members of the oldest geological period, and are usually referred to under
the name of Archaean, or less frequently Azoic rocks. In some of the
uppermost Archaean rocks there have been recently discovered a few
undoubted traces of fossil animals, but with this exception no fossils are
known throughout the great mass of Archaean strata. It is true that some
authorities regard the beds of graphite and other rocks as a proof of the
abundance of plant life, but this supposition is not supported by any
convincing evidence.
The term Azoic[50] applied by some writers to these oldest rocks suggests
the absence of life during the period in which they were formed. Life there
conditions. Such organisms, whether plants or animals, as possessed any
resistant tissues or hard skeletons might be preserved in the oldest rocks,
but as these strata became involved in earth-foldings or were penetrated by
injections of igneous eruptions, the relics of life would be entirely
destroyed. It is, in short, practically hopeless to look for any fragments of
the primitive crust except such as have undergone very considerable
metamorphism, and equally futile to search for any recognisable remains of
primitive life.
In many parts of the world vast thicknesses of rock occur below the
oldest known fossiliferous strata; these consist largely of laminated
crystalline masses composed of quartz, felspar, and other minerals, having
in fact the same composition as granite, but differing in the regular
arrangement of the constituent parts. To such rocks the terms gneiss and
schist have been applied. Rocks of this kind are by no means always of
Archaean age, but many of the earliest known rocks consist of gneisses of
various kinds, associated with altered lavas, metamorphosed ashes, breccias
and other products of volcanic activity; with these there may be limestones,
shales, sandstones, and other strata more or less closely resembling
sedimentary deposits. Such a succession of gneissic rocks has been
described as occupying a wide area in the basin of the St Lawrence river,
and to these enormously thick and widespread masses a late Director of the
Canadian Geological Survey applied the term Laurentian. These Laurentian
rocks, with similar strata in Scandinavia, the north-west Highlands of
Scotland, in certain parts of such mountain ranges as the Alps, Pyrenees,
Carpathians, Himalayas, Andes, Atlas, &c., have been classed together as
members of the oldest geological period, and are usually referred to under
the name of Archaean, or less frequently Azoic rocks. In some of the
uppermost Archaean rocks there have been recently discovered a few
undoubted traces of fossil animals, but with this exception no fossils are
known throughout the great mass of Archaean strata. It is true that some
authorities regard the beds of graphite and other rocks as a proof of the
abundance of plant life, but this supposition is not supported by any
convincing evidence.
The term Azoic[50] applied by some writers to these oldest rocks suggests
the absence of life during the period in which they were formed. Life there
Page 63
must have been, though we are unable to discover its records. The period of
time represented by the Archaean or Pre-Cambrian rocks must be
enormous, and it was in that earliest era that the first links in the chain of
life were forged.
II. Cambrian.
The term Cambrian was adopted by Sedgwick for a series of sedimentary
rocks in North Wales (Cambria). In that district, in South Wales, the
Longmynd Hills, the Malverns, in Scotland, and other regions there occur
more or less highly folded and contorted beds of pebbly conglomerate,
sandstones, shales and slates resting on the uneven surface of an Archaean
foundation.
It is in these Cambrian rocks that trustworthy records of organic life are
first met with. Among the most constant and characteristic fossils of this
period are the extinct and aberrant members of the crustacea, the trilobites;
these with some brachiopods, sponges, and other fossils comprise the oldest
fauna, of which the ancestral types have yet to be discovered. During the
last few decades the number of Cambrian fossils has been considerably
increased, and in certain regions of North America and China there are
found many thousand feet of strata above the typical Archaean rocks and
below the newer fossiliferous beds of Cambrian age. It is reasonable to
suppose that future research may extend the present limits of fossil-bearing
rocks below the horizon, which is marked by the occurrence of the widely
distributed and oldest known trilobite, the genus Olenellus.
The vast thickness of Cambrian strata was for the most part laid down on
the floor of a comparatively deep sea; other members of the series represent
the shingle beaches and coast deposits accumulated on the slopes of
Archaean islands. There have been many conjectures as to the distribution
of land and sea during the deposition of these rocks; but the data are too
imperfect to enable us to restore with any degree of confidence the physical
geography of this Palaeozoic epoch, of which the sediments stood out as
islands of Cambrian land during many succeeding ages.
III. Ordovician.
time represented by the Archaean or Pre-Cambrian rocks must be
enormous, and it was in that earliest era that the first links in the chain of
life were forged.
II. Cambrian.
The term Cambrian was adopted by Sedgwick for a series of sedimentary
rocks in North Wales (Cambria). In that district, in South Wales, the
Longmynd Hills, the Malverns, in Scotland, and other regions there occur
more or less highly folded and contorted beds of pebbly conglomerate,
sandstones, shales and slates resting on the uneven surface of an Archaean
foundation.
It is in these Cambrian rocks that trustworthy records of organic life are
first met with. Among the most constant and characteristic fossils of this
period are the extinct and aberrant members of the crustacea, the trilobites;
these with some brachiopods, sponges, and other fossils comprise the oldest
fauna, of which the ancestral types have yet to be discovered. During the
last few decades the number of Cambrian fossils has been considerably
increased, and in certain regions of North America and China there are
found many thousand feet of strata above the typical Archaean rocks and
below the newer fossiliferous beds of Cambrian age. It is reasonable to
suppose that future research may extend the present limits of fossil-bearing
rocks below the horizon, which is marked by the occurrence of the widely
distributed and oldest known trilobite, the genus Olenellus.
The vast thickness of Cambrian strata was for the most part laid down on
the floor of a comparatively deep sea; other members of the series represent
the shingle beaches and coast deposits accumulated on the slopes of
Archaean islands. There have been many conjectures as to the distribution
of land and sea during the deposition of these rocks; but the data are too
imperfect to enable us to restore with any degree of confidence the physical
geography of this Palaeozoic epoch, of which the sediments stood out as
islands of Cambrian land during many succeeding ages.
III. Ordovician.
Page 64
Since the days when Sedgwick and Murchison first worked out the
succession of Palaeozoic strata in North Wales, there has always existed a
considerable difference of opinion as to the best method of subdividing the
Cambrian-Silurian strata. Later research has shown that the rocks included
by Sedgwick in his Cambrian system, fall naturally into two groups; for the
upper of these Prof. Lapworth has suggested the term Ordovician, from the
name of the Ordovices, who inhabited a part of northern Wales. At the base
of the system we have a series of volcanic and sedimentary rocks to which
Sedgwick gave the name Arenig; above these there occur the Llandeilo
Flags, succeeded by a considerable thickness of rocks known as the Bala
series. The rocks making up these Ordovician sediments consist for the
most part of slates, sandstones and limestones with volcanic ashes and
lavas. Much of the typical Welsh scenery owes its character to the folded
and weathered rocks laid down on the floor of the Ordovician sea, on which
from many centres of volcanic activity lava streams and showers of ash
were spread out between sheets of marine sediment. The Arenig Hills,
Snowdonia, and many other parts of North and South Wales, parts of
Shropshire, Scotland, Sweden, Russia, Bohemia, North America and other
regions consist of great thicknesses of Ordovician strata.
IV. Silurian.
Passing up a stage higher in the geologic series, we have a succession of
conglomerates, sandstones, shales, and limestones; in other words, a series
of beds which represent pebbly shore deposits, the sands and muds of
deeper water, and the accumulated débris of calcareous skeletons of animals
which lived in the clear water of the Silurian sea. The term Silurian (Siluria
was the country of Caractacus and the old Britons known as Silures[51]) was
first applied by Murchison in 1835 to a more comprehensive series of rocks
than are now included in the Silurian system. The rocks of this period occur
in Wales, Shropshire, parts of Scotland, Ireland, Scandinavia, Russia, the
United States and other countries. After the accumulation of the thick
Ordovician sediments, the sea-floor was upraised and in places converted
into ridges or islands of land, of which the detritus formed part of the
material of Silurian deposits. The limestones of the Wenlock ridge have
yielded an abundant fauna, consisting of corals, crinoids, molluscs and
other invertebrates. In this period we have the first representatives of the
succession of Palaeozoic strata in North Wales, there has always existed a
considerable difference of opinion as to the best method of subdividing the
Cambrian-Silurian strata. Later research has shown that the rocks included
by Sedgwick in his Cambrian system, fall naturally into two groups; for the
upper of these Prof. Lapworth has suggested the term Ordovician, from the
name of the Ordovices, who inhabited a part of northern Wales. At the base
of the system we have a series of volcanic and sedimentary rocks to which
Sedgwick gave the name Arenig; above these there occur the Llandeilo
Flags, succeeded by a considerable thickness of rocks known as the Bala
series. The rocks making up these Ordovician sediments consist for the
most part of slates, sandstones and limestones with volcanic ashes and
lavas. Much of the typical Welsh scenery owes its character to the folded
and weathered rocks laid down on the floor of the Ordovician sea, on which
from many centres of volcanic activity lava streams and showers of ash
were spread out between sheets of marine sediment. The Arenig Hills,
Snowdonia, and many other parts of North and South Wales, parts of
Shropshire, Scotland, Sweden, Russia, Bohemia, North America and other
regions consist of great thicknesses of Ordovician strata.
IV. Silurian.
Passing up a stage higher in the geologic series, we have a succession of
conglomerates, sandstones, shales, and limestones; in other words, a series
of beds which represent pebbly shore deposits, the sands and muds of
deeper water, and the accumulated débris of calcareous skeletons of animals
which lived in the clear water of the Silurian sea. The term Silurian (Siluria
was the country of Caractacus and the old Britons known as Silures[51]) was
first applied by Murchison in 1835 to a more comprehensive series of rocks
than are now included in the Silurian system. The rocks of this period occur
in Wales, Shropshire, parts of Scotland, Ireland, Scandinavia, Russia, the
United States and other countries. After the accumulation of the thick
Ordovician sediments, the sea-floor was upraised and in places converted
into ridges or islands of land, of which the detritus formed part of the
material of Silurian deposits. The limestones of the Wenlock ridge have
yielded an abundant fauna, consisting of corals, crinoids, molluscs and
other invertebrates. In this period we have the first representatives of the
Page 65
Vertebrata, discovered in the rocks of Ludlow. In fact, in the Silurian
period, “all the great divisions of the Animal Kingdom were already
represented[52].”
V. Devonian.
By the continued elevation of the Silurian sea-floor, large portions
became dry land, and during the succeeding period most of the British area
formed part of a continental mass. Over the southern part of England, there
still lay an arm of the sea, and in this were laid down the marine sediments
which now form part of Devon, and from which the name Devonian has
been taken as a convenient designation for the strata of this period. In parts
of the northern land, in the region now occupied by Scotland, there were
large inland lakes, on the floor of which vast thicknesses of shingle beds
and coarse sands (“Old Red Sandstone”) were slowly accumulated; and it
has been shown by Sir Archibald Geikie and others that during this epoch
there were considerable outpourings of volcanic material in the Scotch area.
Farther to the West and South-west there was another large lake in which
the so-called Kiltorkan beds of Ireland were deposited. In these Irish
sediments, and others of the same age in Belgium and elsewhere a few
forms of land plants have been discovered; but it is from the Devonian
rocks of North America that most of our knowledge of the flora of this
period has been obtained.
VI. Carboniferous.
From the point of view of palaeobotany, the shales, sandstones, and
seams of coal included in the Carboniferous system are of special interest. It
is from the relics of this Palaeozoic vegetation that the most important
botanical lessons have been learnt.
The following classification of Carboniferous rocks shows the order of
succession of the various beds, and the nature of the rocks which were
formed at this stage in the Earth’s history.
Carboniferous Coal-Measures[53] Upper Coal-Measures.
Transition Series.
Middle Coal-Measures.
period, “all the great divisions of the Animal Kingdom were already
represented[52].”
V. Devonian.
By the continued elevation of the Silurian sea-floor, large portions
became dry land, and during the succeeding period most of the British area
formed part of a continental mass. Over the southern part of England, there
still lay an arm of the sea, and in this were laid down the marine sediments
which now form part of Devon, and from which the name Devonian has
been taken as a convenient designation for the strata of this period. In parts
of the northern land, in the region now occupied by Scotland, there were
large inland lakes, on the floor of which vast thicknesses of shingle beds
and coarse sands (“Old Red Sandstone”) were slowly accumulated; and it
has been shown by Sir Archibald Geikie and others that during this epoch
there were considerable outpourings of volcanic material in the Scotch area.
Farther to the West and South-west there was another large lake in which
the so-called Kiltorkan beds of Ireland were deposited. In these Irish
sediments, and others of the same age in Belgium and elsewhere a few
forms of land plants have been discovered; but it is from the Devonian
rocks of North America that most of our knowledge of the flora of this
period has been obtained.
VI. Carboniferous.
From the point of view of palaeobotany, the shales, sandstones, and
seams of coal included in the Carboniferous system are of special interest. It
is from the relics of this Palaeozoic vegetation that the most important
botanical lessons have been learnt.
The following classification of Carboniferous rocks shows the order of
succession of the various beds, and the nature of the rocks which were
formed at this stage in the Earth’s history.
Carboniferous Coal-Measures[53] Upper Coal-Measures.
Transition Series.
Middle Coal-Measures.
Page 66
Lower Coal-Measures.
Millstone Grit.
Upper limestone shales and Yoredale rocks.
Carboniferous limestone series Carboniferous or Mountain limestone
Lower limestone shales.
Basement conglomerate.
In the classification of Carboniferous rocks adopted in Geikie’s text-book
of Geology the following arrangement is followed for the Carboniferous
limestone series[54]:—
Yoredale group of shales and grits passing down into dark shales and
limestones.
Thick (Scaur or Main) limestone in the south and centre of England and
Carboniferous Ireland, passing northwards into sandstones, shales and coals with
limestone limestones.
series Lower limestone shale of the south and centre of England. The Calciferous
sandstone group of Scotland (marine, estuarine, and terrestrial organisms)
probably represents the Scaur limestone and lower limestone shale, and
graduates downwards insensibly into the Upper Old Red Sandstone.
The thick beds of mountain limestone, with their characteristic marine
fossil shells and corals play an important part in English scenery. In
Derbyshire, West Yorkshire, and other places, the limestone crags and hills
are made up of the raised floor of a comparatively deep Carboniferous sea,
which covered a considerable portion of the British Isles at the beginning of
this epoch.
CARBONIFEROUS ROCKS.
The accumulation of the calcareous skeletons of marine animals, with
masses of coral, veritable shell-banks of extinct oyster-like lamellibranchs,
built up during the lapse of a long period of time, formed widespread
deposits of calcareous sediments. These were eventually succeeded by less
pure calcareous deposits, the sea became shallower, and land detritus found
its way over an area formerly occupied by the clear waters of an open sea.
The shallowing process was gradually continued, and the sea was by some
means converted into a more confined fresh-water or brackish area, in
which were laid down many hundred feet of coarse sandy sediments
derived from the waste of granitic highlands. Finally the conditions became
less constant; the continuous deposition of sandy detritus being interrupted
by the more or less complete filling up of the area of sedimentation, and the
Millstone Grit.
Upper limestone shales and Yoredale rocks.
Carboniferous limestone series Carboniferous or Mountain limestone
Lower limestone shales.
Basement conglomerate.
In the classification of Carboniferous rocks adopted in Geikie’s text-book
of Geology the following arrangement is followed for the Carboniferous
limestone series[54]:—
Yoredale group of shales and grits passing down into dark shales and
limestones.
Thick (Scaur or Main) limestone in the south and centre of England and
Carboniferous Ireland, passing northwards into sandstones, shales and coals with
limestone limestones.
series Lower limestone shale of the south and centre of England. The Calciferous
sandstone group of Scotland (marine, estuarine, and terrestrial organisms)
probably represents the Scaur limestone and lower limestone shale, and
graduates downwards insensibly into the Upper Old Red Sandstone.
The thick beds of mountain limestone, with their characteristic marine
fossil shells and corals play an important part in English scenery. In
Derbyshire, West Yorkshire, and other places, the limestone crags and hills
are made up of the raised floor of a comparatively deep Carboniferous sea,
which covered a considerable portion of the British Isles at the beginning of
this epoch.
CARBONIFEROUS ROCKS.
The accumulation of the calcareous skeletons of marine animals, with
masses of coral, veritable shell-banks of extinct oyster-like lamellibranchs,
built up during the lapse of a long period of time, formed widespread
deposits of calcareous sediments. These were eventually succeeded by less
pure calcareous deposits, the sea became shallower, and land detritus found
its way over an area formerly occupied by the clear waters of an open sea.
The shallowing process was gradually continued, and the sea was by some
means converted into a more confined fresh-water or brackish area, in
which were laid down many hundred feet of coarse sandy sediments
derived from the waste of granitic highlands. Finally the conditions became
less constant; the continuous deposition of sandy detritus being interrupted
by the more or less complete filling up of the area of sedimentation, and the
Page 67
formation of a land surface which supported a luxuriant vegetation, of
which the débris was subsequently converted into beds of coal. By further
subsidence the land was again submerged, and the forest-covered area
became overspread with sands and muds.
Such are the imperfect outlines of the general physical conditions which
are represented by the series of sedimentary strata included in the
Carboniferous system. At the close of this period, the Earth’s surface in
Western Europe was subjected to crust-foldings on a large scale, along lines
running approximately North and South and East and West, the two sets of
movements resulting in the formation of ridges of Carboniferous rocks. The
uppermost series of grits, sandstones and coal-seams were in great part
removed by denudation from the crests of the elevated ridges, but remained
in the intervening troughs or basins where they were less exposed to
denudation. It is the direct consequence of this, that we have our Coal-
Measures preserved in the form of detached basins of upper Carboniferous
beds.
A closer examination of the comparative thickness and succession of
Carboniferous rocks in different parts of Britain shows very clearly that in
the northern area of Scotland and in the North of England the conditions
were different from those which obtained further South. Seeing how much
palaeobotanical interest attaches to these rocks, it is important to treat a
little more fully of their geology.
In parts of Devon, Cornwall and West Somerset, the Devonian strata are
succeeded by a series of folded and contorted rocks which have yielded a
comparatively small number of Carboniferous fossils. To this succession of
limestones, shales and grits the term Culm-Measures was applied by
Sedgwick and Murchison in 1837. The rocks of this series occupy a trough
between the Devonian rocks of North and South Devon. While some
authorities have correlated the Culm-Measures with the Millstone Grit,
others regard them as representing a portion of the true Coal-Measures, as
well as the Carboniferous and Lower Limestone Shale[55]. It has recently
been shown that among the lower Culm strata there occur bands of ancient
deep-sea sediments, consisting of beds of chert containing siliceous casts of
various species of Radiolaria. There can be no doubt that the discovery of
deep-sea fossils in this particular development of the British Carboniferous
system leads to the conclusion that “while the massive deposits of the
which the débris was subsequently converted into beds of coal. By further
subsidence the land was again submerged, and the forest-covered area
became overspread with sands and muds.
Such are the imperfect outlines of the general physical conditions which
are represented by the series of sedimentary strata included in the
Carboniferous system. At the close of this period, the Earth’s surface in
Western Europe was subjected to crust-foldings on a large scale, along lines
running approximately North and South and East and West, the two sets of
movements resulting in the formation of ridges of Carboniferous rocks. The
uppermost series of grits, sandstones and coal-seams were in great part
removed by denudation from the crests of the elevated ridges, but remained
in the intervening troughs or basins where they were less exposed to
denudation. It is the direct consequence of this, that we have our Coal-
Measures preserved in the form of detached basins of upper Carboniferous
beds.
A closer examination of the comparative thickness and succession of
Carboniferous rocks in different parts of Britain shows very clearly that in
the northern area of Scotland and in the North of England the conditions
were different from those which obtained further South. Seeing how much
palaeobotanical interest attaches to these rocks, it is important to treat a
little more fully of their geology.
In parts of Devon, Cornwall and West Somerset, the Devonian strata are
succeeded by a series of folded and contorted rocks which have yielded a
comparatively small number of Carboniferous fossils. To this succession of
limestones, shales and grits the term Culm-Measures was applied by
Sedgwick and Murchison in 1837. The rocks of this series occupy a trough
between the Devonian rocks of North and South Devon. While some
authorities have correlated the Culm-Measures with the Millstone Grit,
others regard them as representing a portion of the true Coal-Measures, as
well as the Carboniferous and Lower Limestone Shale[55]. It has recently
been shown that among the lower Culm strata there occur bands of ancient
deep-sea sediments, consisting of beds of chert containing siliceous casts of
various species of Radiolaria. There can be no doubt that the discovery of
deep-sea fossils in this particular development of the British Carboniferous
system leads to the conclusion that “while the massive deposits of the
Page 68
Carboniferous limestone—formed of the skeletons of calcareous organisms
—were in process of growth in the seas to the North, there existed to the
South-west a deeper ocean in which siliceous organisms predominated and
formed these siliceous radiolarian rocks[56].”
The Upper Culm-Measures consist of conglomerates, grits, sandstones
and shales with some plant remains and other fossils, and constitute a
typical set of shallow water sediments. In Westphalia, the Harz region,
Thuringia, Silesia and Moravia there are rocks corresponding to the Culm-
Measures of Devon, and some of these have also afforded evidence of deep
water conditions.
COAL-MEASURES.
S. W. England, S. Wales, Derbyshire and Yorkshire. In these districts the
Carboniferous limestone reaches a considerable thickness; in the Mendips it
has a thickness of 3000 feet, and in the Pennine chain of 4000 feet. At the
base of this limestone series there occurs in the southern districts the so-
called lower limestone shale, consisting of clays, shales and sandy beds.
Above the limestone we have the Millstone grit and Coal-Measures; but in
the Pennine district there is a series of rocks consisting of impure
limestones and shales, intercalated between the Millstone grit and
Carboniferous limestone; for this group of rocks the term Yoredale series
has been proposed. In the Isle of Man and Derbyshire sheets of lava are
interbedded with the calcareous sediments, affording clear proof of
submarine volcanic eruptions.
N. England and Scotland. In the Carboniferous rocks of Northumberland
we have distinct indications of a shallower sea. The regular succession of
limestone strata in West Yorkshire and other districts, gives place to a series
of thinner beds of limestones, interstratified with shales and impure
calcareous rocks. We have come within the range of land detritus which was
spread out on the floor of a shallow sea. The lowest portion of the Mountain
limestone is here represented by about 200 feet of shales and other rocks
grouped together in the Tuedian series. The Upper Carboniferous limestone
and Yoredale rocks of Yorkshire are represented by sandstones,
carbonaceous limestones and some seams of coal, included in the Bernician
series. Further north, again, another classification has been proposed for the
still more aberrant succession of rocks; the lowest being spoken of as the
Calciferous sandstone, and the upper as the Carboniferous limestone. The
—were in process of growth in the seas to the North, there existed to the
South-west a deeper ocean in which siliceous organisms predominated and
formed these siliceous radiolarian rocks[56].”
The Upper Culm-Measures consist of conglomerates, grits, sandstones
and shales with some plant remains and other fossils, and constitute a
typical set of shallow water sediments. In Westphalia, the Harz region,
Thuringia, Silesia and Moravia there are rocks corresponding to the Culm-
Measures of Devon, and some of these have also afforded evidence of deep
water conditions.
COAL-MEASURES.
S. W. England, S. Wales, Derbyshire and Yorkshire. In these districts the
Carboniferous limestone reaches a considerable thickness; in the Mendips it
has a thickness of 3000 feet, and in the Pennine chain of 4000 feet. At the
base of this limestone series there occurs in the southern districts the so-
called lower limestone shale, consisting of clays, shales and sandy beds.
Above the limestone we have the Millstone grit and Coal-Measures; but in
the Pennine district there is a series of rocks consisting of impure
limestones and shales, intercalated between the Millstone grit and
Carboniferous limestone; for this group of rocks the term Yoredale series
has been proposed. In the Isle of Man and Derbyshire sheets of lava are
interbedded with the calcareous sediments, affording clear proof of
submarine volcanic eruptions.
N. England and Scotland. In the Carboniferous rocks of Northumberland
we have distinct indications of a shallower sea. The regular succession of
limestone strata in West Yorkshire and other districts, gives place to a series
of thinner beds of limestones, interstratified with shales and impure
calcareous rocks. We have come within the range of land detritus which was
spread out on the floor of a shallow sea. The lowest portion of the Mountain
limestone is here represented by about 200 feet of shales and other rocks
grouped together in the Tuedian series. The Upper Carboniferous limestone
and Yoredale rocks of Yorkshire are represented by sandstones,
carbonaceous limestones and some seams of coal, included in the Bernician
series. Further north, again, another classification has been proposed for the
still more aberrant succession of rocks; the lowest being spoken of as the
Calciferous sandstone, and the upper as the Carboniferous limestone. The
Page 69
calciferous sandstone may be compared with the lower limestone shale and
part of the Carboniferous limestone of England. The Carboniferous
limestone of Scotland probably represents the upper part of the limestone of
England and the Yoredale rocks of the Pennine and other areas.
Turning to the upper members of the Carboniferous system—in the Coal-
Measures, as they were called in 1817 by William Smith,—we have a series
of coal seams, sandstones, shales, and ironstones occurring for the most part
in basin-shaped areas. As a general rule, each seam of coal, which varies in
thickness from one inch to thirty feet, rests on a characteristic unstratified
argillaceous rock known as Underclay.
The accompanying diagram (Fig. 4) illustrates the frequent intercalation
of small bands of argillaceous and sandy rocks associated with the seams of
coal.
The usual classification adopted for the British Coal-Measures is that of
Upper, Middle, and Lower Coal-Measures; between the Upper and Middle
divisions there occur certain transition or passage beds which are known as
the Transition series. Continental writers, and more recently Mr Kidston of
Stirling, have attempted with considerable success to correlate the Coal-
producing strata by means of fossil plants[57].
part of the Carboniferous limestone of England. The Carboniferous
limestone of Scotland probably represents the upper part of the limestone of
England and the Yoredale rocks of the Pennine and other areas.
Turning to the upper members of the Carboniferous system—in the Coal-
Measures, as they were called in 1817 by William Smith,—we have a series
of coal seams, sandstones, shales, and ironstones occurring for the most part
in basin-shaped areas. As a general rule, each seam of coal, which varies in
thickness from one inch to thirty feet, rests on a characteristic unstratified
argillaceous rock known as Underclay.
The accompanying diagram (Fig. 4) illustrates the frequent intercalation
of small bands of argillaceous and sandy rocks associated with the seams of
coal.
The usual classification adopted for the British Coal-Measures is that of
Upper, Middle, and Lower Coal-Measures; between the Upper and Middle
divisions there occur certain transition or passage beds which are known as
the Transition series. Continental writers, and more recently Mr Kidston of
Stirling, have attempted with considerable success to correlate the Coal-
producing strata by means of fossil plants[57].
Page 70
10 in. Massive clay-shale with a few coal films in the lower part.
10½ in. Shale full of thin streaks of coal.
14 in. Massive shale with a few streaks of coal and iron pyrites.
5½ in. Bastard coal; more coal than shale.
6½ in. Good coal, with masses of iron pyrites.
1½ in. Coal and seat-rock mixed.
5 in. Seat-rock.
Fig. 4.
Vertical section of the Bassey or Salts Coal seam, Rushton Colliery, Blackburn (Lower
Coal-Measures). From a specimen 4 feet 4 inches in height, presented by Mr P. W. Pickup
to the Manchester Museum, Owens College.
Finally, some reference must be made to the occurrence of Carboniferous
rocks underneath more recent strata. In a geological map, or bird’s-eye view
of a country, we see such rocks as appear at the surface; by means of deep
borings, however, we are occasionally enabled to follow the course of older
beds a considerable distance below the usually accessible part of the Earth’s
crust. In the neighbourhood of London, Dover, and other places we have
10½ in. Shale full of thin streaks of coal.
14 in. Massive shale with a few streaks of coal and iron pyrites.
5½ in. Bastard coal; more coal than shale.
6½ in. Good coal, with masses of iron pyrites.
1½ in. Coal and seat-rock mixed.
5 in. Seat-rock.
Fig. 4.
Vertical section of the Bassey or Salts Coal seam, Rushton Colliery, Blackburn (Lower
Coal-Measures). From a specimen 4 feet 4 inches in height, presented by Mr P. W. Pickup
to the Manchester Museum, Owens College.
Finally, some reference must be made to the occurrence of Carboniferous
rocks underneath more recent strata. In a geological map, or bird’s-eye view
of a country, we see such rocks as appear at the surface; by means of deep
borings, however, we are occasionally enabled to follow the course of older
beds a considerable distance below the usually accessible part of the Earth’s
crust. In the neighbourhood of London, Dover, and other places we have
Page 71
Tertiary and Mesozoic strata forming the surface of the country, but below
these comparatively recent formations, the sinking of deep wells and other
borings have proved the existence of a ridge of Palaeozoic rocks stretching
from the South Wales Coal-field through the South-east of England to
northern France, Belgium and Westphalia. It is from rocks forming part of
this old ridge that characteristic Coal-Measure plants have been obtained
from the Dover boring. In Fig. 5 is shown an almost complete pinnule of
Neuropteris Scheuchzeri Hoffm., a well-known fern, marking a definite
horizon of Upper Carboniferous rocks[58]. The small hairs on the pinnules,
shown in the figure as fine lines lying more or less parallel to the midrib
and across the lateral veins, are a characteristic feature of this species.
Fig. 5.
Imperfect pinnule of Neuropteris Scheuchzeri Hoffm., showing the characteristic hairs as
fine lines traversing the lateral veins. From a specimen obtained from the Dover boring and
now in the British Museum. Nat. size.
VII. Permian.
Reference has already been made to the earth-foldings which marked the
close of Carboniferous times; “the open Mediterranean sea of the
Carboniferous period in Europe was converted into a large inland sea, like
the Caspian of the present day, surrounded by a rocky and hilly continent,
on which grew trees and plants of various kinds[59].” In parts of
Lancashire, Westmoreland, the Eden Valley, and in the East of England
from Sunderland to Nottingham, there occurs a succession of limestones,
sandstones, clays and other rocks with occasional beds of rock-salt and
gypsum, which represent the various forms of sediment and chemical
precipitates formed on the floor of Permian lakes. The poverty of the fauna
and flora of Permian strata points to conditions unfavourable to life; and
there can be little doubt that the characteristic red rocks of St Bees Head,
these comparatively recent formations, the sinking of deep wells and other
borings have proved the existence of a ridge of Palaeozoic rocks stretching
from the South Wales Coal-field through the South-east of England to
northern France, Belgium and Westphalia. It is from rocks forming part of
this old ridge that characteristic Coal-Measure plants have been obtained
from the Dover boring. In Fig. 5 is shown an almost complete pinnule of
Neuropteris Scheuchzeri Hoffm., a well-known fern, marking a definite
horizon of Upper Carboniferous rocks[58]. The small hairs on the pinnules,
shown in the figure as fine lines lying more or less parallel to the midrib
and across the lateral veins, are a characteristic feature of this species.
Fig. 5.
Imperfect pinnule of Neuropteris Scheuchzeri Hoffm., showing the characteristic hairs as
fine lines traversing the lateral veins. From a specimen obtained from the Dover boring and
now in the British Museum. Nat. size.
VII. Permian.
Reference has already been made to the earth-foldings which marked the
close of Carboniferous times; “the open Mediterranean sea of the
Carboniferous period in Europe was converted into a large inland sea, like
the Caspian of the present day, surrounded by a rocky and hilly continent,
on which grew trees and plants of various kinds[59].” In parts of
Lancashire, Westmoreland, the Eden Valley, and in the East of England
from Sunderland to Nottingham, there occurs a succession of limestones,
sandstones, clays and other rocks with occasional beds of rock-salt and
gypsum, which represent the various forms of sediment and chemical
precipitates formed on the floor of Permian lakes. The poverty of the fauna
and flora of Permian strata points to conditions unfavourable to life; and
there can be little doubt that the characteristic red rocks of St Bees Head,
Page 72
and the creamy limestones of the Durham coast are the upraised sediments
of an inland salt-water lake. The term Dyas was proposed by Marcou for
this series of strata as represented in Germany, where the rocks are
conveniently grouped in two series, the Magnesian limestone or Zechstein
and the red sandstones or Rothliegendes. The older and better known name
of Permian was instituted by Murchison for the rocks of this age, from their
extreme development in the old kingdom of Permia in Russia.
Unfortunately considerable confusion has arisen from the employment of
different names for rocks of the same geological period; and the grouping of
the beds varies in different parts of the world. It is of interest to note, that in
the Tyrol, Carinthia, and other places there are found patches of old marine
beds which were originally laid down in an open sea, which extended over
the site of the Mediterranean, into Russia and Asia. In Bohemia, the Harz
district, Autun in Burgundy, and other regions, there are seams of Permian
coal interstratified with the marls and sands. From these last named beds
many fossil plants have been obtained, and important palaeobotanical facts
brought to light by the investigations of continental workers. Volcanic
eruptions, accompanied by lava streams and showers of ash, have been
recognised in the Permian rocks of Scotland, and elsewhere.
In North America, Australia, and India the term Permo-Carboniferous is
often made use of in reference to the continuous and regular sequence of
beds which were formed towards the close of the Carboniferous and into
the succeeding Permian epoch. The enormous series of freshwater Indian
rocks, to which geologists have given the name of the Gondwana system,
includes the sediments of more than one geological period, some of the
older members being regarded as Permo-Carboniferous in age. These Indian
beds, with others in Australia, South Africa, and South America, are of
special interest on account of the characteristic southern hemisphere plants
which they have afforded, and from the association with the fossiliferous
strata of extensive boulder beds pointing to widespread glacial conditions.
VIII. Trias.
As we ascend the geologic series, and pass up to the rocks overlying the
Permian deposits, there are found many indications of a marked change in
the records of animal and plant life. Many of the characteristic Palaeozoic
fossils are no longer represented, and in their place we meet with fresh and
of an inland salt-water lake. The term Dyas was proposed by Marcou for
this series of strata as represented in Germany, where the rocks are
conveniently grouped in two series, the Magnesian limestone or Zechstein
and the red sandstones or Rothliegendes. The older and better known name
of Permian was instituted by Murchison for the rocks of this age, from their
extreme development in the old kingdom of Permia in Russia.
Unfortunately considerable confusion has arisen from the employment of
different names for rocks of the same geological period; and the grouping of
the beds varies in different parts of the world. It is of interest to note, that in
the Tyrol, Carinthia, and other places there are found patches of old marine
beds which were originally laid down in an open sea, which extended over
the site of the Mediterranean, into Russia and Asia. In Bohemia, the Harz
district, Autun in Burgundy, and other regions, there are seams of Permian
coal interstratified with the marls and sands. From these last named beds
many fossil plants have been obtained, and important palaeobotanical facts
brought to light by the investigations of continental workers. Volcanic
eruptions, accompanied by lava streams and showers of ash, have been
recognised in the Permian rocks of Scotland, and elsewhere.
In North America, Australia, and India the term Permo-Carboniferous is
often made use of in reference to the continuous and regular sequence of
beds which were formed towards the close of the Carboniferous and into
the succeeding Permian epoch. The enormous series of freshwater Indian
rocks, to which geologists have given the name of the Gondwana system,
includes the sediments of more than one geological period, some of the
older members being regarded as Permo-Carboniferous in age. These Indian
beds, with others in Australia, South Africa, and South America, are of
special interest on account of the characteristic southern hemisphere plants
which they have afforded, and from the association with the fossiliferous
strata of extensive boulder beds pointing to widespread glacial conditions.
VIII. Trias.
As we ascend the geologic series, and pass up to the rocks overlying the
Permian deposits, there are found many indications of a marked change in
the records of animal and plant life. Many of the characteristic Palaeozoic
fossils are no longer represented, and in their place we meet with fresh and
Page 73
in many cases more highly differentiated organisms. The threefold division
of the rocks of this period which suggested the term Trias to those who first
worked out the succession of the strata, is typically illustrated over a wide
area in Germany, in which the lowest or Bunter series is followed by the
calcareous Muschelkalk, and this again by the clays, rock-salt, and
sandstones of the Keuper series. In the Cheshire plain and in the low ground
of the Midlands, we have a succession of red sandstones, conglomerates,
and layers of rock-salt which correspond to the Bunter and Keuper beds of
German geologists. These Triassic rocks were obviously formed in salt-
water lakes, in which from time to time long continued evaporation gave
rise to extensive deposit of rock-salt and other minerals. From the fact that
it is this type of Triassic sediments which was first made known, it is often
forgotten that the British and German rocks are not the typical
representatives of this geological period. The ‘Alpine’ Trias of the
Mediterranean region, in Asia, North America, and other countries, has a
totally different facies, and includes limestones and dolomites of deep-sea
origin. “The widespread Alpine Trias is the pelagic facies of the formation;
the more restricted German Trias, on the other hand, is a shallow shore, bay
or inland sea formation[60].”
In the Keuper beds of southern Sweden there are found workable seams
of coal, and the beds of this district have yielded numerous well-preserved
examples of the Triassic flora. A more impure coal occurs in the lower
Keuper of Thuringia and S.-W. Germany, and to this group of rocks the
term Lettenkohle is occasionally applied.
In the Rhaetic Alps of Lombardy, in the Tyrol, and in England, from
Yorkshire to Lyme Regis, Devonshire, Somersetshire, and other districts
there are certain strata at the top of the Triassic system known as the
Rhaetic or Penarth beds. The uppermost Rhaetic beds, often described as
the White Lias, afford evidence of a change from the salt lakes of the Trias
to the open sea of the succeeding Jurassic period. Passing beyond this
period of salt lakes and wind-swept barren tracts of land, we enter on
another phase of the earth’s history.
IX. Jurassic.
of the rocks of this period which suggested the term Trias to those who first
worked out the succession of the strata, is typically illustrated over a wide
area in Germany, in which the lowest or Bunter series is followed by the
calcareous Muschelkalk, and this again by the clays, rock-salt, and
sandstones of the Keuper series. In the Cheshire plain and in the low ground
of the Midlands, we have a succession of red sandstones, conglomerates,
and layers of rock-salt which correspond to the Bunter and Keuper beds of
German geologists. These Triassic rocks were obviously formed in salt-
water lakes, in which from time to time long continued evaporation gave
rise to extensive deposit of rock-salt and other minerals. From the fact that
it is this type of Triassic sediments which was first made known, it is often
forgotten that the British and German rocks are not the typical
representatives of this geological period. The ‘Alpine’ Trias of the
Mediterranean region, in Asia, North America, and other countries, has a
totally different facies, and includes limestones and dolomites of deep-sea
origin. “The widespread Alpine Trias is the pelagic facies of the formation;
the more restricted German Trias, on the other hand, is a shallow shore, bay
or inland sea formation[60].”
In the Keuper beds of southern Sweden there are found workable seams
of coal, and the beds of this district have yielded numerous well-preserved
examples of the Triassic flora. A more impure coal occurs in the lower
Keuper of Thuringia and S.-W. Germany, and to this group of rocks the
term Lettenkohle is occasionally applied.
In the Rhaetic Alps of Lombardy, in the Tyrol, and in England, from
Yorkshire to Lyme Regis, Devonshire, Somersetshire, and other districts
there are certain strata at the top of the Triassic system known as the
Rhaetic or Penarth beds. The uppermost Rhaetic beds, often described as
the White Lias, afford evidence of a change from the salt lakes of the Trias
to the open sea of the succeeding Jurassic period. Passing beyond this
period of salt lakes and wind-swept barren tracts of land, we enter on
another phase of the earth’s history.
IX. Jurassic.
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The Jura mountains of western Switzerland consist in great part of folded
and contorted rocks which were originally deposited on the floor of a
Jurassic sea. In England the Jurassic rocks are of special interest, both for
geological and historical reasons, as it is in them that we find a rich fauna
and flora of Mesozoic age, and it was the classification of these beds by
means of their fossil contents that gained for William Smith the title of the
Father of English Geology. A glance at a geological map of England shows
a band of Jurassic rocks stretching across from the Yorkshire coast to
Dorset. These are in a large measure calcareous, argillaceous, and
arenaceous sediments of an open sea; but towards the upper limit of the
series, both freshwater and terrestrial beds are met with. Numerous
fragments of old coral reefs, sea-urchins, crinoids, and other marine fossils
are especially abundant; in the freshwater beds and old surface-soils, as
well as in the marine sandstones and shales, we have remnants of an
exceedingly rich and apparently tropical vegetation. This was an age of
Reptiles as well as an age of Cycads. An interesting feature of these widely
distributed Jurassic strata is the evidence they afford of distinct climatal
zones; there are clear indications, according to the late Dr Neumayr, of a
Mediterranean, a middle European, and a Boreal or Russian province[61].
The subdivisions of the English Jurassic rocks are as follows[62]:—
Purbeck beds
Portland beds Upper
Kimeridge clay
Corallian beds Oolite.
Jurassic Middle
Oxford clay, with Kellaways rock
Great Oolite series
Lower
Inferior Oolite series
Lias
In tracing the several groups across England, and into other parts of
Europe, their characters are naturally found to vary considerably; in one
area a series is made up of typical clear water or comparatively deep sea
sediments, and in another we have shallow water and shore deposits of the
same age. The Lias rocks have been further subdivided into zones by means
of the species of Ammonites which form so characteristic a feature of the
Jurassic fauna. In the lower Oolite strata there are shelly limestones, clays,
sandstones, and beds of lignite and ironstone. Without discussing the other
and contorted rocks which were originally deposited on the floor of a
Jurassic sea. In England the Jurassic rocks are of special interest, both for
geological and historical reasons, as it is in them that we find a rich fauna
and flora of Mesozoic age, and it was the classification of these beds by
means of their fossil contents that gained for William Smith the title of the
Father of English Geology. A glance at a geological map of England shows
a band of Jurassic rocks stretching across from the Yorkshire coast to
Dorset. These are in a large measure calcareous, argillaceous, and
arenaceous sediments of an open sea; but towards the upper limit of the
series, both freshwater and terrestrial beds are met with. Numerous
fragments of old coral reefs, sea-urchins, crinoids, and other marine fossils
are especially abundant; in the freshwater beds and old surface-soils, as
well as in the marine sandstones and shales, we have remnants of an
exceedingly rich and apparently tropical vegetation. This was an age of
Reptiles as well as an age of Cycads. An interesting feature of these widely
distributed Jurassic strata is the evidence they afford of distinct climatal
zones; there are clear indications, according to the late Dr Neumayr, of a
Mediterranean, a middle European, and a Boreal or Russian province[61].
The subdivisions of the English Jurassic rocks are as follows[62]:—
Purbeck beds
Portland beds Upper
Kimeridge clay
Corallian beds Oolite.
Jurassic Middle
Oxford clay, with Kellaways rock
Great Oolite series
Lower
Inferior Oolite series
Lias
In tracing the several groups across England, and into other parts of
Europe, their characters are naturally found to vary considerably; in one
area a series is made up of typical clear water or comparatively deep sea
sediments, and in another we have shallow water and shore deposits of the
same age. The Lias rocks have been further subdivided into zones by means
of the species of Ammonites which form so characteristic a feature of the
Jurassic fauna. In the lower Oolite strata there are shelly limestones, clays,
sandstones, and beds of lignite and ironstone. Without discussing the other
Page 75
subdivisions of the Jurassic period, we may note that in the uppermost
members there are preserved patches of old surface-soils exposed in the
face of the cliffs of the Dorset coast and of the Isle of Portland.
X. Cretaceous.
In the south of England, and in some other districts, it is difficult to draw
any definite line between the uppermost strata of the Jurassic and the lowest
of the Cretaceous period. The rocks of the so-called Wealden series of Kent,
Surrey, Sussex, and the Isle of Wight, are usually classed as Lower
Cretaceous, but there is strong evidence in favour of regarding them as
sediments of the Jurassic period. The Cretaceous rocks of England are
generally speaking parallel to the Jurassic strata, and occupy a stretch of
country from the east of Yorkshire and the Norfolk coast to Dorset in the
south-west. The Chalk downs and cliffs represent the most familiar type of
Cretaceous strata. In the white chalk with its numerous flints, we have part
of the elevated floor of a comparatively deep sea, which extended in
Cretaceous times over a large portion of the east and south-east of England
and other portions of the European continent. On the bed of this sea, beyond
the reach of any river-borne detritus, there accumulated through long ages
the calcareous and siliceous remains of marine animals, to be afterwards
converted into chalk and flints. At the beginning of the period, however,
other conditions obtained, and there extended over the south-east of
England, and parts of north and north-west Germany and Belgium, a lake or
estuary in which were built up deposits of clay, sand and other material,
forming the delta of one or more large rivers. For these sediments the name
Wealden was suggested in 1828. Eventually the gradual subsidence of this
area led to an incursion of the sea, and the delta became overflowed by the
waters of a large Cretaceous sea. At first the sea was shallow, and in it were
laid down coarse sands and other sediments known as the Lower Greensand
rocks. By degrees, as the subsidence continued, the shallows became deep
water, and calcareous material slowly accumulated, to be at last upraised as
beds of white chalk. The distribution of fossils in the Cretaceous rocks of
north and south Europe distinctly points to the existence of two fairly well-
marked sets of organisms in the two regions; no doubt the expression of
climatal zones similar to those recognised in Jurassic times. In North
America, Cretaceous rocks are spread over a wide area, also in North
members there are preserved patches of old surface-soils exposed in the
face of the cliffs of the Dorset coast and of the Isle of Portland.
X. Cretaceous.
In the south of England, and in some other districts, it is difficult to draw
any definite line between the uppermost strata of the Jurassic and the lowest
of the Cretaceous period. The rocks of the so-called Wealden series of Kent,
Surrey, Sussex, and the Isle of Wight, are usually classed as Lower
Cretaceous, but there is strong evidence in favour of regarding them as
sediments of the Jurassic period. The Cretaceous rocks of England are
generally speaking parallel to the Jurassic strata, and occupy a stretch of
country from the east of Yorkshire and the Norfolk coast to Dorset in the
south-west. The Chalk downs and cliffs represent the most familiar type of
Cretaceous strata. In the white chalk with its numerous flints, we have part
of the elevated floor of a comparatively deep sea, which extended in
Cretaceous times over a large portion of the east and south-east of England
and other portions of the European continent. On the bed of this sea, beyond
the reach of any river-borne detritus, there accumulated through long ages
the calcareous and siliceous remains of marine animals, to be afterwards
converted into chalk and flints. At the beginning of the period, however,
other conditions obtained, and there extended over the south-east of
England, and parts of north and north-west Germany and Belgium, a lake or
estuary in which were built up deposits of clay, sand and other material,
forming the delta of one or more large rivers. For these sediments the name
Wealden was suggested in 1828. Eventually the gradual subsidence of this
area led to an incursion of the sea, and the delta became overflowed by the
waters of a large Cretaceous sea. At first the sea was shallow, and in it were
laid down coarse sands and other sediments known as the Lower Greensand
rocks. By degrees, as the subsidence continued, the shallows became deep
water, and calcareous material slowly accumulated, to be at last upraised as
beds of white chalk. The distribution of fossils in the Cretaceous rocks of
north and south Europe distinctly points to the existence of two fairly well-
marked sets of organisms in the two regions; no doubt the expression of
climatal zones similar to those recognised in Jurassic times. In North
America, Cretaceous rocks are spread over a wide area, also in North
Page 76
Africa, India, South Africa, and other parts of the world. Within the Arctic
Circle strata of this age have become famous, chiefly on account of the rich
flora described from them by the Swiss palaeobotanist Heer. The fauna and
flora of this epoch are alike in their advanced state of development and in
the great variety of specific types; the highest class of plants is first met
with at the base of the Cretaceous system.
XI. Tertiary.
“At the close of the Chalk age a change took place both in the
distribution of land and water, and also in the development of organic life,
so great and universal, that it has scarcely been equalled at any other period
of the earth’s geological history[63].” The Tertiary period seems to bring us
suddenly to the threshold of our own times. In England at least, the deposits
of this age are of the nature of loose sands, clays and other materials
containing shells, bones, and fossil plants bearing a close resemblance to
organisms of the present era. The chalk rocks, upheaved from the
Cretaceous sea, stood out as dry land over a large part of Britain; much of
their material was in time removed by the action of denuding agents, and
the rest gradually sank again beneath the waters of Tertiary lakes and
estuaries. In the south of England, and in north Europe generally, the
Tertiary rocks have suffered but little disturbance or folding, but in southern
Europe and other parts of the world, the Tertiary sands have been
compacted and hardened into sandstones, and involved in the gigantic crust-
movements which gave birth to many of our highest mountain chains. The
Alps, Carpathians, Apennines, Himalayas, and other ranges consist to a
large extent of piled up and strangely folded layers of old Tertiary
sediments. The volcanic activity of this age was responsible for the basaltic
lavas of the Giants’ Causeway, the Isle of Staffa, and other parts of western
Scotland.
During the succeeding phases of this period, the distribution of land and
sea was continually changing, climatic conditions varied within wide limits;
and in short wherever Tertiary fossiliferous beds occur, we find distinct
evidence of an age characterised by striking activity both as regards the
action of dynamical as well as of organic forces. Sir Charles Lyell proposed
a subdivision of the strata of this period into Eocene, Miocene, and
Pliocene, founding his classification on the percentage of recent species of
Circle strata of this age have become famous, chiefly on account of the rich
flora described from them by the Swiss palaeobotanist Heer. The fauna and
flora of this epoch are alike in their advanced state of development and in
the great variety of specific types; the highest class of plants is first met
with at the base of the Cretaceous system.
XI. Tertiary.
“At the close of the Chalk age a change took place both in the
distribution of land and water, and also in the development of organic life,
so great and universal, that it has scarcely been equalled at any other period
of the earth’s geological history[63].” The Tertiary period seems to bring us
suddenly to the threshold of our own times. In England at least, the deposits
of this age are of the nature of loose sands, clays and other materials
containing shells, bones, and fossil plants bearing a close resemblance to
organisms of the present era. The chalk rocks, upheaved from the
Cretaceous sea, stood out as dry land over a large part of Britain; much of
their material was in time removed by the action of denuding agents, and
the rest gradually sank again beneath the waters of Tertiary lakes and
estuaries. In the south of England, and in north Europe generally, the
Tertiary rocks have suffered but little disturbance or folding, but in southern
Europe and other parts of the world, the Tertiary sands have been
compacted and hardened into sandstones, and involved in the gigantic crust-
movements which gave birth to many of our highest mountain chains. The
Alps, Carpathians, Apennines, Himalayas, and other ranges consist to a
large extent of piled up and strangely folded layers of old Tertiary
sediments. The volcanic activity of this age was responsible for the basaltic
lavas of the Giants’ Causeway, the Isle of Staffa, and other parts of western
Scotland.
During the succeeding phases of this period, the distribution of land and
sea was continually changing, climatic conditions varied within wide limits;
and in short wherever Tertiary fossiliferous beds occur, we find distinct
evidence of an age characterised by striking activity both as regards the
action of dynamical as well as of organic forces. Sir Charles Lyell proposed
a subdivision of the strata of this period into Eocene, Miocene, and
Pliocene, founding his classification on the percentage of recent species of
Page 77
molluscs contained in the various sets of rocks. His divisions have been
generally adopted. In 1854 Prof. Beyrich proposed to include another
subdivision in the Tertiary system, and to this he gave the name Oligocene.
Occupying a basin-shaped area around London and Paris there are beds
of Eocene sands and clays which were originally deposited as continuous
sheets of sediment in water at first salt, afterwards brackish and to a certain
extent fresh. In the Hampshire cliffs and in some parts of the Isle of Wight,
we have other patches of these oldest Tertiary sediments. Across the south
of Europe, North Africa, Arabia, Persia, the Himalayas, to Java and the
Philippine islands, there existed in early Tertiary times a wide sea
connecting the Atlantic and Pacific oceans; and it may be that in the
Mediterranean of to-day we have a remnant of this large Eocene ocean.
Later in the Tertiary period a similar series of beds was deposited which we
now refer to as the Oligocene strata; such occurs in the cliffs of Headon hill
in the Isle of Wight, containing bones of crocodiles, and turtles, with the
relics of a rich flora preserved in the delta deposits of an Oligocene river. At
a still later stage the British area was probably dry land, and an open sea
existed over the Mediterranean region. In the neighbourhood of Vienna we
have beds of this age represented by a succession of sediments, at first
marine and afterwards freshwater. Miocene beds occur over a considerable
area in Switzerland and the Arctic regions, and they have yielded a rich
harvest to palaeobotanical investigators.
On the coast of Essex, Suffolk, Norfolk, the south of Cornwall, and other
districts there occur beds of shelly sand and gravel long known under the
name of ‘Crag.’ The beds have a very modern aspect; the sands have not
been converted into sandstones, and the shells have undergone but little
change. These materials were for the most part accumulated on the bed of a
shallow sea which swept over a portion of East Anglia in Pliocene times. In
the sediments of this age northern forms of shells and other organisms make
their appearance, and in the Cromer forest-bed there occur portions of
drifted trees with sands, clays and gravels, representing in all probability the
débris thrown down on the banks of an ancient river. At this time the greater
part of the North Sea was probably a low-lying forest-covered region,
through which flowed the waters of a large river, of which part still exists in
the modern Rhine. The lowering of temperature which became distinctly
pronounced in the Pliocene age, continued until the greater part of Britain
generally adopted. In 1854 Prof. Beyrich proposed to include another
subdivision in the Tertiary system, and to this he gave the name Oligocene.
Occupying a basin-shaped area around London and Paris there are beds
of Eocene sands and clays which were originally deposited as continuous
sheets of sediment in water at first salt, afterwards brackish and to a certain
extent fresh. In the Hampshire cliffs and in some parts of the Isle of Wight,
we have other patches of these oldest Tertiary sediments. Across the south
of Europe, North Africa, Arabia, Persia, the Himalayas, to Java and the
Philippine islands, there existed in early Tertiary times a wide sea
connecting the Atlantic and Pacific oceans; and it may be that in the
Mediterranean of to-day we have a remnant of this large Eocene ocean.
Later in the Tertiary period a similar series of beds was deposited which we
now refer to as the Oligocene strata; such occurs in the cliffs of Headon hill
in the Isle of Wight, containing bones of crocodiles, and turtles, with the
relics of a rich flora preserved in the delta deposits of an Oligocene river. At
a still later stage the British area was probably dry land, and an open sea
existed over the Mediterranean region. In the neighbourhood of Vienna we
have beds of this age represented by a succession of sediments, at first
marine and afterwards freshwater. Miocene beds occur over a considerable
area in Switzerland and the Arctic regions, and they have yielded a rich
harvest to palaeobotanical investigators.
On the coast of Essex, Suffolk, Norfolk, the south of Cornwall, and other
districts there occur beds of shelly sand and gravel long known under the
name of ‘Crag.’ The beds have a very modern aspect; the sands have not
been converted into sandstones, and the shells have undergone but little
change. These materials were for the most part accumulated on the bed of a
shallow sea which swept over a portion of East Anglia in Pliocene times. In
the sediments of this age northern forms of shells and other organisms make
their appearance, and in the Cromer forest-bed there occur portions of
drifted trees with sands, clays and gravels, representing in all probability the
débris thrown down on the banks of an ancient river. At this time the greater
part of the North Sea was probably a low-lying forest-covered region,
through which flowed the waters of a large river, of which part still exists in
the modern Rhine. The lowering of temperature which became distinctly
pronounced in the Pliocene age, continued until the greater part of Britain
Page 78
and north Europe experienced a glacial period, and such conditions
obtained as we find to-day in ice-covered Greenland. Finally the ice-sheet
melted, the local glaciers of North Wales, the English Lake district and
other hilly regions, retreated, and after repeated alterations in level, the land
of Great Britain assumed its modern form. The submerged forests and peat
beds familiar in many parts of the coast, the diatomaceous deposits of dried
up lakes, “remain as the very finger touches of the last geological change.”
GEOLOGICAL EVOLUTION.
The agents of change and geological evolution, which we have passed in
brief review, are still constantly at work carrying one step further the history
of the earth. A superficial review of geological history gives us an
impression of recurring and widespread convulsions, and rapidly effected
revolutions in organic life and geographical conditions; on the other hand a
closer comparison of the past and present, with due allowance for the
enormous period of time represented by the records of the rocks, helps us to
realise the continuity of geological evolution. “So that within the whole of
the immense period indicated by the fossiliferous stratified rocks, there is
assuredly not the slightest proof of any break in the uniformity of Nature’s
operations, no indication that events have followed other than a clear and
orderly sequence[64].”
obtained as we find to-day in ice-covered Greenland. Finally the ice-sheet
melted, the local glaciers of North Wales, the English Lake district and
other hilly regions, retreated, and after repeated alterations in level, the land
of Great Britain assumed its modern form. The submerged forests and peat
beds familiar in many parts of the coast, the diatomaceous deposits of dried
up lakes, “remain as the very finger touches of the last geological change.”
GEOLOGICAL EVOLUTION.
The agents of change and geological evolution, which we have passed in
brief review, are still constantly at work carrying one step further the history
of the earth. A superficial review of geological history gives us an
impression of recurring and widespread convulsions, and rapidly effected
revolutions in organic life and geographical conditions; on the other hand a
closer comparison of the past and present, with due allowance for the
enormous period of time represented by the records of the rocks, helps us to
realise the continuity of geological evolution. “So that within the whole of
the immense period indicated by the fossiliferous stratified rocks, there is
assuredly not the slightest proof of any break in the uniformity of Nature’s
operations, no indication that events have followed other than a clear and
orderly sequence[64].”
Page 79
Page 80
CHAPTER IV.
THE PRESERVATION OF PLANTS AS FOSSILS.
“The things, we know, are neither rich nor rare,
But wonder how the devil they got there.”
Pope, Prologue to the Satires.
The discovery of a fossil, whether as an impression on the surface of a
slab of rock or as a piece of petrified wood, naturally leads us back to the
living plant, and invites speculation as to the circumstances which led to the
preservation of the plant fragment. There is a certain fascination in
endeavouring, with more or less success, to picture the exact conditions
which obtained when the leaf or stem was carried along by running water
and finally sealed up in a sedimentary matrix. Attempts to answer the
question—How came the plant remains to be preserved as fossils?—are not
merely of abstract interest appealing to the imagination, but are of
considerable importance in the correct interpretation of the facts which are
to be gleaned from the records of plant-bearing strata.
Before describing any specific examples of the commoner methods of
fossilisation; we shall do well to briefly consider how plants are now
supplying material for the fossils of a future age. In the great majority of
cases, an appreciation of the conditions of sedimentation, and of the varied
circumstances attending the transport and accumulation of vegetable débris,
supplies the solution of a problem akin to that of the fly in amber and the
manner in which it came there.
OLD SURFACE-SOILS.
Seeing that the greater part of the sedimentary strata have been formed in
the sea, and as the sea rather than the land has been for the most part the
scene of rock-building in the past, it is not surprising that fossil plants are
far less numerous than fossil animals. With the exception of the algae and a
few representatives of other classes of plants, which live in the shallow-
water belt round the coast, or in inland lakes and seas, plants are confined to
land-surfaces; and unless their remains are swept along by streams and
THE PRESERVATION OF PLANTS AS FOSSILS.
“The things, we know, are neither rich nor rare,
But wonder how the devil they got there.”
Pope, Prologue to the Satires.
The discovery of a fossil, whether as an impression on the surface of a
slab of rock or as a piece of petrified wood, naturally leads us back to the
living plant, and invites speculation as to the circumstances which led to the
preservation of the plant fragment. There is a certain fascination in
endeavouring, with more or less success, to picture the exact conditions
which obtained when the leaf or stem was carried along by running water
and finally sealed up in a sedimentary matrix. Attempts to answer the
question—How came the plant remains to be preserved as fossils?—are not
merely of abstract interest appealing to the imagination, but are of
considerable importance in the correct interpretation of the facts which are
to be gleaned from the records of plant-bearing strata.
Before describing any specific examples of the commoner methods of
fossilisation; we shall do well to briefly consider how plants are now
supplying material for the fossils of a future age. In the great majority of
cases, an appreciation of the conditions of sedimentation, and of the varied
circumstances attending the transport and accumulation of vegetable débris,
supplies the solution of a problem akin to that of the fly in amber and the
manner in which it came there.
OLD SURFACE-SOILS.
Seeing that the greater part of the sedimentary strata have been formed in
the sea, and as the sea rather than the land has been for the most part the
scene of rock-building in the past, it is not surprising that fossil plants are
far less numerous than fossil animals. With the exception of the algae and a
few representatives of other classes of plants, which live in the shallow-
water belt round the coast, or in inland lakes and seas, plants are confined to
land-surfaces; and unless their remains are swept along by streams and
Page 81
embedded in sediments which are accumulating on the sea floor, the chance
of their preservation is but small. The strata richest in fossil plants are often
those which have been laid down on the floor of an inland lake or spread
out as river-borne sediment under the waters of an estuary. Unlike the hard
endo- and exo-skeletons of animals, the majority of plants are composed of
comparatively soft material, and are less likely to be preserved or to retain
their original form when exposed to the wear and tear which must often
accompany the process of fossilisation.
The Coal-Measure rocks have furnished numberless relics of a
Palaeozoic vegetation, and these occur in various forms of preservation in
rocks laid down in shallow water on the edge of a forest-covered land. The
underclays or unstratified argillaceous beds which nearly always underlie
each seam of coal have often been described as old surface-soils, containing
numerous remains of roots and creeping underground stems of forest trees.
The overlying coal has been regarded as a mass of the carbonised and
compressed débris of luxuriant forests which grew on the actual spot now
occupied by the beds of coal. There are, however, many arguments in
favour of regarding the coal seams as beds of altered vegetable material
which was spread out on the floor of a lagoon or lake, while the underclay
was an old soil covered by shallow water or possibly a swampy surface
tenanted by marsh-loving plants[65].
The Jurassic beds of the Yorkshire Coast, long famous as some of the
richest plant-bearing strata in Britain, and the Wealden rocks of the south
coast afford examples of Mesozoic sediments which were laid down on the
floor of an estuary or large lake. Circumstances have occasionally rendered
possible the preservation of old land-surfaces with the stumps of trees still
in their position of growth. One of the best examples of this in Britain are
the so-called dirt-beds or black bands of Portland and the Dorset Coast. On
the cliffs immediately east of Lulworth Cove, the surface of a ledge of
Purbeck limestone which juts out near the top of the cliffs, is seen to have
the form here and there of rounded projecting bosses or ‘Burrs’ several feet
in diameter. In the centre of each boss there is either an empty depression,
or the remnants of a silicified stem of a coniferous tree. Blocks of limestone
3 to 5 feet long and of about equal thickness may be found lying on the
rocky ledge presenting the appearance of massive sarcophagi in which the
central trough still contains the silicified remains of an entombed tree. The
of their preservation is but small. The strata richest in fossil plants are often
those which have been laid down on the floor of an inland lake or spread
out as river-borne sediment under the waters of an estuary. Unlike the hard
endo- and exo-skeletons of animals, the majority of plants are composed of
comparatively soft material, and are less likely to be preserved or to retain
their original form when exposed to the wear and tear which must often
accompany the process of fossilisation.
The Coal-Measure rocks have furnished numberless relics of a
Palaeozoic vegetation, and these occur in various forms of preservation in
rocks laid down in shallow water on the edge of a forest-covered land. The
underclays or unstratified argillaceous beds which nearly always underlie
each seam of coal have often been described as old surface-soils, containing
numerous remains of roots and creeping underground stems of forest trees.
The overlying coal has been regarded as a mass of the carbonised and
compressed débris of luxuriant forests which grew on the actual spot now
occupied by the beds of coal. There are, however, many arguments in
favour of regarding the coal seams as beds of altered vegetable material
which was spread out on the floor of a lagoon or lake, while the underclay
was an old soil covered by shallow water or possibly a swampy surface
tenanted by marsh-loving plants[65].
The Jurassic beds of the Yorkshire Coast, long famous as some of the
richest plant-bearing strata in Britain, and the Wealden rocks of the south
coast afford examples of Mesozoic sediments which were laid down on the
floor of an estuary or large lake. Circumstances have occasionally rendered
possible the preservation of old land-surfaces with the stumps of trees still
in their position of growth. One of the best examples of this in Britain are
the so-called dirt-beds or black bands of Portland and the Dorset Coast. On
the cliffs immediately east of Lulworth Cove, the surface of a ledge of
Purbeck limestone which juts out near the top of the cliffs, is seen to have
the form here and there of rounded projecting bosses or ‘Burrs’ several feet
in diameter. In the centre of each boss there is either an empty depression,
or the remnants of a silicified stem of a coniferous tree. Blocks of limestone
3 to 5 feet long and of about equal thickness may be found lying on the
rocky ledge presenting the appearance of massive sarcophagi in which the
central trough still contains the silicified remains of an entombed tree. The
Page 82
calcareous sediment no doubt oozed up to envelope the thick stem as it sank
into the soft mud. An examination of the rock just below the bed bearing
these curious circular elevations reveals the existence of a comparatively
narrow band of softer material, which has been worn away by denuding
agents more rapidly than the overlying limestone. This band consists of
partially rounded or subangular stones associated with carbonaceous
material, and probably marks the site of an old surface-soil. This old soil is
well shown in the cliffs and quarries of Portland, and similar dirt-beds occur
at various horizons in the Lower and Middle Purbeck Series[66]. In this case,
then, we have intercalated in a series of limestone beds containing marine
and freshwater shells two or three plant beds containing numerous and
frequently large specimens of cycadean and coniferous stems, lying
horizontally or standing in their original position of growth. These are
vestiges of an ancient forest which spread over a considerable extent of
country towards the close of the Jurassic period. The trunks of cycads, long
familiar in the Isle of Portland as fossil crows’ nests, have usually the form
of round depressed stems with the central portion somewhat hollowed out.
It was supposed by the quarrymen that they were petrified birds’ nests
which had been built in the forks of the trees which grew in the Portland
forest. The beds separating the surface-soils of the Purbeck Series, as seen
in the sections exposed on the cliffs or quarries, point to the subsidence of a
forest-covered area over which beds of water-borne sediment were
gradually deposited, until in time the area became dry land and was again
taken possession of by a subtropical vegetation, to be once more depressed
and sealed up under layers of sediment[67].
A still more striking example of the preservation of forest trees rooted in
an old surface-soil is afforded by the so-called fossil-grove in Victoria Park,
Glasgow, (Frontispiece). The stumps of several trees, varying in diameter
from about one to three feet, are fixed by long forking ‘roots’ in a bed of
shale. In some cases the spreading ‘roots,’ which bear the surface features
of Stigmaria, extend for a distance of more than ten feet from the base of
the trunk. The stem surface is marked by irregular wrinklings which suggest
a fissured bark; but the superficial characters are very imperfectly
preserved. In one place a flattened Lepidodendron stem, about 30 feet long,
lies prone on the shale. Each of the rooted stumps is oval or elliptical in
section, and the long axes of the several stems are approximately parallel,
pointing to some cause operating in a definite direction which gave to the
into the soft mud. An examination of the rock just below the bed bearing
these curious circular elevations reveals the existence of a comparatively
narrow band of softer material, which has been worn away by denuding
agents more rapidly than the overlying limestone. This band consists of
partially rounded or subangular stones associated with carbonaceous
material, and probably marks the site of an old surface-soil. This old soil is
well shown in the cliffs and quarries of Portland, and similar dirt-beds occur
at various horizons in the Lower and Middle Purbeck Series[66]. In this case,
then, we have intercalated in a series of limestone beds containing marine
and freshwater shells two or three plant beds containing numerous and
frequently large specimens of cycadean and coniferous stems, lying
horizontally or standing in their original position of growth. These are
vestiges of an ancient forest which spread over a considerable extent of
country towards the close of the Jurassic period. The trunks of cycads, long
familiar in the Isle of Portland as fossil crows’ nests, have usually the form
of round depressed stems with the central portion somewhat hollowed out.
It was supposed by the quarrymen that they were petrified birds’ nests
which had been built in the forks of the trees which grew in the Portland
forest. The beds separating the surface-soils of the Purbeck Series, as seen
in the sections exposed on the cliffs or quarries, point to the subsidence of a
forest-covered area over which beds of water-borne sediment were
gradually deposited, until in time the area became dry land and was again
taken possession of by a subtropical vegetation, to be once more depressed
and sealed up under layers of sediment[67].
A still more striking example of the preservation of forest trees rooted in
an old surface-soil is afforded by the so-called fossil-grove in Victoria Park,
Glasgow, (Frontispiece). The stumps of several trees, varying in diameter
from about one to three feet, are fixed by long forking ‘roots’ in a bed of
shale. In some cases the spreading ‘roots,’ which bear the surface features
of Stigmaria, extend for a distance of more than ten feet from the base of
the trunk. The stem surface is marked by irregular wrinklings which suggest
a fissured bark; but the superficial characters are very imperfectly
preserved. In one place a flattened Lepidodendron stem, about 30 feet long,
lies prone on the shale. Each of the rooted stumps is oval or elliptical in
section, and the long axes of the several stems are approximately parallel,
pointing to some cause operating in a definite direction which gave to the
Page 83
stems their present form. Near one of the trees, and at a somewhat higher
level than its base, the surface of the rock is clearly ripple-marked, and
takes us back to the time when the sinking forest trees were washed by
waves which left an impress in the soft mud laid down over the submerged
area. The stumps appear to be those of Lepidodendron trees, rooted in
Lower Carboniferous rocks. From their manner of occurrence it would
seem that we have in them a corner of a Palaeozoic forest in which
Lepidodendra played a conspicuous part. The shales and sandstones
containing the fossil trees were originally overlain by a bed of igneous rock
which had been forced up as a sheet of lava into the hardened sands and
clays[68].
Other examples of old surface-soils occur in different parts of the world
and in rocks of various ages. As an instance of a land surface preserved in a
different manner, reference may be made to the thin bands of reddish or
brown material as well as clays and shale which occasionally occur between
the sheets of Tertiary lava in the Western Isles of Scotland and the north-
east of Ireland. In the intervals between successive outpourings of basaltic
lava in the north-west of Europe during the early part of the Tertiary period,
the heated rocks became gradually cooler, and under the influence of
weathering agents a surface-soil was produced fit for the growth of plants.
In some places, too, shallow lakes were formed, and leaves, fruits and twigs
became embedded in lacustrine sediments, to be afterwards sealed up by
later streams of lava. In the face of the cliff at Ardtun Head on the coast of
Mull a leaf-bed is exposed between two masses of gravel underlying a
basaltic lava flow; the impressions of the leaves of Gingko and other plants
from the Tertiary sediments of this district are exceptionally beautiful and
well preserved[69]. A large collection obtained by Mr Starkie Gardner may
be seen in the British Museum.
In 1883 the Malayan island of Krakatoa, 20 miles from Sumatra and
Java, was the scene of an exceptionally violent volcanic explosion. Two-
thirds of the island were blown away, and the remnant was left absolutely
bare of organic life. In 1886 it was found that several plants had already
established themselves on the hardened and weathered crust of the
Krakatoan rocks, the surface of the lavas having been to a large extent
prepared for the growth of the higher plants by the action of certain blue-
green algae which represent some of the lowest types of plant life[70]. We
level than its base, the surface of the rock is clearly ripple-marked, and
takes us back to the time when the sinking forest trees were washed by
waves which left an impress in the soft mud laid down over the submerged
area. The stumps appear to be those of Lepidodendron trees, rooted in
Lower Carboniferous rocks. From their manner of occurrence it would
seem that we have in them a corner of a Palaeozoic forest in which
Lepidodendra played a conspicuous part. The shales and sandstones
containing the fossil trees were originally overlain by a bed of igneous rock
which had been forced up as a sheet of lava into the hardened sands and
clays[68].
Other examples of old surface-soils occur in different parts of the world
and in rocks of various ages. As an instance of a land surface preserved in a
different manner, reference may be made to the thin bands of reddish or
brown material as well as clays and shale which occasionally occur between
the sheets of Tertiary lava in the Western Isles of Scotland and the north-
east of Ireland. In the intervals between successive outpourings of basaltic
lava in the north-west of Europe during the early part of the Tertiary period,
the heated rocks became gradually cooler, and under the influence of
weathering agents a surface-soil was produced fit for the growth of plants.
In some places, too, shallow lakes were formed, and leaves, fruits and twigs
became embedded in lacustrine sediments, to be afterwards sealed up by
later streams of lava. In the face of the cliff at Ardtun Head on the coast of
Mull a leaf-bed is exposed between two masses of gravel underlying a
basaltic lava flow; the impressions of the leaves of Gingko and other plants
from the Tertiary sediments of this district are exceptionally beautiful and
well preserved[69]. A large collection obtained by Mr Starkie Gardner may
be seen in the British Museum.
In 1883 the Malayan island of Krakatoa, 20 miles from Sumatra and
Java, was the scene of an exceptionally violent volcanic explosion. Two-
thirds of the island were blown away, and the remnant was left absolutely
bare of organic life. In 1886 it was found that several plants had already
established themselves on the hardened and weathered crust of the
Krakatoan rocks, the surface of the lavas having been to a large extent
prepared for the growth of the higher plants by the action of certain blue-
green algae which represent some of the lowest types of plant life[70]. We
Page 84
may perhaps assume a somewhat similar state of things to have existed in
the volcanic area in north-west Europe, where the intervals between
successive outpourings of lava are represented by the thin bands of leaf-
beds and old surface-soils.
On the Cheshire Coast at Leasowe[71] and other localities, there is
exposed at low water a tract of black peaty ground studded with old rooted
stumps of conifers and other trees (fig. 6). There is little reason to doubt that
at all events the majority of the trees are in their natural place of growth.
The peaty soil on which they rest contains numerous flattened stems of
reeds and other plants, and is penetrated by roots, probably of some aquatic
or marshy plants which spread over the site of the forest as it became
gradually submerged. A lower forest-bed rests directly on a foundation of
boulder clay. Such submerged forests are by no means uncommon around
the British coast; many of them belong to a comparatively recent period,
posterior to the glacial age. In many cases, however, the tree stumps have
been drifted from the places where they grew and eventually deposited in
their natural position, the roots of the trees, in some cases aided by stones
entangled in their branches, being heavier than the stem portion. There is a
promising field for botanical investigation in the careful analysis of the
floras of submerged forests; the work of Clement Reid, Nathorst, Andersson
and others, serves to illustrate the value of such research in the hands of
competent students.
the volcanic area in north-west Europe, where the intervals between
successive outpourings of lava are represented by the thin bands of leaf-
beds and old surface-soils.
On the Cheshire Coast at Leasowe[71] and other localities, there is
exposed at low water a tract of black peaty ground studded with old rooted
stumps of conifers and other trees (fig. 6). There is little reason to doubt that
at all events the majority of the trees are in their natural place of growth.
The peaty soil on which they rest contains numerous flattened stems of
reeds and other plants, and is penetrated by roots, probably of some aquatic
or marshy plants which spread over the site of the forest as it became
gradually submerged. A lower forest-bed rests directly on a foundation of
boulder clay. Such submerged forests are by no means uncommon around
the British coast; many of them belong to a comparatively recent period,
posterior to the glacial age. In many cases, however, the tree stumps have
been drifted from the places where they grew and eventually deposited in
their natural position, the roots of the trees, in some cases aided by stones
entangled in their branches, being heavier than the stem portion. There is a
promising field for botanical investigation in the careful analysis of the
floras of submerged forests; the work of Clement Reid, Nathorst, Andersson
and others, serves to illustrate the value of such research in the hands of
competent students.
Page 85
Fig. 6. Part of a submerged Forest seen at low water on the Cheshire Coast at Leasowe.
Drawn from a photograph.
The following description by Lyell, taken from his American travels, is of
interest as affording an example of the preservation of a surface-soil:
“On our way home from Charleston, by the railway from Orangeburg, I observed a thin black
line of charred vegetable matter exposed in the perpendicular section of the bank. The sand cast
out in digging the railway had been thrown up on the original soil, on which the pine forest grew;
and farther excavations had laid open the junction of the rubbish and the soil. As geologists, we
may learn from this fact how a thin seam of vegetable matter, an inch or two thick, is often the
only monument to be looked for of an ancient surface of dry land, on which a luxuriant forest
may have grown for thousands of years. Even this seam of friable matter may be washed away
when the region is submerged, and, if not, rain water percolating freely through the sand may, in
the course of ages, gradually carry away the carbon[72].”
FOSSIL WOOD.
In addition to the remnants of ancient soils, and the preservation of plant
fragments in rocks which have been formed on the floor of an inland lake or
an estuary, it is by no means rare to find fossil plants in obviously marine
sediments. In fig. 7 we have a piece of coniferous wood with the shell of an
Ammonite (Aegoceras planicosta Sow.) lying on it; the specimen was
found in the Lower Lias clay at Lyme Regis, and illustrates the accidental
association of a drifted piece of a forest tree with a shell which marks at
once the age and the marine character of the beds. Again in fig. 8 we have a
block of flint partially enclosing a piece of coniferous wood in which the
internal structure has been clearly preserved in silica. This specimen was
found in the chalk, a deposit laid down in the clear and deep water of the
Drawn from a photograph.
The following description by Lyell, taken from his American travels, is of
interest as affording an example of the preservation of a surface-soil:
“On our way home from Charleston, by the railway from Orangeburg, I observed a thin black
line of charred vegetable matter exposed in the perpendicular section of the bank. The sand cast
out in digging the railway had been thrown up on the original soil, on which the pine forest grew;
and farther excavations had laid open the junction of the rubbish and the soil. As geologists, we
may learn from this fact how a thin seam of vegetable matter, an inch or two thick, is often the
only monument to be looked for of an ancient surface of dry land, on which a luxuriant forest
may have grown for thousands of years. Even this seam of friable matter may be washed away
when the region is submerged, and, if not, rain water percolating freely through the sand may, in
the course of ages, gradually carry away the carbon[72].”
FOSSIL WOOD.
In addition to the remnants of ancient soils, and the preservation of plant
fragments in rocks which have been formed on the floor of an inland lake or
an estuary, it is by no means rare to find fossil plants in obviously marine
sediments. In fig. 7 we have a piece of coniferous wood with the shell of an
Ammonite (Aegoceras planicosta Sow.) lying on it; the specimen was
found in the Lower Lias clay at Lyme Regis, and illustrates the accidental
association of a drifted piece of a forest tree with a shell which marks at
once the age and the marine character of the beds. Again in fig. 8 we have a
block of flint partially enclosing a piece of coniferous wood in which the
internal structure has been clearly preserved in silica. This specimen was
found in the chalk, a deposit laid down in the clear and deep water of the
Page 86
Cretaceous sea. The wood must have floated for some time before it
became water-logged and sank to the sea-floor. In the light coloured wood
there occur here and there dark spots which mark the position of siliceous
plugs b, b filling up clean cut holes bored by Teredos in the woody tissue.
The wood became at last enclosed by siliceous sediment and its tissues
penetrated by silica in solution, which gradually replaced and preserved in
wonderful perfection the form of the original tissue. A similar instance of
wood enclosed in flint was figured by Mantell in 1844 in his Medals of
Creation[73].
Fig. 7. Aegoceras planicosta Sow. on a piece of coniferous wood, Lower Lias, Lyme Regis.
From a specimen in the British Museum. Slightly reduced.
became water-logged and sank to the sea-floor. In the light coloured wood
there occur here and there dark spots which mark the position of siliceous
plugs b, b filling up clean cut holes bored by Teredos in the woody tissue.
The wood became at last enclosed by siliceous sediment and its tissues
penetrated by silica in solution, which gradually replaced and preserved in
wonderful perfection the form of the original tissue. A similar instance of
wood enclosed in flint was figured by Mantell in 1844 in his Medals of
Creation[73].
Fig. 7. Aegoceras planicosta Sow. on a piece of coniferous wood, Lower Lias, Lyme Regis.
From a specimen in the British Museum. Slightly reduced.
Page 87
Fig. 8. Piece of coniferous wood in flint, from the Chalk, Croydon. Drawn from a specimen
presented to the British Museum by Mr Murton Holmes. In the side view, shown above
in the figure, the position of the wood is shown by the lighter portion, with holes, b, b,
bored by Teredos or some other wood-eating animal. In the end view, below, the wood is
seen as an irregular cylinder w, w, embedded in a matrix of flint. ⅓ Nat. size.
The specimen represented in fig. 9 illustrates the almost complete
destruction of a piece of wood by some boring animal. The circular and
oval dotted patches represent the filled up cavities made by a Teredo or
some similar wood-boring animal.
Fig. 9. Piece of wood from the Red Crag of Suffolk, riddled with holes filled in with mud.
From a specimen in the York Museum. ⅓ Nat. size.
CONDITIONS OF FOSSILISATION.
presented to the British Museum by Mr Murton Holmes. In the side view, shown above
in the figure, the position of the wood is shown by the lighter portion, with holes, b, b,
bored by Teredos or some other wood-eating animal. In the end view, below, the wood is
seen as an irregular cylinder w, w, embedded in a matrix of flint. ⅓ Nat. size.
The specimen represented in fig. 9 illustrates the almost complete
destruction of a piece of wood by some boring animal. The circular and
oval dotted patches represent the filled up cavities made by a Teredo or
some similar wood-boring animal.
Fig. 9. Piece of wood from the Red Crag of Suffolk, riddled with holes filled in with mud.
From a specimen in the York Museum. ⅓ Nat. size.
CONDITIONS OF FOSSILISATION.
Page 88
Before discussing a few more examples of fossils illustrating different
methods of fossilisation, it may not be out of place to quote a few extracts
from travellers’ narratives which enable us to realise more readily the
circumstances and conditions under which plant remains have been
preserved in the Earth’s crust.
In an account of a journey down the Rawas river in Sumatra, Forbes thus
describes the flooded country:—
“The whole surface of the water was covered, absolutely in a close sheet, with petals, fruits
and leaves, of innumerable species. In placid corners sometimes I noted a collected mass nearly
half a foot deep, among which, on examination, I could scarcely find a leaf that was perfect, or
that remained attached to its rightful neighbour, so that were they to become imbedded in some
soft muddy spot, and in after ages to reappear in a fossil form they would afford a few difficult
puzzles to the palaeontologist, both to separate and to put together[74].”
An interesting example of the mixture of plants and animals in
sedimentary deposits is described by Hooker in his Himalayan Journals:—
“To the geologist the Jheels and Sunderbunds are a most instructive region, as whatever may
be the mean elevation of their waters, a permanent depression of ten to fifteen feet would
submerge an immense tract, which the Ganges, Burrampooter, and Soormah would soon cover
with beds of silt and sand.
“There would be extremely few shells in the beds thus formed, the southern and northern
divisions of which would present two very different floras and faunas, and would in all
probability be referred by future geologists to widely different epochs. To the north, beds of peat
would be formed by grasses, and in other parts temperate and tropical forms of plants and
animals would be preserved in such equally balanced proportions as to confound the
palaeontologist; with the bones of the long-snouted alligator, Gangetic porpoise, Indian cow,
buffalo, rhinoceros, elephant, tiger, deer, bear, and a host of other animals, he would meet with
acorns of several species of oak, pine-cones and magnolia fruits, rose seeds, and Cycas nuts, with
palm nuts, screw-pines, and other tropical productions[75].”
In another place the same author writes:
“On the 12th of January, 1848, the Moozuffer was steaming amongst the low, swampy islands
of the Sunderbunds.... Every now and then the paddles of the steamer tossed up the large fruits of
Nypa fruticans, Thunb., a low stemless palm that grows in the tidal waters of the Indian Ocean,
and bears a large head of nuts. It is a plant of no interest to the common observer, but of much to
the geologist, from the nuts of a similar plant abounding in the Tertiary formations at the mouth
of the Thames, having floated about there in as great profusion as here, till buried deep in the silt
and mud that now forms the island of Sheppey[76].”
DRIFTING OF TREES.
Of the drifting of timber, fruits, &c., we find numerous accounts in the
writings of travellers. Rodway thus describes the formation of vegetable
methods of fossilisation, it may not be out of place to quote a few extracts
from travellers’ narratives which enable us to realise more readily the
circumstances and conditions under which plant remains have been
preserved in the Earth’s crust.
In an account of a journey down the Rawas river in Sumatra, Forbes thus
describes the flooded country:—
“The whole surface of the water was covered, absolutely in a close sheet, with petals, fruits
and leaves, of innumerable species. In placid corners sometimes I noted a collected mass nearly
half a foot deep, among which, on examination, I could scarcely find a leaf that was perfect, or
that remained attached to its rightful neighbour, so that were they to become imbedded in some
soft muddy spot, and in after ages to reappear in a fossil form they would afford a few difficult
puzzles to the palaeontologist, both to separate and to put together[74].”
An interesting example of the mixture of plants and animals in
sedimentary deposits is described by Hooker in his Himalayan Journals:—
“To the geologist the Jheels and Sunderbunds are a most instructive region, as whatever may
be the mean elevation of their waters, a permanent depression of ten to fifteen feet would
submerge an immense tract, which the Ganges, Burrampooter, and Soormah would soon cover
with beds of silt and sand.
“There would be extremely few shells in the beds thus formed, the southern and northern
divisions of which would present two very different floras and faunas, and would in all
probability be referred by future geologists to widely different epochs. To the north, beds of peat
would be formed by grasses, and in other parts temperate and tropical forms of plants and
animals would be preserved in such equally balanced proportions as to confound the
palaeontologist; with the bones of the long-snouted alligator, Gangetic porpoise, Indian cow,
buffalo, rhinoceros, elephant, tiger, deer, bear, and a host of other animals, he would meet with
acorns of several species of oak, pine-cones and magnolia fruits, rose seeds, and Cycas nuts, with
palm nuts, screw-pines, and other tropical productions[75].”
In another place the same author writes:
“On the 12th of January, 1848, the Moozuffer was steaming amongst the low, swampy islands
of the Sunderbunds.... Every now and then the paddles of the steamer tossed up the large fruits of
Nypa fruticans, Thunb., a low stemless palm that grows in the tidal waters of the Indian Ocean,
and bears a large head of nuts. It is a plant of no interest to the common observer, but of much to
the geologist, from the nuts of a similar plant abounding in the Tertiary formations at the mouth
of the Thames, having floated about there in as great profusion as here, till buried deep in the silt
and mud that now forms the island of Sheppey[76].”
DRIFTING OF TREES.
Of the drifting of timber, fruits, &c., we find numerous accounts in the
writings of travellers. Rodway thus describes the formation of vegetable
Page 89
rafts in the rivers of Northern British Guiana:—
“Sometimes a great tree, whose timber is light enough to float, gets entangled in the grass, and
becomes the nucleus of an immense raft, which is continually increasing in size as it gathers up
everything that comes floating down the river[77].”
The undermining of river banks in times of flood, and the transport of the
drifted trees to be eventually deposited in the delta is a familiar occurrence
in many parts of the world. The more striking instances of such wholesale
carrying along of trees are supplied by Bates, Lyell and other writers. In his
description of the Amazon the former writes:
“The currents ran with great force close to the bank, especially when these receded to form
long bays or enseadas, as they are called, and then we made very little headway. In such places
the banks consist of loose earth, a rich crumbling vegetable mould, supporting a growth of most
luxuriant forest, of which the currents almost daily carry away large portions, so that the stream
for several yards out is encumbered with fallen trees, whose branches quiver in the current[78].”
In another place, Bates writes:
“The rainy season had now set in over the region through which the great river flows; the
sand-banks and all the lower lands were already under water, and the tearing current, two or three
miles in breadth, bore along a continuous line of uprooted trees and islets of floating plants[79].”
The rafts of the Mississippi and other rivers described by Lyell afford
instructive examples of the distant transport of vegetable material. The
following passage is taken from the Principles of Geology;
“Within the tropics there are no ice-floes; but, as if to compensate for that mode of
transportation, there are floating islets of matted trees, which are often borne along through
considerable spaces. These are sometimes seen sailing at the distance of fifty or one hundred
miles from the mouth of the Ganges, with living trees standing erect upon them. The Amazons,
the Orinoco, and the Congo also produce these verdant rafts[80].”
After describing the enormous natural rafts of the Atchafalaya, an arm of
the Mississippi, and of the Red river, Lyell goes on to say:
“The prodigious quantity of wood annually drifted down by the Mississippi and its tributaries
is a subject of geological interest, not merely as illustrating the manner in which abundance of
vegetable matter becomes, in the ordinary course of nature, imbedded in submarine and estuary
deposits, but as attesting the constant destruction of soil and transportation of matter to lower
levels by the tendency of rivers to shift their courses.... It is also found in excavating at New
Orleans, even at the depth of several yards below the level of the sea, that the soil of the delta
contains innumerable trunks of trees, layer above layer, some prostrate as if drifted, others broken
off near the bottom, but remaining still erect, and with their roots spreading on all sides, as if in
their natural position[81].”
“Sometimes a great tree, whose timber is light enough to float, gets entangled in the grass, and
becomes the nucleus of an immense raft, which is continually increasing in size as it gathers up
everything that comes floating down the river[77].”
The undermining of river banks in times of flood, and the transport of the
drifted trees to be eventually deposited in the delta is a familiar occurrence
in many parts of the world. The more striking instances of such wholesale
carrying along of trees are supplied by Bates, Lyell and other writers. In his
description of the Amazon the former writes:
“The currents ran with great force close to the bank, especially when these receded to form
long bays or enseadas, as they are called, and then we made very little headway. In such places
the banks consist of loose earth, a rich crumbling vegetable mould, supporting a growth of most
luxuriant forest, of which the currents almost daily carry away large portions, so that the stream
for several yards out is encumbered with fallen trees, whose branches quiver in the current[78].”
In another place, Bates writes:
“The rainy season had now set in over the region through which the great river flows; the
sand-banks and all the lower lands were already under water, and the tearing current, two or three
miles in breadth, bore along a continuous line of uprooted trees and islets of floating plants[79].”
The rafts of the Mississippi and other rivers described by Lyell afford
instructive examples of the distant transport of vegetable material. The
following passage is taken from the Principles of Geology;
“Within the tropics there are no ice-floes; but, as if to compensate for that mode of
transportation, there are floating islets of matted trees, which are often borne along through
considerable spaces. These are sometimes seen sailing at the distance of fifty or one hundred
miles from the mouth of the Ganges, with living trees standing erect upon them. The Amazons,
the Orinoco, and the Congo also produce these verdant rafts[80].”
After describing the enormous natural rafts of the Atchafalaya, an arm of
the Mississippi, and of the Red river, Lyell goes on to say:
“The prodigious quantity of wood annually drifted down by the Mississippi and its tributaries
is a subject of geological interest, not merely as illustrating the manner in which abundance of
vegetable matter becomes, in the ordinary course of nature, imbedded in submarine and estuary
deposits, but as attesting the constant destruction of soil and transportation of matter to lower
levels by the tendency of rivers to shift their courses.... It is also found in excavating at New
Orleans, even at the depth of several yards below the level of the sea, that the soil of the delta
contains innumerable trunks of trees, layer above layer, some prostrate as if drifted, others broken
off near the bottom, but remaining still erect, and with their roots spreading on all sides, as if in
their natural position[81].”
Page 90
The drifting of trees in the ocean is recorded by Darwin in his description
of Keeling Island, and their action as vehicles for the transport of boulders
is illustrated by the same account.
“In the channels of Tierra del Fuego large quantities of drift timber are cast upon the beach, yet
it is extremely rare to meet a tree swimming in the water. These facts may possibly throw light on
single stones, whether angular or rounded, occasionally found embedded in fine sedimentary
masses[82].”
Fruits may often be carried long distances from land, and preserved in
beds far from their original source. Whilst cruising amongst the Solomon
Islands, the Challenger met with fruits of Barringtonia speciosa &c., 130–
150 miles from the coast. Off the coast of New Guinea long lines of drift
wood were seen at right angles to the direction of the river; uprooted trees,
logs, branches, and bark, often floating separately.
“The midribs of the leaves of a pinnate-leaved palm were abundant, and also the stems of a
large cane grass (Saccharum), like that so abundant on the shores of the great river in Fiji.
Various fruits of trees and other fragments were abundant, usually floating confined in the midst
of the small aggregations into which the floating timber was everywhere gathered.... Leaves were
absent except those of the Palm, on the midrib of which some of the pinnæ were still present. The
leaves evidently drop first to the bottom, whilst vegetable drift is floating from a shore; thus, as
the débris sinks in the sea water, a deposit abounding in leaves, but with few fruits and little or no
wood, will be formed near shore, whilst the wood and fruits will sink to the bottom farther off the
land. Much of the wood was floating suspended vertically in the water, and most curiously, logs
and short branch pieces thus floating often occurred in separate groups apart from the
horizontally floating timber. The sunken ends of the wood were not weighted by any attached
masses of soil or other load of any kind; possibly the water penetrates certain kinds of wood
more easily in one direction with regard to its growth than the other, hence one end becomes
water-logged before the other.... The wood which had been longest in the water was bored by a
Pholas[83].”
The bearing of this account on the manner of preservation of fossils, and
the differential sorting so frequently seen in plant beds, is sufficiently
obvious.
As another instance of the great distance to which land plants may be
carried out to sea and finally buried in marine strata, an observation by
Bates may be cited. When 400 miles from the mouth of the main Amazons,
he writes:
“We passed numerous patches of floating grass mingled with tree trunks and withered foliage.
Amongst these masses I espied many fruits of that peculiar Amazonian tree the Ubussú Palm;
this was the last I saw of the great river[84].”
of Keeling Island, and their action as vehicles for the transport of boulders
is illustrated by the same account.
“In the channels of Tierra del Fuego large quantities of drift timber are cast upon the beach, yet
it is extremely rare to meet a tree swimming in the water. These facts may possibly throw light on
single stones, whether angular or rounded, occasionally found embedded in fine sedimentary
masses[82].”
Fruits may often be carried long distances from land, and preserved in
beds far from their original source. Whilst cruising amongst the Solomon
Islands, the Challenger met with fruits of Barringtonia speciosa &c., 130–
150 miles from the coast. Off the coast of New Guinea long lines of drift
wood were seen at right angles to the direction of the river; uprooted trees,
logs, branches, and bark, often floating separately.
“The midribs of the leaves of a pinnate-leaved palm were abundant, and also the stems of a
large cane grass (Saccharum), like that so abundant on the shores of the great river in Fiji.
Various fruits of trees and other fragments were abundant, usually floating confined in the midst
of the small aggregations into which the floating timber was everywhere gathered.... Leaves were
absent except those of the Palm, on the midrib of which some of the pinnæ were still present. The
leaves evidently drop first to the bottom, whilst vegetable drift is floating from a shore; thus, as
the débris sinks in the sea water, a deposit abounding in leaves, but with few fruits and little or no
wood, will be formed near shore, whilst the wood and fruits will sink to the bottom farther off the
land. Much of the wood was floating suspended vertically in the water, and most curiously, logs
and short branch pieces thus floating often occurred in separate groups apart from the
horizontally floating timber. The sunken ends of the wood were not weighted by any attached
masses of soil or other load of any kind; possibly the water penetrates certain kinds of wood
more easily in one direction with regard to its growth than the other, hence one end becomes
water-logged before the other.... The wood which had been longest in the water was bored by a
Pholas[83].”
The bearing of this account on the manner of preservation of fossils, and
the differential sorting so frequently seen in plant beds, is sufficiently
obvious.
As another instance of the great distance to which land plants may be
carried out to sea and finally buried in marine strata, an observation by
Bates may be cited. When 400 miles from the mouth of the main Amazons,
he writes:
“We passed numerous patches of floating grass mingled with tree trunks and withered foliage.
Amongst these masses I espied many fruits of that peculiar Amazonian tree the Ubussú Palm;
this was the last I saw of the great river[84].”
Page 91
The following additional extract from the narrative of the Cruise of
H.M.S. Challenger illustrates in a striking degree the conflicting evidence
which the contents of fossiliferous beds may occasionally afford; it
describes what was observed in an excursion from Sydney to Berowra
Creek, a branch of the main estuary or inlet into which flows the
Hawkesbury river. It was impossible to say where the river came to an end
and the sea began. The Creek is described as a long tortuous arm of the sea,
10 to 15 miles long, with the side walls covered with orchids and
Platycerium. The ferns and palms were abundant in the lateral shady glens;
marine and inland animals lived in close proximity.
“Here is a narrow strip of the sea water, twenty miles distant from the open sea; on a sandy
shallow flat close to its head are to be seen basking in the sun numbers of sting-rays.... All over
these flats, and throughout the whole stretch of the creek, shoals of Grey Mullet are to be met
with; numerous other marine fish inhabit the creek. Porpoises chase the mullet right up to the
commencement of the sand-flat. At the shores of the creek the rocks are covered with masses of
excellent oysters and mussel, and other shell-bearing molluscs are abundant, whilst a small crab
is to be found in numbers in every crevice. On the other hand the water is overhung by numerous
species of forest trees, by orchids and ferns, and other vegetation of all kinds; mangroves grow
only in the shallow bays. The gum trees lean over the water in which swim the Trygon and
mullet, just as willows hang over a pool of carp. The sandy bottom is full of branches and stems
of trees, and is covered in patches here and there by their leaves. Insects constantly fall in the
water, and are devoured by the mullet. Land birds of all kinds fly to and fro across the creek, and
when wounded may easily be drowned in it. Wallabies swim across occasionally, and may add
their bones to the débris at the bottom. Hence here is being formed a sandy deposit, in which may
be found cetacean, marsupial, bird, fish, and insect remains, together with land and sea shells,
and fragments of a vast land flora; yet how restricted is the area occupied by this deposit, and
how easily might surviving fragments of such a record be missed by future geological explorers!
[85]
”
MEANING OF THE TERM ‘FOSSIL.’
The term ‘fossil’ suggests to the lay mind a petrifaction or a replacement
by mineral matter of the plant tissues. In the scientific sense, a fossil plant,
that is a plant or part of a plant whether in the form of a true petrifaction or
a structureless mould or cast, which has been buried in the earth by natural
causes, may be indistinguishable from a piece of recent wood lately fallen
from the parent tree. In the geologically recent peat beds such little altered
fossils (or sub-fossils) are common enough, and even in older rocks the
more resistant parts of plant fragments are often found in a practically
unaltered state. In the leaf impressions on an impervious clay, the brown-
walled epidermis shows scarcely any indication of alteration since it was
deposited in the soft mud of a river’s delta. Such fossil leaves are common
H.M.S. Challenger illustrates in a striking degree the conflicting evidence
which the contents of fossiliferous beds may occasionally afford; it
describes what was observed in an excursion from Sydney to Berowra
Creek, a branch of the main estuary or inlet into which flows the
Hawkesbury river. It was impossible to say where the river came to an end
and the sea began. The Creek is described as a long tortuous arm of the sea,
10 to 15 miles long, with the side walls covered with orchids and
Platycerium. The ferns and palms were abundant in the lateral shady glens;
marine and inland animals lived in close proximity.
“Here is a narrow strip of the sea water, twenty miles distant from the open sea; on a sandy
shallow flat close to its head are to be seen basking in the sun numbers of sting-rays.... All over
these flats, and throughout the whole stretch of the creek, shoals of Grey Mullet are to be met
with; numerous other marine fish inhabit the creek. Porpoises chase the mullet right up to the
commencement of the sand-flat. At the shores of the creek the rocks are covered with masses of
excellent oysters and mussel, and other shell-bearing molluscs are abundant, whilst a small crab
is to be found in numbers in every crevice. On the other hand the water is overhung by numerous
species of forest trees, by orchids and ferns, and other vegetation of all kinds; mangroves grow
only in the shallow bays. The gum trees lean over the water in which swim the Trygon and
mullet, just as willows hang over a pool of carp. The sandy bottom is full of branches and stems
of trees, and is covered in patches here and there by their leaves. Insects constantly fall in the
water, and are devoured by the mullet. Land birds of all kinds fly to and fro across the creek, and
when wounded may easily be drowned in it. Wallabies swim across occasionally, and may add
their bones to the débris at the bottom. Hence here is being formed a sandy deposit, in which may
be found cetacean, marsupial, bird, fish, and insect remains, together with land and sea shells,
and fragments of a vast land flora; yet how restricted is the area occupied by this deposit, and
how easily might surviving fragments of such a record be missed by future geological explorers!
[85]
”
MEANING OF THE TERM ‘FOSSIL.’
The term ‘fossil’ suggests to the lay mind a petrifaction or a replacement
by mineral matter of the plant tissues. In the scientific sense, a fossil plant,
that is a plant or part of a plant whether in the form of a true petrifaction or
a structureless mould or cast, which has been buried in the earth by natural
causes, may be indistinguishable from a piece of recent wood lately fallen
from the parent tree. In the geologically recent peat beds such little altered
fossils (or sub-fossils) are common enough, and even in older rocks the
more resistant parts of plant fragments are often found in a practically
unaltered state. In the leaf impressions on an impervious clay, the brown-
walled epidermis shows scarcely any indication of alteration since it was
deposited in the soft mud of a river’s delta. Such fossil leaves are common
Page 92
in the English Tertiary beds, and even in Palaeozoic rocks it is not
uncommon to find an impression of a plant on a bed of shale from which
the thin brown epidermis may be peeled off the rock, and if microscopically
examined it will be found to have retained intact the contours of the
cuticularised epidermal cells. A striking example of a similar method of
preservation is afforded by the so-called paper-coal of Culm age from the
Province of Toula in Russia[86]. In the Russian area the Carboniferous or
Permian rocks have been subjected to little lateral pressure, and unlike the
beds of the same age in Western Europe, they have not been folded and
compressed by widespread and extensive crust-foldings. Instead of the hard
seams of coal there occur beds of a dark brown laminated material, made up
very largely of the cuticles of Lepidodendroid plants.
From such examples we may naturally pass to fossils in which the plant
structure has been converted into carbonaceous matter or even pure coal.
This form of preservation is especially common in plant-bearing beds at
various geological horizons. In other cases, again, some mineral solution,
oxide of iron, talc, and other substances, has replaced the plant tissues.
From the Coal-Measures of Switzerland Heer has figured numerous
specimens of fern fronds and other plants in which the leaf form has been
left on the dark coloured rock surface as a thin layer of white talcose
material[87]. In the Buntersandstone of the Vosges and other districts the red
imperfectly preserved impressions of plant stems and leaves are familiar
fossils[88]; the carbonaceous substance of the tissues has been replaced by a
brown or red oxide of iron.
INCRUSTATIONS.
Plants frequently occur in the form of incrustations; and in fact
incrustations, which may assume a variety of forms, are the commonest
kind of fossil. The action of incrusting springs, or as they are often termed
petrifying springs, is illustrated at Knaresborough, in Yorkshire, and many
other places where water highly charged with carbonate of lime readily
deposits calcium carbonate on objects placed in the path of the stream.
The travertine deposited in this manner forms an incrustation on plant
fragments, and if the vegetable substance is subsequently removed by the
action of water or decay, a mould of the embedded fragment is left in the
calcareous matrix. An instructive example of this form of preservation was
described in 1868[89] by Sharpe from an old gravel pit near Northampton.
uncommon to find an impression of a plant on a bed of shale from which
the thin brown epidermis may be peeled off the rock, and if microscopically
examined it will be found to have retained intact the contours of the
cuticularised epidermal cells. A striking example of a similar method of
preservation is afforded by the so-called paper-coal of Culm age from the
Province of Toula in Russia[86]. In the Russian area the Carboniferous or
Permian rocks have been subjected to little lateral pressure, and unlike the
beds of the same age in Western Europe, they have not been folded and
compressed by widespread and extensive crust-foldings. Instead of the hard
seams of coal there occur beds of a dark brown laminated material, made up
very largely of the cuticles of Lepidodendroid plants.
From such examples we may naturally pass to fossils in which the plant
structure has been converted into carbonaceous matter or even pure coal.
This form of preservation is especially common in plant-bearing beds at
various geological horizons. In other cases, again, some mineral solution,
oxide of iron, talc, and other substances, has replaced the plant tissues.
From the Coal-Measures of Switzerland Heer has figured numerous
specimens of fern fronds and other plants in which the leaf form has been
left on the dark coloured rock surface as a thin layer of white talcose
material[87]. In the Buntersandstone of the Vosges and other districts the red
imperfectly preserved impressions of plant stems and leaves are familiar
fossils[88]; the carbonaceous substance of the tissues has been replaced by a
brown or red oxide of iron.
INCRUSTATIONS.
Plants frequently occur in the form of incrustations; and in fact
incrustations, which may assume a variety of forms, are the commonest
kind of fossil. The action of incrusting springs, or as they are often termed
petrifying springs, is illustrated at Knaresborough, in Yorkshire, and many
other places where water highly charged with carbonate of lime readily
deposits calcium carbonate on objects placed in the path of the stream.
The travertine deposited in this manner forms an incrustation on plant
fragments, and if the vegetable substance is subsequently removed by the
action of water or decay, a mould of the embedded fragment is left in the
calcareous matrix. An instructive example of this form of preservation was
described in 1868[89] by Sharpe from an old gravel pit near Northampton.
Page 93
He found in a section eight feet high (fig. 10), a mass of incrusted plants of
Chara (a) resting on and overlain by a calcareous paste (c) and (d) made up
of the decomposed material of the overlying rock, and this again resting on
sand. The place where the section occurred was originally the site of a pool
in which Stoneworts grew in abundance. Large blocks of these incrusted
Charas may be seen in the fossil-plant gallery of the British Museum.
Fig. 10. Section of an old pool filled up with a mass of Chara. (From the Geol. Mag. vol. v.
1868, p. 563.)
In the Natural History Museum in the Jardin des Plantes, Paris, one of the
table-cases contains what appear to be small models of flowers in green
wax. These are in reality casts in wax of the moulds or cavities left in a
mass of calcareous travertine, on the decay and disappearance of the
encrusted flowers and other plant fragments[90]. This porous calcareous rock
occurs near Sézanne in Southern France, and is of Eocene age[91]. The plants
were probably blown on to the freshly deposited carbonate of lime, or they
may have simply fallen from the tree on to the incrusting matrix; more
material was afterwards deposited and the flowers were completely
enclosed. Eventually the plant substance decayed, and as the matrix
hardened moulds were left of the vegetable fragments. Wax was artificially
forced into these cavities and the surrounding substance removed by the
action of an acid, and thus perfect casts were obtained of Tertiary flowers.
Darwin has described the preservation of trees in Van Diemen’s land by
means of calcareous substances. In speaking of beds of blown sand
containing branches and roots of trees he says:
“The whole became consolidated by the percolation of calcareous matter; and the cylindrical
cavities left by the decaying of the wood were thus also filled up with a hard pseudo-stalactitical
stone. The weather is now wearing away the softer parts, and in consequence the hard casts of the
Chara (a) resting on and overlain by a calcareous paste (c) and (d) made up
of the decomposed material of the overlying rock, and this again resting on
sand. The place where the section occurred was originally the site of a pool
in which Stoneworts grew in abundance. Large blocks of these incrusted
Charas may be seen in the fossil-plant gallery of the British Museum.
Fig. 10. Section of an old pool filled up with a mass of Chara. (From the Geol. Mag. vol. v.
1868, p. 563.)
In the Natural History Museum in the Jardin des Plantes, Paris, one of the
table-cases contains what appear to be small models of flowers in green
wax. These are in reality casts in wax of the moulds or cavities left in a
mass of calcareous travertine, on the decay and disappearance of the
encrusted flowers and other plant fragments[90]. This porous calcareous rock
occurs near Sézanne in Southern France, and is of Eocene age[91]. The plants
were probably blown on to the freshly deposited carbonate of lime, or they
may have simply fallen from the tree on to the incrusting matrix; more
material was afterwards deposited and the flowers were completely
enclosed. Eventually the plant substance decayed, and as the matrix
hardened moulds were left of the vegetable fragments. Wax was artificially
forced into these cavities and the surrounding substance removed by the
action of an acid, and thus perfect casts were obtained of Tertiary flowers.
Darwin has described the preservation of trees in Van Diemen’s land by
means of calcareous substances. In speaking of beds of blown sand
containing branches and roots of trees he says:
“The whole became consolidated by the percolation of calcareous matter; and the cylindrical
cavities left by the decaying of the wood were thus also filled up with a hard pseudo-stalactitical
stone. The weather is now wearing away the softer parts, and in consequence the hard casts of the
Page 94
roots and branches of the trees project above the surface, and, in a singularly deceptive manner,
resemble the stumps of a dead thicket[92].”
As a somewhat analogous method of preservation to that in travertine,
the occurrence of plants in amber should be mentioned. In Eocene times
there existed over a region, part of which is now the North-east German
coast, an extensive forest of conifers and other trees. Some of the conifers
were rich in resinous secretions which were poured out from wounded
surfaces or from scars left by falling branches. As these flowed as a sticky
mass over the stem or collected on the ground, flowers, leaves, and twigs
blown by the wind or falling from the trees, became embedded in the
exuded resin. Evaporation gradually hardened the resinous substance until
the plant fragments became sealed up in a mass of amber, in precisely the
same manner in which objects are artificially preserved in Canada balsam.
In many cases the amber acts as a petrifying agent, and by penetrating the
tissues of a piece of wood it preserves the minute structural details in
wonderful perfection[93]. Dr Thomas in an account of the amber beds of East
Prussia in 1848, refers to the occurrence of large fossil trees; he writes:
“The continuous changes to which the coast is exposed, often bring to light enormous trunks
of trees, which the common people had long regarded as the trunks of the amber tree, before the
learned declared that they were the stems of palm trees, and in consequence determined the
position of Paradise to be on the coast of East Prussia[94].”
CASTS OF TREES.
In 1887 an enormous fossil plant was discovered in a sandstone quarry at
Clayton near Bradford[95]. The fossil was in the form of a sandstone cast of a
large and repeatedly branched Stigmaria, and it is now in the Owens
College Museum, where it was placed through the instrumentality of Prof.
Williamson. The plant was found spread out in its natural position on the
surface of an arenaceous shale, and overlain by a bed of hard sandstone
identical with the material of which the cast is composed. Williamson has
thus described the manner of formation of the fossil:
“It is obvious that the entire base of the tree became encased in a plastic material, which was
firmly moulded upon these roots whilst the latter retained their organisation sufficiently unaltered
to enable them to resist all superincumbent pressure. This external mould then hardened firmly,
and as the organic materials decayed they were floated out by water which entered the branching
cavity; at a still later period the same water was instrumental in replacing the carbonaceous
elements by the sand of which the entire structure now consists[96].”
resemble the stumps of a dead thicket[92].”
As a somewhat analogous method of preservation to that in travertine,
the occurrence of plants in amber should be mentioned. In Eocene times
there existed over a region, part of which is now the North-east German
coast, an extensive forest of conifers and other trees. Some of the conifers
were rich in resinous secretions which were poured out from wounded
surfaces or from scars left by falling branches. As these flowed as a sticky
mass over the stem or collected on the ground, flowers, leaves, and twigs
blown by the wind or falling from the trees, became embedded in the
exuded resin. Evaporation gradually hardened the resinous substance until
the plant fragments became sealed up in a mass of amber, in precisely the
same manner in which objects are artificially preserved in Canada balsam.
In many cases the amber acts as a petrifying agent, and by penetrating the
tissues of a piece of wood it preserves the minute structural details in
wonderful perfection[93]. Dr Thomas in an account of the amber beds of East
Prussia in 1848, refers to the occurrence of large fossil trees; he writes:
“The continuous changes to which the coast is exposed, often bring to light enormous trunks
of trees, which the common people had long regarded as the trunks of the amber tree, before the
learned declared that they were the stems of palm trees, and in consequence determined the
position of Paradise to be on the coast of East Prussia[94].”
CASTS OF TREES.
In 1887 an enormous fossil plant was discovered in a sandstone quarry at
Clayton near Bradford[95]. The fossil was in the form of a sandstone cast of a
large and repeatedly branched Stigmaria, and it is now in the Owens
College Museum, where it was placed through the instrumentality of Prof.
Williamson. The plant was found spread out in its natural position on the
surface of an arenaceous shale, and overlain by a bed of hard sandstone
identical with the material of which the cast is composed. Williamson has
thus described the manner of formation of the fossil:
“It is obvious that the entire base of the tree became encased in a plastic material, which was
firmly moulded upon these roots whilst the latter retained their organisation sufficiently unaltered
to enable them to resist all superincumbent pressure. This external mould then hardened firmly,
and as the organic materials decayed they were floated out by water which entered the branching
cavity; at a still later period the same water was instrumental in replacing the carbonaceous
elements by the sand of which the entire structure now consists[96].”
Page 95
Although the branches have not been preserved for their whole length,
they extend a distance of 29 feet 6 inches from right to left, and 28 feet in
the opposite direction.
The fossil represented in fig. 1 (p. 10), from the collection of Dr John
Woodward, affords a good example of a well-defined impression. The
surface of the specimen, of which a cast is represented in fig. 1, shows very
clearly the characteristic leaf-cushions and leaf-scars of a Lepidodendron.
The stem was embedded in soft sand, and as the latter became hard and set,
an impression was obtained of the external markings of the Lepidodendron.
Decay subsequently removed the substance of the plant.
Fig. 11. Equisetites columnaris Brongn. From a specimen in the Woodwardian Museum,
Cambridge. ⅓ nat. size.
In fig. 11 some upright stems of a fossil Horse-tail (Equisetites
columnaris) from the Lower Oolite rocks near Scarborough, are seen in a
vertical position in sandstone. On the surface of the fossils there is a thin
film of carbonaceous matter, which is all that remains of the original plant
substance; the stems were probably floated into their present position and
they extend a distance of 29 feet 6 inches from right to left, and 28 feet in
the opposite direction.
The fossil represented in fig. 1 (p. 10), from the collection of Dr John
Woodward, affords a good example of a well-defined impression. The
surface of the specimen, of which a cast is represented in fig. 1, shows very
clearly the characteristic leaf-cushions and leaf-scars of a Lepidodendron.
The stem was embedded in soft sand, and as the latter became hard and set,
an impression was obtained of the external markings of the Lepidodendron.
Decay subsequently removed the substance of the plant.
Fig. 11. Equisetites columnaris Brongn. From a specimen in the Woodwardian Museum,
Cambridge. ⅓ nat. size.
In fig. 11 some upright stems of a fossil Horse-tail (Equisetites
columnaris) from the Lower Oolite rocks near Scarborough, are seen in a
vertical position in sandstone. On the surface of the fossils there is a thin
film of carbonaceous matter, which is all that remains of the original plant
substance; the stems were probably floated into their present position and
Page 96
embedded vertically in an arenaceous matrix. The hollow pith-cavity was
filled with sand, and as the tissues decayed they became in part converted
into a thin coaly layer. The vertical position of such stems as those in fig. 11
naturally suggests their preservation in situ, but in this as in many other
cases the erect manner of occurrence is due to the settling down of the
drifted plants in this particular position.
FOSSIL CASTS.
An example of Stigmaria drawn in fig. 12 further illustrates the
formation of casts[97]. The outer surface with the characteristic spirally
arranged circular depressions, represents the wrinkled bark of the dried
plant; the smaller cylinder, on the left side of the upper end (fig. 12, 2, p)
marks the position of the pith surrounded by the secondary wood, which has
been displaced from its axial position. The pith decayed first, and the space
was filled in with mud; somewhat later the wood and cortex were partially
destroyed, and the rod of material which had been introduced into the pith-
cavity dropped towards one side of the decaying shell of bark.
Fig. 12. Stigmaria ficoides Brongn. 1. Side view, showing wrinkled surface and the scars of
appendages. 2. End view (upper) showing the displaced central cylinder; p, pith, x,
xylem, r, medullary rays. 3. End view (lower). From a specimen in the Woodwardian
Museum. ½ nat. size.
filled with sand, and as the tissues decayed they became in part converted
into a thin coaly layer. The vertical position of such stems as those in fig. 11
naturally suggests their preservation in situ, but in this as in many other
cases the erect manner of occurrence is due to the settling down of the
drifted plants in this particular position.
FOSSIL CASTS.
An example of Stigmaria drawn in fig. 12 further illustrates the
formation of casts[97]. The outer surface with the characteristic spirally
arranged circular depressions, represents the wrinkled bark of the dried
plant; the smaller cylinder, on the left side of the upper end (fig. 12, 2, p)
marks the position of the pith surrounded by the secondary wood, which has
been displaced from its axial position. The pith decayed first, and the space
was filled in with mud; somewhat later the wood and cortex were partially
destroyed, and the rod of material which had been introduced into the pith-
cavity dropped towards one side of the decaying shell of bark.
Fig. 12. Stigmaria ficoides Brongn. 1. Side view, showing wrinkled surface and the scars of
appendages. 2. End view (upper) showing the displaced central cylinder; p, pith, x,
xylem, r, medullary rays. 3. End view (lower). From a specimen in the Woodwardian
Museum. ½ nat. size.
Page 97
As the parenchymatous medullary rays readily decayed, the mud in the
pith extended outwards between the segments of wood which still remained
intact, and so spokes of argillaceous material were formed which filled the
medullary ray cavities. The cortical tissues were decomposed, and their
place taken by more argillaceous material. At one end of the specimen (fig.
12, 3) we find the wood has decayed without its place being afterwards
filled up with foreign material. At the opposite end of the specimen, the
woody tissue has been partially preserved by the infiltration of a solution
containing carbonate of lime (fig. 12, 2).
Numerous instances have been recorded from rocks of various geological
ages of casts of stems standing erect and at right angles to the bedding of
the surrounding rock. These vertical trees occasionally attain a considerable
length, and have been formed by the filling in by sand or mud of a pipe left
by the decay of the stem. It is frequently a matter of some difficulty to
decide how far such fossils are in the position of growth of the tree, or
whether they are merely casts of drifted stems, which happen to have been
deposited in an erect position. The weighting of floating trees by stones
held in the roots, added to the greater density of the root wood, has no doubt
often been the cause of this vertical position. In attempting to determine if
an erect cast is in the original place of growth of the tree, it is important to
bear in mind the great length of time that wood is able to resist decay,
especially under water. The wonderful state of preservation of old piles
found in the bed of a river, and the preservation of wooden portions of
anchors of which the iron has been completely removed by disintegration,
illustrate this power of resistance. In this connection, the following passage
from Lyell’s travels in America is of interest. In describing the site of an old
forest, he writes[98]:
“Some of the stumps, especially those of the fir tribe, take fifty years to rot away, though
exposed in the air to alternations of rain and sunshine, a fact on which every geologist will do
well to reflect, for it is clear that the trees of a forest submerged beneath the water, or still more,
if entirely excluded from the air, by becoming imbedded in sediment, may endure for centuries
without decay, so that there may have been ample time for the slow petrifaction of erect fossil
trees in the Carboniferous and other formations, or for the slow accumulation around them of a
great succession of strata.”
In another place, in speaking of the trees in the Great Dismal Swamp,
Lyell writes:—“When thrown down, they are soon covered by water, and
keeping wet they never decompose, except the sap wood, which is less than
pith extended outwards between the segments of wood which still remained
intact, and so spokes of argillaceous material were formed which filled the
medullary ray cavities. The cortical tissues were decomposed, and their
place taken by more argillaceous material. At one end of the specimen (fig.
12, 3) we find the wood has decayed without its place being afterwards
filled up with foreign material. At the opposite end of the specimen, the
woody tissue has been partially preserved by the infiltration of a solution
containing carbonate of lime (fig. 12, 2).
Numerous instances have been recorded from rocks of various geological
ages of casts of stems standing erect and at right angles to the bedding of
the surrounding rock. These vertical trees occasionally attain a considerable
length, and have been formed by the filling in by sand or mud of a pipe left
by the decay of the stem. It is frequently a matter of some difficulty to
decide how far such fossils are in the position of growth of the tree, or
whether they are merely casts of drifted stems, which happen to have been
deposited in an erect position. The weighting of floating trees by stones
held in the roots, added to the greater density of the root wood, has no doubt
often been the cause of this vertical position. In attempting to determine if
an erect cast is in the original place of growth of the tree, it is important to
bear in mind the great length of time that wood is able to resist decay,
especially under water. The wonderful state of preservation of old piles
found in the bed of a river, and the preservation of wooden portions of
anchors of which the iron has been completely removed by disintegration,
illustrate this power of resistance. In this connection, the following passage
from Lyell’s travels in America is of interest. In describing the site of an old
forest, he writes[98]:
“Some of the stumps, especially those of the fir tribe, take fifty years to rot away, though
exposed in the air to alternations of rain and sunshine, a fact on which every geologist will do
well to reflect, for it is clear that the trees of a forest submerged beneath the water, or still more,
if entirely excluded from the air, by becoming imbedded in sediment, may endure for centuries
without decay, so that there may have been ample time for the slow petrifaction of erect fossil
trees in the Carboniferous and other formations, or for the slow accumulation around them of a
great succession of strata.”
In another place, in speaking of the trees in the Great Dismal Swamp,
Lyell writes:—“When thrown down, they are soon covered by water, and
keeping wet they never decompose, except the sap wood, which is less than
Page 98
an inch thick[99].” We see, then, that trees may have resisted decay for a
sufficiently long time to allow of a considerable deposition of sediment. It
is very difficult to make any computation of the rate of deposition of a
particular set of sedimentary strata, and, therefore, to estimate the length of
time during which the fossil stems must have resisted decay.
PLANTS AND COAL.
The protective qualities of humus acids, apart from the almost complete
absence of Bacteria[100] from the waters of Moor- or Peat-land, is a factor of
great importance in the preservation of plants against decay for many
thousands of years.
From examples of fossil stems or leaves in which the organic material
has been either wholly or in part replaced by coal, we may pass by a
gradual transition to a mass of opaque coal in which no plant structure can
be detected. It is by no means uncommon to notice on the face of a piece of
coal a distinct impression of a plant stem, and in some cases the coal is
obviously made up of a number of flattened and compressed branches or
leaves of which the original tissues have been thoroughly carbonised. A
block of French coal, represented in fig. 13, consists very largely of
laminated bands composed of the long parallel veined leaves of the genus
Cordaites and of the bark of Lepidodendron, Sigillaria, and other Coal-
Measure genera. The long rhizomes and roots below the coal are preserved
as casts in the underclay.
In examining thin sections of coal, pieces of pitted tracheids or crushed
spores are frequently met with as fragments of plant structures which have
withstood decay more effectually than the bulk of the vegetable débris from
which the coal was formed.
The coaly layer on a fossil leaf is often found to be without any trace of
the plant tissues, but not infrequently such carbonised leaves, if treated with
certain reagents and examined microscopically, are seen to retain the
outlines of the epidermal cells of the leaf surface. If a piece of the
Carbonaceous film detached from a fossil leaf is left for some days in a
small quantity of nitric acid containing a crystal of chlorate of potash, and,
after washing with water, is transferred to ammonia, transparent film often
shows very clearly the outlines of the epidermal cell and the form of the
stomata. Such treatment has been found useful in many cases as an aid to
sufficiently long time to allow of a considerable deposition of sediment. It
is very difficult to make any computation of the rate of deposition of a
particular set of sedimentary strata, and, therefore, to estimate the length of
time during which the fossil stems must have resisted decay.
PLANTS AND COAL.
The protective qualities of humus acids, apart from the almost complete
absence of Bacteria[100] from the waters of Moor- or Peat-land, is a factor of
great importance in the preservation of plants against decay for many
thousands of years.
From examples of fossil stems or leaves in which the organic material
has been either wholly or in part replaced by coal, we may pass by a
gradual transition to a mass of opaque coal in which no plant structure can
be detected. It is by no means uncommon to notice on the face of a piece of
coal a distinct impression of a plant stem, and in some cases the coal is
obviously made up of a number of flattened and compressed branches or
leaves of which the original tissues have been thoroughly carbonised. A
block of French coal, represented in fig. 13, consists very largely of
laminated bands composed of the long parallel veined leaves of the genus
Cordaites and of the bark of Lepidodendron, Sigillaria, and other Coal-
Measure genera. The long rhizomes and roots below the coal are preserved
as casts in the underclay.
In examining thin sections of coal, pieces of pitted tracheids or crushed
spores are frequently met with as fragments of plant structures which have
withstood decay more effectually than the bulk of the vegetable débris from
which the coal was formed.
The coaly layer on a fossil leaf is often found to be without any trace of
the plant tissues, but not infrequently such carbonised leaves, if treated with
certain reagents and examined microscopically, are seen to retain the
outlines of the epidermal cells of the leaf surface. If a piece of the
Carbonaceous film detached from a fossil leaf is left for some days in a
small quantity of nitric acid containing a crystal of chlorate of potash, and,
after washing with water, is transferred to ammonia, transparent film often
shows very clearly the outlines of the epidermal cell and the form of the
stomata. Such treatment has been found useful in many cases as an aid to
Page 99
determination[101]. Prof. Zeiller informs me that he has found it particularly
satisfactory in the case of cycadean leaves.
Fig. 13. Part of a coal seam largely made up of Cordaites leaves. Stigmaria and Stigmariopsis
shown in the rock (underclay) underlying the coal. (After Grand’Eury [82] Pl. i. fig. 3.)
FOSSILS IN HALF-RELIEF.
It is sometimes possible to detach the thin lamina representing the
carbonised leaf or other plant fragment from the rock on which it lies and to
mount it whole on a slide. Good examples of plants treated in this way may
be seen in the Edinburgh and British Museums, especially Sphenopteris
fronds from the Carboniferous oil shales of Scotland. In the excellent
collection of fossil plants in Stockholm there are still finer examples of such
specimens, obtained by Dr Nathorst from some of the Triassic plants of
Southern Sweden. In a few instances the tissues of a plant have been
converted into coal in such a manner as to retain the form of the individual
cells, which appear in section as a black framework in a lighter coloured
matrix. Examples of such carbonised tissues were figured by some of the
older writers, and Solms-Laubach has recently[102] described sections of
Palaeozoic plants preserved in this manner. The section represented in fig.
70 is that of a Calamite stem (8 × 9·5 cm.) in which the wood has been
converted into carbonaceous material, but the more delicate tissues have
been almost completely destroyed. The thin and irregular black line a little
distance outside the ring of wood, and forming the limit of the drawing,
probably represents the cuticle. The whole section is embedded in a
homogeneous matrix of calcareous rock, in which the more resistant tissues
of the plant have been left as black patches and faint lines.
satisfactory in the case of cycadean leaves.
Fig. 13. Part of a coal seam largely made up of Cordaites leaves. Stigmaria and Stigmariopsis
shown in the rock (underclay) underlying the coal. (After Grand’Eury [82] Pl. i. fig. 3.)
FOSSILS IN HALF-RELIEF.
It is sometimes possible to detach the thin lamina representing the
carbonised leaf or other plant fragment from the rock on which it lies and to
mount it whole on a slide. Good examples of plants treated in this way may
be seen in the Edinburgh and British Museums, especially Sphenopteris
fronds from the Carboniferous oil shales of Scotland. In the excellent
collection of fossil plants in Stockholm there are still finer examples of such
specimens, obtained by Dr Nathorst from some of the Triassic plants of
Southern Sweden. In a few instances the tissues of a plant have been
converted into coal in such a manner as to retain the form of the individual
cells, which appear in section as a black framework in a lighter coloured
matrix. Examples of such carbonised tissues were figured by some of the
older writers, and Solms-Laubach has recently[102] described sections of
Palaeozoic plants preserved in this manner. The section represented in fig.
70 is that of a Calamite stem (8 × 9·5 cm.) in which the wood has been
converted into carbonaceous material, but the more delicate tissues have
been almost completely destroyed. The thin and irregular black line a little
distance outside the ring of wood, and forming the limit of the drawing,
probably represents the cuticle. The whole section is embedded in a
homogeneous matrix of calcareous rock, in which the more resistant tissues
of the plant have been left as black patches and faint lines.
Page 100
Mention should be made of a special form of preservation which has
been described as fossilisation in half-relief. If a stem is imbedded in sand
or mud, the matrix receives an impression of the plant surface, and if the
hollow pith-cavity is filled with the surrounding sediment, the surface of the
medullary cast will exhibit markings different from those seen on the
surface in contact with the outside of the stem. The space separating the
pith-cast from the mould bearing the impression of the stem surface may
remain empty, or it may be filled with sedimentary material. In half-relief
fossils, on the other hand, we have projecting from the under surface of a
bed a more or less rounded and prominent ridge with certain surface
markings, and fitting into a corresponding groove in the underlying rock on
which the same markings have been impressed. It is conceivable that such a
cast might be obtained if soft plant fragments were lying on a bed of sand,
and were pressed into it by the weight of superincumbent material. The
plant fragment would be squeezed into a depression, and its substance
might eventually be removed and leave no other trace than the half-relief
cast and hollow mould. A twig lying on sand would by its own weight
gradually sink a little below the surface; if it were then blown away or in
some manner removed, the depression would show the surface features of
the twig. When more sand came to be spread out over the depression, it
would find its way into the pattern of the mould, and so produce a cast. If at
a later period when the sand had hardened, the upper portion were separated
from the lower, from the former there would project a rounded cast of the
hollow mould. The preservation of soft algae as half-relief casts has been
doubted by Nathorst[103] and others as an unlikely occurrence in nature.
They prefer to regard such ridges on a rock face as the casts of the trails or
burrows of animals. This question of the preservation of the two sides of a
mould showing the same impression of a plant has long been a difficult
problem; it is discussed by Parkinson in his Organic Remains. In one of the
letters (No. xlvi.), he quotes the objection of a sceptical friend, who refuses
to believe such a manner of preservation possible, “until,” says Parkinson,
“I can inform him if, by involving a guinea in plaster of Paris, I could
obtain two impressions of the king’s head, without any impression of the
reverse[104].”
It would occupy too much space to attempt even a brief reference to the
various materials in which impressions of plants have been preserved.
Carbonaceous matter is the most usual substance, and in some cases it
been described as fossilisation in half-relief. If a stem is imbedded in sand
or mud, the matrix receives an impression of the plant surface, and if the
hollow pith-cavity is filled with the surrounding sediment, the surface of the
medullary cast will exhibit markings different from those seen on the
surface in contact with the outside of the stem. The space separating the
pith-cast from the mould bearing the impression of the stem surface may
remain empty, or it may be filled with sedimentary material. In half-relief
fossils, on the other hand, we have projecting from the under surface of a
bed a more or less rounded and prominent ridge with certain surface
markings, and fitting into a corresponding groove in the underlying rock on
which the same markings have been impressed. It is conceivable that such a
cast might be obtained if soft plant fragments were lying on a bed of sand,
and were pressed into it by the weight of superincumbent material. The
plant fragment would be squeezed into a depression, and its substance
might eventually be removed and leave no other trace than the half-relief
cast and hollow mould. A twig lying on sand would by its own weight
gradually sink a little below the surface; if it were then blown away or in
some manner removed, the depression would show the surface features of
the twig. When more sand came to be spread out over the depression, it
would find its way into the pattern of the mould, and so produce a cast. If at
a later period when the sand had hardened, the upper portion were separated
from the lower, from the former there would project a rounded cast of the
hollow mould. The preservation of soft algae as half-relief casts has been
doubted by Nathorst[103] and others as an unlikely occurrence in nature.
They prefer to regard such ridges on a rock face as the casts of the trails or
burrows of animals. This question of the preservation of the two sides of a
mould showing the same impression of a plant has long been a difficult
problem; it is discussed by Parkinson in his Organic Remains. In one of the
letters (No. xlvi.), he quotes the objection of a sceptical friend, who refuses
to believe such a manner of preservation possible, “until,” says Parkinson,
“I can inform him if, by involving a guinea in plaster of Paris, I could
obtain two impressions of the king’s head, without any impression of the
reverse[104].”
It would occupy too much space to attempt even a brief reference to the
various materials in which impressions of plants have been preserved.
Carbonaceous matter is the most usual substance, and in some cases it
Page 101
occurs in the form of graphite which on dark grey or black rocks has the
appearance of a plant drawn in lead pencil. The impressions of plants on the
Jurassic (Kimeridgian) slates of Solenhofen[105] in Bavaria, like those on the
Triassic sandstones of the Vosges, are usually marked out in red iron oxide.
PETRIFIED TREES.
So far we have chiefly considered examples of plants preserved in
various ways by incrustation, that is, by having been enclosed in some
medium which has received an impression of the surface of the plant in
contact with it. By far the most valuable fossil specimens from a botanical
point of view are however those in which the internal structure has been
preserved; that is in which the preserving medium has not served merely as
an encasing envelope or internal cast, but has penetrated into the body of
the plant fragment and rendered permanent the organization of the tissues.
In almost every Natural History or Geological Museum one meets with
specimens of petrified trees or polished sections of fossil palm stems and
other plants, in which the internal structure has been preserved in siliceous
material, and admits of detailed investigation in thin sections under the
microscope. Silica, calcium carbonate, with usually a certain amount of
carbonate of iron and magnesium carbonate, iron pyrites, amber, and more
rarely calcium fluoride or other substances have taken the place of the
original cell-walls. Of silicified stems, those from Antigua, Egypt, Central
France, Saxony, Brazil, Tasmania[106], and numerous other places afford
good examples. Darwin records numerous silicified stems in Northern
Chili, and the Uspallata Pass. In the central part of the Andes range, 7000
feet high, he describes the occurrence of “Snow-white projecting silicified
columns.... They must have grown,” he adds, “in volcanic soil, and were
subsequently submerged below sea-level, and covered with sedimentary
beds and lava-flows[107].” A striking example of the occurrence of numerous
petrified plant stems has been described by Holmes from the Tertiary
forests of the Yellowstone Park. From the face of a cliff on the north side of
Amethyst mountain “rows of upright trunks stand out on the ledges like the
columns of a ruined temple. On the more gentle slopes farther down, but
where it is still too steep to support vegetation, save a few pines, the
petrified trunks fairly cover the surface, and were at first supposed by us to
be the shattered remains of a recent forest[108].” Marsh[109] and Conwentz[110]
have described silicified trees more than fifty feet in length from a locality
appearance of a plant drawn in lead pencil. The impressions of plants on the
Jurassic (Kimeridgian) slates of Solenhofen[105] in Bavaria, like those on the
Triassic sandstones of the Vosges, are usually marked out in red iron oxide.
PETRIFIED TREES.
So far we have chiefly considered examples of plants preserved in
various ways by incrustation, that is, by having been enclosed in some
medium which has received an impression of the surface of the plant in
contact with it. By far the most valuable fossil specimens from a botanical
point of view are however those in which the internal structure has been
preserved; that is in which the preserving medium has not served merely as
an encasing envelope or internal cast, but has penetrated into the body of
the plant fragment and rendered permanent the organization of the tissues.
In almost every Natural History or Geological Museum one meets with
specimens of petrified trees or polished sections of fossil palm stems and
other plants, in which the internal structure has been preserved in siliceous
material, and admits of detailed investigation in thin sections under the
microscope. Silica, calcium carbonate, with usually a certain amount of
carbonate of iron and magnesium carbonate, iron pyrites, amber, and more
rarely calcium fluoride or other substances have taken the place of the
original cell-walls. Of silicified stems, those from Antigua, Egypt, Central
France, Saxony, Brazil, Tasmania[106], and numerous other places afford
good examples. Darwin records numerous silicified stems in Northern
Chili, and the Uspallata Pass. In the central part of the Andes range, 7000
feet high, he describes the occurrence of “Snow-white projecting silicified
columns.... They must have grown,” he adds, “in volcanic soil, and were
subsequently submerged below sea-level, and covered with sedimentary
beds and lava-flows[107].” A striking example of the occurrence of numerous
petrified plant stems has been described by Holmes from the Tertiary
forests of the Yellowstone Park. From the face of a cliff on the north side of
Amethyst mountain “rows of upright trunks stand out on the ledges like the
columns of a ruined temple. On the more gentle slopes farther down, but
where it is still too steep to support vegetation, save a few pines, the
petrified trunks fairly cover the surface, and were at first supposed by us to
be the shattered remains of a recent forest[108].” Marsh[109] and Conwentz[110]
have described silicified trees more than fifty feet in length from a locality
Page 102
in California where several large forest trees of Tertiary age have been
preserved in volcanic strata. In South Africa on the Drakenberg hills there
occur numerous silicified trunks, occasionally erect and often lying on the
ground, probably of Triassic age[111]. In some instances the specimens
measure several feet in length and diameter. Some of the coniferous stems
seen in Portland, and occasionally met with reared up against a house side,
illustrate the silicification of plant structure on a large scale. These are of
Upper Jurassic (Purbeck) age. From Grand’Croix in France a silicified stem
of Cordaites of Palaeozoic age has been recorded with a length of twenty
meters. The preservation of plants by siliceous infiltrations has long been
known. One of the earliest descriptions of this form of petrifaction in the
British Isles is that of stems found in Lough Neagh, Ireland. In his lectures
on Natural Philosophy, published at Dublin in 1751, Barton gives several
figures of Irish silicified wood, and records the following occurrence in
illustration of the peculiar properties erroneously attributed to the waters of
Lough Neagh. Describing a certain specimen (No. xxvi), he writes:—
“This is a whetstone, which as Mr Anthony Shane, apothecary, who was born very near the
lake, and is now alive, relates, he made by putting a piece of holly in the water of the lake near
his father’s house, and fixing it so as to withstand the motion of the water, and marking the place
so as to distinguish it, he went to Scotland to pursue his studies, and seven years after took up a
stone instead of holly, the metamorphosis having been made in that time. This account he gave
under his handwriting. The shore thereabouts is altogether loose sand, and two rivers discharge
themselves into the lake very near that place[112].”
The well-known petrified trees from the neighbourhood of Lough Neagh
are probably of Pliocene age, but their exact source has been a matter of
dispute[113].
PETRIFIED WOOD.
In 1836 Stokes described certain stems in which the tissues had been
partially mineralised. In describing a specimen of beech from a Roman
aqueduct at Eibsen in Lippe Bückeburg], he says:—
“The wood is, for the most part, in the state of very old dry wood, but there are several
insulated portions, in which the place of the wood has been taken by carbonate of lime. These
portions, as seen on the surface of the horizontal section, are irregularly circular, varying in size,
but generally a little less or more than ⅛ inch in diameter, and they run through the whole
thickness of the specimen in separate, perpendicular columns. The vessels of the wood are
distinctly visible in the carbonate of lime, and are more perfect in their form and size in those
portions of the specimen than in that which remains unchanged[114].”
preserved in volcanic strata. In South Africa on the Drakenberg hills there
occur numerous silicified trunks, occasionally erect and often lying on the
ground, probably of Triassic age[111]. In some instances the specimens
measure several feet in length and diameter. Some of the coniferous stems
seen in Portland, and occasionally met with reared up against a house side,
illustrate the silicification of plant structure on a large scale. These are of
Upper Jurassic (Purbeck) age. From Grand’Croix in France a silicified stem
of Cordaites of Palaeozoic age has been recorded with a length of twenty
meters. The preservation of plants by siliceous infiltrations has long been
known. One of the earliest descriptions of this form of petrifaction in the
British Isles is that of stems found in Lough Neagh, Ireland. In his lectures
on Natural Philosophy, published at Dublin in 1751, Barton gives several
figures of Irish silicified wood, and records the following occurrence in
illustration of the peculiar properties erroneously attributed to the waters of
Lough Neagh. Describing a certain specimen (No. xxvi), he writes:—
“This is a whetstone, which as Mr Anthony Shane, apothecary, who was born very near the
lake, and is now alive, relates, he made by putting a piece of holly in the water of the lake near
his father’s house, and fixing it so as to withstand the motion of the water, and marking the place
so as to distinguish it, he went to Scotland to pursue his studies, and seven years after took up a
stone instead of holly, the metamorphosis having been made in that time. This account he gave
under his handwriting. The shore thereabouts is altogether loose sand, and two rivers discharge
themselves into the lake very near that place[112].”
The well-known petrified trees from the neighbourhood of Lough Neagh
are probably of Pliocene age, but their exact source has been a matter of
dispute[113].
PETRIFIED WOOD.
In 1836 Stokes described certain stems in which the tissues had been
partially mineralised. In describing a specimen of beech from a Roman
aqueduct at Eibsen in Lippe Bückeburg], he says:—
“The wood is, for the most part, in the state of very old dry wood, but there are several
insulated portions, in which the place of the wood has been taken by carbonate of lime. These
portions, as seen on the surface of the horizontal section, are irregularly circular, varying in size,
but generally a little less or more than ⅛ inch in diameter, and they run through the whole
thickness of the specimen in separate, perpendicular columns. The vessels of the wood are
distinctly visible in the carbonate of lime, and are more perfect in their form and size in those
portions of the specimen than in that which remains unchanged[114].”
Page 103
Fig. 14.
A. Araucarioxylon Withami (L. and H.). Radiating lines of crystallisation in secondary
wood, as seen in transverse section.
B. Lepidodendron sp. Concentric lines of crystallisation, and scalariform tracheids, as seen
in longitudinal section.
This partial petrifaction of the structure in patches is often met with in
fossil stems, and may be seriously misleading to those unfamiliar with the
appearance presented by the crystallisation of silica from scattered centres
in a mass of vegetable tissue. A good example of this is afforded by the
gigantic stems discovered in 1829 in the Craigleith Quarry near
Edinburgh[115]. Of those two large stems found in the Sandstone rock, the
longest, originally 11 meters long and 3·3–3·9 meters in girth, is now set up
in the grounds of the British Museum, and a large polished section (1 m. ×
87 cm.) is exhibited in the Fossil-plant Gallery. The other stem is in the
Botanic Garden, Edinburgh. Transverse sections of the wood of the London
specimen show scattered circular patches (fig. 14 A) in the mineralised
wood in which the tracheids are very clearly preserved; while in the other
portion the preservation is much less perfect. The patch of tissue in fig. 14
A shows a portion of the wood of the Craigleith tree [Araucarioxylon
Withami (L. and H.)] in which the mineral matter, consisting of dolomite
with a little silica here and there, has crystallised in such a manner as to
produce what is practically a cone-in-cone structure on a small scale, which
has partially obliterated the structural features. This minute cone-in-cone
structure is not uncommon in petrified tissues; it is precisely similar in
appearance to that described by Cole[116] in certain minerals. The
A. Araucarioxylon Withami (L. and H.). Radiating lines of crystallisation in secondary
wood, as seen in transverse section.
B. Lepidodendron sp. Concentric lines of crystallisation, and scalariform tracheids, as seen
in longitudinal section.
This partial petrifaction of the structure in patches is often met with in
fossil stems, and may be seriously misleading to those unfamiliar with the
appearance presented by the crystallisation of silica from scattered centres
in a mass of vegetable tissue. A good example of this is afforded by the
gigantic stems discovered in 1829 in the Craigleith Quarry near
Edinburgh[115]. Of those two large stems found in the Sandstone rock, the
longest, originally 11 meters long and 3·3–3·9 meters in girth, is now set up
in the grounds of the British Museum, and a large polished section (1 m. ×
87 cm.) is exhibited in the Fossil-plant Gallery. The other stem is in the
Botanic Garden, Edinburgh. Transverse sections of the wood of the London
specimen show scattered circular patches (fig. 14 A) in the mineralised
wood in which the tracheids are very clearly preserved; while in the other
portion the preservation is much less perfect. The patch of tissue in fig. 14
A shows a portion of the wood of the Craigleith tree [Araucarioxylon
Withami (L. and H.)] in which the mineral matter, consisting of dolomite
with a little silica here and there, has crystallised in such a manner as to
produce what is practically a cone-in-cone structure on a small scale, which
has partially obliterated the structural features. This minute cone-in-cone
structure is not uncommon in petrified tissues; it is precisely similar in
appearance to that described by Cole[116] in certain minerals. The
Page 104
crystallisation has been set up along lines radiating from different centres,
and the particles of the tissue have been pushed as it were along these lines.
Fig. 15. Transverse section of the central cylinder of a Carboniferous Lepidodendroid stem
in the collection of Mr Kidston. From Dalmeny, Scotland. s. Silica filling up the central
portion of the pith. p. Remains of the pith tissue. x1. Primary xylem. x2. Secondary xylem.
c. Innermost cortex.
PRESERVATION OF TISSUES.
A somewhat different crystallisation phenomenon is illustrated by the
extremely fine section of a Lepidodendroid plant shown in fig. 15. The
tissues of the primary and secondary wood (x1 and x2) are well preserved
and the particles of the tissue have been pushed as it were along these lines.
Fig. 15. Transverse section of the central cylinder of a Carboniferous Lepidodendroid stem
in the collection of Mr Kidston. From Dalmeny, Scotland. s. Silica filling up the central
portion of the pith. p. Remains of the pith tissue. x1. Primary xylem. x2. Secondary xylem.
c. Innermost cortex.
PRESERVATION OF TISSUES.
A somewhat different crystallisation phenomenon is illustrated by the
extremely fine section of a Lepidodendroid plant shown in fig. 15. The
tissues of the primary and secondary wood (x1 and x2) are well preserved
Page 105
throughout in silica, but scattered through the siliceous matrix there occur
numerous circular patches, as seen in the figure. One of these is more
clearly shown in fig. 14 B drawn from a longitudinal section through the
secondary wood, x2; it will be noticed that where the concentric lines of the
circular patch occur, the scalariform thickenings of the tracheids are sharply
defined, but immediately a tracheid is free of the patch these details are lost.
It would appear that in this case silicification was first completed round
definite isolated centres, and the secondary crystallisation in the matrix
partially obliterated some of the more delicate structural features. The same
phenomenon has been observed in oolitic rocks[117], in which the oolitic
grains have resisted secondary crystallisation and so retained their original
structure.
Among the most important examples of silicified plants are those from a
few localities in Central France. In the neighbourhood of Autun there used
to be found in abundance loose nodules of siliceous rock containing
numerous fragments of seeds, twigs, and leaves of different plants. The rock
of which the broken portions are found on the surface of the ground was
formed about the close of the Carboniferous period.
At the hands of French investigators the microscopic examination of
these fragments of a Palaeozoic vegetation have thrown a flood of light on
the anatomical structure of many extinct types. Sometimes the silica has
penetrated the cavities of the cells and vessels, and the walls have decayed
without their substance being replaced by mineral material. Sections of
tissues preserved in this manner, if soaked in a coloured solution assume an
appearance almost identical with that of stained sections of recent plants.
The spaces left by the decayed walls act as fine capillaries and suck up the
coloured solution[118].
In the Coal-Measure sandstones of England large pieces of woody stems
are occasionally met with in which the mineralisation has been incomplete.
A brown piece of fossil stem lying in a bed of sandstone shows on the
surface a distinct woody texture, and the lines of wood elements are clearly
visible. The whole is, however, very friable and falls to pieces if an attempt
is made to cut thin sections of it; the tracheids of the wood easily fall apart
owing to the walls being imperfectly preserved, and the absence of a
connecting framework such as would have been formed had the membranes
been thoroughly silicified. It is occasionally possible to obtain from
numerous circular patches, as seen in the figure. One of these is more
clearly shown in fig. 14 B drawn from a longitudinal section through the
secondary wood, x2; it will be noticed that where the concentric lines of the
circular patch occur, the scalariform thickenings of the tracheids are sharply
defined, but immediately a tracheid is free of the patch these details are lost.
It would appear that in this case silicification was first completed round
definite isolated centres, and the secondary crystallisation in the matrix
partially obliterated some of the more delicate structural features. The same
phenomenon has been observed in oolitic rocks[117], in which the oolitic
grains have resisted secondary crystallisation and so retained their original
structure.
Among the most important examples of silicified plants are those from a
few localities in Central France. In the neighbourhood of Autun there used
to be found in abundance loose nodules of siliceous rock containing
numerous fragments of seeds, twigs, and leaves of different plants. The rock
of which the broken portions are found on the surface of the ground was
formed about the close of the Carboniferous period.
At the hands of French investigators the microscopic examination of
these fragments of a Palaeozoic vegetation have thrown a flood of light on
the anatomical structure of many extinct types. Sometimes the silica has
penetrated the cavities of the cells and vessels, and the walls have decayed
without their substance being replaced by mineral material. Sections of
tissues preserved in this manner, if soaked in a coloured solution assume an
appearance almost identical with that of stained sections of recent plants.
The spaces left by the decayed walls act as fine capillaries and suck up the
coloured solution[118].
In the Coal-Measure sandstones of England large pieces of woody stems
are occasionally met with in which the mineralisation has been incomplete.
A brown piece of fossil stem lying in a bed of sandstone shows on the
surface a distinct woody texture, and the lines of wood elements are clearly
visible. The whole is, however, very friable and falls to pieces if an attempt
is made to cut thin sections of it; the tracheids of the wood easily fall apart
owing to the walls being imperfectly preserved, and the absence of a
connecting framework such as would have been formed had the membranes
been thoroughly silicified. It is occasionally possible to obtain from
Page 106
petrified plant stems perfect casts in silica or other
substances of the cavity of a sclerenchymatous
fibre, in which the mineral has been deposited not
only in the cavity but in the fine pit-canals
traversing the lignified walls. Such a cast is
represented in fig. 16, the fine lateral projections are
the delicate casts of the pit canals. Numerous
instances of minute and delicate tissues preserved in
silica are recorded in later chapters. A somewhat
unusual type of silicification is met with in some of
the Gondwana rocks of India, in which cycadean
fronds occur as white porcellaneous specimens
showing a certain amount of internal structure in a
siliceous matrix. Specimens of such leaves may be
seen in the British Museum.
COAL-BALLS.
In the Coal-Measures of England, especially in
the neighbourhood of Halifax in Yorkshire, and in
South Lancashire, the seams of coal occasionally
contain calcareous nodules varying in size from a
nut to a man’s head, and consisting of about 70% of
carbonate of calcium and magnesium, and 30% of
oxide of iron, sulphide of iron, &c.[119] The nodules,
often spoken of by English writers as ‘coal-balls,’ Fig. 16. Internal cast of a
contain numerous fragments of plants in which the sclerenchymatous
from the root of a
cell
minute cellular structure is preserved with Cretaceous fern
remarkable perfection. It should be noted that the (Rhizodendron
term coal-ball is also applied to rounded or oppoliense Göpp.). After
Stenzel (86) Pl. iii. fig.
subangular pieces of coal which are occasionally 29. × 240 and reduced to
met with in coal seams, and especially in certain one-half.
French coal fields. To avoid confusion it is better to
speak of the plant-containing nodules as calcareous nodules, restricting the
term coal-ball to true coal pebbles. A section of a calcareous nodule, when
seen under the microscope, presents the appearance of a matrix of a
crystalline calcareous substance containing a heterogeneous mixture of all
substances of the cavity of a sclerenchymatous
fibre, in which the mineral has been deposited not
only in the cavity but in the fine pit-canals
traversing the lignified walls. Such a cast is
represented in fig. 16, the fine lateral projections are
the delicate casts of the pit canals. Numerous
instances of minute and delicate tissues preserved in
silica are recorded in later chapters. A somewhat
unusual type of silicification is met with in some of
the Gondwana rocks of India, in which cycadean
fronds occur as white porcellaneous specimens
showing a certain amount of internal structure in a
siliceous matrix. Specimens of such leaves may be
seen in the British Museum.
COAL-BALLS.
In the Coal-Measures of England, especially in
the neighbourhood of Halifax in Yorkshire, and in
South Lancashire, the seams of coal occasionally
contain calcareous nodules varying in size from a
nut to a man’s head, and consisting of about 70% of
carbonate of calcium and magnesium, and 30% of
oxide of iron, sulphide of iron, &c.[119] The nodules,
often spoken of by English writers as ‘coal-balls,’ Fig. 16. Internal cast of a
contain numerous fragments of plants in which the sclerenchymatous
from the root of a
cell
minute cellular structure is preserved with Cretaceous fern
remarkable perfection. It should be noted that the (Rhizodendron
term coal-ball is also applied to rounded or oppoliense Göpp.). After
Stenzel (86) Pl. iii. fig.
subangular pieces of coal which are occasionally 29. × 240 and reduced to
met with in coal seams, and especially in certain one-half.
French coal fields. To avoid confusion it is better to
speak of the plant-containing nodules as calcareous nodules, restricting the
term coal-ball to true coal pebbles. A section of a calcareous nodule, when
seen under the microscope, presents the appearance of a matrix of a
crystalline calcareous substance containing a heterogeneous mixture of all
Page 107
kinds of plant tissues, usually in the form of broken pieces and in a
confused mass.
Fig. 17. A thin section of a calcareous nodule from the Coal-Measures. Binney collection,
Woodwardian Museum, Cambridge. Very slightly reduced.
A large section of one of these nodules (12·5 cm. × 8·5 cm.) is shown in
fig. 17. It illustrates the manner of occurrence of various fragments of
different plants in which the structure has been more or less perfectly
preserved. In this particular example we see sections of Myeloxylon (I),
Calamites (II), Fern petioles (Rachiopteris) (III), Stigmarian appendages
(IV), Lepidodendroid leaves (V), Myeloxylon pinnules (VI),
Gymnospermous seeds (VII), Twig of a Lepidodendron, showing the central
xylem cylinder and large leaf-bases on the outer cortex, (VIII), Sporangia
and spores of a strobilus (IX), Tangential section of a Myeloxylon petiole
(X), Rachiopteris sp. (XI), Rachiopteris sp. (XII), Band of
sclerenchymatous tissue (XIII), Rachiopteris sp. (XIV).
confused mass.
Fig. 17. A thin section of a calcareous nodule from the Coal-Measures. Binney collection,
Woodwardian Museum, Cambridge. Very slightly reduced.
A large section of one of these nodules (12·5 cm. × 8·5 cm.) is shown in
fig. 17. It illustrates the manner of occurrence of various fragments of
different plants in which the structure has been more or less perfectly
preserved. In this particular example we see sections of Myeloxylon (I),
Calamites (II), Fern petioles (Rachiopteris) (III), Stigmarian appendages
(IV), Lepidodendroid leaves (V), Myeloxylon pinnules (VI),
Gymnospermous seeds (VII), Twig of a Lepidodendron, showing the central
xylem cylinder and large leaf-bases on the outer cortex, (VIII), Sporangia
and spores of a strobilus (IX), Tangential section of a Myeloxylon petiole
(X), Rachiopteris sp. (XI), Rachiopteris sp. (XII), Band of
sclerenchymatous tissue (XIII), Rachiopteris sp. (XIV).
Page 108
The general appearance of a calcareous plant-nodule suggests a soft
pulpy mass of decaying vegetable débris, through which roots were able to
bore their way, as in a piece of peat or leafy mould. Overlying this
accumulation of soft material there was spread out a bed of muddy
sediment containing numerous calcareous shells, which supplied the
percolating water with the material which was afterwards deposited in
portions of the vegetable débris. According to this view the calcareous
nodules of the coal seams represent local patches of a widespread mass of
débris which were penetrated by a carbonated solution, and so preserved as
samples of a decaying mass of vegetation, of which by far the greater
portion became eventually converted into coal[120].
FOSSIL NUCLEI.
In such nodules, we find that not only has the framework of the tissues
been preserved, but frequently the remains of cell contents are clearly seen.
In some cases the cells of a tissue may contain in each cavity a darker
coloured spot, which is probably the mineralised cell nucleus. (Fig. 42, A, 1,
p. 214.) The contents of secretory sacs, such as those containing gum or
resin, are frequently found as black rods filling up the cavity of the cell or
canal. The contents of cells in some cases closely simulate starch grains,
and such may have been actually present in the tissues of a piece of a fossil
dicotyledonous stem described by Thiselton-Dyer from the Lower Eocene
Thanet beds[121], and in the rhizome of a fossil Osmunda recorded by
Carruthers[122]. (Fig. 42, B, p. 214.)
Schultze in 1855[123] recorded the discovery of cellulose by
microchemical tests applied to macerated tissue from Tertiary lignite and
coal. With reference to the possibility of recognising cell contents in fossil
tissue it is interesting to find that Dr Murray of Scarborough had attempted,
and apparently with success, to apply chemical tests to the tissues of
Jurassic leaves. In a letter written to Hutton in 1833 Murray speaks of his
experiments as follows:—
“Reverting to the Oolitic plants, I have again and with better success been experimenting upon
the thin transparent films of leaves, chiefly of Taeniopteris vittata and Cyclopteris, which from
their tenuity offer fine objects for the microscope.... By many delicate trials I have ascertained
the existence still in these leaves of resin and of tannin.... I am seeking among the filmy leaves of
the Fucoides of A. Brongniart for iodine, but hitherto without success, and indeed can hardly
expect it, as probably did iodine exist in them, it must have long ago entered into new
combinations[124].”
pulpy mass of decaying vegetable débris, through which roots were able to
bore their way, as in a piece of peat or leafy mould. Overlying this
accumulation of soft material there was spread out a bed of muddy
sediment containing numerous calcareous shells, which supplied the
percolating water with the material which was afterwards deposited in
portions of the vegetable débris. According to this view the calcareous
nodules of the coal seams represent local patches of a widespread mass of
débris which were penetrated by a carbonated solution, and so preserved as
samples of a decaying mass of vegetation, of which by far the greater
portion became eventually converted into coal[120].
FOSSIL NUCLEI.
In such nodules, we find that not only has the framework of the tissues
been preserved, but frequently the remains of cell contents are clearly seen.
In some cases the cells of a tissue may contain in each cavity a darker
coloured spot, which is probably the mineralised cell nucleus. (Fig. 42, A, 1,
p. 214.) The contents of secretory sacs, such as those containing gum or
resin, are frequently found as black rods filling up the cavity of the cell or
canal. The contents of cells in some cases closely simulate starch grains,
and such may have been actually present in the tissues of a piece of a fossil
dicotyledonous stem described by Thiselton-Dyer from the Lower Eocene
Thanet beds[121], and in the rhizome of a fossil Osmunda recorded by
Carruthers[122]. (Fig. 42, B, p. 214.)
Schultze in 1855[123] recorded the discovery of cellulose by
microchemical tests applied to macerated tissue from Tertiary lignite and
coal. With reference to the possibility of recognising cell contents in fossil
tissue it is interesting to find that Dr Murray of Scarborough had attempted,
and apparently with success, to apply chemical tests to the tissues of
Jurassic leaves. In a letter written to Hutton in 1833 Murray speaks of his
experiments as follows:—
“Reverting to the Oolitic plants, I have again and with better success been experimenting upon
the thin transparent films of leaves, chiefly of Taeniopteris vittata and Cyclopteris, which from
their tenuity offer fine objects for the microscope.... By many delicate trials I have ascertained
the existence still in these leaves of resin and of tannin.... I am seeking among the filmy leaves of
the Fucoides of A. Brongniart for iodine, but hitherto without success, and indeed can hardly
expect it, as probably did iodine exist in them, it must have long ago entered into new
combinations[124].”
Page 109
Apart from this difficulty, it is not surprising that Dr Murray’s search for
iodine was unsuccessful, considering how little algal nature most of the so-
called Fucoids possess.
Some of the most perfectly preserved tissues as regards the details of cell
contents are those of gymnospermous seeds from Autun. In sections of one
of these seeds which I recently had the opportunity of examining in Prof.
Bertrand’s collection, the parenchymatous cells contained very distinct
nuclei and protoplasmic contents. In one portion of the tissue in the nucellus
of Sphaerospermum the cell walls had disappeared, but the nuclei remained
in a remarkable state of preservation. The cells shown in fig. 42 are from
the ground tissue of a petiole of Cycadeoidea gigantea Sew.[125], a
magnificent Cycadean stem from Portland recently added to the British
Museum collection; in the cell A, 1, the nucleus is fairly distinct and in 2
and 4 the contracted cell-contents is clearly seen. Other interesting
examples of fossil nuclei are seen in a Lyginodendron leaf figured by
Williamson and Scott in a recent Memoir on that genus[126]. Each mesophyll
cell contains a single dark nucleus. The mineralisation of the most delicate
tissues and the preservation of the various forms of cell-contents are now
generally admitted by those at all conversant with the possibilities of plant
petrifaction. If we consider what these facts mean—the microscopic
investigation of not only the finest framework but even the very life-
substance of Palaeozoic plants—we feel that the aeons since the days when
these plants lived have been well-nigh obliterated.
Occasionally the plant tissues have assumed a black and somewhat
ragged appearance, giving the impression of charred wood. A section of a
recent burnt piece of wood resembles very closely some of the fossil twigs
from the coal seam nodules. It is possible that in such cases we have
portions of mineralised tissues which were first burnt in a forest fire or by
lightning and then infiltrated with a petrifying solution. An example of one
of these black petrified plants is shown in fig. 74 B. Chap. x. In many of the
fossil plants there are distinct traces of fungus or bacterial ravages, and
occasionally the section of a piece of mineralised wood shows circular
spaces or canals which have the appearance of being the work of some
wood-eating animal, and small oval bodies sometimes occur in such spaces
which may be the coprolites of the xylophagous intruder. (Fig. 24, p. 107.)
FOSSIL PLANTS IN VOLCANIC ASH.
iodine was unsuccessful, considering how little algal nature most of the so-
called Fucoids possess.
Some of the most perfectly preserved tissues as regards the details of cell
contents are those of gymnospermous seeds from Autun. In sections of one
of these seeds which I recently had the opportunity of examining in Prof.
Bertrand’s collection, the parenchymatous cells contained very distinct
nuclei and protoplasmic contents. In one portion of the tissue in the nucellus
of Sphaerospermum the cell walls had disappeared, but the nuclei remained
in a remarkable state of preservation. The cells shown in fig. 42 are from
the ground tissue of a petiole of Cycadeoidea gigantea Sew.[125], a
magnificent Cycadean stem from Portland recently added to the British
Museum collection; in the cell A, 1, the nucleus is fairly distinct and in 2
and 4 the contracted cell-contents is clearly seen. Other interesting
examples of fossil nuclei are seen in a Lyginodendron leaf figured by
Williamson and Scott in a recent Memoir on that genus[126]. Each mesophyll
cell contains a single dark nucleus. The mineralisation of the most delicate
tissues and the preservation of the various forms of cell-contents are now
generally admitted by those at all conversant with the possibilities of plant
petrifaction. If we consider what these facts mean—the microscopic
investigation of not only the finest framework but even the very life-
substance of Palaeozoic plants—we feel that the aeons since the days when
these plants lived have been well-nigh obliterated.
Occasionally the plant tissues have assumed a black and somewhat
ragged appearance, giving the impression of charred wood. A section of a
recent burnt piece of wood resembles very closely some of the fossil twigs
from the coal seam nodules. It is possible that in such cases we have
portions of mineralised tissues which were first burnt in a forest fire or by
lightning and then infiltrated with a petrifying solution. An example of one
of these black petrified plants is shown in fig. 74 B. Chap. x. In many of the
fossil plants there are distinct traces of fungus or bacterial ravages, and
occasionally the section of a piece of mineralised wood shows circular
spaces or canals which have the appearance of being the work of some
wood-eating animal, and small oval bodies sometimes occur in such spaces
which may be the coprolites of the xylophagous intruder. (Fig. 24, p. 107.)
FOSSIL PLANTS IN VOLCANIC ASH.
Page 110
It is well known to geologists that during the Permian and Carboniferous
periods the southern portion of Scotland was the scene of widespread
volcanic activity. Forests were overwhelmed by lava-streams or showers of
ash, and in some districts tree stems and broken plant fragments became
sealed up in a volcanic matrix. Laggan Bay in the north-east corner of the
Isle of Arran, and Pettycur a short distance from Burntisland on the north
shore of the Firth of Forth, are two localities where petrified plants of
Carboniferous age occur in such preservation as allows of a minute
investigation of their internal structure. The occurrence of plants in the
former locality was first discovered by Mr Wünsch of Glasgow; the fossils
occur in association with hardened shales and beds of ash, and are often
exceedingly well preserved[127]. In fig. 18 is reproduced a sketch of a hollow
tree trunk from Arran, probably a Lepidodendron stem, in which only the
outer portion of the bark has been preserved, while the inner cortical tissues
have been removed and the space occupied by volcanic detritus.
Fig. 18. Diagrammatic sketch of a slab cut from a fossil stem (Lepidodendron?) from
Laggan Bay. e, Imperfectly preserved bark of a large stem, extending in patches round
the periphery of the specimen; the oval and circular bodies in the interior are the xylem
portions of the central cylinders of Lepidodendron stems, x1, primary wood, x2, secondary
wood. From a specimen in the Binney collection, Woodwardian Museum, Cambridge. ⅕
nat. size.
periods the southern portion of Scotland was the scene of widespread
volcanic activity. Forests were overwhelmed by lava-streams or showers of
ash, and in some districts tree stems and broken plant fragments became
sealed up in a volcanic matrix. Laggan Bay in the north-east corner of the
Isle of Arran, and Pettycur a short distance from Burntisland on the north
shore of the Firth of Forth, are two localities where petrified plants of
Carboniferous age occur in such preservation as allows of a minute
investigation of their internal structure. The occurrence of plants in the
former locality was first discovered by Mr Wünsch of Glasgow; the fossils
occur in association with hardened shales and beds of ash, and are often
exceedingly well preserved[127]. In fig. 18 is reproduced a sketch of a hollow
tree trunk from Arran, probably a Lepidodendron stem, in which only the
outer portion of the bark has been preserved, while the inner cortical tissues
have been removed and the space occupied by volcanic detritus.
Fig. 18. Diagrammatic sketch of a slab cut from a fossil stem (Lepidodendron?) from
Laggan Bay. e, Imperfectly preserved bark of a large stem, extending in patches round
the periphery of the specimen; the oval and circular bodies in the interior are the xylem
portions of the central cylinders of Lepidodendron stems, x1, primary wood, x2, secondary
wood. From a specimen in the Binney collection, Woodwardian Museum, Cambridge. ⅕
nat. size.
Page 111
The smaller cylindrical structures in the interior of the hollow trunk are
the central woody cylinders of Lepidodendroid trees; each consists of an
axial pith surrounded by a band of primary wood and a broader zone of
secondary wood. One of the axes probably belonged to the stem of which
only the shell has been preserved, the others must have come from other
trees and may have been floated in by water[128]. The microscopic details of
the wood and outer cortex have in this instance been preserved in a
calcareous material, which was no doubt derived by water percolating
through the volcanic ash. It is frequently found that in fossil trees or twigs a
separation of the tissues has taken place along such natural lines of
weakness as the cambium or the phellogen, before the petrifying medium
had time to permeate the entire structure. Tree stems recently killed by lava
streams during volcanic eruptions at the present day supply a parallel with
the Palaeozoic forest trees of Carboniferous times.
Guillemard in describing a volcanic crater in Celebes, speaks of burnt
trees still standing in the lava stream, “so charred at the base of the trunk
that we could easily push them down[129].” An interesting case is quoted by
Hooker in his Himalayan Journals, illustrating the occurrence of a hollow
shell of a tree, in which the outer portions of a stem had been left while the
inner portions had disappeared, the wood being hollow and so favourable to
the production of a current of air which accelerated the destruction of the
internal tissues.
On the coast near Burntisland on the Firth of Forth blocks of rock are met
with in which numerous plant fragments of Carboniferous age are scattered
in a confused mass through a calcareous volcanic matrix. The twigs, leaves,
spores, and other portions are in small fragments, and their delicate cells are
often preserved in wonderful perfection.
CONDITIONS OF PRESERVATION.
The manner of occurrence of plants in sandstones, shales or other rocks is
often of considerable importance to the botanist and geologist, as an aid to
the correct interpretation of the actual conditions which obtained at the time
when the plant remains were accumulating in beds of sediment. To attempt
to restore the conditions under which any set of plants became preserved,
we have to carefully consider each special case. A nest of seeds preserved
as internal casts in a mass of sandstone, such as is represented by the block
of Carboniferous sandstone in fig. 19, suggests a quiet spot in an eddy
the central woody cylinders of Lepidodendroid trees; each consists of an
axial pith surrounded by a band of primary wood and a broader zone of
secondary wood. One of the axes probably belonged to the stem of which
only the shell has been preserved, the others must have come from other
trees and may have been floated in by water[128]. The microscopic details of
the wood and outer cortex have in this instance been preserved in a
calcareous material, which was no doubt derived by water percolating
through the volcanic ash. It is frequently found that in fossil trees or twigs a
separation of the tissues has taken place along such natural lines of
weakness as the cambium or the phellogen, before the petrifying medium
had time to permeate the entire structure. Tree stems recently killed by lava
streams during volcanic eruptions at the present day supply a parallel with
the Palaeozoic forest trees of Carboniferous times.
Guillemard in describing a volcanic crater in Celebes, speaks of burnt
trees still standing in the lava stream, “so charred at the base of the trunk
that we could easily push them down[129].” An interesting case is quoted by
Hooker in his Himalayan Journals, illustrating the occurrence of a hollow
shell of a tree, in which the outer portions of a stem had been left while the
inner portions had disappeared, the wood being hollow and so favourable to
the production of a current of air which accelerated the destruction of the
internal tissues.
On the coast near Burntisland on the Firth of Forth blocks of rock are met
with in which numerous plant fragments of Carboniferous age are scattered
in a confused mass through a calcareous volcanic matrix. The twigs, leaves,
spores, and other portions are in small fragments, and their delicate cells are
often preserved in wonderful perfection.
CONDITIONS OF PRESERVATION.
The manner of occurrence of plants in sandstones, shales or other rocks is
often of considerable importance to the botanist and geologist, as an aid to
the correct interpretation of the actual conditions which obtained at the time
when the plant remains were accumulating in beds of sediment. To attempt
to restore the conditions under which any set of plants became preserved,
we have to carefully consider each special case. A nest of seeds preserved
as internal casts in a mass of sandstone, such as is represented by the block
of Carboniferous sandstone in fig. 19, suggests a quiet spot in an eddy
Page 112
where seeds were deposited in the sandy sediment. Delicate leaf structures
with sporangia still intact, point to quietly flowing water and a transport of
no great distance. Occasionally the large number of delicate and light plant
fragments, associated it may be with insect wings, may favour the idea of a
wind storm which swept along the lighter pieces from a forest-clad slope
and deposited them in the water of a lake. In some Tertiary plant-beds the
manner of occurrence of leaves and flowers is such as to suggest a seasonal
alternation, and the different layers of plant débris may be correlated with
definite seasons of growth[130].
Fig. 19. Piece of Coal-Measures Sandstone with casts of Trigonocarpon seeds, from Peel
Quarry near Wigan. From a specimen in the Manchester Museum, Owens College. ½
nat. size.
The predominance of certain classes of plants in a particular bed may be
due to purely mechanical causes and to differential sorting by water, or it
may be that the district traversed by the stream which carried down the
fragments was occupied almost exclusively by one set of plants. The trees
from higher ground may be deposited in a different part of a river’s course
to those growing in the plains or lowland marshes. It is obviously
impossible to lay down any definite rules as to the reading of plant records,
as aids to the elucidation of past physical and botanical conditions. Each
case must be separately considered, and the various probabilities taken into
account, judging by reference to the analogy of present day conditions.
Various attempts, more or less successful, have been made to imitate the
natural processes of plant mineralisation[131]. By soaking sections of wood
for some time in different solutions, and then exposing them to heat, the
with sporangia still intact, point to quietly flowing water and a transport of
no great distance. Occasionally the large number of delicate and light plant
fragments, associated it may be with insect wings, may favour the idea of a
wind storm which swept along the lighter pieces from a forest-clad slope
and deposited them in the water of a lake. In some Tertiary plant-beds the
manner of occurrence of leaves and flowers is such as to suggest a seasonal
alternation, and the different layers of plant débris may be correlated with
definite seasons of growth[130].
Fig. 19. Piece of Coal-Measures Sandstone with casts of Trigonocarpon seeds, from Peel
Quarry near Wigan. From a specimen in the Manchester Museum, Owens College. ½
nat. size.
The predominance of certain classes of plants in a particular bed may be
due to purely mechanical causes and to differential sorting by water, or it
may be that the district traversed by the stream which carried down the
fragments was occupied almost exclusively by one set of plants. The trees
from higher ground may be deposited in a different part of a river’s course
to those growing in the plains or lowland marshes. It is obviously
impossible to lay down any definite rules as to the reading of plant records,
as aids to the elucidation of past physical and botanical conditions. Each
case must be separately considered, and the various probabilities taken into
account, judging by reference to the analogy of present day conditions.
Various attempts, more or less successful, have been made to imitate the
natural processes of plant mineralisation[131]. By soaking sections of wood
for some time in different solutions, and then exposing them to heat, the
Page 113
organic substance of the cell walls has been replaced by a deposit of oxide
of iron and other substances. Fern leaves heated to redness between pieces
of shale have been reduced to a condition very similar to that of fossil
fronds. Pieces of wood left for centuries in disused mines have been found
in a state closely resembling lignite[132]. Attempts have also been made to
reproduce the conditions under which vegetable tissues were converted into
coal, but as yet these have not yielded results of much scientific value. The
Geysers of Yellowstone Park have thrown some light on the manner in
which wood may be petrified by the percolation of siliceous solutions; and
it has been suggested that the silicification of plants may have been effected
by the waters of hot springs holding silica in solution. Examples of wood in
process of petrifaction in the Geyser district of North America have been
recorded by Kuntze[133], and discussed by Schweinfurth[134], Solms-
Laubach[135] and others[136]. The latter expresses the opinion that by a long
continuance of such action as may now be observed in the neighbourhood
of hot springs, the organic substance of wood might be replaced by
siliceous material. The exact manner of replacement needs more thorough
investigation. Kuntze describes the appearance of forest trees which have
been reached by the waters of neighbouring Geysers. The siliceous solution
rises in the wood by capillarity; the leaves, branches and bark are gradually
lost, and the outer tissues of the wood become hardened and petrified as the
result of evaporation from the exposed surface of the stem. The products of
decay going on in the plant tissues must be taken into account, and the
double decomposition which might result. There is no apparent reason why
experiments undertaken with pieces of recent wood exposed to permeation
by various calcareous and siliceous solutions under different conditions
should not furnish useful results.
of iron and other substances. Fern leaves heated to redness between pieces
of shale have been reduced to a condition very similar to that of fossil
fronds. Pieces of wood left for centuries in disused mines have been found
in a state closely resembling lignite[132]. Attempts have also been made to
reproduce the conditions under which vegetable tissues were converted into
coal, but as yet these have not yielded results of much scientific value. The
Geysers of Yellowstone Park have thrown some light on the manner in
which wood may be petrified by the percolation of siliceous solutions; and
it has been suggested that the silicification of plants may have been effected
by the waters of hot springs holding silica in solution. Examples of wood in
process of petrifaction in the Geyser district of North America have been
recorded by Kuntze[133], and discussed by Schweinfurth[134], Solms-
Laubach[135] and others[136]. The latter expresses the opinion that by a long
continuance of such action as may now be observed in the neighbourhood
of hot springs, the organic substance of wood might be replaced by
siliceous material. The exact manner of replacement needs more thorough
investigation. Kuntze describes the appearance of forest trees which have
been reached by the waters of neighbouring Geysers. The siliceous solution
rises in the wood by capillarity; the leaves, branches and bark are gradually
lost, and the outer tissues of the wood become hardened and petrified as the
result of evaporation from the exposed surface of the stem. The products of
decay going on in the plant tissues must be taken into account, and the
double decomposition which might result. There is no apparent reason why
experiments undertaken with pieces of recent wood exposed to permeation
by various calcareous and siliceous solutions under different conditions
should not furnish useful results.
Page 114
Page 115
CHAPTER V.
DIFFICULTIES AND SOURCES OF ERROR IN THE DETERMINATION OF FOSSIL
PLANTS.
“Robinson Crusoe did not feel bound to conclude, from the single human footprint which he
saw in the sand, that the maker of the impression had only one leg.”
Huxley’s Hume, p. 105, 1879.
The student of palaeobotany has perhaps to face more than his due share
of difficulties and fruitful sources of error; but on the other hand there is the
compensating advantage that trustworthy conclusions arrived at possess a
special value. While always on the alert for rational explanations of obscure
phenomena by means of the analogy supplied by existing causes, and ready
to draw from a wide knowledge of recent botany, in the interpretation of
problems furnished by fossil plants, the palaeobotanist must be constantly
alive to the necessity for cautious statement. That there is the greatest need
of moderation and safe reasoning in dealing with the botanical problems of
past ages, will be apparent to anyone possessing but a superficial
acquaintance with fossil plant literature. The necessity for a botanical and
geological training has already been referred to in a previous chapter.
It would serve no useful purpose, and would occupy no inconsiderable
space, to refer at length to the numerous mistakes which have been
committed by experienced writers on the subject of fossil plants. Laymen
might find in such a list of blunders a mere comedy of errors, but the
palaeobotanist must see in them serious warnings against dogmatic
conclusions or expressions of opinion on imperfect data and insufficient
evidence. The description of a fragment of a handle of a Wedgwood teapot
as a curious form of Calamite[137] and similar instances of unusual
determinations need not detain us as examples of instructive errors. The late
Prof. Williamson has on more than one occasion expressed himself in no
undecided manner as to the futility of attempting to determine specific
forms among fossil plants, without the aid of internal structure[138]; and even
in the case of well-preserved petrifactions he always refused to commit
DIFFICULTIES AND SOURCES OF ERROR IN THE DETERMINATION OF FOSSIL
PLANTS.
“Robinson Crusoe did not feel bound to conclude, from the single human footprint which he
saw in the sand, that the maker of the impression had only one leg.”
Huxley’s Hume, p. 105, 1879.
The student of palaeobotany has perhaps to face more than his due share
of difficulties and fruitful sources of error; but on the other hand there is the
compensating advantage that trustworthy conclusions arrived at possess a
special value. While always on the alert for rational explanations of obscure
phenomena by means of the analogy supplied by existing causes, and ready
to draw from a wide knowledge of recent botany, in the interpretation of
problems furnished by fossil plants, the palaeobotanist must be constantly
alive to the necessity for cautious statement. That there is the greatest need
of moderation and safe reasoning in dealing with the botanical problems of
past ages, will be apparent to anyone possessing but a superficial
acquaintance with fossil plant literature. The necessity for a botanical and
geological training has already been referred to in a previous chapter.
It would serve no useful purpose, and would occupy no inconsiderable
space, to refer at length to the numerous mistakes which have been
committed by experienced writers on the subject of fossil plants. Laymen
might find in such a list of blunders a mere comedy of errors, but the
palaeobotanist must see in them serious warnings against dogmatic
conclusions or expressions of opinion on imperfect data and insufficient
evidence. The description of a fragment of a handle of a Wedgwood teapot
as a curious form of Calamite[137] and similar instances of unusual
determinations need not detain us as examples of instructive errors. The late
Prof. Williamson has on more than one occasion expressed himself in no
undecided manner as to the futility of attempting to determine specific
forms among fossil plants, without the aid of internal structure[138]; and even
in the case of well-preserved petrifactions he always refused to commit
Page 116
himself to definite specific diagnoses. In his remarks in this connection,
Williamson no doubt allowed himself to express a much needed warning in
too sweeping language. It is one of the most serious drawbacks in
palaeobotanical researches that in the majority of cases the specimens of
plants are both fragmentary and without any trace of internal structure.
Specimens in which the anatomical characters have been preserved
necessarily possess far greater value from the botanist’s point of view than
those in which no such petrifaction has occurred. On the other hand,
however, it is perfectly possible with due care to obtain trustworthy and
valuable results from the examination of structureless casts and
impressions. In dealing with the less promising forms of plant fossils, there
is in the first place the danger of trusting to superficial resemblance.
Hundreds of fossil plants have been described under the names of existing
genera on the strength of a supposed agreement in external form; but such
determinations are very frequently not only valueless but dangerously
misleading. Unless the evidence is of the best, it is a serious mistake to
make use of recent generic designations. If we consider the difficulties
which would attend an attempt to determine the leaves, fragments of stems
and other detached portions of various recent genera, we can better
appreciate the greater probability of error in the case of imperfectly
preserved fossil fragments.
EXTERNAL RESEMBLANCE.
The portions of stems represented in figures 20 and 21, exhibit a fairly
close resemblance to one another; in the absence of microscopical sections
or of the reproductive organs it would be practically impossible to
discriminate with any certainty between fossil specimens of the plants
shown in the drawings. Examples such as these, and many others which
might be cited, serve to illustrate the possibility of confusion not merely
between different genera of the same family, but even between members of
different classes or groups. The long slender branches of the Polygonum
represented in (fig. 21) would naturally be referred to Equisetum in the
absence of the flowers (fig. 20 B), or without a careful examination of the
insignificant scaly leaves borne at the nodes. The resemblance between
Casuarina and Ephedra and the British species of Equisetum, or such a
tropical form as E. debile, speaks for itself.
Williamson no doubt allowed himself to express a much needed warning in
too sweeping language. It is one of the most serious drawbacks in
palaeobotanical researches that in the majority of cases the specimens of
plants are both fragmentary and without any trace of internal structure.
Specimens in which the anatomical characters have been preserved
necessarily possess far greater value from the botanist’s point of view than
those in which no such petrifaction has occurred. On the other hand,
however, it is perfectly possible with due care to obtain trustworthy and
valuable results from the examination of structureless casts and
impressions. In dealing with the less promising forms of plant fossils, there
is in the first place the danger of trusting to superficial resemblance.
Hundreds of fossil plants have been described under the names of existing
genera on the strength of a supposed agreement in external form; but such
determinations are very frequently not only valueless but dangerously
misleading. Unless the evidence is of the best, it is a serious mistake to
make use of recent generic designations. If we consider the difficulties
which would attend an attempt to determine the leaves, fragments of stems
and other detached portions of various recent genera, we can better
appreciate the greater probability of error in the case of imperfectly
preserved fossil fragments.
EXTERNAL RESEMBLANCE.
The portions of stems represented in figures 20 and 21, exhibit a fairly
close resemblance to one another; in the absence of microscopical sections
or of the reproductive organs it would be practically impossible to
discriminate with any certainty between fossil specimens of the plants
shown in the drawings. Examples such as these, and many others which
might be cited, serve to illustrate the possibility of confusion not merely
between different genera of the same family, but even between members of
different classes or groups. The long slender branches of the Polygonum
represented in (fig. 21) would naturally be referred to Equisetum in the
absence of the flowers (fig. 20 B), or without a careful examination of the
insignificant scaly leaves borne at the nodes. The resemblance between
Casuarina and Ephedra and the British species of Equisetum, or such a
tropical form as E. debile, speaks for itself.
Page 117
Fig. 20.
A. Restio tetraphylla Labill. (Monocotyledon).
B. Equisetum variegatum Schleich. (Vascular Cryptogam).
C. Equisetum debile Roxb. (Vascular Cryptogam)
D. Casuarina stricta Dryand. (Dicotyledon).
E. Ephedra distachya Linn. (Gymnosperm). (A–E ½ nat. size).
A. Restio tetraphylla Labill. (Monocotyledon).
B. Equisetum variegatum Schleich. (Vascular Cryptogam).
C. Equisetum debile Roxb. (Vascular Cryptogam)
D. Casuarina stricta Dryand. (Dicotyledon).
E. Ephedra distachya Linn. (Gymnosperm). (A–E ½ nat. size).
Page 118
Fig. 21. Polygonum Equisetiforme Sibth. and Sm. A. Showing habit of plant. ½ nat. size. The
two flowers towards the apex of one branch, drawn to a larger scale in B. C. Node with
small leaf and ochrea characteristic of Polygonaceæ. From a plant in the Cambridge
Botanic Garden.
two flowers towards the apex of one branch, drawn to a larger scale in B. C. Node with
small leaf and ochrea characteristic of Polygonaceæ. From a plant in the Cambridge
Botanic Garden.
Page 119
Fig. 22. Kaulfussia æsculifolia Blume. From a specimen from Java in the British Museum
herbarium. ⅓ nat. size.
Endless examples might be quoted illustrating the absolute futility, in
many cases, of relying on external features even for the purpose of class
distinction. An acquaintance with the general habit and appearance of only
the better known members of a family, frequently leads to serious mistakes.
The specimen shown in fig. 22 is a leaf of a tropical fern Kaulfussia, a
genus now living in South-eastern Asia, and a member of one of the most
important and interesting families of the Filicinæ, the Marrattiaceæ; its form
herbarium. ⅓ nat. size.
Endless examples might be quoted illustrating the absolute futility, in
many cases, of relying on external features even for the purpose of class
distinction. An acquaintance with the general habit and appearance of only
the better known members of a family, frequently leads to serious mistakes.
The specimen shown in fig. 22 is a leaf of a tropical fern Kaulfussia, a
genus now living in South-eastern Asia, and a member of one of the most
important and interesting families of the Filicinæ, the Marrattiaceæ; its form
Page 120
is widely different from that which one is accustomed to associate with fern
fronds. It is unlikely that the impression of a sterile leaf of Kaulfussia
would be recognised as a portion of a fern plant.
Similarly in another exceedingly important group of plants, the
Cycadaceæ[139], the examples usually met with in botanical gardens are quite
insufficient as standards of comparison when we are dealing with fossil
forms. Familiarity with a few commoner types leads us to regard them as
typical for the whole family. In Mesozoic times cycadean plants were far
more numerous and widely distributed than at the present time, and to
adequately study the numerous fossil examples we need as thorough an
acquaintance as possible with the comparatively small number of surviving
genera and species. The less common and more isolated species of an
existing family may often be of far greater importance to the palaeobotanist
than the common and more typical forms. This importance of rare and little
known types will be more fully illustrated in the chapters dealing with the
Cycadaceæ and other plant groups. Among Dicotyledons, the Natural Order
Proteaceæ, at present characteristic of South Africa and Australia, and also
represented in South America and the Pacific Islands, is of considerable
interest to the student of fossil Angiosperms. In a valuable address delivered
before the Linnean Society[140] in 1870 Bentham drew attention to the
marked ‘protean’ character of the members of this family. He laid special
stress on this particular division of the Dicotyledons in view of certain far-
reaching conclusions, which had been based on the occurrence in different
parts of Europe of fossil leaves supposed to be those of Proteaceous
genera[141]. Speaking of detached leaves, Bentham says:—“I do not know of
a single one which, in outline or venation, is exclusively characteristic of
the order, or of any one of its genera.” Species of Grevillea, Hakea and a
few other genera are more or less familiar in plant houses, but the leaf-
forms illustrated by the commoner members of the family convey no idea
of the enormous variation which is met with not only in the family as a
whole, but in the different species of the same genus. The striking diversity
of leaf within the limits of a single genus will be dealt with more fully in
volume ii. under the head of Fossil Dicotyledons.
VENATION CHARACTERS.
There is a common source of danger in attempting to carry too far the
venation characters as tests of affinity. The parallel venation of
fronds. It is unlikely that the impression of a sterile leaf of Kaulfussia
would be recognised as a portion of a fern plant.
Similarly in another exceedingly important group of plants, the
Cycadaceæ[139], the examples usually met with in botanical gardens are quite
insufficient as standards of comparison when we are dealing with fossil
forms. Familiarity with a few commoner types leads us to regard them as
typical for the whole family. In Mesozoic times cycadean plants were far
more numerous and widely distributed than at the present time, and to
adequately study the numerous fossil examples we need as thorough an
acquaintance as possible with the comparatively small number of surviving
genera and species. The less common and more isolated species of an
existing family may often be of far greater importance to the palaeobotanist
than the common and more typical forms. This importance of rare and little
known types will be more fully illustrated in the chapters dealing with the
Cycadaceæ and other plant groups. Among Dicotyledons, the Natural Order
Proteaceæ, at present characteristic of South Africa and Australia, and also
represented in South America and the Pacific Islands, is of considerable
interest to the student of fossil Angiosperms. In a valuable address delivered
before the Linnean Society[140] in 1870 Bentham drew attention to the
marked ‘protean’ character of the members of this family. He laid special
stress on this particular division of the Dicotyledons in view of certain far-
reaching conclusions, which had been based on the occurrence in different
parts of Europe of fossil leaves supposed to be those of Proteaceous
genera[141]. Speaking of detached leaves, Bentham says:—“I do not know of
a single one which, in outline or venation, is exclusively characteristic of
the order, or of any one of its genera.” Species of Grevillea, Hakea and a
few other genera are more or less familiar in plant houses, but the leaf-
forms illustrated by the commoner members of the family convey no idea
of the enormous variation which is met with not only in the family as a
whole, but in the different species of the same genus. The striking diversity
of leaf within the limits of a single genus will be dealt with more fully in
volume ii. under the head of Fossil Dicotyledons.
VENATION CHARACTERS.
There is a common source of danger in attempting to carry too far the
venation characters as tests of affinity. The parallel venation of
Page 121
Monocotyledons is by no means a safe guide to follow in all cases as a
distinguishing feature of this class of plants. In addition to such leaves as
those of the Gymnosperm Cordaites and detached pinnæ of Cycads, there
are certain species of Dicotyledons which correspond in the character of
their venation to Monocotyledonous leaves. Eryngium montanum Coult., E.
Lassauxi Dcne., and other species of this genus of Umbelliferæ agree
closely with such a plant as Pandanus or other Monocotyledons; similarly
the long linear leaves of Richea dracophylla, R. Br., one of the Ericaceæ,
are identical in form with many monocotyledonous leaves. Instances might
also be quoted of monocotyledonous leaves, such as species of Smilax and
others which Lindley included in his family of Dictyogens which
correspond closely with some types of Dicotyledons[142]. Venation
characters must be used with care even in determining classes or groups,
and with still greater reserve if relied on as family or generic tests.
It is too frequently the case that while we are conversant with the most
detailed histological structure of a fossil plant stem, its external form is a
matter of conjecture. The conditions which have favoured the petrifaction
of plant tissues have as a rule not been favourable for the preservation of
good casts or impressions of the external features; and, on the other hand, in
the best impressions of fern fronds or other plants, in which the finest veins
are clearly marked, there is no trace of internal structure. It is, however,
frequently the case that a knowledge of the internal structure of a particular
plant enables us to interpret certain features in a structureless cast which
could not be understood without the help of histological facts. A particularly
interesting example of anatomical knowledge affording a key to apparently
abnormal peculiarities in a specimen preserved by incrustation, is afforded
by the fructification of the genus Sphenophyllum. Some few years ago
Williamson described in detail the structure of a fossil strobilus (i.e. cone)
from the Coal-Measures, but owing to the isolated occurrence of the
specimens he was unable to determine the plant to which the strobilus
belonged. On re-examining some strobili of Sphenophyllum, preserved by
incrustation, in the light of Williamson’s descriptions, Zeiller was able to
explain certain features in his specimens which had hitherto been a puzzle,
and he demonstrated that Williamson’s cone was that of a Sphenophyllum.
Similar examples might be quoted, but enough has been said to emphasize
the importance of dealing as far as possible with both petrifactions and
incrustations. The facts derived from a study of a plant in one form of
distinguishing feature of this class of plants. In addition to such leaves as
those of the Gymnosperm Cordaites and detached pinnæ of Cycads, there
are certain species of Dicotyledons which correspond in the character of
their venation to Monocotyledonous leaves. Eryngium montanum Coult., E.
Lassauxi Dcne., and other species of this genus of Umbelliferæ agree
closely with such a plant as Pandanus or other Monocotyledons; similarly
the long linear leaves of Richea dracophylla, R. Br., one of the Ericaceæ,
are identical in form with many monocotyledonous leaves. Instances might
also be quoted of monocotyledonous leaves, such as species of Smilax and
others which Lindley included in his family of Dictyogens which
correspond closely with some types of Dicotyledons[142]. Venation
characters must be used with care even in determining classes or groups,
and with still greater reserve if relied on as family or generic tests.
It is too frequently the case that while we are conversant with the most
detailed histological structure of a fossil plant stem, its external form is a
matter of conjecture. The conditions which have favoured the petrifaction
of plant tissues have as a rule not been favourable for the preservation of
good casts or impressions of the external features; and, on the other hand, in
the best impressions of fern fronds or other plants, in which the finest veins
are clearly marked, there is no trace of internal structure. It is, however,
frequently the case that a knowledge of the internal structure of a particular
plant enables us to interpret certain features in a structureless cast which
could not be understood without the help of histological facts. A particularly
interesting example of anatomical knowledge affording a key to apparently
abnormal peculiarities in a specimen preserved by incrustation, is afforded
by the fructification of the genus Sphenophyllum. Some few years ago
Williamson described in detail the structure of a fossil strobilus (i.e. cone)
from the Coal-Measures, but owing to the isolated occurrence of the
specimens he was unable to determine the plant to which the strobilus
belonged. On re-examining some strobili of Sphenophyllum, preserved by
incrustation, in the light of Williamson’s descriptions, Zeiller was able to
explain certain features in his specimens which had hitherto been a puzzle,
and he demonstrated that Williamson’s cone was that of a Sphenophyllum.
Similar examples might be quoted, but enough has been said to emphasize
the importance of dealing as far as possible with both petrifactions and
incrustations. The facts derived from a study of a plant in one form of
Page 122
preservation may enable us to interpret or to amplify the data afforded by
specimens preserved in another form.
DECORTICATED STEMS.
The fact that plants usually occur in detached fragments, and that they
have often been sorted by water, and that portions of the same plant have
been embedded in sediment considerable distances apart, is a constant
source of difficulty. Deciduous leaves, cones, or angiospermous flowers,
and other portions of a plant which become naturally separated from the
parent tree, are met with as detached specimens, and it is comparatively
seldom that we have the necessary data for reuniting the isolated members.
As the result of the partial decay and separation of portions of the same
stem or branch, the wood and bark may be separately preserved. Darwin[143]
describes how the bark often falls from Eucalyptus trees, and hangs in long
shreds, which swing about in the wind, and give to the woods a desolate
and untidy appearance. In the passage already quoted from the narrative of
the voyage of the Challenger, illustrations are afforded of the manner in
which detached portions of plants are likely to be preserved in a fossil state.
The epidermal layer of a leaf or the surface tissues of a twig may be
detached from the underlying tissues and separately preserved[144]. It is
exceedingly common for a stem to be partially decorticated before
preservation, and the appearance presented by a cast or impression of the
surface of a woody cylinder, and by the same stem with a part or the whole
of its cortex intact is strikingly different. The late Prof. Balfour[145] draws
attention to this source of error in his text-book of palaeobotany, and gives
figures illustrating the different appearance presented by a branch of
Araucaria imbricata Pav. when seen with its bark intact and more or less
decorticated. Specimens that are now recognised as casts of stems from
which the cortex had been more or less completely removed before
preservation, were originally described under distinct generic names, such
as Bergeria, Knorria and others. These are now known to be imperfect
examples of Sigillarian or Lepidodendroid plants. Grand’Eury[146] quotes the
bark of Lepidodendron Veltheimianum Presl. as a fossil which has been
described under twenty-eight specific names, and placed in several genera.
Since the microscopical examination of fossil plant-anatomy was
rendered possible, a more correct interpretation of decorticated and
incomplete specimens has been considerably facilitated. The examination of
specimens preserved in another form.
DECORTICATED STEMS.
The fact that plants usually occur in detached fragments, and that they
have often been sorted by water, and that portions of the same plant have
been embedded in sediment considerable distances apart, is a constant
source of difficulty. Deciduous leaves, cones, or angiospermous flowers,
and other portions of a plant which become naturally separated from the
parent tree, are met with as detached specimens, and it is comparatively
seldom that we have the necessary data for reuniting the isolated members.
As the result of the partial decay and separation of portions of the same
stem or branch, the wood and bark may be separately preserved. Darwin[143]
describes how the bark often falls from Eucalyptus trees, and hangs in long
shreds, which swing about in the wind, and give to the woods a desolate
and untidy appearance. In the passage already quoted from the narrative of
the voyage of the Challenger, illustrations are afforded of the manner in
which detached portions of plants are likely to be preserved in a fossil state.
The epidermal layer of a leaf or the surface tissues of a twig may be
detached from the underlying tissues and separately preserved[144]. It is
exceedingly common for a stem to be partially decorticated before
preservation, and the appearance presented by a cast or impression of the
surface of a woody cylinder, and by the same stem with a part or the whole
of its cortex intact is strikingly different. The late Prof. Balfour[145] draws
attention to this source of error in his text-book of palaeobotany, and gives
figures illustrating the different appearance presented by a branch of
Araucaria imbricata Pav. when seen with its bark intact and more or less
decorticated. Specimens that are now recognised as casts of stems from
which the cortex had been more or less completely removed before
preservation, were originally described under distinct generic names, such
as Bergeria, Knorria and others. These are now known to be imperfect
examples of Sigillarian or Lepidodendroid plants. Grand’Eury[146] quotes the
bark of Lepidodendron Veltheimianum Presl. as a fossil which has been
described under twenty-eight specific names, and placed in several genera.
Since the microscopical examination of fossil plant-anatomy was
rendered possible, a more correct interpretation of decorticated and
incomplete specimens has been considerably facilitated. The examination of
Page 123
tangential sections taken at different levels in the cortex of such a plant as
Lepidodendron brings out the distribution of thin and thick-walled tissue.
Regularly placed prominences on such a stem as the Knorria shown in fig.
23 are due to the existence in the original stem of spirally disposed areas of
thin-walled and less resistant tissue; as decay proceeded, the thinner cells
would be the first to disappear, and depressions would thus be formed in the
surrounding thicker walled and stronger tissue. If the stem became
embedded in mud or sand before the more resistant tissue had time to
decay, but after the removal of the thin-walled cells, the surrounding
sediment would fill up the depressions and finally, after the complete decay
of the stem, the impression on the mould or on the cast, formed by the
filling up of the space left by the stem, would have the form of regularly
disposed projections marking the position of the more delicate tissues. The
specimen represented in the figure is an exceedingly interesting and well
preserved example of a Coal-Measure stem combining in itself
representatives of what were formerly spoken of as distinct genera.
Lepidodendron brings out the distribution of thin and thick-walled tissue.
Regularly placed prominences on such a stem as the Knorria shown in fig.
23 are due to the existence in the original stem of spirally disposed areas of
thin-walled and less resistant tissue; as decay proceeded, the thinner cells
would be the first to disappear, and depressions would thus be formed in the
surrounding thicker walled and stronger tissue. If the stem became
embedded in mud or sand before the more resistant tissue had time to
decay, but after the removal of the thin-walled cells, the surrounding
sediment would fill up the depressions and finally, after the complete decay
of the stem, the impression on the mould or on the cast, formed by the
filling up of the space left by the stem, would have the form of regularly
disposed projections marking the position of the more delicate tissues. The
specimen represented in the figure is an exceedingly interesting and well
preserved example of a Coal-Measure stem combining in itself
representatives of what were formerly spoken of as distinct genera.
Page 124
Fig. 23. A dichotomously branched Lepidodendroid stem (Knorria mirabilis Ren. and
Zeill.). After Renault and Zeiller[147]. (¼ nat. size.) The original specimen is in the Natural
History Museum, Paris.
The surface of the fossil as seen at e affords a typical example of the
Knorria type of stem; the spirally disposed peg-like projections are the casts
of cavities formed by the decay of the delicate cells surrounding each leaf-
trace bundle on its way through the cortex of the stem. The surface g
exhibits a somewhat different appearance, owing to the fact that we have
the cast of the stem taken at a slightly different level. The surface of the
thick layer of coal at a shows very clearly the outlines of the leaf-cushions;
on the somewhat deeper surfaces b, c and d the leaf-cushions are but faintly
indicated, and the long narrow lines on the coal at c represent the leaf-traces
in the immediate neighbourhood of the leaf-cushions.
IMPERFECT CASTS.
Zeill.). After Renault and Zeiller[147]. (¼ nat. size.) The original specimen is in the Natural
History Museum, Paris.
The surface of the fossil as seen at e affords a typical example of the
Knorria type of stem; the spirally disposed peg-like projections are the casts
of cavities formed by the decay of the delicate cells surrounding each leaf-
trace bundle on its way through the cortex of the stem. The surface g
exhibits a somewhat different appearance, owing to the fact that we have
the cast of the stem taken at a slightly different level. The surface of the
thick layer of coal at a shows very clearly the outlines of the leaf-cushions;
on the somewhat deeper surfaces b, c and d the leaf-cushions are but faintly
indicated, and the long narrow lines on the coal at c represent the leaf-traces
in the immediate neighbourhood of the leaf-cushions.
IMPERFECT CASTS.
Page 125
It is not uncommon among the older plant-bearing rocks to find a piece
of sandstone or shale of which the surface exhibits a somewhat irregular
reticulate pattern, the long and oval meshes having the form of slightly
raised bosses. The size of such a reticulum may vary from one in which the
pattern is barely visible to the unaided eye to one with meshes more than an
inch in length. The generic name Lyginodendron[148] was proposed several
years ago (1843) for a specimen having such a pattern on its surface, but
without any clue having been found as to the meaning of the elongated
raised areas separated from one another by a narrow groove. At a later date
Williamson investigated the anatomy of some petrified fragments of a
Carboniferous plant which suggested a possible explanation of the surface
features in the structureless specimens. The name Lyginodendron was
applied to this newly discovered plant, of which one characteristic was
found to be the occurrence of a hypodermal band of strong thick-walled
tissue arranged in the form of a network with the meshes occupied by thin-
walled parenchyma. If such a stem were undergoing gradual decay, the
more delicate tissue of the meshes would be destroyed first and the harder
framework left. A cast of such a partially decayed stem would take the
form, therefore, of projecting areas, corresponding to the hollowed out areas
of decayed tissue, and intervening depressions corresponding to the
projecting framework of the more resistant fibrous tissue. A precisely
similar arrangement of hypodermal strengthening tissue occurs in various
Palaeozoic and other plants, and casts presenting a corresponding
appearance cannot be referred with certainty to one special genus; such
casts are of no real scientific value[149].
The old generic terms Artisia and Sternbergia illustrate another source of
error which can be avoided only by means of a knowledge of internal
structure. The former name was proposed by Sternberg and the latter by
Artis for precisely similar Carboniferous fossils, having the form of
cylindrical bodies marked by numerous transverse annular ridges and
grooves. These fossils are now known to be casts of the large discoid pith of
the genus Cordaites, an extinct type of Palaeozoic Gymnosperms.
Calamites and Tylodendron afford other instances of plants in which the
supposed surface characters have been shown to be those of the pith-cast.
The former genus is described at length in a later chapter, but the latter may
be briefly referred to. A cast, apparently of a stem, from the Permian rocks
of Russia was figured in 1870 under the name Tylodendron; the surface
of sandstone or shale of which the surface exhibits a somewhat irregular
reticulate pattern, the long and oval meshes having the form of slightly
raised bosses. The size of such a reticulum may vary from one in which the
pattern is barely visible to the unaided eye to one with meshes more than an
inch in length. The generic name Lyginodendron[148] was proposed several
years ago (1843) for a specimen having such a pattern on its surface, but
without any clue having been found as to the meaning of the elongated
raised areas separated from one another by a narrow groove. At a later date
Williamson investigated the anatomy of some petrified fragments of a
Carboniferous plant which suggested a possible explanation of the surface
features in the structureless specimens. The name Lyginodendron was
applied to this newly discovered plant, of which one characteristic was
found to be the occurrence of a hypodermal band of strong thick-walled
tissue arranged in the form of a network with the meshes occupied by thin-
walled parenchyma. If such a stem were undergoing gradual decay, the
more delicate tissue of the meshes would be destroyed first and the harder
framework left. A cast of such a partially decayed stem would take the
form, therefore, of projecting areas, corresponding to the hollowed out areas
of decayed tissue, and intervening depressions corresponding to the
projecting framework of the more resistant fibrous tissue. A precisely
similar arrangement of hypodermal strengthening tissue occurs in various
Palaeozoic and other plants, and casts presenting a corresponding
appearance cannot be referred with certainty to one special genus; such
casts are of no real scientific value[149].
The old generic terms Artisia and Sternbergia illustrate another source of
error which can be avoided only by means of a knowledge of internal
structure. The former name was proposed by Sternberg and the latter by
Artis for precisely similar Carboniferous fossils, having the form of
cylindrical bodies marked by numerous transverse annular ridges and
grooves. These fossils are now known to be casts of the large discoid pith of
the genus Cordaites, an extinct type of Palaeozoic Gymnosperms.
Calamites and Tylodendron afford other instances of plants in which the
supposed surface characters have been shown to be those of the pith-cast.
The former genus is described at length in a later chapter, but the latter may
be briefly referred to. A cast, apparently of a stem, from the Permian rocks
of Russia was figured in 1870 under the name Tylodendron; the surface
Page 126
being characterised by spirally arranged lozenge-shaped projections,
described as leaf-scars. Specimens were eventually discovered in which the
supposed stem was shown to be a cast of the large pith of a plant possessing
secondary wood very like that of the recent genus Araucaria. The
projecting portions, instead of being leaf-cushions, were found to be the
casts of depressions in the inner face of the wood where strands of vascular
tissue bent outwards on their way to the leaves. If a cast is made of the
comparatively large pith of Araucaria imbricata the features of
Tylodendron are fairly closely reproduced[150].
A dried Bracken frond lying on the ground in the Autumn presents a very
different appearance as regards the form of the ultimate segments of the
frond to that of a freshly cut leaf. In the former the edges of the pinnules are
strongly recurved, and their shape is considerably altered. Immersed in
water for some time fern fronds or other leaves undergo maceration, and the
more delicate lamina of the leaf rots away much more rapidly than the
scaffolding of veins. Among fossil fern fronds differences in the form of the
pinnules and in the shape and extent of the lamina, to which a specific value
is assigned, are no doubt in many cases merely the expression either of
differences in the state of the leaves at the time of fossilisation or of the
different conditions under which they became embedded. Differential decay
and disorganisation of plant tissues are factors of considerable importance
with regard to the fossilisation of plants. As Lindley[151] and later writers
have suggested, the absence or comparative scarcity of certain forms of
plants from a particular fossil flora may in some cases be due to their rapid
decay and non-preservation as fossils; it does not necessarily mean that
such plants were unrepresented in the vegetation of that period. The
decayed rhizomes of the Bracken fern often seen hanging from the roadside
banks on a heath or moorland, and consisting of flat dark coloured bands of
resistant sclerenchyma in a loose sheath of the hard shrivelled tissue, are in
striking contrast to the perfect stem. A rotting Palm stem is gradually
reduced to a loose stringy mass consisting of vascular strands of which the
connecting parenchymatous tissue has been entirely removed. It must
frequently have happened that detached vascular bundles or strands and
plates of hard strengthening tissue have been preserved as fossils and
mistaken for complete portions of plants.
MINERAL DEPOSITS SIMULATING PLANTS.
described as leaf-scars. Specimens were eventually discovered in which the
supposed stem was shown to be a cast of the large pith of a plant possessing
secondary wood very like that of the recent genus Araucaria. The
projecting portions, instead of being leaf-cushions, were found to be the
casts of depressions in the inner face of the wood where strands of vascular
tissue bent outwards on their way to the leaves. If a cast is made of the
comparatively large pith of Araucaria imbricata the features of
Tylodendron are fairly closely reproduced[150].
A dried Bracken frond lying on the ground in the Autumn presents a very
different appearance as regards the form of the ultimate segments of the
frond to that of a freshly cut leaf. In the former the edges of the pinnules are
strongly recurved, and their shape is considerably altered. Immersed in
water for some time fern fronds or other leaves undergo maceration, and the
more delicate lamina of the leaf rots away much more rapidly than the
scaffolding of veins. Among fossil fern fronds differences in the form of the
pinnules and in the shape and extent of the lamina, to which a specific value
is assigned, are no doubt in many cases merely the expression either of
differences in the state of the leaves at the time of fossilisation or of the
different conditions under which they became embedded. Differential decay
and disorganisation of plant tissues are factors of considerable importance
with regard to the fossilisation of plants. As Lindley[151] and later writers
have suggested, the absence or comparative scarcity of certain forms of
plants from a particular fossil flora may in some cases be due to their rapid
decay and non-preservation as fossils; it does not necessarily mean that
such plants were unrepresented in the vegetation of that period. The
decayed rhizomes of the Bracken fern often seen hanging from the roadside
banks on a heath or moorland, and consisting of flat dark coloured bands of
resistant sclerenchyma in a loose sheath of the hard shrivelled tissue, are in
striking contrast to the perfect stem. A rotting Palm stem is gradually
reduced to a loose stringy mass consisting of vascular strands of which the
connecting parenchymatous tissue has been entirely removed. It must
frequently have happened that detached vascular bundles or strands and
plates of hard strengthening tissue have been preserved as fossils and
mistaken for complete portions of plants.
MINERAL DEPOSITS SIMULATING PLANTS.
Page 127
Apart from the necessity of keeping in view the possible differences in
form due to the state of the plant fragments at the time of preservation, and
the marked contrast between the same species preserved in different kinds
of rock, there are numerous sources of error which belong to an entirely
different category. The so-called moss-agates and the well-known dendritic
markings of black oxide of manganese, are among the better known
instances of purely inorganic structures simulating plant forms.
An interesting example of this striking similarity between a purely
mineral deposit and the external form of a plant is afforded by some
specimens originally described as impressions of the oldest known fern.
The frontispiece to a well-known work on fossil plants, Le monde des
plantes avant l’apparition de l’homme[152], represents a fern-like fossil on
the surface of a piece of Silurian slate. The supposed plant was named
Eopteris Morierei Sap., and it is occasionally referred to as the oldest land
plant in books of comparatively recent date. In the Museum of the School
of Mines, Berlin, there are some specimens of Angers slate on some of
which the cleavage face shows a shallow longitudinal groove bearing on
either side somewhat irregularly oblong and oval appendages of which the
surface is traversed by fine vein-like markings. A careful examination of the
slate reveals the fact that these apparent fern pinnules are merely films of
iron pyrites deposited from a solution which was introduced along the
rachis-like channel. Many of the extraordinary structures described as
plants by Reinsch[153] in his Memoir on the minute structure of coal have
been shown to be of purely mineral origin.
The innumerable casts of animal-burrows and trails as well as the casts of
egg-cases and various other bodies, which have been described as fossil
algae, must be included among the most fruitful sources of error.
It requires but a short experience of microscopical investigation of fossil
plant structures to discover numerous pitfalls in the appearance presented
by sections of calcareous and siliceous nodules. The juxtaposition of tissues
apparently parts of the same plant, and the penetration by growing roots of
partially decayed plant débris, serve to mislead an unpractised observer. In
sections of the English ‘calcareous nodules’ one very frequently finds the
tissue of Stigmarian appendages occupying every conceivable position, and
preserved in places admirably calculated to lead to false interpretations. The
more minute investigation of tissues is often rendered difficult by deceptive
form due to the state of the plant fragments at the time of preservation, and
the marked contrast between the same species preserved in different kinds
of rock, there are numerous sources of error which belong to an entirely
different category. The so-called moss-agates and the well-known dendritic
markings of black oxide of manganese, are among the better known
instances of purely inorganic structures simulating plant forms.
An interesting example of this striking similarity between a purely
mineral deposit and the external form of a plant is afforded by some
specimens originally described as impressions of the oldest known fern.
The frontispiece to a well-known work on fossil plants, Le monde des
plantes avant l’apparition de l’homme[152], represents a fern-like fossil on
the surface of a piece of Silurian slate. The supposed plant was named
Eopteris Morierei Sap., and it is occasionally referred to as the oldest land
plant in books of comparatively recent date. In the Museum of the School
of Mines, Berlin, there are some specimens of Angers slate on some of
which the cleavage face shows a shallow longitudinal groove bearing on
either side somewhat irregularly oblong and oval appendages of which the
surface is traversed by fine vein-like markings. A careful examination of the
slate reveals the fact that these apparent fern pinnules are merely films of
iron pyrites deposited from a solution which was introduced along the
rachis-like channel. Many of the extraordinary structures described as
plants by Reinsch[153] in his Memoir on the minute structure of coal have
been shown to be of purely mineral origin.
The innumerable casts of animal-burrows and trails as well as the casts of
egg-cases and various other bodies, which have been described as fossil
algae, must be included among the most fruitful sources of error.
It requires but a short experience of microscopical investigation of fossil
plant structures to discover numerous pitfalls in the appearance presented
by sections of calcareous and siliceous nodules. The juxtaposition of tissues
apparently parts of the same plant, and the penetration by growing roots of
partially decayed plant débris, serve to mislead an unpractised observer. In
sections of the English ‘calcareous nodules’ one very frequently finds the
tissue of Stigmarian appendages occupying every conceivable position, and
preserved in places admirably calculated to lead to false interpretations. The
more minute investigation of tissues is often rendered difficult by deceptive
Page 128
appearances simulating original structures, but which are in reality the
result of mineralisation. It is no easy matter in some cases to discover
whether a particular cell in a fossil tissue was originally thick-walled, or
whether its sclerous appearance is due to the deposition of mineral matter
on the inside of the thin cell-membrane. Examples of such sources of error
as have been briefly referred to, and others, will be found in various parts of
the descriptive portions of this book.
Fig. 24. A. Section of partially disorganised tissue attacked by some boring animal. c, c,
coprolites; d, a tunnel made by the borer through the plant tissue.
B. Transverse section of a Lepidodendroid leaf, of which the inner tissues have been
destroyed and the cavity filled with coprolites; simulating a sporangium containing
spores. (A and B from specimens in the Botanical Laboratory collection, Cambridge.)
TRACES OF WOOD-BORERS IN PETRIFIED TISSUE.
There is one other form of pitfall which should be briefly noticed. In
sections of petrified plants one occasionally finds clean cut canals
penetrating a mass of tissue, and differing in their manner of occurrence and
in their somewhat larger size from ordinary secretory ducts. Such tunnels or
result of mineralisation. It is no easy matter in some cases to discover
whether a particular cell in a fossil tissue was originally thick-walled, or
whether its sclerous appearance is due to the deposition of mineral matter
on the inside of the thin cell-membrane. Examples of such sources of error
as have been briefly referred to, and others, will be found in various parts of
the descriptive portions of this book.
Fig. 24. A. Section of partially disorganised tissue attacked by some boring animal. c, c,
coprolites; d, a tunnel made by the borer through the plant tissue.
B. Transverse section of a Lepidodendroid leaf, of which the inner tissues have been
destroyed and the cavity filled with coprolites; simulating a sporangium containing
spores. (A and B from specimens in the Botanical Laboratory collection, Cambridge.)
TRACES OF WOOD-BORERS IN PETRIFIED TISSUE.
There is one other form of pitfall which should be briefly noticed. In
sections of petrified plants one occasionally finds clean cut canals
penetrating a mass of tissue, and differing in their manner of occurrence and
in their somewhat larger size from ordinary secretory ducts. Such tunnels or
Page 129
canals are probably the work of a wood-boring animal. An example is
illustrated in fig. 24 A. Similarly it is not unusual to meet with groups or
nests of spherical or elliptical bodies lying among plant tissues, and having
the appearance of spores. Such spore-like bodies appear on close
examination to be made up of finely comminuted particles of tissue, and in
all probability they are the coprolites of some xylophagous animal.
Examples of such coprolites are shown in fig. 24 A[154], and in fig. 24 B an
interesting manner of occurrence of these misleading bodies is represented.
The framework of cells enclosing the nest of coprolites in fig. 24 B,
represents the outer tissues of a Lepidodendroid or a Sigillarian leaf; the
inner tissues have been destroyed and the cavity is now occupied by what
may possibly be the excreta of the wood-eating animal.
Some of the oval spore-like structures met with in plant tissues may, as
Renault has suggested, be the eggs of an Arthropod[155]. In a section of a
calcareous Coal-Measure nodule in the Williamson collection (British
Museum)[156] there occur several fungal spores or possibly oogonia lying
among imperfectly preserved Stigmarian appendages. Associated with these
are numerous dark coloured and larger bodies consisting of a cavity
bounded by a simple membrane; the larger bodies may well be the eggs of
some Arthropod or other animal.
PHOTOGRAPHY AND ILLUSTRATION.
In looking through the collections of Coal-Measure plants in the
Museums of Berlin, Vienna and other continental towns, one cannot fail to
be struck with the larger size of many of the specimens as compared with
those usually seen in English Museums. The facilities afforded in the State
Collieries of Germany to the scientific investigator may account in part at
least for the better specimens which he is able to obtain. It would no doubt
be a great gain to our collections of Coal-Measure plants if arrangements
could be made in some collieries for the preservation of the finer specimens
met with in the working of the seams, instead of breaking up the slabs of
shale and consigning everything to the waste heaps. There is one more point
which should be alluded to in connection with possible sources of error, and
that is the essential importance of accuracy in the illustration of specimens,
especially as regard type-specimens. It is often impossible to inspect the
original fossils which have served as types, and it is of the utmost
importance that the published figures should be as faithful as possible. M.
illustrated in fig. 24 A. Similarly it is not unusual to meet with groups or
nests of spherical or elliptical bodies lying among plant tissues, and having
the appearance of spores. Such spore-like bodies appear on close
examination to be made up of finely comminuted particles of tissue, and in
all probability they are the coprolites of some xylophagous animal.
Examples of such coprolites are shown in fig. 24 A[154], and in fig. 24 B an
interesting manner of occurrence of these misleading bodies is represented.
The framework of cells enclosing the nest of coprolites in fig. 24 B,
represents the outer tissues of a Lepidodendroid or a Sigillarian leaf; the
inner tissues have been destroyed and the cavity is now occupied by what
may possibly be the excreta of the wood-eating animal.
Some of the oval spore-like structures met with in plant tissues may, as
Renault has suggested, be the eggs of an Arthropod[155]. In a section of a
calcareous Coal-Measure nodule in the Williamson collection (British
Museum)[156] there occur several fungal spores or possibly oogonia lying
among imperfectly preserved Stigmarian appendages. Associated with these
are numerous dark coloured and larger bodies consisting of a cavity
bounded by a simple membrane; the larger bodies may well be the eggs of
some Arthropod or other animal.
PHOTOGRAPHY AND ILLUSTRATION.
In looking through the collections of Coal-Measure plants in the
Museums of Berlin, Vienna and other continental towns, one cannot fail to
be struck with the larger size of many of the specimens as compared with
those usually seen in English Museums. The facilities afforded in the State
Collieries of Germany to the scientific investigator may account in part at
least for the better specimens which he is able to obtain. It would no doubt
be a great gain to our collections of Coal-Measure plants if arrangements
could be made in some collieries for the preservation of the finer specimens
met with in the working of the seams, instead of breaking up the slabs of
shale and consigning everything to the waste heaps. There is one more point
which should be alluded to in connection with possible sources of error, and
that is the essential importance of accuracy in the illustration of specimens,
especially as regard type-specimens. It is often impossible to inspect the
original fossils which have served as types, and it is of the utmost
importance that the published figures should be as faithful as possible. M.
Page 130
Crépin[157] of Brussels, in an article on the use of photography in illustrating,
has given some examples of the confusion and mistakes caused by
imperfect drawings. It does not require a long experience of palaeobotanical
work to demonstrate the need of care in the execution of drawings for
reproduction.
has given some examples of the confusion and mistakes caused by
imperfect drawings. It does not require a long experience of palaeobotanical
work to demonstrate the need of care in the execution of drawings for
reproduction.
Page 131
Page 132
CHAPTER VI.
NOMENCLATURE.
“I do not think more credit is due to a man for defining a species, than to a carpenter for
making a box.”
Charles Darwin, Life and Letters, Vol. I., p. 371.
Any attempt to discuss at length the difficult and thorny question of
nomenclature would be entirely out of place in an elementary book on fossil
plants, but there are certain important points to which it may be well to
draw attention. When a student enters the field of independent research, he
is usually but imperfectly acquainted with the principles of nomenclature
which should be followed in palaeontological work. After losing himself in
a maze of endless synonyms and confused terminology, he recognises the
desirability of adopting some definite and consistent plan in his method of
naming genera and species. It is extremely probable that whatever system is
made use of, it will be called in question by some critics as not being in
strict conformity with accepted rules. The opportunities for criticism in
matters relating to nomenclature are particularly numerous, and the critic
who may be but imperfectly familiar with the subject-matter of a scientific
work is not slow to avail himself of some supposed eccentricity on the part
of the author in the manner of terminology. The true value of work may be
obscured by laying too much emphasis on the imperfections of a somewhat
heterodox nomenclature. On the other hand good systematic work is often
seriously spoilt by a want of attention to generally accepted rules in naming
and defining species. It is essential that those who take up systematic
research should pay attention to the necessary though secondary question of
technical description.
RULES FOR NOMENCLATURE.
In inventing a new generic or specific name, it is well to adhere to some
definite plan as regards the form or termination of the words used. To deal
with this subject in detail, or to recapitulate a series of rules as to the best
method of constructing names whether descriptive or personal, would take
NOMENCLATURE.
“I do not think more credit is due to a man for defining a species, than to a carpenter for
making a box.”
Charles Darwin, Life and Letters, Vol. I., p. 371.
Any attempt to discuss at length the difficult and thorny question of
nomenclature would be entirely out of place in an elementary book on fossil
plants, but there are certain important points to which it may be well to
draw attention. When a student enters the field of independent research, he
is usually but imperfectly acquainted with the principles of nomenclature
which should be followed in palaeontological work. After losing himself in
a maze of endless synonyms and confused terminology, he recognises the
desirability of adopting some definite and consistent plan in his method of
naming genera and species. It is extremely probable that whatever system is
made use of, it will be called in question by some critics as not being in
strict conformity with accepted rules. The opportunities for criticism in
matters relating to nomenclature are particularly numerous, and the critic
who may be but imperfectly familiar with the subject-matter of a scientific
work is not slow to avail himself of some supposed eccentricity on the part
of the author in the manner of terminology. The true value of work may be
obscured by laying too much emphasis on the imperfections of a somewhat
heterodox nomenclature. On the other hand good systematic work is often
seriously spoilt by a want of attention to generally accepted rules in naming
and defining species. It is essential that those who take up systematic
research should pay attention to the necessary though secondary question of
technical description.
RULES FOR NOMENCLATURE.
In inventing a new generic or specific name, it is well to adhere to some
definite plan as regards the form or termination of the words used. To deal
with this subject in detail, or to recapitulate a series of rules as to the best
method of constructing names whether descriptive or personal, would take
Page 133
us beyond the limits of a single chapter. The student should refer for
guidance to such recognised rules as those drawn up by the late Mr
Strickland and others at the instance of the British Association[158].
It is not infrequently the case that the same generic name has been
applied to a fossil and to a recent species. Such a double use of the same
term should always be avoided as likely to lead to confusion, and as tending
to admit a divorce between botany and palaeobotany.
In the course of describing a collection of fossil species, various
problems are bound to present themselves as regards the best method of
dealing with certain generic or specific names. A few general suggestions
may prove of use to those who are likely to be confronted with the
intricacies of scientific and pseudoscientific terminology.
In writing the name of a species, it is important to append the name, often
in an abbreviated form, of the author who first proposed the accepted
specific designation. Stigmaria ficoides Brongn. written in this form records
the fact that Brongniart was the author of the specific name ficoides. It
means, moreover, that Brongniart not only suggested the name, but that he
was the first to give either a figure or a diagnosis of this particular fossil. It
is frequently the case that a specific name is proposed for a new species,
without either figures or description; such a name is usually regarded as a
nomen nudum, and must yield priority to the name which was first
accompanied by some description or illustration sufficiently accurate to
afford a means of recognition. A practice which may be recommended on
the score of convenience is to write the name of the author of a species in
brackets if he was not the first to use the generic as well as the specific
name. Onychiopsis Mantelli (Brongn.) tells us that Brongniart founded the
species, but made use of some other generic name than that which is now
accepted. This leads us to another point of some importance. Brongniart
described this characteristic Wealden fern under the name Sphenopteris
Mantelli; Sphenopteris being one of those extremely useful provisional
generic terms which are used in cases where we have no satisfactory proof
of precise botanical affinity. Sphenopteris stands for fern fronds having a
certain habit, form of segment and venation, and in this wide sense it
necessarily includes representatives of various divisions and genera of
Filices. If an example of a sphenopteroid frond is discovered with sori or
spores sufficiently well preserved to enable us to determine its botanical
guidance to such recognised rules as those drawn up by the late Mr
Strickland and others at the instance of the British Association[158].
It is not infrequently the case that the same generic name has been
applied to a fossil and to a recent species. Such a double use of the same
term should always be avoided as likely to lead to confusion, and as tending
to admit a divorce between botany and palaeobotany.
In the course of describing a collection of fossil species, various
problems are bound to present themselves as regards the best method of
dealing with certain generic or specific names. A few general suggestions
may prove of use to those who are likely to be confronted with the
intricacies of scientific and pseudoscientific terminology.
In writing the name of a species, it is important to append the name, often
in an abbreviated form, of the author who first proposed the accepted
specific designation. Stigmaria ficoides Brongn. written in this form records
the fact that Brongniart was the author of the specific name ficoides. It
means, moreover, that Brongniart not only suggested the name, but that he
was the first to give either a figure or a diagnosis of this particular fossil. It
is frequently the case that a specific name is proposed for a new species,
without either figures or description; such a name is usually regarded as a
nomen nudum, and must yield priority to the name which was first
accompanied by some description or illustration sufficiently accurate to
afford a means of recognition. A practice which may be recommended on
the score of convenience is to write the name of the author of a species in
brackets if he was not the first to use the generic as well as the specific
name. Onychiopsis Mantelli (Brongn.) tells us that Brongniart founded the
species, but made use of some other generic name than that which is now
accepted. This leads us to another point of some importance. Brongniart
described this characteristic Wealden fern under the name Sphenopteris
Mantelli; Sphenopteris being one of those extremely useful provisional
generic terms which are used in cases where we have no satisfactory proof
of precise botanical affinity. Sphenopteris stands for fern fronds having a
certain habit, form of segment and venation, and in this wide sense it
necessarily includes representatives of various divisions and genera of
Filices. If an example of a sphenopteroid frond is discovered with sori or
spores sufficiently well preserved to enable us to determine its botanical
Page 134
position within narrower limits, we may with advantage employ another
genus in place of the purely artificial form-genus which was originally
chosen as a consequence of imperfect knowledge. Fronds of this Wealden
fern have recently been found with well defined fertile segments having a
form apparently identical with that which characterises the polypodiaceous
genus Onychium. For this reason the name Onychiopsis has been adopted. It
is safer and more convenient to use a name which differs in its termination
from that of the recent plant with which we believe the fossil to be closely
related. A common custom is to slightly alter the recent name by adding the
termination -opsis or -ites. There are several other provisional generic terms
that are often used in Fossil Botany, and which might be advantageously
chosen in many cases where the misleading resemblance of external form
has often given rise to the use of a name implying affinities which cannot be
satisfactorily demonstrated.
It was the custom of some of the earliest writers, in spite of their habit of
using the names of recent Flowering plants for extinct Palaeozoic species of
Vascular Cryptogams, to adopt also general and comprehensive terms. We
find such a name as Lithoxylon employed by Lhwyd[159] in 1699 as a
convenient designation for fossil wood.
THE RULE OF PRIORITY.
One of the most important and frequently disputed questions associated
with the naming of species is that of priority. No name given to a plant in
pre-Linnaean days need be considered, as our present system of
nomenclature dates from the institution of the binominal system by
Linnaeus. As a general rule, which it is advisable to follow, the specific
name which was first given to a plant, if accompanied by a figure or
diagnosis, should take priority over a name of later date. If A in 1850
describes a species under a certain name, and in 1860 B proposes a new
name for the same species, either in ignorance of the older name or from
disapproval of A’s choice of a specific term, the later name should not be
allowed to supersede A’s original designation. Such a rule is not only just to
the original author, but is one which, if generally observed, would lead to
less confusion and would diminish unnecessary multiplication of specific
names. Some writers would have us conform in all cases to this rule of
priority, which they consistently adhere to apart from all considerations of
convenience or long-established custom. There are, however, cogent
genus in place of the purely artificial form-genus which was originally
chosen as a consequence of imperfect knowledge. Fronds of this Wealden
fern have recently been found with well defined fertile segments having a
form apparently identical with that which characterises the polypodiaceous
genus Onychium. For this reason the name Onychiopsis has been adopted. It
is safer and more convenient to use a name which differs in its termination
from that of the recent plant with which we believe the fossil to be closely
related. A common custom is to slightly alter the recent name by adding the
termination -opsis or -ites. There are several other provisional generic terms
that are often used in Fossil Botany, and which might be advantageously
chosen in many cases where the misleading resemblance of external form
has often given rise to the use of a name implying affinities which cannot be
satisfactorily demonstrated.
It was the custom of some of the earliest writers, in spite of their habit of
using the names of recent Flowering plants for extinct Palaeozoic species of
Vascular Cryptogams, to adopt also general and comprehensive terms. We
find such a name as Lithoxylon employed by Lhwyd[159] in 1699 as a
convenient designation for fossil wood.
THE RULE OF PRIORITY.
One of the most important and frequently disputed questions associated
with the naming of species is that of priority. No name given to a plant in
pre-Linnaean days need be considered, as our present system of
nomenclature dates from the institution of the binominal system by
Linnaeus. As a general rule, which it is advisable to follow, the specific
name which was first given to a plant, if accompanied by a figure or
diagnosis, should take priority over a name of later date. If A in 1850
describes a species under a certain name, and in 1860 B proposes a new
name for the same species, either in ignorance of the older name or from
disapproval of A’s choice of a specific term, the later name should not be
allowed to supersede A’s original designation. Such a rule is not only just to
the original author, but is one which, if generally observed, would lead to
less confusion and would diminish unnecessary multiplication of specific
names. Some writers would have us conform in all cases to this rule of
priority, which they consistently adhere to apart from all considerations of
convenience or long-established custom. There are, however, cogent
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reasons for maintaining a certain amount of freedom. While accepting
priority as a good rule in most cases, it is unwise to allow ourselves to be
too servile in our conformity to a principle which was framed in the
interests of convenience, if the strict application of the rule clearly makes
for confusion and inconvenience. A name may have been in use for say
eighty years, and has become perfectly familiar as the recognised
designation of a particular fossil; it is discovered, however, that an older
name was proposed for the same species ninety years ago, and therefore
according to the priority rule, we must accustom ourselves to a new name in
place of one which is thoroughly established by long usage. From a
scientific point of view, the ideal of nomenclature is to be plain and
intelligible. To prefer priority to established usage entails obscurity and
confusion. If priority is to be the rule which we must invariably obey in the
shadowy hope that by such means finality in nomenclature[160] may be
reached, it becomes necessary for the student to devote no inconsiderable
portion of his time to antiquarian research, with a view to discover whether
a particular name may be stamped with the hallmark of ‘the very first.’
While admitting the advisability of retaining as a general principle the
original generic or specific name, the extreme subservience to ‘the priority
craze’ without regard to convenience, would seem to lead irresistibly to the
view that “botanists who waste their time over priority are like boys who,
when sent on an errand, spend their time in playing by the roadside[161].”
TERMINOLOGY AND CONVENIENCE.
There is another point which cannot be satisfactorily settled in all cases
by a rigid adherence to an arbitrary rule. How far should we regard a
generic name in the sense of a mere mark or sign to denote a particular
plant, or to what extent may we accept the literal meaning of the generic
term as an index of the affinity or character of the plant? If we consider the
etymology of many generic names, we soon find that they are entirely
inappropriate as aids in recognizing the true taxonomic position of the
plants to which they are applied. The generic name Calamites was first
suggested by the supposed resemblance of this Palaeozoic plant to recent
reeds. If considered etymologically, it is merely a record of a past mistake,
but it would be absurd to discard such a well-known name on the grounds
that the genus is a Vascular Cryptogam and far removed from reeds. On the
other hand, there often arise cases which present a real difficulty. The
priority as a good rule in most cases, it is unwise to allow ourselves to be
too servile in our conformity to a principle which was framed in the
interests of convenience, if the strict application of the rule clearly makes
for confusion and inconvenience. A name may have been in use for say
eighty years, and has become perfectly familiar as the recognised
designation of a particular fossil; it is discovered, however, that an older
name was proposed for the same species ninety years ago, and therefore
according to the priority rule, we must accustom ourselves to a new name in
place of one which is thoroughly established by long usage. From a
scientific point of view, the ideal of nomenclature is to be plain and
intelligible. To prefer priority to established usage entails obscurity and
confusion. If priority is to be the rule which we must invariably obey in the
shadowy hope that by such means finality in nomenclature[160] may be
reached, it becomes necessary for the student to devote no inconsiderable
portion of his time to antiquarian research, with a view to discover whether
a particular name may be stamped with the hallmark of ‘the very first.’
While admitting the advisability of retaining as a general principle the
original generic or specific name, the extreme subservience to ‘the priority
craze’ without regard to convenience, would seem to lead irresistibly to the
view that “botanists who waste their time over priority are like boys who,
when sent on an errand, spend their time in playing by the roadside[161].”
TERMINOLOGY AND CONVENIENCE.
There is another point which cannot be satisfactorily settled in all cases
by a rigid adherence to an arbitrary rule. How far should we regard a
generic name in the sense of a mere mark or sign to denote a particular
plant, or to what extent may we accept the literal meaning of the generic
term as an index of the affinity or character of the plant? If we consider the
etymology of many generic names, we soon find that they are entirely
inappropriate as aids in recognizing the true taxonomic position of the
plants to which they are applied. The generic name Calamites was first
suggested by the supposed resemblance of this Palaeozoic plant to recent
reeds. If considered etymologically, it is merely a record of a past mistake,
but it would be absurd to discard such a well-known name on the grounds
that the genus is a Vascular Cryptogam and far removed from reeds. On the
other hand, there often arise cases which present a real difficulty. The
Page 136
following example conveniently illustrates two distinct points of view as
regards generic nomenclature. In 1875 Saporta described and figured a
fragment of a fossil plant from the Jurassic beds of France as Cycadorachis
armata[162]; the name being chosen in the belief that the specimen was part
of a cycadean petiole, and there were good grounds for such a view. A few
years ago Mr Rufford discovered more perfect specimens, in the Wealden
rocks of Sussex, clearly belonging to Saporta’s genus, and these afforded
definite evidence that Saporta had been deceived by the imperfection of the
specimens as to their true botanical position. Owing to the obviously
misleading name first given to this plant, I ventured to substitute
Withamia[163] for Cycadorachis, and chose such a term in preference to one
denoting affinity, on account of the difficulty of placing the plant in a
definite class or family. On the other hand, it has been objected that the
original name, despite its meaningless meaning—if the expression may be
used—should be retained. A friendly critic[164], in writing of the proposed
change of Cycadorachis, urges the importance of adhering to the name
which was first applied to a genus. The same author pertinently remarks
that we can no more dispense with a nomenclature than we can dispense
with language. We may extend the comparison and point out that in
language, as in scientific nomenclature, conciseness, clearness and
convenience should be kept in view as guiding principles.
The student must judge for himself what course to follow in each case.
While adhering as far as possible to a consistent plan, he must take care that
he does not allow his own judgment to be completely over-ridden by a blind
obedience to fixed rules, which if pressed too far may defeat their own
ends.
regards generic nomenclature. In 1875 Saporta described and figured a
fragment of a fossil plant from the Jurassic beds of France as Cycadorachis
armata[162]; the name being chosen in the belief that the specimen was part
of a cycadean petiole, and there were good grounds for such a view. A few
years ago Mr Rufford discovered more perfect specimens, in the Wealden
rocks of Sussex, clearly belonging to Saporta’s genus, and these afforded
definite evidence that Saporta had been deceived by the imperfection of the
specimens as to their true botanical position. Owing to the obviously
misleading name first given to this plant, I ventured to substitute
Withamia[163] for Cycadorachis, and chose such a term in preference to one
denoting affinity, on account of the difficulty of placing the plant in a
definite class or family. On the other hand, it has been objected that the
original name, despite its meaningless meaning—if the expression may be
used—should be retained. A friendly critic[164], in writing of the proposed
change of Cycadorachis, urges the importance of adhering to the name
which was first applied to a genus. The same author pertinently remarks
that we can no more dispense with a nomenclature than we can dispense
with language. We may extend the comparison and point out that in
language, as in scientific nomenclature, conciseness, clearness and
convenience should be kept in view as guiding principles.
The student must judge for himself what course to follow in each case.
While adhering as far as possible to a consistent plan, he must take care that
he does not allow his own judgment to be completely over-ridden by a blind
obedience to fixed rules, which if pressed too far may defeat their own
ends.
Page 137
Page 138
PART II. SYSTEMATIC.
Page 139
CHAPTER VII.
THALLOPHYTA.
The divisions of the plant kingdom dealt with in the following chapters of Volume I. are taken
in their natural sequence, beginning with the lowest and passing gradually to the highest groups.
The list of the classes and families included in Chapters VII.–XI. is given in the table of contents
preceding Chapter I.
Thallophytes are of the simplest type, but they exhibit a very wide range
as regards both the structure and differentiation of the vegetative body and
the methods of reproduction. In some cases the individual consists of a
minute simple cell which multiplies by cell-division; in others the body or
thallus is made up of a number of similar units, while in a great number of
forms there is a well-marked physiological division of labour, as expressed
both in the external division of the thallus into distinct organs
corresponding in function to the root, stem, and leaves of the higher plants,
and further in the high degree of histological differentiation of the tissues.
In other thallophytes, again, the thallus is a coenocyte either unseptate or
incompletely septate; that is, the individual consists of a single cell differing
from a true plant-cell, in the stricter sense of the term, in possessing several
nuclei, in other words, the thallus is divided up into compartments by
transverse septa, but each division contains more than one nucleus. Such
coenocytic plants may show well-marked external differentiation of the
thallus into members or parts subserving different functions.
A similar wide range is covered by the methods of reproduction among
thallophytes.
I. PERIDINIALES.
The organisms included under this head are of little importance from a
palaeontological point of view, but a brief reference may be made to them
as a section of the Thallophyta.
The Peridiniales include very small single-celled organisms which have
often been described as occupying a position on the borderland between
animals and plants, lying on the “shadowy boundary between animal and
THALLOPHYTA.
The divisions of the plant kingdom dealt with in the following chapters of Volume I. are taken
in their natural sequence, beginning with the lowest and passing gradually to the highest groups.
The list of the classes and families included in Chapters VII.–XI. is given in the table of contents
preceding Chapter I.
Thallophytes are of the simplest type, but they exhibit a very wide range
as regards both the structure and differentiation of the vegetative body and
the methods of reproduction. In some cases the individual consists of a
minute simple cell which multiplies by cell-division; in others the body or
thallus is made up of a number of similar units, while in a great number of
forms there is a well-marked physiological division of labour, as expressed
both in the external division of the thallus into distinct organs
corresponding in function to the root, stem, and leaves of the higher plants,
and further in the high degree of histological differentiation of the tissues.
In other thallophytes, again, the thallus is a coenocyte either unseptate or
incompletely septate; that is, the individual consists of a single cell differing
from a true plant-cell, in the stricter sense of the term, in possessing several
nuclei, in other words, the thallus is divided up into compartments by
transverse septa, but each division contains more than one nucleus. Such
coenocytic plants may show well-marked external differentiation of the
thallus into members or parts subserving different functions.
A similar wide range is covered by the methods of reproduction among
thallophytes.
I. PERIDINIALES.
The organisms included under this head are of little importance from a
palaeontological point of view, but a brief reference may be made to them
as a section of the Thallophyta.
The Peridiniales include very small single-celled organisms which have
often been described as occupying a position on the borderland between
animals and plants, lying on the “shadowy boundary between animal and
Page 140
vegetable life.” The individuals are rarely naked, more frequently they are
covered with a cellulose or mucilaginous investment which has frequently
the form of two or more minute armour-like plates of a limiting membrane.
The chromatophores are green, yellow, brown or colourless. Simple
division is the usual method of reproduction, but spores have been
described as occurring in some species. The motile forms are provided with
cilia. The Peridiniaceae, a section of the Peridiniales, are regarded as nearly
related to the Diatoms.
The Peridiniales play an important rôle in the Plankton flora of the sea
and freshwater lakes, and have a world-wide distribution. In the narrative of
the Challenger cruise they are described as occasionally filling the tow-nets
with a yellow coloured slime[165]. Some genera, such as Ceratium, are found
in enormous numbers off the British coast.
As an example of the occurrence of fossil representatives of the
Peridiniaceae reference may be made to one of two species of Peridinium
described by Ehrenberg in 1836. These were found in a siliceous rock
described as Cretaceous in age from Delitzsch in Saxony. A comparison of
Ehrenberg’s figures of the fossil species Peridinium pyrophorum Ehrenb.
[166]
, with those of the recent species Peridinium divergens Ehrenb., as given
by Schütt[167] and other writers, brings out clearly the very close
resemblance if not identity of the two forms. Bütschli[168] in his account of
the Dinoflagellata in Bronn’s Thier-Reich confirms Ehrenberg’s
determination of Peridinium pyrophorum, and points out its striking
agreement with the recent species.
II. COCCOSPHERES AND RHABDOSPHERES.
(Organisms of doubtful affinity.)
Our knowledge of these minute calcareous organisms is derived from
Huxley’s description of coccoliths from the Atlantic in 1857, and from the
accounts of Wallich, John Murray, and other writers. In the first volume of
the narrative of the Challenger cruise[169] and in the volume on deep-sea
deposits[170] these minute forms of life are figured and described. In the
latter volume both genera are spoken of as extremely abundant in the
surface waters of the tropical and temperate regions of the open ocean, and
as forming an important constituent of the Globigerine ooze; they are said
covered with a cellulose or mucilaginous investment which has frequently
the form of two or more minute armour-like plates of a limiting membrane.
The chromatophores are green, yellow, brown or colourless. Simple
division is the usual method of reproduction, but spores have been
described as occurring in some species. The motile forms are provided with
cilia. The Peridiniaceae, a section of the Peridiniales, are regarded as nearly
related to the Diatoms.
The Peridiniales play an important rôle in the Plankton flora of the sea
and freshwater lakes, and have a world-wide distribution. In the narrative of
the Challenger cruise they are described as occasionally filling the tow-nets
with a yellow coloured slime[165]. Some genera, such as Ceratium, are found
in enormous numbers off the British coast.
As an example of the occurrence of fossil representatives of the
Peridiniaceae reference may be made to one of two species of Peridinium
described by Ehrenberg in 1836. These were found in a siliceous rock
described as Cretaceous in age from Delitzsch in Saxony. A comparison of
Ehrenberg’s figures of the fossil species Peridinium pyrophorum Ehrenb.
[166]
, with those of the recent species Peridinium divergens Ehrenb., as given
by Schütt[167] and other writers, brings out clearly the very close
resemblance if not identity of the two forms. Bütschli[168] in his account of
the Dinoflagellata in Bronn’s Thier-Reich confirms Ehrenberg’s
determination of Peridinium pyrophorum, and points out its striking
agreement with the recent species.
II. COCCOSPHERES AND RHABDOSPHERES.
(Organisms of doubtful affinity.)
Our knowledge of these minute calcareous organisms is derived from
Huxley’s description of coccoliths from the Atlantic in 1857, and from the
accounts of Wallich, John Murray, and other writers. In the first volume of
the narrative of the Challenger cruise[169] and in the volume on deep-sea
deposits[170] these minute forms of life are figured and described. In the
latter volume both genera are spoken of as extremely abundant in the
surface waters of the tropical and temperate regions of the open ocean, and
as forming an important constituent of the Globigerine ooze; they are said
Page 141
to occur entangled in the gelatinous substance of the Radiolarians, Diatoms,
and Foraminifera, and are very common in the stomachs of Salps,
Pteropods and other pelagic animals. Rhabdospheres are rare in regions
where the temperature of the water sinks below 65° F.; the Coccospheres
occur in tropical and temperate latitudes, and extend further north and south
than the Rhabdospheres. As regards their botanical position, John Murray
expresses the view that they are in all probability pelagic algae.
In the interesting memoir by Schütt on the Pflanzenleben der Hochsee[171]
there occurs a short reference to the forms described in the Challenger
Reports, but they were not obtained by the staff of the Hensen Plankton
Expedition and Schütt’s remarks are not based therefore on personal
observations. While admitting the existence of such bodies, he points out
that Zoologists have referred Coccospheres and Rhabdospheres to the algae
as organisms which cannot be included in any group of animals, and Schütt
is unable to recognise a sufficient reason for referring them to this class of
plants. It is suggested indeed that they may be purely inorganic structures.
and Foraminifera, and are very common in the stomachs of Salps,
Pteropods and other pelagic animals. Rhabdospheres are rare in regions
where the temperature of the water sinks below 65° F.; the Coccospheres
occur in tropical and temperate latitudes, and extend further north and south
than the Rhabdospheres. As regards their botanical position, John Murray
expresses the view that they are in all probability pelagic algae.
In the interesting memoir by Schütt on the Pflanzenleben der Hochsee[171]
there occurs a short reference to the forms described in the Challenger
Reports, but they were not obtained by the staff of the Hensen Plankton
Expedition and Schütt’s remarks are not based therefore on personal
observations. While admitting the existence of such bodies, he points out
that Zoologists have referred Coccospheres and Rhabdospheres to the algae
as organisms which cannot be included in any group of animals, and Schütt
is unable to recognise a sufficient reason for referring them to this class of
plants. It is suggested indeed that they may be purely inorganic structures.
Page 142
Fig. 25. (From Murray and Blackman).
A, Coccosphere × 1300. B, Rhabdosphere × 900. C, Portion of the same × 1300. D,
Rhabdosphere of another type, in optical section × 1900. E, The same in surface view ×
1900. F, End of one of the trumpet-shaped appendages of E.
The most recent account of these two genera is by Messrs G. Murray and
Blackman a short notice in Nature for April 1, 1897[172]. Numerous
examples of Coccospheres and Rhabdospheres were obtained by Capt.
Milner of the R.M.S. Para during a voyage to Barbados by allowing the sea
water to enter the feed-pipe of the boiler through a fine muslin net. All the
forms described in the Challenger Reports were met with, and an
examination of the material by means of extremely high objectives has
confirmed the original account of the genera, and added some points to our
previous knowledge.
Coccospheres (fig. 25 A). Spherical bodies of exceedingly small size,
consisting of a central protoplasmic vesicle covered with overlapping
circular calcareous scales, each of which is attached to the minute cell by a
A, Coccosphere × 1300. B, Rhabdosphere × 900. C, Portion of the same × 1300. D,
Rhabdosphere of another type, in optical section × 1900. E, The same in surface view ×
1900. F, End of one of the trumpet-shaped appendages of E.
The most recent account of these two genera is by Messrs G. Murray and
Blackman a short notice in Nature for April 1, 1897[172]. Numerous
examples of Coccospheres and Rhabdospheres were obtained by Capt.
Milner of the R.M.S. Para during a voyage to Barbados by allowing the sea
water to enter the feed-pipe of the boiler through a fine muslin net. All the
forms described in the Challenger Reports were met with, and an
examination of the material by means of extremely high objectives has
confirmed the original account of the genera, and added some points to our
previous knowledge.
Coccospheres (fig. 25 A). Spherical bodies of exceedingly small size,
consisting of a central protoplasmic vesicle covered with overlapping
circular calcareous scales, each of which is attached to the minute cell by a
Page 143
button-like projection. The scales are frequently found detached and are
then spoken of as Coccoliths.
Rhabdospheres (fig. 25 B–F). Spherical bodies, extremely minute,
consisting of a single cell, on the surface of which are embedded numerous
calcareous plates bearing long blunt spines (fig. 25, C) or beautiful trumpet-
like appendages (fig. 25, D–F). The detached plates of Rhabdospheres are
known as Rhabdoliths.
In addition to the text-figures of Coccospheres and Rhabdospheres in the
Challenger Reports, the same structures are shown in samples of
globigerine ooze figured in Plate XI. of the Monograph on deep-sea
deposits. In a recent number of Nature Messrs Dixon and Joly[173] have
announced the discovery of Coccoliths and Coccospheres in the coastal
waters off South County Dublin. They estimate that in one sample of water
taken about three miles from the Irish coast there were 200 Coccoliths in
each cubic centimetre of sea water.
The interest of these calcareous bodies from a palaeobotanical point of
view lies in the fact that similar forms have been recognized in the Chalk
and the Upper Lias. Sorby, in his memorable Address delivered before the
Geological Society in 1879, refers to the abundance of Coccoliths in
sections of chalk which he examined[174]. Rothpletz[175] has recently recorded
the occurrence of numerous Coccoliths, 5–12 µ in diameter, associated with
the skeleton of a horny sponge (Phymatoderma) of Liassic age.
The question of the nature of Coccospheres and Rhabdospheres cannot
be regarded as definitely settled. It has been shown by J. Murray, and more
recently by G. Murray and V. H. Blackman, that on the solution of the
calcareous material by a weak acid there remains a small gelatinous body
apparently protoplasmic in nature. We may at least express the opinion that
Schütt’s suggestion as to their being inorganic must be ruled out of court. It
would appear that they are extremely minute unicellular organisms
characterised by a delicate calcareous armour consisting of numerous plates
or scales. We know nothing as to their life-history, and cannot attempt to
determine their affinities with any degree of certainty until further facts are
before us. It is not improbable that they are algae of an extremely minute
size, and the evidence so far obtained would lead us to regard them as
complete individuals rather than the reproductive cells of some larger
then spoken of as Coccoliths.
Rhabdospheres (fig. 25 B–F). Spherical bodies, extremely minute,
consisting of a single cell, on the surface of which are embedded numerous
calcareous plates bearing long blunt spines (fig. 25, C) or beautiful trumpet-
like appendages (fig. 25, D–F). The detached plates of Rhabdospheres are
known as Rhabdoliths.
In addition to the text-figures of Coccospheres and Rhabdospheres in the
Challenger Reports, the same structures are shown in samples of
globigerine ooze figured in Plate XI. of the Monograph on deep-sea
deposits. In a recent number of Nature Messrs Dixon and Joly[173] have
announced the discovery of Coccoliths and Coccospheres in the coastal
waters off South County Dublin. They estimate that in one sample of water
taken about three miles from the Irish coast there were 200 Coccoliths in
each cubic centimetre of sea water.
The interest of these calcareous bodies from a palaeobotanical point of
view lies in the fact that similar forms have been recognized in the Chalk
and the Upper Lias. Sorby, in his memorable Address delivered before the
Geological Society in 1879, refers to the abundance of Coccoliths in
sections of chalk which he examined[174]. Rothpletz[175] has recently recorded
the occurrence of numerous Coccoliths, 5–12 µ in diameter, associated with
the skeleton of a horny sponge (Phymatoderma) of Liassic age.
The question of the nature of Coccospheres and Rhabdospheres cannot
be regarded as definitely settled. It has been shown by J. Murray, and more
recently by G. Murray and V. H. Blackman, that on the solution of the
calcareous material by a weak acid there remains a small gelatinous body
apparently protoplasmic in nature. We may at least express the opinion that
Schütt’s suggestion as to their being inorganic must be ruled out of court. It
would appear that they are extremely minute unicellular organisms
characterised by a delicate calcareous armour consisting of numerous plates
or scales. We know nothing as to their life-history, and cannot attempt to
determine their affinities with any degree of certainty until further facts are
before us. It is not improbable that they are algae of an extremely minute
size, and the evidence so far obtained would lead us to regard them as
complete individuals rather than the reproductive cells of some larger
Page 144
organism. Mr George Murray is of opinion that they are certainly algae, but
he considers that they cannot be included in any existing family. It is
conceivable that they may be minute eggs or reproductive cells of animals
or plants, but on the whole the balance of probability would seem to be in
favour of regarding them as autonomous organisms.
III. SCHIZOPHYTA.
A. SCHIZOPHYCEAE (Cyanophyceae).
B. SCHIZOMYCETES (Bacteria).
In this group are included small single-celled plants of an extremely low
type of organisation, in which reproduction takes the form of multiplication
by simple cell-division, or the formation of spores. The characteristic
method of reproduction by division has given rise to the general term
Fission-plants for this lowest sub-class in the vegetable kingdom. In many
cases the members of this sub-class contain chlorophyll, and associated
with it a blue-green colouring matter; such plants are classed together as the
Blue-green algae, Cyanophyceae, or Schizophyceae. Others, again, are
destitute of chlorophyll, and may be conveniently designated
Schizomycetes or Fission-fungi. Seeing how close is the resemblance and
relationship between the members of the sub-class, it has been the custom
to include them as two parallel series under the general head, Schizophyta,
rather than to incorporate them among the Algae and Fungi respectively.
A. SCHIZOPHYCEAE (Cyanophyceae or Blue-green Algae).
Chroococcaceae. Thallus of a single cell, the cells may be either free, or
more usually joined together in colonies enveloped by a common gelatinous
matrix, formed by the mucilaginous degeneration of the outer portion of the
cell-walls. Reproduction by means of simple division or resting cells.
Nostocaceae. Thallus consists of simple or branched rows of cells in
which special cells known as heterocysts often occur. Reproduction by
means of germ-plants or hormogonia, or by resting cells specially modified
to resist unfavourable conditions.
he considers that they cannot be included in any existing family. It is
conceivable that they may be minute eggs or reproductive cells of animals
or plants, but on the whole the balance of probability would seem to be in
favour of regarding them as autonomous organisms.
III. SCHIZOPHYTA.
A. SCHIZOPHYCEAE (Cyanophyceae).
B. SCHIZOMYCETES (Bacteria).
In this group are included small single-celled plants of an extremely low
type of organisation, in which reproduction takes the form of multiplication
by simple cell-division, or the formation of spores. The characteristic
method of reproduction by division has given rise to the general term
Fission-plants for this lowest sub-class in the vegetable kingdom. In many
cases the members of this sub-class contain chlorophyll, and associated
with it a blue-green colouring matter; such plants are classed together as the
Blue-green algae, Cyanophyceae, or Schizophyceae. Others, again, are
destitute of chlorophyll, and may be conveniently designated
Schizomycetes or Fission-fungi. Seeing how close is the resemblance and
relationship between the members of the sub-class, it has been the custom
to include them as two parallel series under the general head, Schizophyta,
rather than to incorporate them among the Algae and Fungi respectively.
A. SCHIZOPHYCEAE (Cyanophyceae or Blue-green Algae).
Chroococcaceae. Thallus of a single cell, the cells may be either free, or
more usually joined together in colonies enveloped by a common gelatinous
matrix, formed by the mucilaginous degeneration of the outer portion of the
cell-walls. Reproduction by means of simple division or resting cells.
Nostocaceae. Thallus consists of simple or branched rows of cells in
which special cells known as heterocysts often occur. Reproduction by
means of germ-plants or hormogonia, or by resting cells specially modified
to resist unfavourable conditions.
Page 145
In both families the individuals are surrounded by a gelatinous envelope,
which in some genera assumes the form of a conspicuous and
comparatively resistant sheath. Marine, freshwater, and aerial forms are
represented among recent genera. Several species occur as endophytes,
living in the tissues or mucilage-containing spaces in the bodies of higher
plants. In addition to the frequent occurrence of blue-green algae in
freshwater streams and on damp surfaces, certain forms are particularly
abundant in the open sea[176], and in lakes or meres[177] where they are the
cause of what is known in some parts of the country as “the breaking of the
meres” (“Fleurs d’eau”). From the narrative of the cruise of the Challenger,
we learn that the Oscillariaceae are especially abundant in the surface
waters of the ocean. The “sea sawdust” so named by Cook’s sailors[178], and
the same floating scum collected by Darwin[179], affords an illustration of the
abundance of some of these blue-green algae in the sea.
Another manner of occurrence of these plants has been recorded by
different writers, which is of special importance from the point of view of
fossil algae. On the shores of the Great Salt Lake, Utah, there are found
numerous small oolitic calcareous bodies thrown up by the waves[180]. These
are coated with the cells of Glœocapsa and Glœotheca, two genera of the
Chroococcaceae. Sections of the grains reveal the presence of the same
forms in the interior of the calcareous matrix, and it has been concluded, on
good evidence that the algae are responsible for the deposition of the
carbonate of lime of the oolitic grains. By extracting the carbonic acid
which they require as a source of food, from the waters of the lake, the
solvent power of the water is decreased and carbonate of lime is thrown
down. In similar white grains from the Red Sea[181] there is a central nucleus
in the form of a grain of sand, and cells of Chroococcaceae occur in the
surrounding carbonate of lime as in the Salt Lake oolite. Prof. Cohn of
Breslau in 1862 demonstrated the importance of low forms of plant life in
the deposition of the Carlsbad “Sprudelstein[182].” On the bottom of Lough
Belvedere, near Mullingar in Ireland[183], there occur numerous spherical
calcareous pebbles, of all sizes up to that of a filbert. From a pond in
Michigan (U.S.A.)[184] similar bodies have been obtained varying in
diameter from one to three and a half inches. In the former pebbles a
species of Schizothrix, one of the Nostocaceae occurs in abundance, in the
form of chains of small cells enclosed in the characteristic and
comparatively hard tubular sheath, and associated with Schizothrix
which in some genera assumes the form of a conspicuous and
comparatively resistant sheath. Marine, freshwater, and aerial forms are
represented among recent genera. Several species occur as endophytes,
living in the tissues or mucilage-containing spaces in the bodies of higher
plants. In addition to the frequent occurrence of blue-green algae in
freshwater streams and on damp surfaces, certain forms are particularly
abundant in the open sea[176], and in lakes or meres[177] where they are the
cause of what is known in some parts of the country as “the breaking of the
meres” (“Fleurs d’eau”). From the narrative of the cruise of the Challenger,
we learn that the Oscillariaceae are especially abundant in the surface
waters of the ocean. The “sea sawdust” so named by Cook’s sailors[178], and
the same floating scum collected by Darwin[179], affords an illustration of the
abundance of some of these blue-green algae in the sea.
Another manner of occurrence of these plants has been recorded by
different writers, which is of special importance from the point of view of
fossil algae. On the shores of the Great Salt Lake, Utah, there are found
numerous small oolitic calcareous bodies thrown up by the waves[180]. These
are coated with the cells of Glœocapsa and Glœotheca, two genera of the
Chroococcaceae. Sections of the grains reveal the presence of the same
forms in the interior of the calcareous matrix, and it has been concluded, on
good evidence that the algae are responsible for the deposition of the
carbonate of lime of the oolitic grains. By extracting the carbonic acid
which they require as a source of food, from the waters of the lake, the
solvent power of the water is decreased and carbonate of lime is thrown
down. In similar white grains from the Red Sea[181] there is a central nucleus
in the form of a grain of sand, and cells of Chroococcaceae occur in the
surrounding carbonate of lime as in the Salt Lake oolite. Prof. Cohn of
Breslau in 1862 demonstrated the importance of low forms of plant life in
the deposition of the Carlsbad “Sprudelstein[182].” On the bottom of Lough
Belvedere, near Mullingar in Ireland[183], there occur numerous spherical
calcareous pebbles, of all sizes up to that of a filbert. From a pond in
Michigan (U.S.A.)[184] similar bodies have been obtained varying in
diameter from one to three and a half inches. In the former pebbles a
species of Schizothrix, one of the Nostocaceae occurs in abundance, in the
form of chains of small cells enclosed in the characteristic and
comparatively hard tubular sheath, and associated with Schizothrix
Page 146
fasciculata there have been found Nostoc cells and the siliceous frustules of
Diatoms. In the Michigan nodules the same Schizothrix occurs, associated
with Stigonema and Dichothrix, other genera of the Nostocaceae. One of
the Michigan pebbles is shown in section in fig. 32 D.
OOLITIC STRUCTURE.
The connection between the well-known oolitic structure, characteristic
of rocks of various ages in all parts of the world, and the presence of algal
cells is of the greatest interest from a geological point of view. In recent
years considerable attention has been paid to the structure of oolitic rocks,
and in many instances there have been found in the calcareous grains
tubular structures suggestive of simple cylindrical plants, which have
probably been concerned in the deposition of the carbonate of lime of
which the granules consist. In 1880 Messrs Nicholson and Etheridge[185]
recorded the occurrence of such a tubular structure in calcareous nodules
obtained from a rock of Ordovician age in the Girvan district of Scotland.
These Authors considered the tubes to be those of some Rhizopod, and
proposed to designate the fossil Girvanella.
Girvanella (fig. 26).
Messrs Nicholson and Etheridge defined the genus as follows:—
“Microscopic tubuli, with arenaceous or calcareous (?) walls, flexuous or contorted, circular in
section, forming loosely compacted masses. The tubes, apparently simple cylinders, without
perforations in their sides, and destitute of internal partitions or other structures of a similar
kind.”
Diatoms. In the Michigan nodules the same Schizothrix occurs, associated
with Stigonema and Dichothrix, other genera of the Nostocaceae. One of
the Michigan pebbles is shown in section in fig. 32 D.
OOLITIC STRUCTURE.
The connection between the well-known oolitic structure, characteristic
of rocks of various ages in all parts of the world, and the presence of algal
cells is of the greatest interest from a geological point of view. In recent
years considerable attention has been paid to the structure of oolitic rocks,
and in many instances there have been found in the calcareous grains
tubular structures suggestive of simple cylindrical plants, which have
probably been concerned in the deposition of the carbonate of lime of
which the granules consist. In 1880 Messrs Nicholson and Etheridge[185]
recorded the occurrence of such a tubular structure in calcareous nodules
obtained from a rock of Ordovician age in the Girvan district of Scotland.
These Authors considered the tubes to be those of some Rhizopod, and
proposed to designate the fossil Girvanella.
Girvanella (fig. 26).
Messrs Nicholson and Etheridge defined the genus as follows:—
“Microscopic tubuli, with arenaceous or calcareous (?) walls, flexuous or contorted, circular in
section, forming loosely compacted masses. The tubes, apparently simple cylinders, without
perforations in their sides, and destitute of internal partitions or other structures of a similar
kind.”
Page 147
Fig. 26. Girvanella problematica, Eth. and Nich. Tubules of Girvanella lying in various
positions and surrounding an inorganic ‘nucleus’ or centre. From a section of Wenlock
limestone, May Hill. × 65
Since this diagnosis was published very many examples of similar
tubular fossils have been described by several writers in rocks from widely
separated geological horizons. The accompanying sketch (Fig. 26), drawn
from a micro-photograph kindly lent to me by Mr Wethered of Cheltenham,
who has made oolitic grains a special subject of careful investigation,
affords a good example of the occurrence of such tubular structures in an
oolitic grain of Silurian age from the Wenlock limestone of May Hill,
Gloucestershire[186]. In the centre is a crystalline core or nucleus round
which the tubules have grown, and presumably they had an important share
in the deposition of the calcareous substance. The nature of Girvanella, and
still more its exact position in the organic world, is quite uncertain; it is
mentioned rather as à propos of the association of recent Cyanophyceae
with oolitic structure, than as a well-defined genus of fossil algae.
In the typo description of the calcareous nodules from Michigan, Murray
speaks of the Schizothrix filaments at the surface of the pebbles as fairly
intact, while nearer the centre only sheaths were met with. It is conceivable
that in some of the tubular structures referred to Girvanella we have the
mineralised sheaths of a fossil Cyanophyceous genus[187]. The organic
nature of these tubules has been a matter of dispute, but we may probably
positions and surrounding an inorganic ‘nucleus’ or centre. From a section of Wenlock
limestone, May Hill. × 65
Since this diagnosis was published very many examples of similar
tubular fossils have been described by several writers in rocks from widely
separated geological horizons. The accompanying sketch (Fig. 26), drawn
from a micro-photograph kindly lent to me by Mr Wethered of Cheltenham,
who has made oolitic grains a special subject of careful investigation,
affords a good example of the occurrence of such tubular structures in an
oolitic grain of Silurian age from the Wenlock limestone of May Hill,
Gloucestershire[186]. In the centre is a crystalline core or nucleus round
which the tubules have grown, and presumably they had an important share
in the deposition of the calcareous substance. The nature of Girvanella, and
still more its exact position in the organic world, is quite uncertain; it is
mentioned rather as à propos of the association of recent Cyanophyceae
with oolitic structure, than as a well-defined genus of fossil algae.
In the typo description of the calcareous nodules from Michigan, Murray
speaks of the Schizothrix filaments at the surface of the pebbles as fairly
intact, while nearer the centre only sheaths were met with. It is conceivable
that in some of the tubular structures referred to Girvanella we have the
mineralised sheaths of a fossil Cyanophyceous genus[187]. The organic
nature of these tubules has been a matter of dispute, but we may probably
Page 148
assume with safety that in some at least of the fossil oolitic grains there are
distinct traces of some simple organism which was in all likelihood a plant.
Some authors have suggested that Girvanella is a calcareous alga which
should be included in the family Siphoneae[188]. As a matter of fact we must
be content for the present to leave its precise nature as still sub judice, and
while regarding it as probably an alga, we may venture to consider it more
fittingly discussed under the Schizophyta than elsewhere.
Wethered[189] would go so far as to refer oolitic structure in general to an
organic origin. While admitting that a Girvanella-like structure has been
very frequently met with in oolitic rocks, it would be unwise to adopt so
far-reaching a conclusion. It is at least premature to refer the formation of
all oolitic structure to algal agency, and the evidence adduced is by no
means convincing in every case. The discovery of Girvanella and allied
forms in rocks from the Cambrian[190], Ordovician, Silurian, Carboniferous,
Jurassic and other systems is a striking fact, and lends support to the view
that oolitic structure is in many cases intimately associated with the
presence of a simple tubular organism. Among recent algae we find
different genera, and representatives of different families, growing in such a
manner and under such circumstances as are favourable to the formation of
a ball-like mass of algal threads, which may or may not be encrusted with
carbonate of lime. Similarly as regards oolitic grains of various sizes, and
the occurrence in rocks of calcareous nodules, the tubular structure is not
always of precisely the same type, and cannot always be included under the
genus Girvanella.
Several observers have recorded the occurrence of low forms of plant-life
in the waters of thermal springs. It has been already mentioned that Cohn
described the occurrence of simple plants in the warm Carlsbad Springs,
and fission-plants of various types have been discovered in the thermal
waters of Iceland, the Azores[191], New Zealand, the Yellowstone Park,
Japan, India, and numerous other places.
A few years ago Mr Weed, of the geological survey of the United States,
published an interesting account of the formation of calcareous travertine
and siliceous sinter in the Yellowstone Park district[192]. This author
emphasizes the important rôle of certain forms of plants in the building up
of the calcareous and siliceous material. Among other forms of frequent
occurrence, Calothrix gypsophila and a species Leptothrix are mentioned,
distinct traces of some simple organism which was in all likelihood a plant.
Some authors have suggested that Girvanella is a calcareous alga which
should be included in the family Siphoneae[188]. As a matter of fact we must
be content for the present to leave its precise nature as still sub judice, and
while regarding it as probably an alga, we may venture to consider it more
fittingly discussed under the Schizophyta than elsewhere.
Wethered[189] would go so far as to refer oolitic structure in general to an
organic origin. While admitting that a Girvanella-like structure has been
very frequently met with in oolitic rocks, it would be unwise to adopt so
far-reaching a conclusion. It is at least premature to refer the formation of
all oolitic structure to algal agency, and the evidence adduced is by no
means convincing in every case. The discovery of Girvanella and allied
forms in rocks from the Cambrian[190], Ordovician, Silurian, Carboniferous,
Jurassic and other systems is a striking fact, and lends support to the view
that oolitic structure is in many cases intimately associated with the
presence of a simple tubular organism. Among recent algae we find
different genera, and representatives of different families, growing in such a
manner and under such circumstances as are favourable to the formation of
a ball-like mass of algal threads, which may or may not be encrusted with
carbonate of lime. Similarly as regards oolitic grains of various sizes, and
the occurrence in rocks of calcareous nodules, the tubular structure is not
always of precisely the same type, and cannot always be included under the
genus Girvanella.
Several observers have recorded the occurrence of low forms of plant-life
in the waters of thermal springs. It has been already mentioned that Cohn
described the occurrence of simple plants in the warm Carlsbad Springs,
and fission-plants of various types have been discovered in the thermal
waters of Iceland, the Azores[191], New Zealand, the Yellowstone Park,
Japan, India, and numerous other places.
A few years ago Mr Weed, of the geological survey of the United States,
published an interesting account of the formation of calcareous travertine
and siliceous sinter in the Yellowstone Park district[192]. This author
emphasizes the important rôle of certain forms of plants in the building up
of the calcareous and siliceous material. Among other forms of frequent
occurrence, Calothrix gypsophila and a species Leptothrix are mentioned,
Page 149
the former being a member of the Nostocaceae, allied to Rivularia, and the
latter a genus of Schizomycetes. In many of the springs there are found
masses of algal jelly like those previously described by Cohn in the
Carlsbad waters. Sections of such dried jelly showed a number of interlaced
filaments with glassy silica between them. Weed refers to the occurrence of
small gritty particles in this mucilaginous material. These are calcareous
oolitic granules which are eventually cemented together into a compact and
firm mass of travertine by the continued deposition of carbonate of lime.
The presence of the plant filaments is often difficult to recognise in the
“leathery sheet of tough gelatinous material,” or in “the skeins of delicate
white filaments” which make up the travertine deposits.
BORINGS IN SHELLS.
Under the head of Cyanophyceae, mention should be made of the recent
genus Hyella[193], which occurs as a perforating or boring alga in the
calcareous shells of molluscs. On dissolving the carbonate of lime of shells
perforated by this alga, the latter is isolated and appears to consist of rows
of small cells, with possibly some sporangia containing spores. Other
boring algae have been recorded among the Chlorophyceae, and recently a
member of the Rhodophyceae[194] has been found living in the substance of
calcareous shells. Such examples are worthy of note in view of the not
infrequent occurrence of fossil corals, shells and fish-scales, which have
evidently been bored by an organism resembling in form and manner of
occurrence these recent algal borers.
The occurrence of small ramifying tubes in recent and fossil corals, fish-
scales, and bones was long ago pointed out by Quekett[195], Kölliker[196],
Rose[197] and other writers[198]. These narrow tubular cavities have generally
been attributed to the boring action of some parasitic organism, either a
fungus or an alga. In 1876 Duncan published two important papers[199]
dealing with the occurrence of such tubes in recent corals, as well as in the
calcareous skeleton of Calceolina, Goniophyllum and other Palaeozoic,
Mesozoic and Tertiary species of corals. This writer attributed the formation
of the cavities in the case of the fossil species to the action of a fungus
which he named Palaeachlya perforans, and considered as very nearly
related to Achlya penetrans found in the “dense sclerenchyma” of recent
corals. In fig. 27 A. is reproduced one of the drawings given by Rose[200] in
his paper published in 1855; it shows a section of a fish-scale from the
latter a genus of Schizomycetes. In many of the springs there are found
masses of algal jelly like those previously described by Cohn in the
Carlsbad waters. Sections of such dried jelly showed a number of interlaced
filaments with glassy silica between them. Weed refers to the occurrence of
small gritty particles in this mucilaginous material. These are calcareous
oolitic granules which are eventually cemented together into a compact and
firm mass of travertine by the continued deposition of carbonate of lime.
The presence of the plant filaments is often difficult to recognise in the
“leathery sheet of tough gelatinous material,” or in “the skeins of delicate
white filaments” which make up the travertine deposits.
BORINGS IN SHELLS.
Under the head of Cyanophyceae, mention should be made of the recent
genus Hyella[193], which occurs as a perforating or boring alga in the
calcareous shells of molluscs. On dissolving the carbonate of lime of shells
perforated by this alga, the latter is isolated and appears to consist of rows
of small cells, with possibly some sporangia containing spores. Other
boring algae have been recorded among the Chlorophyceae, and recently a
member of the Rhodophyceae[194] has been found living in the substance of
calcareous shells. Such examples are worthy of note in view of the not
infrequent occurrence of fossil corals, shells and fish-scales, which have
evidently been bored by an organism resembling in form and manner of
occurrence these recent algal borers.
The occurrence of small ramifying tubes in recent and fossil corals, fish-
scales, and bones was long ago pointed out by Quekett[195], Kölliker[196],
Rose[197] and other writers[198]. These narrow tubular cavities have generally
been attributed to the boring action of some parasitic organism, either a
fungus or an alga. In 1876 Duncan published two important papers[199]
dealing with the occurrence of such tubes in recent corals, as well as in the
calcareous skeleton of Calceolina, Goniophyllum and other Palaeozoic,
Mesozoic and Tertiary species of corals. This writer attributed the formation
of the cavities in the case of the fossil species to the action of a fungus
which he named Palaeachlya perforans, and considered as very nearly
related to Achlya penetrans found in the “dense sclerenchyma” of recent
corals. In fig. 27 A. is reproduced one of the drawings given by Rose[200] in
his paper published in 1855; it shows a section of a fish-scale from the
Page 150
Kimeridge clay which has been attacked by a boring organism. Rose
attributes the dichotomously branched canals to some “infusorial parasite.”
Fig. 27. A, Section of a fish-scale from the Kimeridge Clay, showing branched canals, made
by a boring organism, × 85. B, Section of a Solen shell, penetrated in all directions by the
boring thallus of Ostracoblabe (a fungus?), × 330. C, Piece of the thallus of Ostracoblabe
isolated by decalcification, × 745. A, after Rose. B and C, after Bornet and Flahault.
In the important paper by MM. Bornet and Flahault on perforating algae
a full description is given of various boring forms belonging to the
Chlorophyceae and the Cyanophyceae[201]. The canals which these algae
produce in calcareous shells and other hard substances are of the same type
as those previously described in fossil corals, fish-scales and bones. In
dealing with living perforating Thallophytes the colour and other cell-
contents often enable us to distinguish between algae and fungi, but in fossil
specimens such tests cannot be applied. The fossil tubular borings may or
may not show traces of the transverse septa and reproductive cells; it is
often the case that no trace of the organism has been left, but only the canals
by which it penetrated the calcareous or bony skeleton. In some of the
examples of Palaeachlya figured by Duncan there appear to be numerous
attributes the dichotomously branched canals to some “infusorial parasite.”
Fig. 27. A, Section of a fish-scale from the Kimeridge Clay, showing branched canals, made
by a boring organism, × 85. B, Section of a Solen shell, penetrated in all directions by the
boring thallus of Ostracoblabe (a fungus?), × 330. C, Piece of the thallus of Ostracoblabe
isolated by decalcification, × 745. A, after Rose. B and C, after Bornet and Flahault.
In the important paper by MM. Bornet and Flahault on perforating algae
a full description is given of various boring forms belonging to the
Chlorophyceae and the Cyanophyceae[201]. The canals which these algae
produce in calcareous shells and other hard substances are of the same type
as those previously described in fossil corals, fish-scales and bones. In
dealing with living perforating Thallophytes the colour and other cell-
contents often enable us to distinguish between algae and fungi, but in fossil
specimens such tests cannot be applied. The fossil tubular borings may or
may not show traces of the transverse septa and reproductive cells; it is
often the case that no trace of the organism has been left, but only the canals
by which it penetrated the calcareous or bony skeleton. In some of the
examples of Palaeachlya figured by Duncan there appear to be numerous
Page 151
spores in some of the sections, but it is generally a very difficult and often
an impossible task to discriminate between the borings of fungi and algae in
fossil material.
Fig. 27 B, which is copied from one of Bornet and Flahault’s drawings,
represents a piece of Solen shell riddled with small canals made by the
organism which has been named by the French authors Ostracoblabe
implexa, and regarded by them as a fungus. Fig. 27 C represents a small
piece of the vegetative body of Ostracoblabe obtained from a decalcified
shell. In endeavouring to determine the organism which has produced
borings in fossil corals or shells, it must be borne in mind that some forms
of canals or passages may have been the work of perforating sponges, but
these are larger in diameter than those made by algae or fungi. By some
writers[202] the tubular cavities in shells have been referred to true algae, but
others consider them to be of fungal origin.
As an example of a fossil alga referred to the Cyanophyceae, the genus
Zonatrichites[203] may be quoted. Bornemann, who first described the
specimens, points out the close resemblance in habit to some members of
the recent Rivulariaceae.
Zonatrichites.
The author of the genus defines it as follows:—
“A calcareous alga, with radially arranged filaments, forming hemispherical or kidney-shaped
layers, growing on or enclosing other bodies. Parallel or concentric zones are seen in cross-
section, formed by the periodic growth of the alga, the older and dead layers serving as a
foundation on which the young filaments grow in radially arranged groups.”
The nodules which are apparently formed by species of this genus occur
in various sizes and shapes; Bornemann describes one hemispherical mass 8
cm. broad and 4 cm. thick. In some cases the organism has given rise to
oolitic spherules, which in radial section exhibit the branched tubular cells
spreading in fan-shaped groups from the centre of the oolitic grain. The
section parallel to the surface of a nodule presents the appearance of a
number of circular or elliptical tubes cut across transversely or more or less
obliquely. The resemblance between the fossil and a specimen of the recent
species Zonatrichia calcivora Braun, is certainly very close, but it is very
difficult, in the absence of material exhibiting more detailed structure than
an impossible task to discriminate between the borings of fungi and algae in
fossil material.
Fig. 27 B, which is copied from one of Bornet and Flahault’s drawings,
represents a piece of Solen shell riddled with small canals made by the
organism which has been named by the French authors Ostracoblabe
implexa, and regarded by them as a fungus. Fig. 27 C represents a small
piece of the vegetative body of Ostracoblabe obtained from a decalcified
shell. In endeavouring to determine the organism which has produced
borings in fossil corals or shells, it must be borne in mind that some forms
of canals or passages may have been the work of perforating sponges, but
these are larger in diameter than those made by algae or fungi. By some
writers[202] the tubular cavities in shells have been referred to true algae, but
others consider them to be of fungal origin.
As an example of a fossil alga referred to the Cyanophyceae, the genus
Zonatrichites[203] may be quoted. Bornemann, who first described the
specimens, points out the close resemblance in habit to some members of
the recent Rivulariaceae.
Zonatrichites.
The author of the genus defines it as follows:—
“A calcareous alga, with radially arranged filaments, forming hemispherical or kidney-shaped
layers, growing on or enclosing other bodies. Parallel or concentric zones are seen in cross-
section, formed by the periodic growth of the alga, the older and dead layers serving as a
foundation on which the young filaments grow in radially arranged groups.”
The nodules which are apparently formed by species of this genus occur
in various sizes and shapes; Bornemann describes one hemispherical mass 8
cm. broad and 4 cm. thick. In some cases the organism has given rise to
oolitic spherules, which in radial section exhibit the branched tubular cells
spreading in fan-shaped groups from the centre of the oolitic grain. The
section parallel to the surface of a nodule presents the appearance of a
number of circular or elliptical tubes cut across transversely or more or less
obliquely. The resemblance between the fossil and a specimen of the recent
species Zonatrichia calcivora Braun, is certainly very close, but it is very
difficult, in the absence of material exhibiting more detailed structure than
Page 152
is shown in the specimens described by Bornemann, to decide with any
certainty the true position of the fossil. The figures do not enable us to
recognise any trace of cells in the radiating tubes. It is possible that we have
in Zonatrichites an example of a Cyanophyceous genus in which only the
sheaths of the filaments have been preserved. In any case it is probable that
this Mesozoic species affords another instance of a fossil alga which has
been responsible for certain oolitic or other structures in limestone rocks.
The species described by Bornemann was obtained from a Breccia near
Lissau in Silesia, of Keuper age.
M. Renault has recently described certain minute structures in a
Palaeozoic coprolite to which he gives the name Gloioconis Borneti[204], and
which he regards as a Permian gelatinous alga similar to the well-known
recent genus Glœocapsa. The appearances revealed in a section of the
coprolite are interpreted by this author as a collection of small colonies of a
unicellular gelatinous alga in various stages of development. Renault’s
figure shows a spherical group of faintly outlined and cloudy bodies, most
of which include one or two small dark spots. The latter are regarded as the
cells of the alga, and the surrounding cloudy substance is described as the
gelatinous sheath. The absence of a nucleus in these extremely minute fossil
cells (8–10 µ in diameter) is referred to as an argument in favour of
referring the organism to the Cyanophyceae rather than to the
Chlorophyceae. It is possible that the ill-defined structure described by
Renault may be a petrified alga, but there is not sufficient evidence to
warrant a decided opinion; the absence of nuclei can hardly be taken
seriously in such a case as this as an argument in favour of the
Cyanophyceae.
CYANOPHYCEAE.
Although our exact knowledge of fossil Cyanophyceae is extremely
small, it is probable that such simple forms of plants existed in abundance
during the past ages in the earth’s history. Several writers have expressed
the opinion that the blue-green algae may be taken as the modern
representatives of those earliest plants which first existed on an archaean
land-surface. The living species possess the power of resisting unfavourable
conditions in a marked degree, and are able to adapt themselves to very
different surroundings. Their occurrence in hot springs proves them capable
of living under conditions which are fatal to most plants, and suggests the
certainty the true position of the fossil. The figures do not enable us to
recognise any trace of cells in the radiating tubes. It is possible that we have
in Zonatrichites an example of a Cyanophyceous genus in which only the
sheaths of the filaments have been preserved. In any case it is probable that
this Mesozoic species affords another instance of a fossil alga which has
been responsible for certain oolitic or other structures in limestone rocks.
The species described by Bornemann was obtained from a Breccia near
Lissau in Silesia, of Keuper age.
M. Renault has recently described certain minute structures in a
Palaeozoic coprolite to which he gives the name Gloioconis Borneti[204], and
which he regards as a Permian gelatinous alga similar to the well-known
recent genus Glœocapsa. The appearances revealed in a section of the
coprolite are interpreted by this author as a collection of small colonies of a
unicellular gelatinous alga in various stages of development. Renault’s
figure shows a spherical group of faintly outlined and cloudy bodies, most
of which include one or two small dark spots. The latter are regarded as the
cells of the alga, and the surrounding cloudy substance is described as the
gelatinous sheath. The absence of a nucleus in these extremely minute fossil
cells (8–10 µ in diameter) is referred to as an argument in favour of
referring the organism to the Cyanophyceae rather than to the
Chlorophyceae. It is possible that the ill-defined structure described by
Renault may be a petrified alga, but there is not sufficient evidence to
warrant a decided opinion; the absence of nuclei can hardly be taken
seriously in such a case as this as an argument in favour of the
Cyanophyceae.
CYANOPHYCEAE.
Although our exact knowledge of fossil Cyanophyceae is extremely
small, it is probable that such simple forms of plants existed in abundance
during the past ages in the earth’s history. Several writers have expressed
the opinion that the blue-green algae may be taken as the modern
representatives of those earliest plants which first existed on an archaean
land-surface. The living species possess the power of resisting unfavourable
conditions in a marked degree, and are able to adapt themselves to very
different surroundings. Their occurrence in hot springs proves them capable
of living under conditions which are fatal to most plants, and suggests the
Page 153
possibility of their occurrence in the heated waters which probably
constituted the medium in which vegetable life began. An interesting
example of the growth of blue-green algae under unfavourable conditions
was recorded in 1886 by Dr Treub[205] of the Buitenzorg Gardens, Java. In
1883 a considerable part of the island Krakatoa, situated in the Straits of
Sunda, between Sumatra and Java, was entirely destroyed by a terrific
volcanic explosion. What remained had been reduced to a lifeless mass of
hot volcanic ashes. Three years later, Treub visited the island, and found
that several plants had already established themselves on the volcanic rocks.
Various ferns and flowering plants were recorded in Treub’s description of
this newly established flora. It seemed that the barren rocky surface had
been prepared for the more highly organised plants by the action of certain
forms of Cyanophyceae, which were able to live under conditions which
would be fatal to more complex types.
In the petrified tissues of fossil plants there are occasionally found small
spherical vesicles, with delicate limiting membranes, in the cavities of
parenchymatous cells or in the elements of vascular tissue. Some of these
spherical inclusions have been described as possibly simple forms of
endophytic algae[206], such as we are now familiar with in species of the
Cyanophyceae and other algae. So far, however, no recorded instance of
such fossil endophytic algae is entirely satisfactory. Some of the cells
figured by Williamson as possibly algae, endophytic in the tissues of Coal-
Measure plants, are no doubt thin-walled vesicles which formed part of a
highly vacuolated cell-contents. Examples of such vesicles in living and
fossil cells are shown in fig. 42. The fact that the contents of living plant
tissues have been erroneously described as endophytic organisms, should
serve as a warning against describing fossil endophytes without the test of
good evidence to support them.
The description of a fossil Nostoc by the late Prof. Heer[207] from the
Tertiary rocks of Switzerland cannot be accepted as a trustworthy example
of a fossil plant, much less of a genus of recent algae. The application of
recent generic names to fossils which are possibly not even organic must do
more harm than good.
B. SCHIZOMYCETES (Bacteria).
constituted the medium in which vegetable life began. An interesting
example of the growth of blue-green algae under unfavourable conditions
was recorded in 1886 by Dr Treub[205] of the Buitenzorg Gardens, Java. In
1883 a considerable part of the island Krakatoa, situated in the Straits of
Sunda, between Sumatra and Java, was entirely destroyed by a terrific
volcanic explosion. What remained had been reduced to a lifeless mass of
hot volcanic ashes. Three years later, Treub visited the island, and found
that several plants had already established themselves on the volcanic rocks.
Various ferns and flowering plants were recorded in Treub’s description of
this newly established flora. It seemed that the barren rocky surface had
been prepared for the more highly organised plants by the action of certain
forms of Cyanophyceae, which were able to live under conditions which
would be fatal to more complex types.
In the petrified tissues of fossil plants there are occasionally found small
spherical vesicles, with delicate limiting membranes, in the cavities of
parenchymatous cells or in the elements of vascular tissue. Some of these
spherical inclusions have been described as possibly simple forms of
endophytic algae[206], such as we are now familiar with in species of the
Cyanophyceae and other algae. So far, however, no recorded instance of
such fossil endophytic algae is entirely satisfactory. Some of the cells
figured by Williamson as possibly algae, endophytic in the tissues of Coal-
Measure plants, are no doubt thin-walled vesicles which formed part of a
highly vacuolated cell-contents. Examples of such vesicles in living and
fossil cells are shown in fig. 42. The fact that the contents of living plant
tissues have been erroneously described as endophytic organisms, should
serve as a warning against describing fossil endophytes without the test of
good evidence to support them.
The description of a fossil Nostoc by the late Prof. Heer[207] from the
Tertiary rocks of Switzerland cannot be accepted as a trustworthy example
of a fossil plant, much less of a genus of recent algae. The application of
recent generic names to fossils which are possibly not even organic must do
more harm than good.
B. SCHIZOMYCETES (Bacteria).
Page 154
It is impossible to draw a sharp line between the two subdivisions of the
Schizophyta. The so-called Fission-Fungi or Bacteria differ from the
Schizophyceae or Fission-Algae in the cell-contents being either colourless,
blood-red or green, but never blue-green. We may regard the Bacteria,
generally, as the lowest forms of plants; they are extremely simple
organisms which have been derived from some primitive types which
possessed the power of independent existence and contained chlorophyll—
that important substance which enables a plant to obtain its carbon first-
hand from the carbon dioxide of the atmosphere.
Bacteria may be briefly described as single-celled plants, and as de Bary
suggested comparable in shape to a billiard ball, a lead pencil or a
corkscrew[208]. A single spherical or cylindrical cell measures about 1 µ in
diameter[209]. They occur either singly or in filaments, or as masses of
various shapes consisting of numberless bacterial cells. The nature and
manner of life of Bacteria, and their extraordinary power of successfully
resisting the most unfavourable conditions, render it probable that they
constitute an extremely ancient group of organisms.
The wonderful perfection of preservation of many fossil plants enables us
to investigate the contents of petrified cells and to examine in minutest
detail the histology of extinct plants. To those who are familiar with the
possibilities of microscopical research as applied to silicified and calcified
fossil tissues, it is by no means incredible that evidence has been detected
of the existence of Bacteria as far back in the history of the earth as the
Carboniferous and Devonian periods.
Were there no trustworthy records of the occurrence of Bacteria in
Palaeozoic times, it would still be a natural supposition that these
ubiquitous organisms must have been abundantly represented. It has been
suggested as a probable conclusion that some forms of Bacteria, which
produced chemical changes in the soil necessary for the nutrition of plants,
must have existed contemporaneously with the oldest vegetation[210].
The paper-coal of Toula, which in some places reaches a thickness of 20
cm., is a plant-bed of exceptional interest. It differs from ordinary coal in
being made up of numberless thin brown-papery sheets associated with a
darker coloured substance largely composed of ulmic acid. Prof. Zeiller[211],
in an interesting account of the papery layers, has shown that they consist of
Schizophyta. The so-called Fission-Fungi or Bacteria differ from the
Schizophyceae or Fission-Algae in the cell-contents being either colourless,
blood-red or green, but never blue-green. We may regard the Bacteria,
generally, as the lowest forms of plants; they are extremely simple
organisms which have been derived from some primitive types which
possessed the power of independent existence and contained chlorophyll—
that important substance which enables a plant to obtain its carbon first-
hand from the carbon dioxide of the atmosphere.
Bacteria may be briefly described as single-celled plants, and as de Bary
suggested comparable in shape to a billiard ball, a lead pencil or a
corkscrew[208]. A single spherical or cylindrical cell measures about 1 µ in
diameter[209]. They occur either singly or in filaments, or as masses of
various shapes consisting of numberless bacterial cells. The nature and
manner of life of Bacteria, and their extraordinary power of successfully
resisting the most unfavourable conditions, render it probable that they
constitute an extremely ancient group of organisms.
The wonderful perfection of preservation of many fossil plants enables us
to investigate the contents of petrified cells and to examine in minutest
detail the histology of extinct plants. To those who are familiar with the
possibilities of microscopical research as applied to silicified and calcified
fossil tissues, it is by no means incredible that evidence has been detected
of the existence of Bacteria as far back in the history of the earth as the
Carboniferous and Devonian periods.
Were there no trustworthy records of the occurrence of Bacteria in
Palaeozoic times, it would still be a natural supposition that these
ubiquitous organisms must have been abundantly represented. It has been
suggested as a probable conclusion that some forms of Bacteria, which
produced chemical changes in the soil necessary for the nutrition of plants,
must have existed contemporaneously with the oldest vegetation[210].
The paper-coal of Toula, which in some places reaches a thickness of 20
cm., is a plant-bed of exceptional interest. It differs from ordinary coal in
being made up of numberless thin brown-papery sheets associated with a
darker coloured substance largely composed of ulmic acid. Prof. Zeiller[211],
in an interesting account of the papery layers, has shown that they consist of
Page 155
the cuticles of a Lepidodendroid plant, Bothrodendron. An examination of a
piece of one of the sheets at once reveals the existence of a regular network
of which the walls of the meshes are the outlines of the epidermal cells, the
meshes being bridged across by a thin light brown membrane which
represents the layer of cuticularised cell-wall of each epidermal cell. At
regular intervals and disposed in a spiral arrangement, we find small gaps in
the papery cuticle which mark the position of the Bothrodendron leaves.
These Palaeozoic cuticles are not petrified; they are only slightly altered,
and have retained the power of swelling in water, being able to take up
stains like recent tissues. It may reasonably be assumed that the persistent
cuticles owe their preservation to a greater power of resistance to
destructive agents than was possessed by the other tissues of the plant. It is
by no means unlikely, as Renault[212] has recently suggested, that as the
Bothrodendron stem-fragments lay in the swamps or marshes the tissues
were gradually eaten away by Bacteria, but the cuticles successfully resisted
the attacks of the bacterial saprophytes. The same observer has described
what he regards as the actual organism which effected this wholesale
destruction, under the name Micrococcus Zeilleri. He finds, after treating
the cuticles with ammonia to remove the ulmic acid, that there occur
numerous minute spherical bodies, each surrounded by a thin envelope,
either singly or in groups on the surface of the cuticular membrane. These
vary in size from ·5µ to 1µ in diameter. I have not been able to detect any
satisfactory proof of such Micrococci in specimens of the paper-coal which
were treated according to Renault’s method, but it is extremely probable
that this unusual method of preservation of stem-cuticles is the result of
selective bacterial action.
Renault believes that some of the minute spherulitic structures which are
seen in sections of decayed tissues of Palaeozoic plants owe their origin, in
part, to the ravages of bacteria. The disorganisation of parenchymatous cells
gives rise to a gelatinous substance in which needle-like crystals of silica
may be deposited, from a siliceous solution, in a matrix which has resulted
from bacterial activity. In some of the sections of tissues figured by
Renault[213] the outlines of a few cells are still indicated by fragments of the
partially decayed wall, while in other cells the walls have been completely
destroyed by Bacteria of which some are preserved in the centre of the cell-
area, forming a kind of nucleus to the siliceous spherulites.
piece of one of the sheets at once reveals the existence of a regular network
of which the walls of the meshes are the outlines of the epidermal cells, the
meshes being bridged across by a thin light brown membrane which
represents the layer of cuticularised cell-wall of each epidermal cell. At
regular intervals and disposed in a spiral arrangement, we find small gaps in
the papery cuticle which mark the position of the Bothrodendron leaves.
These Palaeozoic cuticles are not petrified; they are only slightly altered,
and have retained the power of swelling in water, being able to take up
stains like recent tissues. It may reasonably be assumed that the persistent
cuticles owe their preservation to a greater power of resistance to
destructive agents than was possessed by the other tissues of the plant. It is
by no means unlikely, as Renault[212] has recently suggested, that as the
Bothrodendron stem-fragments lay in the swamps or marshes the tissues
were gradually eaten away by Bacteria, but the cuticles successfully resisted
the attacks of the bacterial saprophytes. The same observer has described
what he regards as the actual organism which effected this wholesale
destruction, under the name Micrococcus Zeilleri. He finds, after treating
the cuticles with ammonia to remove the ulmic acid, that there occur
numerous minute spherical bodies, each surrounded by a thin envelope,
either singly or in groups on the surface of the cuticular membrane. These
vary in size from ·5µ to 1µ in diameter. I have not been able to detect any
satisfactory proof of such Micrococci in specimens of the paper-coal which
were treated according to Renault’s method, but it is extremely probable
that this unusual method of preservation of stem-cuticles is the result of
selective bacterial action.
Renault believes that some of the minute spherulitic structures which are
seen in sections of decayed tissues of Palaeozoic plants owe their origin, in
part, to the ravages of bacteria. The disorganisation of parenchymatous cells
gives rise to a gelatinous substance in which needle-like crystals of silica
may be deposited, from a siliceous solution, in a matrix which has resulted
from bacterial activity. In some of the sections of tissues figured by
Renault[213] the outlines of a few cells are still indicated by fragments of the
partially decayed wall, while in other cells the walls have been completely
destroyed by Bacteria of which some are preserved in the centre of the cell-
area, forming a kind of nucleus to the siliceous spherulites.
Page 156
BACILLI.
In addition to the Micrococcus described by Renault from the Toula
paper-coal, there are a host of other forms which have been minutely
diagnosed and figured by Profs. Renault and Bertrand[214]. These authors
have discovered what they believe to be well-defined species of
Micrococcus and Bacillus ranging in age from Devonian to Jurassic. The
material which has afforded the somewhat startling results of their
investigations consists partly of the coprolites of reptiles and fishes, and of
silicified and calcified plant tissues.
Bacillus Permicus. Ren. and Bert.[215] (Fig. 28 B.)
This Bacillus, which was discovered in sections of a Permian coprolite
from Central France, has the form of cylindrical rods 12–14µ in length, and
1·3–1·5µ broad, rounded at each end. The rods occur either singly or
occasionally, two or three individuals are joined end to end. Fig. 28 B
represents a piece of one of Renault and Bertrand’s sections; the small rods
are clearly seen lying in various directions in the homogeneous matrix of
the coprolite. Each individual is said to be surrounded by an extremely
minute empty space ·4µ in width, originally occupied by the Bacillus
membrane, the central rod representing the mineralised cell-contents. In this
example the petrifying substance was probably derived from the phosphate
of calcium of bones which were attacked by Bacteria. I am indebted to Prof.
Renault for an opportunity of examining specimens of this and other fossil
Bacteria, and in this particular case there is undoubtedly strong evidence in
favour of the author’s determination.
In addition to the Micrococcus described by Renault from the Toula
paper-coal, there are a host of other forms which have been minutely
diagnosed and figured by Profs. Renault and Bertrand[214]. These authors
have discovered what they believe to be well-defined species of
Micrococcus and Bacillus ranging in age from Devonian to Jurassic. The
material which has afforded the somewhat startling results of their
investigations consists partly of the coprolites of reptiles and fishes, and of
silicified and calcified plant tissues.
Bacillus Permicus. Ren. and Bert.[215] (Fig. 28 B.)
This Bacillus, which was discovered in sections of a Permian coprolite
from Central France, has the form of cylindrical rods 12–14µ in length, and
1·3–1·5µ broad, rounded at each end. The rods occur either singly or
occasionally, two or three individuals are joined end to end. Fig. 28 B
represents a piece of one of Renault and Bertrand’s sections; the small rods
are clearly seen lying in various directions in the homogeneous matrix of
the coprolite. Each individual is said to be surrounded by an extremely
minute empty space ·4µ in width, originally occupied by the Bacillus
membrane, the central rod representing the mineralised cell-contents. In this
example the petrifying substance was probably derived from the phosphate
of calcium of bones which were attacked by Bacteria. I am indebted to Prof.
Renault for an opportunity of examining specimens of this and other fossil
Bacteria, and in this particular case there is undoubtedly strong evidence in
favour of the author’s determination.
Page 157
Fig. 28. A, Bacillus Tieghemi Ren. and Micrococcus Guignardi Ren. B, Bacillus Permicus
Ren. (After Renault.)
Bacillus Tieghemi Ren.[216] and Micrococcus Guignardi Ren.[217] (Fig. 28 A.)
Renault has given the name Bacillus Tieghemi to certain minute rods 6–
10µ, in length, and 2·2–3·8µ broad, often containing a dark coloured
spherical spore-like body 2µ in diameter, which have been found in the
tissues of a Coal-Measure plant.
The name Micrococcus Guignardi has been applied to more or less
spherical bodies 2·2µ in diameter, also met with in silicified plants.
A portion of one of Renault’s figures is reproduced in Fig. 28 A. The faint
and broken lines mark the position of the middle lamellae of
parenchymatous cells from the pith of a Calamite. The tissue has been
almost completely destroyed, but the more resistant middle lamellae have
been partially preserved. The short and broad rods represent what Renault
terms Bacillus Tieghemi; the small circle in the middle of some of these
being referred to as a spore, and in one specimen shown in the figure, the
second rod at right angles to the first is described as a small daughter-
Bacillus formed by the germination of the central spore.
The isolated circles in the figure are referred to Micrococcus.
FOSSIL BACTERIA.
It is unnecessary to give an account of the numerous examples of
Micrococci and Bacilli described by Renault from Devonian,
Ren. (After Renault.)
Bacillus Tieghemi Ren.[216] and Micrococcus Guignardi Ren.[217] (Fig. 28 A.)
Renault has given the name Bacillus Tieghemi to certain minute rods 6–
10µ, in length, and 2·2–3·8µ broad, often containing a dark coloured
spherical spore-like body 2µ in diameter, which have been found in the
tissues of a Coal-Measure plant.
The name Micrococcus Guignardi has been applied to more or less
spherical bodies 2·2µ in diameter, also met with in silicified plants.
A portion of one of Renault’s figures is reproduced in Fig. 28 A. The faint
and broken lines mark the position of the middle lamellae of
parenchymatous cells from the pith of a Calamite. The tissue has been
almost completely destroyed, but the more resistant middle lamellae have
been partially preserved. The short and broad rods represent what Renault
terms Bacillus Tieghemi; the small circle in the middle of some of these
being referred to as a spore, and in one specimen shown in the figure, the
second rod at right angles to the first is described as a small daughter-
Bacillus formed by the germination of the central spore.
The isolated circles in the figure are referred to Micrococcus.
FOSSIL BACTERIA.
It is unnecessary to give an account of the numerous examples of
Micrococci and Bacilli described by Renault from Devonian,
Page 158
Carboniferous, Permian and Jurassic rocks. We may, however, in a few
words consider the general question of the existence and possible
determination of fossil Bacteria.
In 1877 Prof. Van Tieghem[218] of Paris drew attention to the method of
operation and plan of attack of Bacillus amylobacter as a destructive agent
in the decay of plant débris in water. He was able to follow the gradual
disorganisation of the tissues and the various steps in the ‘butyric
fermentation’ effected by this Bacterium. Similarly the same author[219] was
able to detect the action of an allied organism in some silicified tissues from
the Carboniferous nodules of Grand-Croix, a well-known locality for
petrified plants near Saint-Étienne. He recognised also the traces of the
Bacillus itself in the partially destroyed plant tissues. The Palaeozoic
Bacteria made use of some cellulose-dissolving ferment of which the action
is clearly demonstrated in sections of silicified tissues. Many of the
phenomena described by Renault and Bertrand as due to similar Bacterial
action, afford additional evidence that the gradual disorganisation of
vegetable tissues was effected in precisely the same manner as at the
present day.
In some cases we have I believe trustworthy examples of the Bacteria
themselves, both in coprolites and plant-tissues, but it is more than probable
that some of the recorded examples are not of any scientific value. The
examination of petrified tissues under the higher powers of a microscope
often reveals the existence of numerous spherical particles and rod-like
bodies which agree in shape with Micrococci or Bacilli. Minute crystals of
mineral substances may occur in the siliceous or calcareous matrix of a
petrified plant which simulate minute organic forms. Vogelsang[220] in his
important work die Krystalliten has thrown considerable light on the
ontogeny of crystals, and the minute globulites and other forms of incipient
crystallisation might well be mistaken for Bacterial cells. Granting,
however, that we have satisfactory evidence, both direct and indirect, that
some forms of Bacteria lived in the decaying tissues of Palaeozoic plants,
and in the intestines of reptiles and other animals, we cannot safely proceed
to specific diagnoses and determinations[221].
Renault has pointed out that fossil Bacteria may often be more readily
detected than living forms owing to the presence of a brown ulmic
substance which results from the carbonisation of the protoplasm. He is
words consider the general question of the existence and possible
determination of fossil Bacteria.
In 1877 Prof. Van Tieghem[218] of Paris drew attention to the method of
operation and plan of attack of Bacillus amylobacter as a destructive agent
in the decay of plant débris in water. He was able to follow the gradual
disorganisation of the tissues and the various steps in the ‘butyric
fermentation’ effected by this Bacterium. Similarly the same author[219] was
able to detect the action of an allied organism in some silicified tissues from
the Carboniferous nodules of Grand-Croix, a well-known locality for
petrified plants near Saint-Étienne. He recognised also the traces of the
Bacillus itself in the partially destroyed plant tissues. The Palaeozoic
Bacteria made use of some cellulose-dissolving ferment of which the action
is clearly demonstrated in sections of silicified tissues. Many of the
phenomena described by Renault and Bertrand as due to similar Bacterial
action, afford additional evidence that the gradual disorganisation of
vegetable tissues was effected in precisely the same manner as at the
present day.
In some cases we have I believe trustworthy examples of the Bacteria
themselves, both in coprolites and plant-tissues, but it is more than probable
that some of the recorded examples are not of any scientific value. The
examination of petrified tissues under the higher powers of a microscope
often reveals the existence of numerous spherical particles and rod-like
bodies which agree in shape with Micrococci or Bacilli. Minute crystals of
mineral substances may occur in the siliceous or calcareous matrix of a
petrified plant which simulate minute organic forms. Vogelsang[220] in his
important work die Krystalliten has thrown considerable light on the
ontogeny of crystals, and the minute globulites and other forms of incipient
crystallisation might well be mistaken for Bacterial cells. Granting,
however, that we have satisfactory evidence, both direct and indirect, that
some forms of Bacteria lived in the decaying tissues of Palaeozoic plants,
and in the intestines of reptiles and other animals, we cannot safely proceed
to specific diagnoses and determinations[221].
Renault has pointed out that fossil Bacteria may often be more readily
detected than living forms owing to the presence of a brown ulmic
substance which results from the carbonisation of the protoplasm. He is
Page 159
forced to admit, however, that such diagnostic characters as are obtained by
Bacteriologists by means of cultures cannot be utilised when we are dealing
with fossil examples! We are told that “Partout où nous avons cherché des
Bacteriaceés, nous en avons rencontré.”[222] This indeed is the danger; an
extended examination of fossil sections under an immersion-lens must
almost inevitably lead to the discovery of minute bodies of a more or less
spherical form which might be Micrococci. To measure, and name such
bodies as definite species of Micrococci is, I believe, but wasted energy and
an attempt to compass the impossible.
Specialists tell us that the accurate determination of species of recent
Bacteria is practically hopeless: may we not reasonably conclude that the
attempt to specifically diagnose fossil forms is absolutely hopeless? “The
imagination of man is naturally sublime, delighted with whatever is remote
and extraordinary—”, but it is to be deplored if the fascination of fossil
bacteriology is allowed to warp sound scientific sense.
IV. ALGAE.
A. DIATOMACEAE. (Diatoms.)
B. CHLOROPHYCEAE. (Green algae.)
C. RHODOPHYCEAE. (Red algae.)
D. PHAEOPHYCEAE. (Brown algae.)
The presence of chlorophyll is one common characteristic of the
numerous plants included in the Algae. The generally adopted classification
rests in part on an artificial distinction, namely the prevailing colour of the
plant.
It must be definitely admitted, at the outset, that palaeobotany has so far
afforded extremely little trustworthy information as to the past history of
algae. Were we to measure the importance of the geological history of these
plants by the number of recorded fossil species, we should arrive at a totally
wrong and misleading estimate. By far the greater number of the supposed
fossil algae have no claim to be regarded as authentic records of this class
of Thallophytes. It has been justly said that palaeontologists have been in
the habit of referring to algae such impressions or markings on rocks as
Bacteriologists by means of cultures cannot be utilised when we are dealing
with fossil examples! We are told that “Partout où nous avons cherché des
Bacteriaceés, nous en avons rencontré.”[222] This indeed is the danger; an
extended examination of fossil sections under an immersion-lens must
almost inevitably lead to the discovery of minute bodies of a more or less
spherical form which might be Micrococci. To measure, and name such
bodies as definite species of Micrococci is, I believe, but wasted energy and
an attempt to compass the impossible.
Specialists tell us that the accurate determination of species of recent
Bacteria is practically hopeless: may we not reasonably conclude that the
attempt to specifically diagnose fossil forms is absolutely hopeless? “The
imagination of man is naturally sublime, delighted with whatever is remote
and extraordinary—”, but it is to be deplored if the fascination of fossil
bacteriology is allowed to warp sound scientific sense.
IV. ALGAE.
A. DIATOMACEAE. (Diatoms.)
B. CHLOROPHYCEAE. (Green algae.)
C. RHODOPHYCEAE. (Red algae.)
D. PHAEOPHYCEAE. (Brown algae.)
The presence of chlorophyll is one common characteristic of the
numerous plants included in the Algae. The generally adopted classification
rests in part on an artificial distinction, namely the prevailing colour of the
plant.
It must be definitely admitted, at the outset, that palaeobotany has so far
afforded extremely little trustworthy information as to the past history of
algae. Were we to measure the importance of the geological history of these
plants by the number of recorded fossil species, we should arrive at a totally
wrong and misleading estimate. By far the greater number of the supposed
fossil algae have no claim to be regarded as authentic records of this class
of Thallophytes. It has been justly said that palaeontologists have been in
the habit of referring to algae such impressions or markings on rocks as
Page 160
cannot well be included in any other group. “A fossil alga,” has often been
the dernier ressort of the doubtful student.
LARGE SEAWEEDS.
Before discussing our knowledge, or rather lack of knowledge, of fossil
algae at greater length, it will be well to briefly consider the manner of
occurrence and botanical nature of existing forms. In the sea and in fresh
water, as well as in damp places and even in situations subject to periods of
drought, algae occur in abundance in all parts of the world. We find them
attaining full development and reproducing themselves at a temperature of
−1° C. in the Arctic Seas, and again living in enormous numbers in the
waters of thermal springs. Around the coast-line of land areas, and on the
floor of shallow seas algae exhibit a remarkable wealth of form and
luxuriance of growth. As regards habit and structure, there is every
gradation from algae in which the whole individual consists of a thin-walled
unseptate vesicle, to those in which the thallus attains a length unsurpassed
by any other plant, and of which the anatomical features clearly express a
well-marked physiological division of labour such as occurs in the highest
plants.
The large and leathery seaweeds which flourish in the extreme northern
and southern seas are plants which it is reasonable to suppose might well
have left traces of their existence in ancient sediments. Sir Joseph Hooker,
in his account of the Antarctic flora[223], investigated during Sir James
Ross’s voyage in H.M. ships Erebus and Terror, has given an exceedingly
interesting description of the gigantic brown seaweeds of southern latitudes.
The trunks are described as usually 5–10 feet long, and as thick as a human
thigh, dividing towards the summit into numerous pendulous branches
which are again broken up into sprays with linear ‘leaves.’ Hooker records
how a captain of a brig employed his crew for two bitterly cold days in
collecting Lessonia stems which had been washed up on the beach, thinking
they were trunks of trees fit for burning. On our own coasts we are familiar
with the common Laminaria, the large brown seaweed with long and strap-
shaped or digitate fronds which grows on the rocks below low-tide level.
The frond passes downwards into a thick and tough stipe firmly attached to
the ground by special holdfasts. A transverse section of the stalk of a fairly
old plant presents an appearance not unlike that of a section of a woody
plant. In the centre there is a well-defined axial region or pith consisting of
the dernier ressort of the doubtful student.
LARGE SEAWEEDS.
Before discussing our knowledge, or rather lack of knowledge, of fossil
algae at greater length, it will be well to briefly consider the manner of
occurrence and botanical nature of existing forms. In the sea and in fresh
water, as well as in damp places and even in situations subject to periods of
drought, algae occur in abundance in all parts of the world. We find them
attaining full development and reproducing themselves at a temperature of
−1° C. in the Arctic Seas, and again living in enormous numbers in the
waters of thermal springs. Around the coast-line of land areas, and on the
floor of shallow seas algae exhibit a remarkable wealth of form and
luxuriance of growth. As regards habit and structure, there is every
gradation from algae in which the whole individual consists of a thin-walled
unseptate vesicle, to those in which the thallus attains a length unsurpassed
by any other plant, and of which the anatomical features clearly express a
well-marked physiological division of labour such as occurs in the highest
plants.
The large and leathery seaweeds which flourish in the extreme northern
and southern seas are plants which it is reasonable to suppose might well
have left traces of their existence in ancient sediments. Sir Joseph Hooker,
in his account of the Antarctic flora[223], investigated during Sir James
Ross’s voyage in H.M. ships Erebus and Terror, has given an exceedingly
interesting description of the gigantic brown seaweeds of southern latitudes.
The trunks are described as usually 5–10 feet long, and as thick as a human
thigh, dividing towards the summit into numerous pendulous branches
which are again broken up into sprays with linear ‘leaves.’ Hooker records
how a captain of a brig employed his crew for two bitterly cold days in
collecting Lessonia stems which had been washed up on the beach, thinking
they were trunks of trees fit for burning. On our own coasts we are familiar
with the common Laminaria, the large brown seaweed with long and strap-
shaped or digitate fronds which grows on the rocks below low-tide level.
The frond passes downwards into a thick and tough stipe firmly attached to
the ground by special holdfasts. A transverse section of the stalk of a fairly
old plant presents an appearance not unlike that of a section of a woody
plant. In the centre there is a well-defined axial region or pith consisting of
Page 161
thick walled, long and narrow tubes pursuing a generally vertical though
irregular course, and embedded in a matrix of gelatinous substance derived
from the mucilaginous degeneration of the outer portions of the cell-walls.
The greater part of such a section consists, however, of regularly disposed
rows of cells which have obviously been formed by the activity of a zone of
dividing or meristematic elements. The occurrence of distinct concentric
rings in this secondary tissue clearly points to some periodicity of growth
which is expressed by the alternation of narrow and broader cells. In the
Antarctic genus Lessonia, the stem reaches a girth equal to that of a man’s
thigh, and in structure it agrees closely with the smaller stem of Laminaria.
In these large algal stems, the cells are not lignified as in woody plants, and
in longitudinal section they have for the most part the form of somewhat
elongated parenchyma, differing widely in appearance from the tracheids or
vessels of woody plants. At the periphery of the Laminaria stem,
represented in fig. 29, there occur numerous and comparatively large
mucilage ducts.
Fig. 29. A, Transverse section of the stipe of a Laminaria, slightly enlarged. B, A
small piece of the tissue between the central ‘pith’ and ‘cortex’ showing the
radially disposed secondary elements more highly magnified.
irregular course, and embedded in a matrix of gelatinous substance derived
from the mucilaginous degeneration of the outer portions of the cell-walls.
The greater part of such a section consists, however, of regularly disposed
rows of cells which have obviously been formed by the activity of a zone of
dividing or meristematic elements. The occurrence of distinct concentric
rings in this secondary tissue clearly points to some periodicity of growth
which is expressed by the alternation of narrow and broader cells. In the
Antarctic genus Lessonia, the stem reaches a girth equal to that of a man’s
thigh, and in structure it agrees closely with the smaller stem of Laminaria.
In these large algal stems, the cells are not lignified as in woody plants, and
in longitudinal section they have for the most part the form of somewhat
elongated parenchyma, differing widely in appearance from the tracheids or
vessels of woody plants. At the periphery of the Laminaria stem,
represented in fig. 29, there occur numerous and comparatively large
mucilage ducts.
Fig. 29. A, Transverse section of the stipe of a Laminaria, slightly enlarged. B, A
small piece of the tissue between the central ‘pith’ and ‘cortex’ showing the
radially disposed secondary elements more highly magnified.
Page 162
In certain algae of different families the thallus is encrusted with
carbonate of lime, and is thus rendered much more resistant. The Diatoms,
on the other hand, possess still more durable siliceous tests which are
particularly well adapted to resist the solvent action of water and other
agents of destruction. It is these calcareous and siliceous forms which
supply the greater part of the trustworthy data furnished by fossil algae.
SCARCITY OF FOSSIL ALGAE.
It remains to consider some of the causes to which we may attribute the
scarcity of fossil algae, and the possible sources of error which beset any
attempt to describe or assign names to impressions and casts simulating
algal forms.
In the first place, the delicate nature of algal cells is a serious obstacle to
fossilisation. Even in plants in which the woody stems have been preserved
by a siliceous or calcareous solution, we frequently find the more delicate
cells represented by a mass of crystalline matter without any trace of the
cell-walls being preserved. In such plants as algae, where the cell-walls are
not lignified, but consist of cellulose or some special form of cellulose,
which readily breaks down into a mucilaginous product, the tissues have
but a small chance of withstanding the wear and tear of fossilisation.
The danger of relying on external form as a means of recognition is
especially patent in the case of those numerous markings or impressions
frequently met with on rocks, and which resemble in outline the thallus of
recent algae. Among animals, such as certain Polyzoa, the flat branching
body of various algae is closely simulated, and in other plants, such as the
frondose liverworts, the same thalloid and branched form of body is again
met with. Some of the much dissected Aphlebia leaves of ferns (e.g.
Rhacophyllum species) bear a striking resemblance to fossil algae; and
numerous other examples might be quoted. In palaeobotanical literature we
find a host of names, such as Chondrites, Fucoides[224], Caulerpites and
others applied to indefinite and indistinct surface markings which happen to
resemble in shape certain of the better known genera of recent seaweeds.
The close parallelism in outward form displayed by different genera and
families of algae is in itself sufficient argument against the use of recent
generic names for fossils of which the algal nature is often more than
doubtful. Were external form to be accepted as a trustworthy guide, in the
carbonate of lime, and is thus rendered much more resistant. The Diatoms,
on the other hand, possess still more durable siliceous tests which are
particularly well adapted to resist the solvent action of water and other
agents of destruction. It is these calcareous and siliceous forms which
supply the greater part of the trustworthy data furnished by fossil algae.
SCARCITY OF FOSSIL ALGAE.
It remains to consider some of the causes to which we may attribute the
scarcity of fossil algae, and the possible sources of error which beset any
attempt to describe or assign names to impressions and casts simulating
algal forms.
In the first place, the delicate nature of algal cells is a serious obstacle to
fossilisation. Even in plants in which the woody stems have been preserved
by a siliceous or calcareous solution, we frequently find the more delicate
cells represented by a mass of crystalline matter without any trace of the
cell-walls being preserved. In such plants as algae, where the cell-walls are
not lignified, but consist of cellulose or some special form of cellulose,
which readily breaks down into a mucilaginous product, the tissues have
but a small chance of withstanding the wear and tear of fossilisation.
The danger of relying on external form as a means of recognition is
especially patent in the case of those numerous markings or impressions
frequently met with on rocks, and which resemble in outline the thallus of
recent algae. Among animals, such as certain Polyzoa, the flat branching
body of various algae is closely simulated, and in other plants, such as the
frondose liverworts, the same thalloid and branched form of body is again
met with. Some of the much dissected Aphlebia leaves of ferns (e.g.
Rhacophyllum species) bear a striking resemblance to fossil algae; and
numerous other examples might be quoted. In palaeobotanical literature we
find a host of names, such as Chondrites, Fucoides[224], Caulerpites and
others applied to indefinite and indistinct surface markings which happen to
resemble in shape certain of the better known genera of recent seaweeds.
The close parallelism in outward form displayed by different genera and
families of algae is in itself sufficient argument against the use of recent
generic names for fossils of which the algal nature is often more than
doubtful. Were external form to be accepted as a trustworthy guide, in the
Page 163
absence of internal structure and reproductive organs, such a genus as
Caulerpa[225] would afford material for numerous generic designations. A
comparison of the different species of this Siphoneous green alga brings out
very clearly the exceedingly protean nature of this interesting genus, and
serves as one instance among many of the small taxonomic value which can
be attached to external configuration. Caulerpa pusilla Mart. and Her., C.
taxifolia (Vahl.), C. plumaris Forsk., C. abies-marina J. Ag., C. ericifolia
(Turn.), C. hypnoides (R. Br.), C. cactoides (Turn.), C. scalpelli formis (R.
Br.), and others clearly illustrate the almost endless variety of form
exhibited by the species of a single genus of algae. We constantly find in the
several classes of plants a repetition of the same form either in the whole or
in the separate members of the vegetative body, and but a slight
acquaintance with plant types should lead us to use the test of external
resemblance with the greatest possible caution. To emphasize this danger
may seem merely the needless reiteration of a self-evident fact, but there is,
perhaps, no source of error which has been more responsible for the
creation of numerous worthless species among fossil plants.
Caulerpa[225] would afford material for numerous generic designations. A
comparison of the different species of this Siphoneous green alga brings out
very clearly the exceedingly protean nature of this interesting genus, and
serves as one instance among many of the small taxonomic value which can
be attached to external configuration. Caulerpa pusilla Mart. and Her., C.
taxifolia (Vahl.), C. plumaris Forsk., C. abies-marina J. Ag., C. ericifolia
(Turn.), C. hypnoides (R. Br.), C. cactoides (Turn.), C. scalpelli formis (R.
Br.), and others clearly illustrate the almost endless variety of form
exhibited by the species of a single genus of algae. We constantly find in the
several classes of plants a repetition of the same form either in the whole or
in the separate members of the vegetative body, and but a slight
acquaintance with plant types should lead us to use the test of external
resemblance with the greatest possible caution. To emphasize this danger
may seem merely the needless reiteration of a self-evident fact, but there is,
perhaps, no source of error which has been more responsible for the
creation of numerous worthless species among fossil plants.
Page 164
Page 165
Fig. 30. 1. Rill-mark (after Williamson). 2. Trail made by a seaweed dragged along a soft
plaster of Paris surface (after Nathorst). 3. Tracks made by Goniada maculata, a
Polychaet (after Nathorst). 4. Burrow of an insect. 4a. Section of the gallery (after
Zeiller).
There is, however, another category of impressions and casts of common
occurrence in sedimentary rocks which requires a brief notice. Very many
of the fossil algae described in text-books and palaeobotanical memoirs
have been shown to be of animal origin, and to be merely the casts of tracks
and burrows. A few examples will best serve to illustrate the identity of
many of the fossils referred to algae with animal trails and with impressions
produced by inorganic agency.
Dr Nathorst of Stockholm has done more than any other worker to
demonstrate the true nature of many of the species of Chondrites, Cruziana,
Spirophyton, Eophyton, and numerous other genera. In 1867 there were
discovered in certain Cambrian beds of Vestrogothia, long convex and
furrowed structures in sandstone rocks which were described as the remains
of some comparatively highly organised plant, and described under the
generic name Eophyton[226]. By many authors these fossils have been
plaster of Paris surface (after Nathorst). 3. Tracks made by Goniada maculata, a
Polychaet (after Nathorst). 4. Burrow of an insect. 4a. Section of the gallery (after
Zeiller).
There is, however, another category of impressions and casts of common
occurrence in sedimentary rocks which requires a brief notice. Very many
of the fossil algae described in text-books and palaeobotanical memoirs
have been shown to be of animal origin, and to be merely the casts of tracks
and burrows. A few examples will best serve to illustrate the identity of
many of the fossils referred to algae with animal trails and with impressions
produced by inorganic agency.
Dr Nathorst of Stockholm has done more than any other worker to
demonstrate the true nature of many of the species of Chondrites, Cruziana,
Spirophyton, Eophyton, and numerous other genera. In 1867 there were
discovered in certain Cambrian beds of Vestrogothia, long convex and
furrowed structures in sandstone rocks which were described as the remains
of some comparatively highly organised plant, and described under the
generic name Eophyton[226]. By many authors these fossils have been
Page 166
referred to algae, but Nathorst has shown that the frond of an alga trailed
along the surface of soft plaster of Paris produces a finely furrowed groove
(fig. 30, 2) which would afford a cast similar to that of Eophyton. The same
author has also adduced good reasons for believing that the Eophytons of
Cambrian rocks may represent the trails made by the tentacles of a Medusa
having a habit similar to that of Polydonia frondosa Ag. Impressions of
Medusae have been described by Nathorst from the beds in which Eophyton
occurs; and the specimens in the Stockholm Museum afford a remarkable
instance of the rare preservation of a soft-bodied organism[227]. By allowing
various animals to crawl over a soft-prepared surface it is possible to obtain
moulds and casts which suggest in a striking manner the branched thallus of
an alga. The tracks of the Polychaet, Goniada maculata Örstd.[228], one of
the Glyceridae, are always branched and very algal-like in form (fig. 30, 3).
Many of the so-called fossil algae are undoubtedly mere tracks or trails of
this type. In the fossil-plant gallery of the British Museum there are several
specimens of small branched casts, clearly marked as whitish fossils on a
dark grey rock of Lower Eocene age from Bognor; these were described by
Mantell and Brongniart[229] as an alga, but there is little doubt of their being
of the same category as the track shown in fig. 30, 3.
FOSSILS SIMULATING ALGAE.
The well-known half-relief casts met with in Cambrian, Silurian and
Carboniferous rocks, and known as Cruziana or Bilobites, are probably
casts of the tracks of Crustaceans. The impression left by a King-Crab
(Limulus) as it walks over a soft surface affords an example of this form of
cast. It has been suggested that some of the Bilobites may be the casts of an
organism like Balanoglossus[230], a worm-like animal supposed by some to
have vertebrate affinities. The resemblance between some of the lower
Palaeozoic Bilobites and the external features of a Balanoglossus is very
striking, and such a comparison is worth considering in view of the fact that
soft-bodied animals have occasionally left distinct impressions on ancient
sediments.
The literature on the subject of fossil algae versus inorganic and animal
markings is too extensive and too wearisome to consider in a short
summary; the student will find a sufficient amount of such controversial
writing—with references to more—in the works quoted below[231].
along the surface of soft plaster of Paris produces a finely furrowed groove
(fig. 30, 2) which would afford a cast similar to that of Eophyton. The same
author has also adduced good reasons for believing that the Eophytons of
Cambrian rocks may represent the trails made by the tentacles of a Medusa
having a habit similar to that of Polydonia frondosa Ag. Impressions of
Medusae have been described by Nathorst from the beds in which Eophyton
occurs; and the specimens in the Stockholm Museum afford a remarkable
instance of the rare preservation of a soft-bodied organism[227]. By allowing
various animals to crawl over a soft-prepared surface it is possible to obtain
moulds and casts which suggest in a striking manner the branched thallus of
an alga. The tracks of the Polychaet, Goniada maculata Örstd.[228], one of
the Glyceridae, are always branched and very algal-like in form (fig. 30, 3).
Many of the so-called fossil algae are undoubtedly mere tracks or trails of
this type. In the fossil-plant gallery of the British Museum there are several
specimens of small branched casts, clearly marked as whitish fossils on a
dark grey rock of Lower Eocene age from Bognor; these were described by
Mantell and Brongniart[229] as an alga, but there is little doubt of their being
of the same category as the track shown in fig. 30, 3.
FOSSILS SIMULATING ALGAE.
The well-known half-relief casts met with in Cambrian, Silurian and
Carboniferous rocks, and known as Cruziana or Bilobites, are probably
casts of the tracks of Crustaceans. The impression left by a King-Crab
(Limulus) as it walks over a soft surface affords an example of this form of
cast. It has been suggested that some of the Bilobites may be the casts of an
organism like Balanoglossus[230], a worm-like animal supposed by some to
have vertebrate affinities. The resemblance between some of the lower
Palaeozoic Bilobites and the external features of a Balanoglossus is very
striking, and such a comparison is worth considering in view of the fact that
soft-bodied animals have occasionally left distinct impressions on ancient
sediments.
The literature on the subject of fossil algae versus inorganic and animal
markings is too extensive and too wearisome to consider in a short
summary; the student will find a sufficient amount of such controversial
writing—with references to more—in the works quoted below[231].
Page 167
In the Stockholm Museum of Palaeobotany there is an exceedingly
interesting collection of plaster casts obtained by Dr Nathorst in his
experiments on the manufacture of fossil ‘algae,’ which afford convincing
proof of the value and correctness of his general conclusions.
The pressure of the hand on a soft moist surface produces a raised pattern
like a branched and delicate thallus. The well-known Oldhamia antiqua
Forbes and Oldhamia radiata Forbes[232], from the Cambrian rocks of
Ireland may, in part at least, owe their origin to mechanical causes, and we
have no sufficient evidence for including them among the select class of
true fossil algae. Sollas[233] has shown that the structure known as Oldhamia
radiata is not merely superficial but that it extends across the cleavage-
planes. Oldhamia is recorded from Lower Palaeozoic rocks in the
Pyrenees[234] by Barrois, who agrees with Salter, Göppert and others in
classing the fossil among the algae. The photograph accompanying Barrois’
description does not, however, add further evidence in favour of accepting
Oldhamia as a genus of fossil algae.
The burrows made by Gryllotalpa vulgaris Latr., the Mole-cricket, have
been shown by Zeiller to bear a close resemblance to a branch of a conifer
in half-relief (fig. 30, 4), or to such a supposed algal genus as
Phymatoderma[235].
In fig. 30, 1, we have what might well be described as a fossil alga. This
is merely a cast of a miniature river-system such as one frequently sees cut
out by the small rills of water flowing over a gently-sloping sandy beach. A
cast figured and described by Newberry as an alga, Dendrophycus
triassicus[236], from the Trias of the Connecticut Valley, is practically
identical with the rill-marks shown in fig. 30, 1. The cracks produced in
drying and contracting sediment may form moulds in which casts are
subsequently produced by the deposition of an overlying layer of sand, and
such casts have been erroneously referred to algal impressions[237].
Dawson[238] has figured two good examples of Carboniferous rill-marks
from Nova Scotia in his paper on Palaeozoic burrows and tracks of
invertebrate animals.
RECOGNITION OF FOSSIL ALGAE.
interesting collection of plaster casts obtained by Dr Nathorst in his
experiments on the manufacture of fossil ‘algae,’ which afford convincing
proof of the value and correctness of his general conclusions.
The pressure of the hand on a soft moist surface produces a raised pattern
like a branched and delicate thallus. The well-known Oldhamia antiqua
Forbes and Oldhamia radiata Forbes[232], from the Cambrian rocks of
Ireland may, in part at least, owe their origin to mechanical causes, and we
have no sufficient evidence for including them among the select class of
true fossil algae. Sollas[233] has shown that the structure known as Oldhamia
radiata is not merely superficial but that it extends across the cleavage-
planes. Oldhamia is recorded from Lower Palaeozoic rocks in the
Pyrenees[234] by Barrois, who agrees with Salter, Göppert and others in
classing the fossil among the algae. The photograph accompanying Barrois’
description does not, however, add further evidence in favour of accepting
Oldhamia as a genus of fossil algae.
The burrows made by Gryllotalpa vulgaris Latr., the Mole-cricket, have
been shown by Zeiller to bear a close resemblance to a branch of a conifer
in half-relief (fig. 30, 4), or to such a supposed algal genus as
Phymatoderma[235].
In fig. 30, 1, we have what might well be described as a fossil alga. This
is merely a cast of a miniature river-system such as one frequently sees cut
out by the small rills of water flowing over a gently-sloping sandy beach. A
cast figured and described by Newberry as an alga, Dendrophycus
triassicus[236], from the Trias of the Connecticut Valley, is practically
identical with the rill-marks shown in fig. 30, 1. The cracks produced in
drying and contracting sediment may form moulds in which casts are
subsequently produced by the deposition of an overlying layer of sand, and
such casts have been erroneously referred to algal impressions[237].
Dawson[238] has figured two good examples of Carboniferous rill-marks
from Nova Scotia in his paper on Palaeozoic burrows and tracks of
invertebrate animals.
RECOGNITION OF FOSSIL ALGAE.
Page 168
Fig. 31. Chondrites verisimilis Salt. Wenlock limestone, Dudley. From a specimen in the
British Museum (V. 2550). Slightly reduced.
The specimen represented in fig. 31 affords an example of a fairly well-
known fossil from the Wenlock limestone, originally described by Salter as
Chondrites verisimilis Salt, from Dudley[239]. He regarded it as an alga, and
the graphitic impression agrees closely in form with the thallus of some
small seaweeds. A closer examination of the fossil reveals a curious and
characteristic irregular wrinkling on the graphite surface, which suggests an
organism of more chitinous and firmer material than that of an alga.
A similar and probably an identical fossil is described and figured by
Lapworth[240] in an appendix to a paper by Walter Keeping on the geology of
Central Wales, under the name of Odontocaulis Keepingi Lap. and regarded
as a dendroid graptolite. In any case we have no satisfactory grounds for
including these fossils in the plant-kingdom.
How then are we to recognise the traces of ancient algae? There is no
golden rule, and we must admit the difficulty of separating real fossil algae
from markings made by animal or mechanical agency. The presence of a
carbonaceous film is occasionally a help, but its occurrence is no sure test
of plant origin, nor is its absence a fatal objection to an organic origin.
While being fully alive to the small value of external resemblance, and to
the numerous agents which have been shown to be capable of producing
appearances indistinguishable from plant impressions, we must not go too
far in a purely negative direction.
An important contribution to the subject of fossil algae has lately
appeared by Prof. Rothpletz[241]. He deals more particularly with the much
discussed Flysch[242] Fucoids of Tertiary age, and while refusing to accept
certain examples as fossil algae, he brings forward weighty arguments in
favour of including several other forms among the algae. He is of opinion
that most of the main divisions of the algae are represented among the
British Museum (V. 2550). Slightly reduced.
The specimen represented in fig. 31 affords an example of a fairly well-
known fossil from the Wenlock limestone, originally described by Salter as
Chondrites verisimilis Salt, from Dudley[239]. He regarded it as an alga, and
the graphitic impression agrees closely in form with the thallus of some
small seaweeds. A closer examination of the fossil reveals a curious and
characteristic irregular wrinkling on the graphite surface, which suggests an
organism of more chitinous and firmer material than that of an alga.
A similar and probably an identical fossil is described and figured by
Lapworth[240] in an appendix to a paper by Walter Keeping on the geology of
Central Wales, under the name of Odontocaulis Keepingi Lap. and regarded
as a dendroid graptolite. In any case we have no satisfactory grounds for
including these fossils in the plant-kingdom.
How then are we to recognise the traces of ancient algae? There is no
golden rule, and we must admit the difficulty of separating real fossil algae
from markings made by animal or mechanical agency. The presence of a
carbonaceous film is occasionally a help, but its occurrence is no sure test
of plant origin, nor is its absence a fatal objection to an organic origin.
While being fully alive to the small value of external resemblance, and to
the numerous agents which have been shown to be capable of producing
appearances indistinguishable from plant impressions, we must not go too
far in a purely negative direction.
An important contribution to the subject of fossil algae has lately
appeared by Prof. Rothpletz[241]. He deals more particularly with the much
discussed Flysch[242] Fucoids of Tertiary age, and while refusing to accept
certain examples as fossil algae, he brings forward weighty arguments in
favour of including several other forms among the algae. He is of opinion
that most of the main divisions of the algae are represented among the
Page 169
Flysch Fucoids, but considers that the Phaeophyceae are the most
numerous.
Rothpletz’s work is chiefly interesting as illustrating the application of
microscopic examination and chemical analysis to the determination of
fossil algae. Although he makes out a good case in favour of restoring many
of the Tertiary fossils to the plant kingdom, the material at his disposal does
not admit of satisfactory botanical diagnosis.
No doubt some of the fossils from the Silurian and Cambrian rocks are
true algae, and Nathorst has pointed out that such a species as Hall’s
Sphenothallus angustifolius[243] may well be an alga. Additional examples
might be quoted from Bornemann and other writers, but in view of the
attempts which are sometimes made to trace the development of more
recent plants to more than doubtful Lower Palaeozoic Algae, one must
agree with Nathorst’s opinion,—“Je crois que l’on rend un bien mauvais
service à la théorie de l’évolution, en essayant de baser l’arbre généalogique
des algues fossiles sur des corps aussi douteux que les Bilobites,
Crossochorda, Eophyton, etc.[244]”
There are many carbonaceous impressions on rocks of different ages
which it is reasonable to refer to algal origin, and although such are of little
or no botanical value, it may be a convenience to refer to them under a
definite term. The comprehensive generic name Algites[245] has been
suggested as a convenient designation for impressions or casts which are
probably those of algae.
SUPPOSED FOSSIL ALGAE.
Some of the fossils described by Mr Kidston from British Carboniferous
rocks as probably algae present an undoubted algal appearance, and might
be placed in the genus Algites; but in some cases—e.g. Chondrites
plumosa[246] Kidst. from the Calciferous Sandstone of Eskdale, one feels
much more doubtful; in this particular instance the impressions suggest the
fine roots of a water-plant.
The statement is occasionally made that the numerous fossil algae and
the absence of higher plants in the older strata justify the description of the
oldest rocks as belonging to the ‘age of algae.’ Such an assertion rests on an
unsound basis, and is rather the expression of what might be expected than
what has been proved to be the case. The oldest plants with which we are at
numerous.
Rothpletz’s work is chiefly interesting as illustrating the application of
microscopic examination and chemical analysis to the determination of
fossil algae. Although he makes out a good case in favour of restoring many
of the Tertiary fossils to the plant kingdom, the material at his disposal does
not admit of satisfactory botanical diagnosis.
No doubt some of the fossils from the Silurian and Cambrian rocks are
true algae, and Nathorst has pointed out that such a species as Hall’s
Sphenothallus angustifolius[243] may well be an alga. Additional examples
might be quoted from Bornemann and other writers, but in view of the
attempts which are sometimes made to trace the development of more
recent plants to more than doubtful Lower Palaeozoic Algae, one must
agree with Nathorst’s opinion,—“Je crois que l’on rend un bien mauvais
service à la théorie de l’évolution, en essayant de baser l’arbre généalogique
des algues fossiles sur des corps aussi douteux que les Bilobites,
Crossochorda, Eophyton, etc.[244]”
There are many carbonaceous impressions on rocks of different ages
which it is reasonable to refer to algal origin, and although such are of little
or no botanical value, it may be a convenience to refer to them under a
definite term. The comprehensive generic name Algites[245] has been
suggested as a convenient designation for impressions or casts which are
probably those of algae.
SUPPOSED FOSSIL ALGAE.
Some of the fossils described by Mr Kidston from British Carboniferous
rocks as probably algae present an undoubted algal appearance, and might
be placed in the genus Algites; but in some cases—e.g. Chondrites
plumosa[246] Kidst. from the Calciferous Sandstone of Eskdale, one feels
much more doubtful; in this particular instance the impressions suggest the
fine roots of a water-plant.
The statement is occasionally made that the numerous fossil algae and
the absence of higher plants in the older strata justify the description of the
oldest rocks as belonging to the ‘age of algae.’ Such an assertion rests on an
unsound basis, and is rather the expression of what might be expected than
what has been proved to be the case. The oldest plants with which we are at
Page 170
all closely acquainted are of such a type as to forcibly suggest that in the
lowest fossiliferous rocks we are still very far from the sediments of that
age which witnessed the dawn of plant life.
Many of the obscure markings on rock surfaces which have been referred
to existing genera of algae or described as new genera, are much too
doubtful to be included even under such a comprehensive name as Algites.
Space does not admit of further reference to determinations of this type
which abound in palaeontological literature.
It would be very difficult to produce satisfactory evidence for the algal
nature of many of the supposed fossil algae from Cambrian rocks[247]; there
has been a special tendency to recognise algal remains in the oldest
fossiliferous strata, due in part no doubt to the fallacy that in that period
nothing higher than Thallophytes is likely to have existed. The so-called
Phycodes referred to by Credner[248] as characteristic of the Cambrian rocks
of the Fichtelgebirge (“Phycoden-Schiefer”) is probably of inorganic origin,
and comparable to the genus Vexillum of Saporta[249] and other writers,
which Solms-Laubach has described as being formed every day in the soft
mud of our ponds where local currents are checked by branches and other
obstacles[250]. There are several good specimens of Phycodes in the
Bergakademie of Berlin and in the Leipzig Museum which, I believe,
clearly demonstrate the absence of all satisfactory evidence of an algal
origin.
We may next pass to a short description of a few representative types of
algae, which may reasonably be classed under definite families, and
accepted as evidence possessing some botanical value.
A. DIATOMACEAE (Bacillariaceae).
This family occupies a somewhat isolated position among the algae, and
is best considered as a distinct subdivision rather than as a family of the
Phaeophyceae or Brown algae, with which it possesses as a common
characteristic a brown-colouring matter.
Single-celled plants consisting of a simple protoplasmic body containing
a nucleus and brown colouring matter (diatomin) associated with the
chlorophyll. The cell-wall is in the form of two halves, known as valves,
lowest fossiliferous rocks we are still very far from the sediments of that
age which witnessed the dawn of plant life.
Many of the obscure markings on rock surfaces which have been referred
to existing genera of algae or described as new genera, are much too
doubtful to be included even under such a comprehensive name as Algites.
Space does not admit of further reference to determinations of this type
which abound in palaeontological literature.
It would be very difficult to produce satisfactory evidence for the algal
nature of many of the supposed fossil algae from Cambrian rocks[247]; there
has been a special tendency to recognise algal remains in the oldest
fossiliferous strata, due in part no doubt to the fallacy that in that period
nothing higher than Thallophytes is likely to have existed. The so-called
Phycodes referred to by Credner[248] as characteristic of the Cambrian rocks
of the Fichtelgebirge (“Phycoden-Schiefer”) is probably of inorganic origin,
and comparable to the genus Vexillum of Saporta[249] and other writers,
which Solms-Laubach has described as being formed every day in the soft
mud of our ponds where local currents are checked by branches and other
obstacles[250]. There are several good specimens of Phycodes in the
Bergakademie of Berlin and in the Leipzig Museum which, I believe,
clearly demonstrate the absence of all satisfactory evidence of an algal
origin.
We may next pass to a short description of a few representative types of
algae, which may reasonably be classed under definite families, and
accepted as evidence possessing some botanical value.
A. DIATOMACEAE (Bacillariaceae).
This family occupies a somewhat isolated position among the algae, and
is best considered as a distinct subdivision rather than as a family of the
Phaeophyceae or Brown algae, with which it possesses as a common
characteristic a brown-colouring matter.
Single-celled plants consisting of a simple protoplasmic body containing
a nucleus and brown colouring matter (diatomin) associated with the
chlorophyll. The cell-wall is in the form of two halves, known as valves,
Page 171
which fit into one another like the two portions of a pill-box. The cell-wall
contains a large amount of silica, and the siliceous cases of the diatoms are
commonly spoken of as the valves of the individual, or the frustules.
Diatoms exhibit a characteristic creeping movement, and are reproduced by
division, also by the development of spores in various forms[251].
The recent members of the family have an exceedingly wide distribution,
occurring both in freshwater and in the sea. Owing to the lightness of the
frustules, they are frequently carried along in the air, and atmospheric dust
falling on ships at sea has been found to contain large numbers of
diatoms[252]. The siliceous valves are abundant in guano deposits, and they
have been found also in association with volcanic material. Diatomaceous
deposits are now being formed in the Yellowstone Park district; “they cover
many square miles in the vicinity of active or extinct hot spring vents of the
park, and are often three feet, four feet, and sometimes five to six feet
thick[253].” The gradual accumulation of the siliceous tests on the floor of a
fresh-water lake results in the formation of a sediment consisting in part of
pure silica. Such deposits, often spoken of as kieselguhr or diatomite, and
used as a polishing material, occur in many parts of Britain, marking the
sites of dried-up pools or lakes. At the northern end of the island of Skye
there occurs an unusually pure deposit of diatomite overlain by peat and
turf, and extending over an area of fifty-eight square miles. Many of the
individuals in this deposit were in all probability carried into the lake by
running water, while others lived in the lake and after death their tests
contributed to the siliceous deposit[254]. The late Dr Ehrenberg published
numerous papers on diatomaceous deposits in different parts of the world,
and in his great work, Zur Mikrogeologie[255], he gave numerous and
beautifully executed illustrations of such siliceous accumulations. In many
of the samples he figures one sees fragments of plant tissues, spores of
conifers and ferns, associated with the diatom tests. The occurrence of the
pollen grains of coniferous trees in lacustrine and marine deposits is not
surprising in view of their abundance in Lake Constance and other lakes. It
is stated that the pollen of conifers in the Norwegian fiords plays an
important part in the nourishment of the Rhizopod Saccamina[256].
DIATOMACEOUS OOZE.
In the waters of the ocean diatoms are of frequent occurrence, and very
widely distributed. Sir Joseph Hooker records the existence of masses of
contains a large amount of silica, and the siliceous cases of the diatoms are
commonly spoken of as the valves of the individual, or the frustules.
Diatoms exhibit a characteristic creeping movement, and are reproduced by
division, also by the development of spores in various forms[251].
The recent members of the family have an exceedingly wide distribution,
occurring both in freshwater and in the sea. Owing to the lightness of the
frustules, they are frequently carried along in the air, and atmospheric dust
falling on ships at sea has been found to contain large numbers of
diatoms[252]. The siliceous valves are abundant in guano deposits, and they
have been found also in association with volcanic material. Diatomaceous
deposits are now being formed in the Yellowstone Park district; “they cover
many square miles in the vicinity of active or extinct hot spring vents of the
park, and are often three feet, four feet, and sometimes five to six feet
thick[253].” The gradual accumulation of the siliceous tests on the floor of a
fresh-water lake results in the formation of a sediment consisting in part of
pure silica. Such deposits, often spoken of as kieselguhr or diatomite, and
used as a polishing material, occur in many parts of Britain, marking the
sites of dried-up pools or lakes. At the northern end of the island of Skye
there occurs an unusually pure deposit of diatomite overlain by peat and
turf, and extending over an area of fifty-eight square miles. Many of the
individuals in this deposit were in all probability carried into the lake by
running water, while others lived in the lake and after death their tests
contributed to the siliceous deposit[254]. The late Dr Ehrenberg published
numerous papers on diatomaceous deposits in different parts of the world,
and in his great work, Zur Mikrogeologie[255], he gave numerous and
beautifully executed illustrations of such siliceous accumulations. In many
of the samples he figures one sees fragments of plant tissues, spores of
conifers and ferns, associated with the diatom tests. The occurrence of the
pollen grains of coniferous trees in lacustrine and marine deposits is not
surprising in view of their abundance in Lake Constance and other lakes. It
is stated that the pollen of conifers in the Norwegian fiords plays an
important part in the nourishment of the Rhizopod Saccamina[256].
DIATOMACEOUS OOZE.
In the waters of the ocean diatoms are of frequent occurrence, and very
widely distributed. Sir Joseph Hooker records the existence of masses of
Page 172
diatomaceous ooze over a wide area in Antarctic regions[257]. Along the
shores of the Victoria Barrier, a perpendicular wall of ice, between one and
two hundred feet above sea-level, the soundings were found to be
invariably charged with diatom remains, and from the base of the ice-wall
there appeared to be in process of formation a bank of these tests stretching
north for a distance of 200 miles. The more extended researches conducted
during the cruise of the Challenger have clearly proved the enormous
accumulations of diatoms now being formed on the ocean-bed[258]. South of
latitude 45° S. there is now being built up a vast deposit which may be
eventually upraised as a fairly pure siliceous rock. From extreme northern
latitudes Nansen has recently recorded the occurrence of these lowly
organised plants. He writes,—“I found a whole world of diatoms and other
microscopical organisms, both vegetable and animal, living in the fresh-
water pools on the Polar drift-ice, and constantly travelling from Siberia to
the east coast of Greenland[259].” In warmer latitudes diatoms abound in the
surface waters, but there they are associated with numerous other forms of
the Plankton vegetation. The waters of the Amazon carry with them into the
sea large numbers of fresh-water forms, which are floated out to sea and
finally added to the rock-building material which is constantly
accumulating on the ocean floor[260]. No definite results have so far been
obtained as to the geographical and bathymetrical distribution of marine
diatoms.
The enormous number of recent species precludes any attempt to give a
description of the better-known forms. It is more important for us to realize
how common and widely distributed are the living genera. The hard and
almost indestructible valves have been frequently found in a fossil
condition, often forming thick and extensive masses of siliceous rock. From
diatom-beds now forming in lakes and on the ocean-bed we pass to deposits
such as those in Skye and elsewhere, which mark the site of recently dried-
up sheets of water, and so to older rocks of Tertiary age formed under
similar conditions. Among the many examples of diatomaceous deposits of
Tertiary and Cretaceous age mention should be made of those of Berlin,
Königsberg, Bilin in Bohemia, and Richmond in Virginia. The diatoms in
the beds of Berlin are regarded as fresh-water, and those of Richmond as
marine. It has been pointed out by Pfitzer that it is a comparatively easy
matter to distinguish between fresh-water and marine forms of diatoms. The
diatomaceous rocks of Bilin are known as polishing slates; they attain a
shores of the Victoria Barrier, a perpendicular wall of ice, between one and
two hundred feet above sea-level, the soundings were found to be
invariably charged with diatom remains, and from the base of the ice-wall
there appeared to be in process of formation a bank of these tests stretching
north for a distance of 200 miles. The more extended researches conducted
during the cruise of the Challenger have clearly proved the enormous
accumulations of diatoms now being formed on the ocean-bed[258]. South of
latitude 45° S. there is now being built up a vast deposit which may be
eventually upraised as a fairly pure siliceous rock. From extreme northern
latitudes Nansen has recently recorded the occurrence of these lowly
organised plants. He writes,—“I found a whole world of diatoms and other
microscopical organisms, both vegetable and animal, living in the fresh-
water pools on the Polar drift-ice, and constantly travelling from Siberia to
the east coast of Greenland[259].” In warmer latitudes diatoms abound in the
surface waters, but there they are associated with numerous other forms of
the Plankton vegetation. The waters of the Amazon carry with them into the
sea large numbers of fresh-water forms, which are floated out to sea and
finally added to the rock-building material which is constantly
accumulating on the ocean floor[260]. No definite results have so far been
obtained as to the geographical and bathymetrical distribution of marine
diatoms.
The enormous number of recent species precludes any attempt to give a
description of the better-known forms. It is more important for us to realize
how common and widely distributed are the living genera. The hard and
almost indestructible valves have been frequently found in a fossil
condition, often forming thick and extensive masses of siliceous rock. From
diatom-beds now forming in lakes and on the ocean-bed we pass to deposits
such as those in Skye and elsewhere, which mark the site of recently dried-
up sheets of water, and so to older rocks of Tertiary age formed under
similar conditions. Among the many examples of diatomaceous deposits of
Tertiary and Cretaceous age mention should be made of those of Berlin,
Königsberg, Bilin in Bohemia, and Richmond in Virginia. The diatoms in
the beds of Berlin are regarded as fresh-water, and those of Richmond as
marine. It has been pointed out by Pfitzer that it is a comparatively easy
matter to distinguish between fresh-water and marine forms of diatoms. The
diatomaceous rocks of Bilin are known as polishing slates; they attain a
Page 173
thickness of 50 feet. In these, as in many other cases, the deposit has
become cemented together as a hard flinty or glassy rock, in which the
cementing material was formed by the solution of some of the diatom
tests[261]. In many cases in which calcareous and siliceous rocks reveal no
direct evidence of organic origin it is probable that they were originally
formed by the accumulation of plants of which the structure has been
completely obliterated by secondary causes. The genus Gallionella plays an
important part in the composition of the Bilin beds. Occasionally
impressions of leaves and other organic remains are found associated with
the diatoms in the siliceous rocks. In the British Museum (Botanical
department) a large block of white powdery rock is exhibited as an example
of a diatomaceous deposit of Tertiary age from Australia. It is described as
being largely made up of the tests of fresh-water diatoms, such as Navicula,
Gomphonema, Cymbella, Synedra, and others.
FOSSIL DIATOMS.
The abundance of Diatoms in Cretaceous rocks of the Paris basin has
recently been recorded by Cayeux[262]; it would seem that these algae had
already assumed an important rôle as rock-builders in pre-Tertiary times.
Cayeux points out that the silica of these Cretaceous diatomaceous frustules
has often been replaced by carbonate of calcium.
In addition to the occurrence of Diatoms in the various diatomaceous
deposits, their siliceous tests may occasionally be recognised in argillaceous
or other sediments. Shrubsole and Kitton[263] have described several species
of Diatoms from the London Clay of Lower Eocene age. In many localities
in the London basin the clay obtained from well-sinkings presented the
appearance of being dusted with sulphur-like particles of a dark bronze or
golden colour which glistened in the sunlight. These yellow bodies have
been found to be diatomaceous frustules in which the silica has been
replaced by iron pyrites. The genus Coscinodiscus is one of the commonest
forms recorded from the London Clay[264].
Without further considering individual examples of diatomaceous rocks
we may briefly notice the general facts of the geological history of the
family. As Ehrenberg pointed out several years ago, the Tertiary and
Cretaceous species of diatoms show a very marked resemblance to living
forms. In many cases the species are identical, and the fossil deposits as a
whole seem to differ in no special respect from those now being built up.
become cemented together as a hard flinty or glassy rock, in which the
cementing material was formed by the solution of some of the diatom
tests[261]. In many cases in which calcareous and siliceous rocks reveal no
direct evidence of organic origin it is probable that they were originally
formed by the accumulation of plants of which the structure has been
completely obliterated by secondary causes. The genus Gallionella plays an
important part in the composition of the Bilin beds. Occasionally
impressions of leaves and other organic remains are found associated with
the diatoms in the siliceous rocks. In the British Museum (Botanical
department) a large block of white powdery rock is exhibited as an example
of a diatomaceous deposit of Tertiary age from Australia. It is described as
being largely made up of the tests of fresh-water diatoms, such as Navicula,
Gomphonema, Cymbella, Synedra, and others.
FOSSIL DIATOMS.
The abundance of Diatoms in Cretaceous rocks of the Paris basin has
recently been recorded by Cayeux[262]; it would seem that these algae had
already assumed an important rôle as rock-builders in pre-Tertiary times.
Cayeux points out that the silica of these Cretaceous diatomaceous frustules
has often been replaced by carbonate of calcium.
In addition to the occurrence of Diatoms in the various diatomaceous
deposits, their siliceous tests may occasionally be recognised in argillaceous
or other sediments. Shrubsole and Kitton[263] have described several species
of Diatoms from the London Clay of Lower Eocene age. In many localities
in the London basin the clay obtained from well-sinkings presented the
appearance of being dusted with sulphur-like particles of a dark bronze or
golden colour which glistened in the sunlight. These yellow bodies have
been found to be diatomaceous frustules in which the silica has been
replaced by iron pyrites. The genus Coscinodiscus is one of the commonest
forms recorded from the London Clay[264].
Without further considering individual examples of diatomaceous rocks
we may briefly notice the general facts of the geological history of the
family. As Ehrenberg pointed out several years ago, the Tertiary and
Cretaceous species of diatoms show a very marked resemblance to living
forms. In many cases the species are identical, and the fossil deposits as a
whole seem to differ in no special respect from those now being built up.
Page 174
With the exception of two species of Liassic Diatoms, no trustworthy
examples of the Diatomaceae have been found below the Cretaceous series.
The oldest known Diatoms were discovered by Rothpletz[265] among the
fibres of an Upper Lias sponge from Boll in Württemberg. They occur as
small thimble-shaped siliceous tests with coccoliths and foraminifera in the
horny skeleton of Phymatoderma, a genus formerly regarded as an alga.
Rothpletz describes two species which he includes in the genus Pyxidicula,
P. bollensis and P. liasica. This generic name of Ehrenberg is used by
Schütt[266] as a subgenus of Stephanopyxis.
Seeing how great a resemblance there is between the recent and
Cretaceous species, and how many examples there are of Tertiary diatom
deposits, it is not a little surprising that the past history of these plants has
not been traced to earlier periods. In 1876 Castracane[267], an Italian
diatomist, gave an account of certain species of diatoms said to have been
found in a block of coal from Liverpool obtained from the English Coal-
Measures. The species were found to be identical with recent forms. It is
generally agreed that these specimens cannot have been from the coal itself,
but that they must have been living forms which had come to be associated
with the coal. The late Prof. Williamson spent many years examining thin
sections and other preparations of coal from various parts of the world, but
he never found a trace of any fossil diatom. There is no apparent reason
why diatoms should not be found in Pre-Cretaceous rocks, and the
microscopic investigation of old sediments may well lead to their discovery.
Prof. Bertrand of Lille, who has devoted himself for some time past to a
detailed microscopical examination of coal, informs me that he has so far
failed to discover any trace of Palaeozoic diatomaceous tests.
BACTRYLLIUM.
The genus Bactryllium is often quoted in text-books as a probable
example of a Triassic diatom. It was first described by Heer[268] from the
Trias of Switzerland and North Italy, also from the neighbourhood of
Heidelberg, and regarded as an extinct member of the Diatomaceae. Heer
defined the genus as follows:
“Small bodies, with parallel sides, rounded at either end, the surface traversed by one or two
longitudinal grooves.”
examples of the Diatomaceae have been found below the Cretaceous series.
The oldest known Diatoms were discovered by Rothpletz[265] among the
fibres of an Upper Lias sponge from Boll in Württemberg. They occur as
small thimble-shaped siliceous tests with coccoliths and foraminifera in the
horny skeleton of Phymatoderma, a genus formerly regarded as an alga.
Rothpletz describes two species which he includes in the genus Pyxidicula,
P. bollensis and P. liasica. This generic name of Ehrenberg is used by
Schütt[266] as a subgenus of Stephanopyxis.
Seeing how great a resemblance there is between the recent and
Cretaceous species, and how many examples there are of Tertiary diatom
deposits, it is not a little surprising that the past history of these plants has
not been traced to earlier periods. In 1876 Castracane[267], an Italian
diatomist, gave an account of certain species of diatoms said to have been
found in a block of coal from Liverpool obtained from the English Coal-
Measures. The species were found to be identical with recent forms. It is
generally agreed that these specimens cannot have been from the coal itself,
but that they must have been living forms which had come to be associated
with the coal. The late Prof. Williamson spent many years examining thin
sections and other preparations of coal from various parts of the world, but
he never found a trace of any fossil diatom. There is no apparent reason
why diatoms should not be found in Pre-Cretaceous rocks, and the
microscopic investigation of old sediments may well lead to their discovery.
Prof. Bertrand of Lille, who has devoted himself for some time past to a
detailed microscopical examination of coal, informs me that he has so far
failed to discover any trace of Palaeozoic diatomaceous tests.
BACTRYLLIUM.
The genus Bactryllium is often quoted in text-books as a probable
example of a Triassic diatom. It was first described by Heer[268] from the
Trias of Switzerland and North Italy, also from the neighbourhood of
Heidelberg, and regarded as an extinct member of the Diatomaceae. Heer
defined the genus as follows:
“Small bodies, with parallel sides, rounded at either end, the surface traversed by one or two
longitudinal grooves.”
Page 175
(fig. 32, C.) Several species have been figured by Heer from beds of
Muschelkalk, Keuper and Rhaetic age. He describes the wall as thick and
firm (fig. 32, C. ii.) and probably composed of silica, with a hollow interior.
The specimen shown in fig. 32, C. was found in the Rhaetic beds, and
named by Heer Bactryllium deplanatum; it has a length of 4·5 mm.; the
surface is transversely striated and traversed by a single longitudinal
groove. Stefani[269] has given reasons in favour of removing Bactryllium
from the plant to the animal kingdom; he points out that the specimens are
too large for diatoms, and moreover that they are asymmetrical in form and
possessed a calcareous and not a siliceous shell. He would place the fossil
among the Pteropods, comparing it with such genera as Cuvierina and
Hyalaea. In view of Stefani’s opinion we cannot attach any importance to
this supposed diatom, especially as it has generally been regarded as at best
but an unsatisfactory genus.
Muschelkalk, Keuper and Rhaetic age. He describes the wall as thick and
firm (fig. 32, C. ii.) and probably composed of silica, with a hollow interior.
The specimen shown in fig. 32, C. was found in the Rhaetic beds, and
named by Heer Bactryllium deplanatum; it has a length of 4·5 mm.; the
surface is transversely striated and traversed by a single longitudinal
groove. Stefani[269] has given reasons in favour of removing Bactryllium
from the plant to the animal kingdom; he points out that the specimens are
too large for diatoms, and moreover that they are asymmetrical in form and
possessed a calcareous and not a siliceous shell. He would place the fossil
among the Pteropods, comparing it with such genera as Cuvierina and
Hyalaea. In view of Stefani’s opinion we cannot attach any importance to
this supposed diatom, especially as it has generally been regarded as at best
but an unsatisfactory genus.
Page 176
Fig. 32. A, Lithothamnion mamillosum Gümb. (i) In section, (ii) surface view [after Gümbel.
(i) × 320, (ii) nat. size. B, Sycidium melo Sandb. (i) Surface view, (ii) transverse section
(after Deecke). C, Bactryllium deplanatum Heer. (i) Surface view, (ii) section, showing the
thick wall and hollow interior (after Heer). D, Calcareous pebble from a lake in
Michigan. Rather less than nat. size (after Murray).
B. CHLOROPHYCEAE (Green Algae).
Thallus unseptate, having the form of a vesicle or a variously branched
coenocyte, which may or may not be encrusted with carbonate of lime, or of
filaments composed of cells containing a single nucleus, or of cells in which
more than one nucleus occurs; in other instances consisting of a plate of
cells or a cell-mass. Asexual reproduction by zoospores and other
reproductive cells; sexual reproduction by means of the conjugation of
similar gametes or by the fertilisation of a typical egg-cell by a motile
spermatozoid.
This family of algae is represented at the present day by numerous and
widely distributed marine and fresh-water genera, as well as by genera
growing in moist air or as endophytes in the tissues of higher plants[270].
(i) × 320, (ii) nat. size. B, Sycidium melo Sandb. (i) Surface view, (ii) transverse section
(after Deecke). C, Bactryllium deplanatum Heer. (i) Surface view, (ii) section, showing the
thick wall and hollow interior (after Heer). D, Calcareous pebble from a lake in
Michigan. Rather less than nat. size (after Murray).
B. CHLOROPHYCEAE (Green Algae).
Thallus unseptate, having the form of a vesicle or a variously branched
coenocyte, which may or may not be encrusted with carbonate of lime, or of
filaments composed of cells containing a single nucleus, or of cells in which
more than one nucleus occurs; in other instances consisting of a plate of
cells or a cell-mass. Asexual reproduction by zoospores and other
reproductive cells; sexual reproduction by means of the conjugation of
similar gametes or by the fertilisation of a typical egg-cell by a motile
spermatozoid.
This family of algae is represented at the present day by numerous and
widely distributed marine and fresh-water genera, as well as by genera
growing in moist air or as endophytes in the tissues of higher plants[270].
Page 177
Seeing how very few fossil forms have been described which have any
claim to inclusion in this subdivision of the Algae, it is unnecessary to
enumerate or define the various families of the Chlorophyceae. It is true
that many species have been figured as examples of different genera of
green algae, but few of these possess any scientific value. There is,
however, one division of the Chlorophyceae, the Siphoneae, which must be
treated at some length on account of its importance from a palaeobotanical
and geological point of view.
a. Siphoneae.
Thallus consisting of simple or branched cells very rarely divided by
septa, and containing many nuclei. In certain genera the branches form a
pseudoparenchymatous tissue by their repeated branching, and as a result of
the intimate felting together of the branched cells. Reproduction is effected
either by the conjugation of similar gametes or by the fertilisation of an
egg-cell.
Vaucheria and Botrydium are two well-known British genera of this
order, but most of the recent representatives live in tropical and subtropical
seas. The most striking characteristic feature of this division of the
Chlorophyceae is the fact that the thallus of a siphoneous alga consists of an
unseptate coenocyte; the plant may be extremely small and simple, or it
may reach a length of several inches, but in all cases the body does not
consist of more than one cell or coenocyte.
From a palaeontological standpoint the Siphoneae are of exceptional
interest. It is impossible to do more than refer to a few of the living and
fossil genera. There are numerous fossil representatives already known, and
there can be little doubt that further research would be productive of
valuable results.
As examples of the order, a few genera may be described belonging to
the three families Caulerpaceae, Codiaceae, and Dasycladaceae.
α. Caulerpaceae.
Thallus unseptate, showing an extraordinary variation in the external
differentiation of the plant-body. Reproduction is effected by means of
detached portions of the parent plant.
claim to inclusion in this subdivision of the Algae, it is unnecessary to
enumerate or define the various families of the Chlorophyceae. It is true
that many species have been figured as examples of different genera of
green algae, but few of these possess any scientific value. There is,
however, one division of the Chlorophyceae, the Siphoneae, which must be
treated at some length on account of its importance from a palaeobotanical
and geological point of view.
a. Siphoneae.
Thallus consisting of simple or branched cells very rarely divided by
septa, and containing many nuclei. In certain genera the branches form a
pseudoparenchymatous tissue by their repeated branching, and as a result of
the intimate felting together of the branched cells. Reproduction is effected
either by the conjugation of similar gametes or by the fertilisation of an
egg-cell.
Vaucheria and Botrydium are two well-known British genera of this
order, but most of the recent representatives live in tropical and subtropical
seas. The most striking characteristic feature of this division of the
Chlorophyceae is the fact that the thallus of a siphoneous alga consists of an
unseptate coenocyte; the plant may be extremely small and simple, or it
may reach a length of several inches, but in all cases the body does not
consist of more than one cell or coenocyte.
From a palaeontological standpoint the Siphoneae are of exceptional
interest. It is impossible to do more than refer to a few of the living and
fossil genera. There are numerous fossil representatives already known, and
there can be little doubt that further research would be productive of
valuable results.
As examples of the order, a few genera may be described belonging to
the three families Caulerpaceae, Codiaceae, and Dasycladaceae.
α. Caulerpaceae.
Thallus unseptate, showing an extraordinary variation in the external
differentiation of the plant-body. Reproduction is effected by means of
detached portions of the parent plant.
Page 178
The genus Caulerpa, represented by a few species in the Mediterranean
and by many tropical forms, has already been alluded to as a striking
example of a plant which appears under a great many different forms[271]. As
a recent writer has said, “Nature seems to have shown in this genus the
utmost possibilities of the siphoneous thallus[272],” Fragments of coniferous
twigs, the tracks and burrows of various animals and other objects have
been described by several authors as fossil species of Caulerpa. As an
illustration of the identification of a very doubtful fossil as a species of
Caulerpites, reference may be made to such a form as C. cactoides Göpp.
[273]
from Silurian and Cambrian rocks. There are several examples of this
fossil in the Brussels Museum which probably owe their origin to some
burrowing animal, and may be compared with Zeiller’s figures of the
tunnels made by the mole-cricket (fig. 30, 4)[274].
Mr Murray, of the British Museum, has recently described what he
regards as a trustworthy example of a fossil Caulerpa from the Kimeridge
Clay near Weymouth[275]. Specimens of the fossil were first figured in a
book on the geology of the Dorset coast as casts of an equisetaceous
plant[276].
To this fossil Murray has assigned the name Caulerpa Carruthersi, and
given to it a scientific diagnosis. The best specimens have the form of a
slender central axis, giving off at fairly regular intervals whorls of short and
somewhat clavate branches; they bear a superficial resemblance to such a
recent species as Caulerpa cactoides Ag. An examination of several
examples of this fossil leads me to express the opinion that there is not
sufficient reason for assigning to them the name of a recent genus of
algae[277]. To use the generic name of a recent plant without following the
common custom of adding on the termination “ites” (i.e. Caulerpites) is as
a general rule to be avoided in dealing with fossil forms; and there are, I
believe, no satisfactory grounds for referring to these fossils as trustworthy
examples of a Mesozoic alga.
In the present case I am disposed to regard the Caulerpa-like casts as of
animal rather than plant origin. The clavate branches have the form of very
deep moulds in the hard brown rock which have been filled in with blue
mud. It is hardly conceivable that the branches of a soft watery plant such
as Caulerpa could leave more than a faint impression on an old sea-floor.
The specimens occur in different positions in the matrix of the rock and
and by many tropical forms, has already been alluded to as a striking
example of a plant which appears under a great many different forms[271]. As
a recent writer has said, “Nature seems to have shown in this genus the
utmost possibilities of the siphoneous thallus[272],” Fragments of coniferous
twigs, the tracks and burrows of various animals and other objects have
been described by several authors as fossil species of Caulerpa. As an
illustration of the identification of a very doubtful fossil as a species of
Caulerpites, reference may be made to such a form as C. cactoides Göpp.
[273]
from Silurian and Cambrian rocks. There are several examples of this
fossil in the Brussels Museum which probably owe their origin to some
burrowing animal, and may be compared with Zeiller’s figures of the
tunnels made by the mole-cricket (fig. 30, 4)[274].
Mr Murray, of the British Museum, has recently described what he
regards as a trustworthy example of a fossil Caulerpa from the Kimeridge
Clay near Weymouth[275]. Specimens of the fossil were first figured in a
book on the geology of the Dorset coast as casts of an equisetaceous
plant[276].
To this fossil Murray has assigned the name Caulerpa Carruthersi, and
given to it a scientific diagnosis. The best specimens have the form of a
slender central axis, giving off at fairly regular intervals whorls of short and
somewhat clavate branches; they bear a superficial resemblance to such a
recent species as Caulerpa cactoides Ag. An examination of several
examples of this fossil leads me to express the opinion that there is not
sufficient reason for assigning to them the name of a recent genus of
algae[277]. To use the generic name of a recent plant without following the
common custom of adding on the termination “ites” (i.e. Caulerpites) is as
a general rule to be avoided in dealing with fossil forms; and there are, I
believe, no satisfactory grounds for referring to these fossils as trustworthy
examples of a Mesozoic alga.
In the present case I am disposed to regard the Caulerpa-like casts as of
animal rather than plant origin. The clavate branches have the form of very
deep moulds in the hard brown rock which have been filled in with blue
mud. It is hardly conceivable that the branches of a soft watery plant such
as Caulerpa could leave more than a faint impression on an old sea-floor.
The specimens occur in different positions in the matrix of the rock and
Page 179
they are not confined to the lines of bedding; in none of the examples is
there any trace of carbonaceous matter in association with the deep moulds.
On the whole, then, this Kimeridge fossil cannot, I believe, be accepted as
an authentic example of a Mesozoic Caulerpa.
It is not improbable that some of the supposed fossil algae may be casts
of egg-cases or spawn-clusters of animals. In Ellis’ Natural History of the
Corallines[278] there is a drawing representing a number of disc-like ovaries
attached to a tough ligament, and referred to the mollusc Buccinum, which
bears a certain resemblance to the Weymouth fossil. A similar body is
figured by Fuchs[279] in an important memoir on supposed fossil algae.
It is not suggested that the Caulerpa Carruthersi of Murray should be
regarded as the cast of some molluscan egg-case attached to a slender axis,
but it is important to bear in mind the possibility of matching such
extremely doubtful fossils with other organic bodies than the thallus of a
Caulerpa. In an example of an egg-case in the Cambridge Zoological
Museum, referred to a species of Pyrula, there is a hard, long and slender
axis, bearing a series of semicircular chambers divided into radial
compartments. The whole is hard and horny and might well be preserved as
a fossil.
β. Codiaceae.
The members of this Order present a considerable diversity of form as
regards the shape of the plant-body; the thallus of some species is encrusted
with carbonate of lime. The order is widely distributed in tropical and
temperate seas.
Among the recent genera Penicillus and Codium may be chosen as
important types from the point of view of fossil representatives.
Codium.
The thallus of Codium consists of a spongy mass of tubular cell-branches
which are differentiated into two fairly distinct regions, an outer peripheral
layer in which the branches have long club-shaped terminations, and an
inner region consisting of loosely interwoven filaments.
there any trace of carbonaceous matter in association with the deep moulds.
On the whole, then, this Kimeridge fossil cannot, I believe, be accepted as
an authentic example of a Mesozoic Caulerpa.
It is not improbable that some of the supposed fossil algae may be casts
of egg-cases or spawn-clusters of animals. In Ellis’ Natural History of the
Corallines[278] there is a drawing representing a number of disc-like ovaries
attached to a tough ligament, and referred to the mollusc Buccinum, which
bears a certain resemblance to the Weymouth fossil. A similar body is
figured by Fuchs[279] in an important memoir on supposed fossil algae.
It is not suggested that the Caulerpa Carruthersi of Murray should be
regarded as the cast of some molluscan egg-case attached to a slender axis,
but it is important to bear in mind the possibility of matching such
extremely doubtful fossils with other organic bodies than the thallus of a
Caulerpa. In an example of an egg-case in the Cambridge Zoological
Museum, referred to a species of Pyrula, there is a hard, long and slender
axis, bearing a series of semicircular chambers divided into radial
compartments. The whole is hard and horny and might well be preserved as
a fossil.
β. Codiaceae.
The members of this Order present a considerable diversity of form as
regards the shape of the plant-body; the thallus of some species is encrusted
with carbonate of lime. The order is widely distributed in tropical and
temperate seas.
Among the recent genera Penicillus and Codium may be chosen as
important types from the point of view of fossil representatives.
Codium.
The thallus of Codium consists of a spongy mass of tubular cell-branches
which are differentiated into two fairly distinct regions, an outer peripheral
layer in which the branches have long club-shaped terminations, and an
inner region consisting of loosely interwoven filaments.
Page 180
Codium Bursa L. and C. tomentosum Huds. are two well-known British
species, the former presents the appearance of a spongy ball of cells, and in
the latter the thallus is divided up into dichotomously forked branches[280].
In this genus the thallus is not encrusted with carbonate of lime, at least in
recent species.
Sphaerocodium. Fig. 37, D.
Rothpletz[281] instituted this genus for certain small spherical or oval
bodies varying from 1 mm. to 2 cm. in diameter, which have been found on
crinoid stems or shell fragments of Triassic age. Each spherical body
consists of dichotomously branched single-celled filaments, between 50 and
100µ in breadth, and from 300–500µ in height. The tubular cavities
occasionally swell out into spherical spaces which are regarded by
Rothpletz as sporangia.
There is not sufficient evidence that Sphaerocodium Bornemanni Roth.
has been correctly referred to the Codiaceae. The sporangia-like swellings
described by the author of the species are not by any means conclusive as
characters of important taxonomic value. Figure 37, D, illustrates the
general structure of the fossil as seen in a transverse section of one of the
calcareous grains.
Like Girvanella, which has been referred by some writers to the
Siphoneae, Sphaerocodium occurs in the form of oolitic grains. In the
Triassic Raibler and St Cassian beds of the Tyrol, as well as in rocks of
Rhaetic age in the Eastern Alps, it makes up large masses of limestone.
Rothpletz compares the structure of this genus with that of the recent alga
Codium adhaerens Ag., but it is wiser to regard such tubular structures as
Girvanella, Siphonema[282] and Sphaerocodium as closely allied organisms,
which are probably algae, but too imperfectly known to be referred to any
particular family.
Penicillus.
The recent genus Penicillus is one of those algae formerly included
among animals. Fig. 33, O, has been copied from a drawing of a species of
Penicillus given by Lamouroux[283] under the generic name of Nesea in his
species, the former presents the appearance of a spongy ball of cells, and in
the latter the thallus is divided up into dichotomously forked branches[280].
In this genus the thallus is not encrusted with carbonate of lime, at least in
recent species.
Sphaerocodium. Fig. 37, D.
Rothpletz[281] instituted this genus for certain small spherical or oval
bodies varying from 1 mm. to 2 cm. in diameter, which have been found on
crinoid stems or shell fragments of Triassic age. Each spherical body
consists of dichotomously branched single-celled filaments, between 50 and
100µ in breadth, and from 300–500µ in height. The tubular cavities
occasionally swell out into spherical spaces which are regarded by
Rothpletz as sporangia.
There is not sufficient evidence that Sphaerocodium Bornemanni Roth.
has been correctly referred to the Codiaceae. The sporangia-like swellings
described by the author of the species are not by any means conclusive as
characters of important taxonomic value. Figure 37, D, illustrates the
general structure of the fossil as seen in a transverse section of one of the
calcareous grains.
Like Girvanella, which has been referred by some writers to the
Siphoneae, Sphaerocodium occurs in the form of oolitic grains. In the
Triassic Raibler and St Cassian beds of the Tyrol, as well as in rocks of
Rhaetic age in the Eastern Alps, it makes up large masses of limestone.
Rothpletz compares the structure of this genus with that of the recent alga
Codium adhaerens Ag., but it is wiser to regard such tubular structures as
Girvanella, Siphonema[282] and Sphaerocodium as closely allied organisms,
which are probably algae, but too imperfectly known to be referred to any
particular family.
Penicillus.
The recent genus Penicillus is one of those algae formerly included
among animals. Fig. 33, O, has been copied from a drawing of a species of
Penicillus given by Lamouroux[283] under the generic name of Nesea in his
Page 181
treatise on the genera of Polyps published in 1821. He describes the genus
as a brush-like Polyp with a simple stem.
The thallus consists of a stout stem terminating in a brush-like tuft of fine
dichotomously-branched filaments. The apical branches are divided by
regular constrictions into short oval or rod-like segments which may be
encrusted with carbonate of lime. A few of the segments from the terminal
tuft of a recent Penicillus are shown in fig. 35, E. Each of these calcareous
segments has the form of an oval shell perforated at each end, and the wall
is pierced by numerous fine canals. Penicillus is represented by about 10
recent species, which with one exception live in tropical seas.
The recognition of Penicillus, or a very similar type, in a fossil condition
is due to Munier-Chalmas[284]. This keen observer has rendered great service
to palaeobotany by directing attention to the calcareous algae in the Paris
basin beds, and by proving that many of the fossils from these Tertiary
deposits have been erroneously included by previous writers among the
Foraminifera[285]. It is greatly to be desired that Prof. Munier-Chalmas may
soon publish a monograph on the fossil Siphoneous forms of which he
possesses a unique collection.
Ovulites. Figs. 33, K, L, and 35, F.
In his Natural History of Invertebrate Animals, Lamarck described some
small oval bodies from the Calcaire Grossier (Eocene) of the Paris basin
under the name of Ovulites. He defined them as follows:—“Polypier
pierreux, libre, ovuliforme ou cylindracé, creux intérieurement, souvent
percé aux deux bouts. Pores très petits, régulièrement disposés à la
surface[286].”
as a brush-like Polyp with a simple stem.
The thallus consists of a stout stem terminating in a brush-like tuft of fine
dichotomously-branched filaments. The apical branches are divided by
regular constrictions into short oval or rod-like segments which may be
encrusted with carbonate of lime. A few of the segments from the terminal
tuft of a recent Penicillus are shown in fig. 35, E. Each of these calcareous
segments has the form of an oval shell perforated at each end, and the wall
is pierced by numerous fine canals. Penicillus is represented by about 10
recent species, which with one exception live in tropical seas.
The recognition of Penicillus, or a very similar type, in a fossil condition
is due to Munier-Chalmas[284]. This keen observer has rendered great service
to palaeobotany by directing attention to the calcareous algae in the Paris
basin beds, and by proving that many of the fossils from these Tertiary
deposits have been erroneously included by previous writers among the
Foraminifera[285]. It is greatly to be desired that Prof. Munier-Chalmas may
soon publish a monograph on the fossil Siphoneous forms of which he
possesses a unique collection.
Ovulites. Figs. 33, K, L, and 35, F.
In his Natural History of Invertebrate Animals, Lamarck described some
small oval bodies from the Calcaire Grossier (Eocene) of the Paris basin
under the name of Ovulites. He defined them as follows:—“Polypier
pierreux, libre, ovuliforme ou cylindracé, creux intérieurement, souvent
percé aux deux bouts. Pores très petits, régulièrement disposés à la
surface[286].”
Page 182
Fig. 33. A and B, Cymopolia barbata (L.); A, transverse section of the calcareous cylinder. B,
verticillate branches and sporangium after removal of the calcareous matrix (A and B
after Munier-Chalmas). C and D, Acicularia Andrussowi Solms (C, after Andrussowi; D,
after Solms). E, Acicularia Miocenica Reuss; section of a spicula (after Reuss). F and G,
Acicularia sp. (after Carpenter), F × 40; G × 20. H, Acicularia Schencki (Möb.) (after
Solms). I, Acetabularia Mediterranea Lamx.; section of the cap (after Falkenberg). K and
L, Ovulites margaritula (Lam.) (after Munier-Chalmas); K slightly enlarged; L, a piece of
the thallus more highly magnified. M, Cymopolia barbata (L.) (after Ellis, nat. size). N, C.
barbata (L.); the surface of the thallus; magnified. O, Penicillus pyramidalis (Lamx.)
(after Lamouroux, nat. size).
The specimens are referred to two species, Ovulites margaritula and O.
elongata.
By some subsequent writers[287] these calcareous fossils, like miniature
birds’ eggs with a hole at either end, were included among the Zoophytes.
Carpenter and others afterwards referred Ovulites to the Foraminifera, and
compared the genus with Lagena[288]. The single specimens of Ovulites have
a length of 2–6 mm. At each end there is usually a fairly large and
somewhat irregular hole (fig. 35, F), and in some rarer cases there may be
two apertures at the broader end of an Ovulite. A good example of Ovulites
verticillate branches and sporangium after removal of the calcareous matrix (A and B
after Munier-Chalmas). C and D, Acicularia Andrussowi Solms (C, after Andrussowi; D,
after Solms). E, Acicularia Miocenica Reuss; section of a spicula (after Reuss). F and G,
Acicularia sp. (after Carpenter), F × 40; G × 20. H, Acicularia Schencki (Möb.) (after
Solms). I, Acetabularia Mediterranea Lamx.; section of the cap (after Falkenberg). K and
L, Ovulites margaritula (Lam.) (after Munier-Chalmas); K slightly enlarged; L, a piece of
the thallus more highly magnified. M, Cymopolia barbata (L.) (after Ellis, nat. size). N, C.
barbata (L.); the surface of the thallus; magnified. O, Penicillus pyramidalis (Lamx.)
(after Lamouroux, nat. size).
The specimens are referred to two species, Ovulites margaritula and O.
elongata.
By some subsequent writers[287] these calcareous fossils, like miniature
birds’ eggs with a hole at either end, were included among the Zoophytes.
Carpenter and others afterwards referred Ovulites to the Foraminifera, and
compared the genus with Lagena[288]. The single specimens of Ovulites have
a length of 2–6 mm. At each end there is usually a fairly large and
somewhat irregular hole (fig. 35, F), and in some rarer cases there may be
two apertures at the broader end of an Ovulite. A good example of Ovulites
Page 183
margaritula with two pores at the broader end is figured by Michelin[289].
The surface of the shell when seen under a low magnifying power appears
to be covered over with regularly arranged circular pores, which are the
external openings of fine canals (fig. 33, L).
In 1878 Munier-Chalmas expressed the opinion, which was supported by
strong evidence, that Ovulites should be referred to the siphoneous algae[290].
He regarded it as generically identical with Penicillus (Coralliodendron,
Kützing). It has already been pointed out that in Penicillus the apical tuft of
filaments is partially calcareous (fig. 33, O)[291]. The individual calcareous
segments agree almost exactly with the fossil Ovulites. As a rule the
Ovulites occur as separate egg- or rod-like bodies, but Munier-Chalmas
informs me that occasionally two or three have been found joined end to
end in their natural position. The terminal holes in the fossil specimens
represent the apertures left after the detachment of the calcareous segments
from the uncalcified filaments of the alga. The segments with two holes at
the broader end were no doubt situated at the base of dichotomising
branches as shown in fig. 33, K. The restoration of Ovulites, shown in fig.
33, K, bears a striking resemblance to the figure of an Australian Penicillus
given by Harvey in his Phycologia Australica[292].
It is probable that these Eocene forms agreed closely in habit with the
recent species of Penicillus. The portions preserved as fossils are segments
of the filaments which probably formed a terminal brush of fine branches
supported on a stem. The retention of the original generic name Ovulites is
on the whole better than the inclusion of the fossil species in the recent
genus. The Tertiary species lived in warm seas of the Lower and Middle
Eocene of England, Belgium, France and Italy.
Halimeda.
An example of an Eocene species of Halimeda has been recorded by
Fuchs from Greifenstein under the name of Halimeda Saportae[293]. The
impression has the form of a branched plant consisting of wedge-shaped or
oval segments, and there is a close resemblance to the thallus of a recent
Halimeda, e.g. H. gracilis Harv. It is not improbable that Fuchs’
determination is correct, but without more definite evidence than is afforded
The surface of the shell when seen under a low magnifying power appears
to be covered over with regularly arranged circular pores, which are the
external openings of fine canals (fig. 33, L).
In 1878 Munier-Chalmas expressed the opinion, which was supported by
strong evidence, that Ovulites should be referred to the siphoneous algae[290].
He regarded it as generically identical with Penicillus (Coralliodendron,
Kützing). It has already been pointed out that in Penicillus the apical tuft of
filaments is partially calcareous (fig. 33, O)[291]. The individual calcareous
segments agree almost exactly with the fossil Ovulites. As a rule the
Ovulites occur as separate egg- or rod-like bodies, but Munier-Chalmas
informs me that occasionally two or three have been found joined end to
end in their natural position. The terminal holes in the fossil specimens
represent the apertures left after the detachment of the calcareous segments
from the uncalcified filaments of the alga. The segments with two holes at
the broader end were no doubt situated at the base of dichotomising
branches as shown in fig. 33, K. The restoration of Ovulites, shown in fig.
33, K, bears a striking resemblance to the figure of an Australian Penicillus
given by Harvey in his Phycologia Australica[292].
It is probable that these Eocene forms agreed closely in habit with the
recent species of Penicillus. The portions preserved as fossils are segments
of the filaments which probably formed a terminal brush of fine branches
supported on a stem. The retention of the original generic name Ovulites is
on the whole better than the inclusion of the fossil species in the recent
genus. The Tertiary species lived in warm seas of the Lower and Middle
Eocene of England, Belgium, France and Italy.
Halimeda.
An example of an Eocene species of Halimeda has been recorded by
Fuchs from Greifenstein under the name of Halimeda Saportae[293]. The
impression has the form of a branched plant consisting of wedge-shaped or
oval segments, and there is a close resemblance to the thallus of a recent
Halimeda, e.g. H. gracilis Harv. It is not improbable that Fuchs’
determination is correct, but without more definite evidence than is afforded
Page 184
by a mere impression it is a little rash to make use of the recent generic
name.
γ. Dasycladaceae.
In this family of Siphoneae are included a number of genera represented
by species living in tropical and subtropical seas.
The thallus consists of an elongated axial cell fixed to the substratum by
basal rhizoids, and bearing whorls of lateral appendages of limited growth
which may be either simple or branched. Many of the lateral branches bear
sporangia or spores. The thallus is in many species encrusted with carbonate
of lime.
The two genera Acetabularia and Cymopolia may be briefly described as
recent types which are represented by trustworthy fossil forms.
name.
γ. Dasycladaceae.
In this family of Siphoneae are included a number of genera represented
by species living in tropical and subtropical seas.
The thallus consists of an elongated axial cell fixed to the substratum by
basal rhizoids, and bearing whorls of lateral appendages of limited growth
which may be either simple or branched. Many of the lateral branches bear
sporangia or spores. The thallus is in many species encrusted with carbonate
of lime.
The two genera Acetabularia and Cymopolia may be briefly described as
recent types which are represented by trustworthy fossil forms.
Page 185
Fig. 34. Acetabularia mediterranea Lamx. From a specimen in the Cambridge Botanical
Museum (nat. size).
Acetabularia. Figs. 33, I, and 34.
With the exception of A. mediterranea Lamx. (fig. 34) the few living
species of this genus are confined to tropical seas.
The habit of Acetabularia is well illustrated by the photograph of a
cluster of plants of A. mediterranea Lamx.[294] reproduced in fig. 34. The
thallus consists of a delicate stalk attached to the substratum by a tuft of
basal holdfasts, and expanded distally into a small circular disc 10–12 mm.
Museum (nat. size).
Acetabularia. Figs. 33, I, and 34.
With the exception of A. mediterranea Lamx. (fig. 34) the few living
species of this genus are confined to tropical seas.
The habit of Acetabularia is well illustrated by the photograph of a
cluster of plants of A. mediterranea Lamx.[294] reproduced in fig. 34. The
thallus consists of a delicate stalk attached to the substratum by a tuft of
basal holdfasts, and expanded distally into a small circular disc 10–12 mm.
Page 186
in diameter and more or less concave above. This terminal cap is made up
of a number of laterally fused appendages given off from the upper part of
the stalk in the form of a crowded whorl. The whole thallus resembles a
small and long-stalked calcareous fungus. In each radially elongated
compartment of the fertile cap (fig. 33, I) there are several sporangia
(gametangia) developed; these eventually open and produce numerous
ciliated gametes which give rise to zygospores by conjugation. Fig. 33, I,
represents the cap of an Acetabularia in radial section and surface-view; the
two radial compartments seen in section contain the elliptical gametangia;
the circular markings at the base of the figure are scars of sterile deciduous
branches.
The whole plant is unicellular, each chamber in the disc being in open
communication with the stem of the plant.
Acicularia. Fig. 33, C–H.
In a recent monograph on the Acetabularieae, Solms-Laubach[295] has
described a new type of these algae which is of special importance from the
point of view of the past history of the family. Möbius described an
example of Acetabularia in 1889 under the name A. Schencki; this species
has since been placed in D’Archiac’s genus Acicularia[296]. Acicularia
Schencki[297] bears a close resemblance as regards external form to
Acetabularia mediterranea. In the latter species the walls of the terminal
disc compartments are calcified, and the cavity of each of the laterally fused
members contains numerous free spores; in Acicularia, the cavity of each
disc-ray is occupied by a calcareous substance in the form of a spicule
containing numerous cavities in each of which is a single sporangium. A
single spicule is seen in fig. 33, H, showing the spherical pockets in which
the sporangia were originally situated. This species, Acicularia Schencki,
has been recorded from Martinique, Guadeloupe, Brazil, and a few other
places.
The genus Acicularia was founded by D’Archiac for certain minute
calcareous spicules found in the Eocene sands (Calcaire Grossier) of the
Paris basin. D’Archiac describes one species, Acicularia pavantina, which
he defines as follows:—“Polypier aciculaire, élargi, et légèrement
comprimé à sa partie supérieure, qui est échancrée au milieu. Surface
couverte de petits pores simples, nombreux, disposés irrégulièrement[298].”
of a number of laterally fused appendages given off from the upper part of
the stalk in the form of a crowded whorl. The whole thallus resembles a
small and long-stalked calcareous fungus. In each radially elongated
compartment of the fertile cap (fig. 33, I) there are several sporangia
(gametangia) developed; these eventually open and produce numerous
ciliated gametes which give rise to zygospores by conjugation. Fig. 33, I,
represents the cap of an Acetabularia in radial section and surface-view; the
two radial compartments seen in section contain the elliptical gametangia;
the circular markings at the base of the figure are scars of sterile deciduous
branches.
The whole plant is unicellular, each chamber in the disc being in open
communication with the stem of the plant.
Acicularia. Fig. 33, C–H.
In a recent monograph on the Acetabularieae, Solms-Laubach[295] has
described a new type of these algae which is of special importance from the
point of view of the past history of the family. Möbius described an
example of Acetabularia in 1889 under the name A. Schencki; this species
has since been placed in D’Archiac’s genus Acicularia[296]. Acicularia
Schencki[297] bears a close resemblance as regards external form to
Acetabularia mediterranea. In the latter species the walls of the terminal
disc compartments are calcified, and the cavity of each of the laterally fused
members contains numerous free spores; in Acicularia, the cavity of each
disc-ray is occupied by a calcareous substance in the form of a spicule
containing numerous cavities in each of which is a single sporangium. A
single spicule is seen in fig. 33, H, showing the spherical pockets in which
the sporangia were originally situated. This species, Acicularia Schencki,
has been recorded from Martinique, Guadeloupe, Brazil, and a few other
places.
The genus Acicularia was founded by D’Archiac for certain minute
calcareous spicules found in the Eocene sands (Calcaire Grossier) of the
Paris basin. D’Archiac describes one species, Acicularia pavantina, which
he defines as follows:—“Polypier aciculaire, élargi, et légèrement
comprimé à sa partie supérieure, qui est échancrée au milieu. Surface
couverte de petits pores simples, nombreux, disposés irrégulièrement[298].”
Page 187
The same species is figured also in Michelin’s Iconographie
Zoophytologique, and described as an organism of which the exact
zoological position is uncertain[299]. After these fossils had been placed in
various divisions of the animal kingdom, Carpenter[300] described several
specimens as portions of foraminifera. Finally, Munier-Chalmas removed
Acicularia to the plant kingdom, and “with rare divination” placed the
genus among the Acetabularieae. The history of our knowledge of the true
nature of Acicularia is of unusual interest. Some of the specimens of this
genus figured in Carpenter’s monograph have the form of imperfect long
and narrow bodies tapering to a point at one end and broad at the other (fig.
33, F and G); they are joined together laterally and pitted with numerous
small cavities. From the resemblance of such specimens to a fragment of
the terminal fertile disc of the recent Acetabularias, Munier-Chalmas
referred the fossils to this type of algae. In the living species which were
then known the radiating chambers of the disc contained loose sporangia,
without any calcareous matrix filling the cavity of the chambers. In the
fossil Acicularias, on the other hand, the manner of preservation of the
pitted calcareous spicules pointed to the occurrence of sporangia embedded
in cavities in a calcareous matrix. Subsequent to Munier-Chalmas’
somewhat daring conclusions as to the relation of Acicularia to
Acetabularia, Solms-Laubach found that the species originally described by
Möbius as Acetabularia Schencki from Guadeloupe presented exactly those
characters in which the fossil specimens differ from Acetabularia. The
genus Acicularia formerly restricted to fossil species is now applied also to
this single living species Acicularia Schencki.
The genus is thus defined by Solms-Laubach:—
“Discus fertilis terminalis e radiis inter se conjunctis formatus, coronis et inferiore et superiore
praeditis, sporae massa mucosa calce incrustata coalitae, pro radio spiculam solidam cuneatam
formantes[301].”
As Solms-Laubach points out in his recent monograph, Munier-Chalmas’
conjecture, “which had little to support it in the fossil material, has been
more recently proved true in the most brilliant fashion by the discovery of a
living species of this genus.”
• • • • •
Zoophytologique, and described as an organism of which the exact
zoological position is uncertain[299]. After these fossils had been placed in
various divisions of the animal kingdom, Carpenter[300] described several
specimens as portions of foraminifera. Finally, Munier-Chalmas removed
Acicularia to the plant kingdom, and “with rare divination” placed the
genus among the Acetabularieae. The history of our knowledge of the true
nature of Acicularia is of unusual interest. Some of the specimens of this
genus figured in Carpenter’s monograph have the form of imperfect long
and narrow bodies tapering to a point at one end and broad at the other (fig.
33, F and G); they are joined together laterally and pitted with numerous
small cavities. From the resemblance of such specimens to a fragment of
the terminal fertile disc of the recent Acetabularias, Munier-Chalmas
referred the fossils to this type of algae. In the living species which were
then known the radiating chambers of the disc contained loose sporangia,
without any calcareous matrix filling the cavity of the chambers. In the
fossil Acicularias, on the other hand, the manner of preservation of the
pitted calcareous spicules pointed to the occurrence of sporangia embedded
in cavities in a calcareous matrix. Subsequent to Munier-Chalmas’
somewhat daring conclusions as to the relation of Acicularia to
Acetabularia, Solms-Laubach found that the species originally described by
Möbius as Acetabularia Schencki from Guadeloupe presented exactly those
characters in which the fossil specimens differ from Acetabularia. The
genus Acicularia formerly restricted to fossil species is now applied also to
this single living species Acicularia Schencki.
The genus is thus defined by Solms-Laubach:—
“Discus fertilis terminalis e radiis inter se conjunctis formatus, coronis et inferiore et superiore
praeditis, sporae massa mucosa calce incrustata coalitae, pro radio spiculam solidam cuneatam
formantes[301].”
As Solms-Laubach points out in his recent monograph, Munier-Chalmas’
conjecture, “which had little to support it in the fossil material, has been
more recently proved true in the most brilliant fashion by the discovery of a
living species of this genus.”
• • • • •
Page 188
1. Acicularia Andrussowi Solms[302]. Fig. 33, C and D. This species was
first described by Andrussow[303] as Acetabularia miocenica from the
Crimea. It occurs in Miocene rocks south of Sevastopol, and, with Ostrea
and Pecten, forms masses of white limestone.
In each sporangial ray of the disc the cavity contains a calcareous spicula
bearing spore cavities in four rows. “Round each spore-cavity there is a
circular zone which stands out, when viewed in reflected light, through its
white colour against the central mass of the spicule, though a sharp contour
is not visible[304].” Fig. 33, C, is taken from a somewhat diagrammatic
sketch by Andrussow; it shows ten of the fertile rays of the disc. The thick
walls of the chambers are seen in the two lowest rays, and in the next two
rays the spore-cavities are represented. A more accurate drawing, from
Solms-Laubach’s memoir, is reproduced in fig. 33, D. The calcareous
spicule with numerous spore-cavities shown in fig. 33, H, is from a fertile
ray of the recent species Acicularia Schencki. This corresponds to the spore-
containing calcareous matrix in each ray of the disc of Acicularia
Andrussowi Solms. The spicule copied in fig. 33, F from one of Carpenter’s
drawings[305] of an Eocene specimen bears the closest resemblance to the
recent spicule of fig. 33, H, and emphasizes the very close relationship
between the fossil forms and the single rare tropical species.
2. Acicularia miocenica Reuss. Another Tertiary species has been
described under this name by Reuss[306] from the Miocene of the Vienna
district, from the Leithakalk of Moravia and elsewhere. It agrees very
closely with the recent species A. Schencki. A section of one of the spicules
of this species is shown in fig. 33, E; the dark patches represent the pockets
in the calcareous spicule which were originally occupied by sporangia and
spores.
Cymopolia. Fig. 33, A, B, M and N.
The genus Cymopolia is at present represented by two species, C.
barbata (L.) and C. mexicana, Ag., living in the Gulf of Mexico and off the
Canary Islands.
Cymopolia and Acetabularia, with several other calcareous algae, are
figured by Ellis and other writers as members of the animal kingdom. Ellis
first described by Andrussow[303] as Acetabularia miocenica from the
Crimea. It occurs in Miocene rocks south of Sevastopol, and, with Ostrea
and Pecten, forms masses of white limestone.
In each sporangial ray of the disc the cavity contains a calcareous spicula
bearing spore cavities in four rows. “Round each spore-cavity there is a
circular zone which stands out, when viewed in reflected light, through its
white colour against the central mass of the spicule, though a sharp contour
is not visible[304].” Fig. 33, C, is taken from a somewhat diagrammatic
sketch by Andrussow; it shows ten of the fertile rays of the disc. The thick
walls of the chambers are seen in the two lowest rays, and in the next two
rays the spore-cavities are represented. A more accurate drawing, from
Solms-Laubach’s memoir, is reproduced in fig. 33, D. The calcareous
spicule with numerous spore-cavities shown in fig. 33, H, is from a fertile
ray of the recent species Acicularia Schencki. This corresponds to the spore-
containing calcareous matrix in each ray of the disc of Acicularia
Andrussowi Solms. The spicule copied in fig. 33, F from one of Carpenter’s
drawings[305] of an Eocene specimen bears the closest resemblance to the
recent spicule of fig. 33, H, and emphasizes the very close relationship
between the fossil forms and the single rare tropical species.
2. Acicularia miocenica Reuss. Another Tertiary species has been
described under this name by Reuss[306] from the Miocene of the Vienna
district, from the Leithakalk of Moravia and elsewhere. It agrees very
closely with the recent species A. Schencki. A section of one of the spicules
of this species is shown in fig. 33, E; the dark patches represent the pockets
in the calcareous spicule which were originally occupied by sporangia and
spores.
Cymopolia. Fig. 33, A, B, M and N.
The genus Cymopolia is at present represented by two species, C.
barbata (L.) and C. mexicana, Ag., living in the Gulf of Mexico and off the
Canary Islands.
Cymopolia and Acetabularia, with several other calcareous algae, are
figured by Ellis and other writers as members of the animal kingdom. Ellis
Page 189
speaks of the species of Cymopolia which he figures as the Rosary Bead-
Coralline of Jamaica.
Fig. 33, M, has been drawn from a figure published by Ellis in his
Natural History of the Corallines published in 1755[307]. The thallus has the
form of a repeatedly forked body, of which the branches are divided into
cylindrical joints thickly encrusted with carbonate of lime, but constricted
and uncalcified at the limits of each segment. A tuft of hairs is given off
from the terminal segment of each branch. The axis of each branch of the
thallus is occupied by a cylindrical and unseptate cell which gives off
crowded whorls of lateral branches. In the lower part of fig. 33, M, the
calcareous investment has been removed, and the branches are seen as fine
hair-like appendages of the central cell. The branches given off from the
constricted portions of the axis are unbranched simple appendages, but the
others terminate in bladder-like swellings, each of which bears an apical
sporangium. The sporangia are surrounded and enclosed by the swollen tips
of four to six branches which spring from the summit of the sporangial
branch. Fig. 33, A, represents part of a transverse section through the
calcareous outer portion of a branch of Cymopolia; the darker portions or
cavities in the calcareous matrix were originally occupied by the lateral
branches and sporangia[308].
In Fig. 33, B, the sporangial branch with the terminal sporangium and
three of the investing branches are more clearly shown, the surrounding
calcareous investment and the thallus having been removed by the action of
an acid.
In a transverse section of a branch from which the organic matter had
been removed, and only the calcareous matrix left, one would see a central
circular cavity surrounded by a thick calcareous wall perforated by radially
disposed canals and containing globular cavities; the canals and cavities
being occupied in the living plant by branches and sporangia respectively.
The two circular cavities shown in the figure mark the position of the
sporangia which are borne on branches with somewhat swollen tips. From
the summit the left-hand sporangial branch shown in fig. 33, A, three of the
secondary branches are represented by channels in the calcareous matrix;
the two black dots on the face of the sporangiophore being the scars of the
remaining two secondary branches.
Coralline of Jamaica.
Fig. 33, M, has been drawn from a figure published by Ellis in his
Natural History of the Corallines published in 1755[307]. The thallus has the
form of a repeatedly forked body, of which the branches are divided into
cylindrical joints thickly encrusted with carbonate of lime, but constricted
and uncalcified at the limits of each segment. A tuft of hairs is given off
from the terminal segment of each branch. The axis of each branch of the
thallus is occupied by a cylindrical and unseptate cell which gives off
crowded whorls of lateral branches. In the lower part of fig. 33, M, the
calcareous investment has been removed, and the branches are seen as fine
hair-like appendages of the central cell. The branches given off from the
constricted portions of the axis are unbranched simple appendages, but the
others terminate in bladder-like swellings, each of which bears an apical
sporangium. The sporangia are surrounded and enclosed by the swollen tips
of four to six branches which spring from the summit of the sporangial
branch. Fig. 33, A, represents part of a transverse section through the
calcareous outer portion of a branch of Cymopolia; the darker portions or
cavities in the calcareous matrix were originally occupied by the lateral
branches and sporangia[308].
In Fig. 33, B, the sporangial branch with the terminal sporangium and
three of the investing branches are more clearly shown, the surrounding
calcareous investment and the thallus having been removed by the action of
an acid.
In a transverse section of a branch from which the organic matter had
been removed, and only the calcareous matrix left, one would see a central
circular cavity surrounded by a thick calcareous wall perforated by radially
disposed canals and containing globular cavities; the canals and cavities
being occupied in the living plant by branches and sporangia respectively.
The two circular cavities shown in the figure mark the position of the
sporangia which are borne on branches with somewhat swollen tips. From
the summit the left-hand sporangial branch shown in fig. 33, A, three of the
secondary branches are represented by channels in the calcareous matrix;
the two black dots on the face of the sporangiophore being the scars of the
remaining two secondary branches.
Page 190
By the lateral contact of the swollen ends of the ultimate branches
enclosing the sporangia the whole surface of the thallus, when examined
with a lens, presents a pitted appearance. Each pit or circular depression
(fig. 33, N) marks the position of the swollen tip of a branch.
This form of thallus represents a type which is met with in several
members of the Dasycladaceae. It would carry us beyond the limits of a
short account to describe additional recent genera which throw light on the
numerous fossil species. For further information as to the recent members
of the family, the student should refer to Murray’s Seaweeds[309], and for a
more detailed memoir on the group to Wille’s recent contribution to the
Pflanzenfamilien[310] of Engler and Prantl. Among the various special
contributions to our knowledge of the Dasycladaceae, those by Munier-
Chalmas[311], Cramer[312], Solms-Laubach[313], and Church[314], may be
mentioned.
PALAEOZOIC SIPHONEAE.
The publication of a short preliminary note by Prof. Munier-Chalmas in
the Comptes Rendus for 1877 was the means of calling attention to the
exceptional importance of the calcareous Siphoneae as algae possessing an
interesting past history, of which satisfactory records had been preserved in
rocks of various ages. Decaisne had pointed out in 1842 that certain marine
organisms previously regarded as animals should be transferred to the plant
kingdom. Such seaweeds as Halimeda, Udotea, Penicillus and others were
thus assigned to their correct position. Many fossil algae belonging to this
group continued to be dealt with as Foraminifera until Munier-Chalmas
demonstrated their true affinities. In Gümbel’s monograph on the so-called
Nullipores found in limestone rocks, published in 1871[315], several
examples of siphoneous algae are included among the fossil Protozoa.
In recent years there have been several additions to an already long list of
fossil Siphoneae. In addition to the numerous and well-preserved
specimens, representing a large number of generic and specific forms,
which have been collected from the Eocene of the Paris basin, there is
plenty of evidence of the abundance of the members of the Dasycladaceae
in the Triassic seas. In the Triassic limestones of the Tyrol, as well as in
other regions, the calcareous bodies of siphoneous algae have played no
inconsiderable part as agents of rock-building[316]. Genera have been
recorded from Silurian and other Palaeozoic horizons, and there is no doubt
enclosing the sporangia the whole surface of the thallus, when examined
with a lens, presents a pitted appearance. Each pit or circular depression
(fig. 33, N) marks the position of the swollen tip of a branch.
This form of thallus represents a type which is met with in several
members of the Dasycladaceae. It would carry us beyond the limits of a
short account to describe additional recent genera which throw light on the
numerous fossil species. For further information as to the recent members
of the family, the student should refer to Murray’s Seaweeds[309], and for a
more detailed memoir on the group to Wille’s recent contribution to the
Pflanzenfamilien[310] of Engler and Prantl. Among the various special
contributions to our knowledge of the Dasycladaceae, those by Munier-
Chalmas[311], Cramer[312], Solms-Laubach[313], and Church[314], may be
mentioned.
PALAEOZOIC SIPHONEAE.
The publication of a short preliminary note by Prof. Munier-Chalmas in
the Comptes Rendus for 1877 was the means of calling attention to the
exceptional importance of the calcareous Siphoneae as algae possessing an
interesting past history, of which satisfactory records had been preserved in
rocks of various ages. Decaisne had pointed out in 1842 that certain marine
organisms previously regarded as animals should be transferred to the plant
kingdom. Such seaweeds as Halimeda, Udotea, Penicillus and others were
thus assigned to their correct position. Many fossil algae belonging to this
group continued to be dealt with as Foraminifera until Munier-Chalmas
demonstrated their true affinities. In Gümbel’s monograph on the so-called
Nullipores found in limestone rocks, published in 1871[315], several
examples of siphoneous algae are included among the fossil Protozoa.
In recent years there have been several additions to an already long list of
fossil Siphoneae. In addition to the numerous and well-preserved
specimens, representing a large number of generic and specific forms,
which have been collected from the Eocene of the Paris basin, there is
plenty of evidence of the abundance of the members of the Dasycladaceae
in the Triassic seas. In the Triassic limestones of the Tyrol, as well as in
other regions, the calcareous bodies of siphoneous algae have played no
inconsiderable part as agents of rock-building[316]. Genera have been
recorded from Silurian and other Palaeozoic horizons, and there is no doubt
Page 191
that the Verticillate Siphoneae of to-day are the remnants of an extremely
ancient family, which in former periods was represented by a much more
widely distributed and more varied assemblage of species. There is
probably no more promising field of work in the domain of fossil algae than
the further investigation of the numerous forms included in Munier-
Chalmas’ class of Siphoneae Verticillatae. A brief description of a few
genera from different geological horizons must suffice to draw attention to
the character of the data for a phylogenetic history of this group.
The fossil examples of the genus Cymopolia (Polytrypa) were originally
described by Defrance[317] in the Dictionnaire des Sciences Naturelles as
small polyps under the generic name Polytrypa.
In the Eocene sands of the Paris basin there have been found numerous
specimens of short, calcareous tubes which Munier-Chalmas has shewn are
no doubt the isolated segments of an alga practically identical with the
recent Cymopolia. A section[318] through one of the fossil segments presents
precisely the same features as those which are represented in fig. 33, A. The
habit of the Eocene alga and its minute structure were apparently almost
identical with those of the recent species, Cymopolia barbata. The two
drawings of Cymopolia reproduced in fig. 33, A and B, have been copied
from Munier-Chalmas’ note in the Comptes Rendus[319]; the corresponding
figures given by this author of the Eocene species (Cymopolia elongata
Deb.) are practically identical with figs. A and B, and show no points of real
difference. The segments of the thallus of the fossil species, as figured by
Defrance[320], appear to be rather longer than those of the recent species. The
calcareous investment of the axial cell of the thallus was traversed by
regular verticils of branches or ‘leaves’; the central branch of each whorl
terminates in an oval sporangial cavity, exactly as in fig. 33, A and B; and
from the top of this branch there is given off a ring of slender prolongations
which terminate on the surface of the calcareous tube as regularly disposed
depressions, which were no doubt originally occupied by their swollen
distal ends as in the recent species.
ancient family, which in former periods was represented by a much more
widely distributed and more varied assemblage of species. There is
probably no more promising field of work in the domain of fossil algae than
the further investigation of the numerous forms included in Munier-
Chalmas’ class of Siphoneae Verticillatae. A brief description of a few
genera from different geological horizons must suffice to draw attention to
the character of the data for a phylogenetic history of this group.
The fossil examples of the genus Cymopolia (Polytrypa) were originally
described by Defrance[317] in the Dictionnaire des Sciences Naturelles as
small polyps under the generic name Polytrypa.
In the Eocene sands of the Paris basin there have been found numerous
specimens of short, calcareous tubes which Munier-Chalmas has shewn are
no doubt the isolated segments of an alga practically identical with the
recent Cymopolia. A section[318] through one of the fossil segments presents
precisely the same features as those which are represented in fig. 33, A. The
habit of the Eocene alga and its minute structure were apparently almost
identical with those of the recent species, Cymopolia barbata. The two
drawings of Cymopolia reproduced in fig. 33, A and B, have been copied
from Munier-Chalmas’ note in the Comptes Rendus[319]; the corresponding
figures given by this author of the Eocene species (Cymopolia elongata
Deb.) are practically identical with figs. A and B, and show no points of real
difference. The segments of the thallus of the fossil species, as figured by
Defrance[320], appear to be rather longer than those of the recent species. The
calcareous investment of the axial cell of the thallus was traversed by
regular verticils of branches or ‘leaves’; the central branch of each whorl
terminates in an oval sporangial cavity, exactly as in fig. 33, A and B; and
from the top of this branch there is given off a ring of slender prolongations
which terminate on the surface of the calcareous tube as regularly disposed
depressions, which were no doubt originally occupied by their swollen
distal ends as in the recent species.
Page 192
Vermiporella.
This generic name was proposed by Stolley for certain branched and
curved tubes found in Silurian boulders from the North German drift[321].
The tubes have a diameter of ·5–1 mm., and are perforated by radial canals
which probably mark the position of verticils of branches given off at right
angles to the central axis. The surface of the tubes is divided into regular
hexagonal areas.
The resemblance of these Silurian fossils to Diplopora and other genera
favours their inclusion in the Verticillate Siphoneae.
Sycidium. Fig. 32, B.
The fossils included in this genus were first described by Sandberger
from the middle Devonian rocks of the Eifel, and referred by him to the
animal kingdom. More recently Deecke has suggested the removal of the
genus to the calcareous Siphoneae, and such a view appears perfectly
reasonable, although without more data it is not possible to speak with
absolute certainty.
Sycidium melo. (Sandb.) Fig. 32, B. The specimen represented in fig. 32,
B (i), (ii), drawn from Deecke’s figures[322], has the form of a small oval
calcareous body, 1 mm. in transverse diameter and 1–1·3 mm. in
longitudinal diameter. It is pointed at one end and flattened at the other. At
the flatter end there is a circular depression, continued into a funnel-shaped
cavity, and on the walls of this cavity there are 18–20 radially disposed ribs,
which extend over the surface of the whole body. A series of transverse ribs
intersects the vertical ribs at right angles. The calcareous wall is perforated
by numerous whorls of circular pores, and the internal cavity is a simple
undivided space. Each of these oval bodies (fig. 33, B) is probably the
segment of a thallus, and the perforations in the wall may have been
originally occupied by lateral prolongations from the unseptate axial cell of
the thallus. Sycidium bears a fairly close resemblance to the Tertiary
Ovulites.
Diplopora. Fig. 35, A and B.
This generic name was proposed by Stolley for certain branched and
curved tubes found in Silurian boulders from the North German drift[321].
The tubes have a diameter of ·5–1 mm., and are perforated by radial canals
which probably mark the position of verticils of branches given off at right
angles to the central axis. The surface of the tubes is divided into regular
hexagonal areas.
The resemblance of these Silurian fossils to Diplopora and other genera
favours their inclusion in the Verticillate Siphoneae.
Sycidium. Fig. 32, B.
The fossils included in this genus were first described by Sandberger
from the middle Devonian rocks of the Eifel, and referred by him to the
animal kingdom. More recently Deecke has suggested the removal of the
genus to the calcareous Siphoneae, and such a view appears perfectly
reasonable, although without more data it is not possible to speak with
absolute certainty.
Sycidium melo. (Sandb.) Fig. 32, B. The specimen represented in fig. 32,
B (i), (ii), drawn from Deecke’s figures[322], has the form of a small oval
calcareous body, 1 mm. in transverse diameter and 1–1·3 mm. in
longitudinal diameter. It is pointed at one end and flattened at the other. At
the flatter end there is a circular depression, continued into a funnel-shaped
cavity, and on the walls of this cavity there are 18–20 radially disposed ribs,
which extend over the surface of the whole body. A series of transverse ribs
intersects the vertical ribs at right angles. The calcareous wall is perforated
by numerous whorls of circular pores, and the internal cavity is a simple
undivided space. Each of these oval bodies (fig. 33, B) is probably the
segment of a thallus, and the perforations in the wall may have been
originally occupied by lateral prolongations from the unseptate axial cell of
the thallus. Sycidium bears a fairly close resemblance to the Tertiary
Ovulites.
Diplopora. Fig. 35, A and B.
Page 193
This genus of algae is characteristic of Triassic rocks, and is especially
abundant in Muschelkalk and Lower Keuper limestones of the Alps, Silesia,
and elsewhere. The thallus, or rather the calcareous portion of the thallus,
has the form of a thick-walled tube, with a diameter of about 4 mm., and
occasionally reaching a length of 50 mm. At one end the tube has a rounded
and closed termination, and the wall is pierced throughout its whole length
by regular whorls of fine canals. Diplopora agrees with Cymopolia in its
main features.
Fig. 35. A, B, Diplopora. × 2. C, D, Gyroporella (after Benecke. × 4). E, Calcareous
segments of Penicillus, from a specimen in the British Museum. × 5. F, a single segment
of Ovulites margaritula Lam. × 4. G, Confervites chantransioides Born. (after
Bornemann. × 150).
Fig. 35, A, affords a diagrammatic view of a Diplopora tube, and shews
the arrangement of the numerous whorls of canals. In fig. 35, B, a piece of
abundant in Muschelkalk and Lower Keuper limestones of the Alps, Silesia,
and elsewhere. The thallus, or rather the calcareous portion of the thallus,
has the form of a thick-walled tube, with a diameter of about 4 mm., and
occasionally reaching a length of 50 mm. At one end the tube has a rounded
and closed termination, and the wall is pierced throughout its whole length
by regular whorls of fine canals. Diplopora agrees with Cymopolia in its
main features.
Fig. 35. A, B, Diplopora. × 2. C, D, Gyroporella (after Benecke. × 4). E, Calcareous
segments of Penicillus, from a specimen in the British Museum. × 5. F, a single segment
of Ovulites margaritula Lam. × 4. G, Confervites chantransioides Born. (after
Bornemann. × 150).
Fig. 35, A, affords a diagrammatic view of a Diplopora tube, and shews
the arrangement of the numerous whorls of canals. In fig. 35, B, a piece of
Page 194
limestone is represented containing several Diploporas cut across
transversely and more or less obliquely. In an obliquely transverse section
of a tube perforated by horizontal canals the cavities of the canals
necessarily appear as holes or discontinuous canals in the substance of the
calcareous wall. The manner of occurrence of the specimens points to the
abundance of this genus in the Triassic seas, and suggests that the
calcareous tubes of Diplopora may have been important factors in the
building up of limestone sediments[323]. In many instances no doubt the
carbonate of lime of the thallus has been dissolved and recrystallised, and
the original form completely obliterated. As in the rocks built up largely of
calcareous Florideae (p. 185) which have lost their structure, it is a
legitimate inference that some of the limestone rocks which shew no trace
of organic structure may have been in part derived from the calcareous
incrustation of various algal genera.
Gyroporella. Fig. 35, C and D.
In this genus from the Alpine Trias the structure of the calcareous tube is
very similar to that in Diplopora, but in Gyroporella the canals form less
distinct whorls and are closed externally by a small plate, as seen in figs.
35, C and D.
As Solms-Laubach has pointed out, the branch-systems of Diplopora,
Gyroporella and other older genera are much simpler than in the Tertiary
genera Dactylopora and others[324].
A species of Gyroporella, G. bellerophontis, has recently been described
by Rothpletz[325] from Permian rocks in the Southern Tyrol. The thallus is
tubular in form and has a diameter of ·5–1 mm.
Dactylopora.
The genus Dactylopora was founded by Lamarck[326] on some fossil
specimens from the Calcaire Grossier and included among the Zoophytes.
D’Orbigny afterwards included it among the Foraminifera, and the structure
of the calcareous body has been described by Carpenter[327] and other
writers on the Foraminifera. In a specimen of Dactylopora cylindracea
Lam. from the Paris basin, for which I am indebted to Munier-Chalmas, the
tubular thallus measures 4 mm. in diameter; at the complete end it is closed
transversely and more or less obliquely. In an obliquely transverse section
of a tube perforated by horizontal canals the cavities of the canals
necessarily appear as holes or discontinuous canals in the substance of the
calcareous wall. The manner of occurrence of the specimens points to the
abundance of this genus in the Triassic seas, and suggests that the
calcareous tubes of Diplopora may have been important factors in the
building up of limestone sediments[323]. In many instances no doubt the
carbonate of lime of the thallus has been dissolved and recrystallised, and
the original form completely obliterated. As in the rocks built up largely of
calcareous Florideae (p. 185) which have lost their structure, it is a
legitimate inference that some of the limestone rocks which shew no trace
of organic structure may have been in part derived from the calcareous
incrustation of various algal genera.
Gyroporella. Fig. 35, C and D.
In this genus from the Alpine Trias the structure of the calcareous tube is
very similar to that in Diplopora, but in Gyroporella the canals form less
distinct whorls and are closed externally by a small plate, as seen in figs.
35, C and D.
As Solms-Laubach has pointed out, the branch-systems of Diplopora,
Gyroporella and other older genera are much simpler than in the Tertiary
genera Dactylopora and others[324].
A species of Gyroporella, G. bellerophontis, has recently been described
by Rothpletz[325] from Permian rocks in the Southern Tyrol. The thallus is
tubular in form and has a diameter of ·5–1 mm.
Dactylopora.
The genus Dactylopora was founded by Lamarck[326] on some fossil
specimens from the Calcaire Grossier and included among the Zoophytes.
D’Orbigny afterwards included it among the Foraminifera, and the structure
of the calcareous body has been described by Carpenter[327] and other
writers on the Foraminifera. In a specimen of Dactylopora cylindracea
Lam. from the Paris basin, for which I am indebted to Munier-Chalmas, the
tubular thallus measures 4 mm. in diameter; at the complete end it is closed
Page 195
and bluntly rounded. The wall of the tube is perforated by numerous canals,
and contains oval cavities which were no doubt originally occupied by
sporangia. The shape of the specimens is similar to that of Diplopora, but
the canals and cavities present a characteristic and more complex
appearance, when seen in a transverse section of the wall, than in the older
genus Diplopora. Gümbel has given a detailed account of this Tertiary
genus in his memoir on Die sogenannten Nulliporen[328]; he distinguishes
between Dactyloporella and Gyroporella by the existence of cavities in the
calcareous wall of the tube in the former genus, and by their absence in the
latter. The oval cavities in a Dactyloporella were originally occupied by
sporangia; in Diplopora and Gyroporella the sporangia were probably
borne externally and on an uncalcified portion of the thallus.
• • • • •
In addition to the few examples of fossil species described above there
are numerous others of considerable interest, which illustrate the great
wealth of form among the Tertiary and other representatives of the
Verticillate Siphoneae.
Reference has already been made to Vermiporella as an example of a
Silurian genus. Other genera have been described by Stolley from Silurian
boulders in the North-German drift under the names Palaeoporella,
Dasyporella and Rhabdoporella[329]; the latter genus is compared with the
Triassic Diplopora, and the two preceding with the recent Bornetella.
Schlüter has transferred a supposed Devonian Foraminiferal genus,
Coelotrochium[330], to the list of Palaeozoic Siphoneae. Munier-Chalmas
regards some of the fossils described by Saporta under the name of
Goniolina[331], and classed among the inflorescences of pro-angiospermous
plants, as examples of Jurassic Siphoneae. The shape and surface-features
of some of the examples of Goniolina suggest a comparison with Echinoid
spines, but the resemblance which many of the forms in the Sorbonne
collection present to large calcareous Siphoneae is still more striking. A
comparison of Saporta’s fig. 5, Pl. xxxiii. and fig. 4, Pl. xxxii. in volume iv.
of the Flore Jurassique, with the figures given by Solms-Laubach[332] and
Cramer[333] of species of Bornetella brings out a close similarity between
Goniolina and recent algae; the chief difference being the greater size of the
fossil forms. The possibility of confounding Echinoid spines with
and contains oval cavities which were no doubt originally occupied by
sporangia. The shape of the specimens is similar to that of Diplopora, but
the canals and cavities present a characteristic and more complex
appearance, when seen in a transverse section of the wall, than in the older
genus Diplopora. Gümbel has given a detailed account of this Tertiary
genus in his memoir on Die sogenannten Nulliporen[328]; he distinguishes
between Dactyloporella and Gyroporella by the existence of cavities in the
calcareous wall of the tube in the former genus, and by their absence in the
latter. The oval cavities in a Dactyloporella were originally occupied by
sporangia; in Diplopora and Gyroporella the sporangia were probably
borne externally and on an uncalcified portion of the thallus.
• • • • •
In addition to the few examples of fossil species described above there
are numerous others of considerable interest, which illustrate the great
wealth of form among the Tertiary and other representatives of the
Verticillate Siphoneae.
Reference has already been made to Vermiporella as an example of a
Silurian genus. Other genera have been described by Stolley from Silurian
boulders in the North-German drift under the names Palaeoporella,
Dasyporella and Rhabdoporella[329]; the latter genus is compared with the
Triassic Diplopora, and the two preceding with the recent Bornetella.
Schlüter has transferred a supposed Devonian Foraminiferal genus,
Coelotrochium[330], to the list of Palaeozoic Siphoneae. Munier-Chalmas
regards some of the fossils described by Saporta under the name of
Goniolina[331], and classed among the inflorescences of pro-angiospermous
plants, as examples of Jurassic Siphoneae. The shape and surface-features
of some of the examples of Goniolina suggest a comparison with Echinoid
spines, but the resemblance which many of the forms in the Sorbonne
collection present to large calcareous Siphoneae is still more striking. A
comparison of Saporta’s fig. 5, Pl. xxxiii. and fig. 4, Pl. xxxii. in volume iv.
of the Flore Jurassique, with the figures given by Solms-Laubach[332] and
Cramer[333] of species of Bornetella brings out a close similarity between
Goniolina and recent algae; the chief difference being the greater size of the
fossil forms. The possibility of confounding Echinoid spines with
Page 196
calcareous Siphoneae is illustrated by Rothpletz[334], who has expressed the
opinion that Gümbel’s Haploporella fasciculata is not an alga but the spine
of a sea-urchin.
Among Cretaceous forms, in addition to Goniolina, which passes
upwards from Jurassic rocks, Triploporella[335] and other genera have been
recorded.
Uteria[336] is an interesting type of Tertiary genera; it occurs in the form of
barrel-shaped rings, which are probably the detached segments of a form in
which the central axial cell was encrusted with carbonate of lime, but the
sporangia and the whorls of branches differed from those of Cymopolia in
being without a calcareous investment.
b. Confervoideae.
Without attempting to describe at length the fossil forms referred to this
division of the Chlorophyceae, there is one fossil which deserves a passing
notice. Brongniart in 1828[337] instituted the generic term Confervites for
filamentous fossils resembling recent species of confervoid algae.
Numerous fossils have been referred to this genus by different authors, but
they are for the most part valueless and need not be further considered. In
1887 Bornemann described some new forms which he referred to this genus
from the Cambrian rocks of Sardinia. He describes the red marble of San
Pietra, near Masne, as being in places full of the delicate remains of algae
having the form of branched filaments, and appearing in sections of the
rock as white lines on a dark crystalline matrix. In fig. 35, G, one of these
Sardinian specimens is represented. This form is named Confervites
Chantransioides[338]; the thallus consists of branched cell-filaments, having
a breadth of 6–7µ, and composed of ovate cells. It is possible that this is a
fragment of a Cambrian alga, but the figures and descriptions do not afford
by any means convincing evidence. From post-Tertiary beds various genera,
such as Vaucheria and others, have been recorded, but they possess but little
botanical value.
C. INCERTAE SEDIS.
Fossils in Boghead ‘Coal’ referred by some authors to the Chlorophyceae.
opinion that Gümbel’s Haploporella fasciculata is not an alga but the spine
of a sea-urchin.
Among Cretaceous forms, in addition to Goniolina, which passes
upwards from Jurassic rocks, Triploporella[335] and other genera have been
recorded.
Uteria[336] is an interesting type of Tertiary genera; it occurs in the form of
barrel-shaped rings, which are probably the detached segments of a form in
which the central axial cell was encrusted with carbonate of lime, but the
sporangia and the whorls of branches differed from those of Cymopolia in
being without a calcareous investment.
b. Confervoideae.
Without attempting to describe at length the fossil forms referred to this
division of the Chlorophyceae, there is one fossil which deserves a passing
notice. Brongniart in 1828[337] instituted the generic term Confervites for
filamentous fossils resembling recent species of confervoid algae.
Numerous fossils have been referred to this genus by different authors, but
they are for the most part valueless and need not be further considered. In
1887 Bornemann described some new forms which he referred to this genus
from the Cambrian rocks of Sardinia. He describes the red marble of San
Pietra, near Masne, as being in places full of the delicate remains of algae
having the form of branched filaments, and appearing in sections of the
rock as white lines on a dark crystalline matrix. In fig. 35, G, one of these
Sardinian specimens is represented. This form is named Confervites
Chantransioides[338]; the thallus consists of branched cell-filaments, having
a breadth of 6–7µ, and composed of ovate cells. It is possible that this is a
fragment of a Cambrian alga, but the figures and descriptions do not afford
by any means convincing evidence. From post-Tertiary beds various genera,
such as Vaucheria and others, have been recorded, but they possess but little
botanical value.
C. INCERTAE SEDIS.
Fossils in Boghead ‘Coal’ referred by some authors to the Chlorophyceae.
Page 197
During the last few years much has been written by two French authors,
Dr Renault and Prof. Bertrand, on the subject of the so-called Boghead of
France, Scotland, and other countries. They hold the view that the formation
of the extensive beds of this carbonaceous material was due to the
accumulation and preservation of enormous numbers of minute algae which
lived in Permo-Carboniferous lakes.
In an article contributed to Science-Progress in 1895 I ventured to
express doubts as to the correctness of the conclusions of MM. Renault and
Bertrand[339]. Since then Prof. Bertrand has very kindly demonstrated to me
many of his microscopic preparations of various Bogheads, and I am
indebted to Prof. Bayley Balfour of Edinburgh for an opportunity of
examining a series of sections of the Scotch Boghead. The examination of
these specimens has convinced me of the difficulties of the problems which
many investigators have tried to solve, but it has by no means led me to
entirely adopt the views expressed by MM. Bertrand and Renault.
BOGHEAD.
The Boghead or Torbanite of Scotland was rendered famous by a
protracted lawsuit tried in Edinburgh from July 29th to August 4th, 1853. A
lease had been granted by Mr and Mrs Gillespie, of Torbanehill, in
Fifeshire, to Messrs James Russell and Son, coal-masters of Falkirk, of “the
whole coal, ironstone, iron-ore, limestone, and fire-clay (but not to
comprehend copper, or any other minerals whatsoever, except those
specified) with lands of Torbanehill[340].” After the Boghead had been
worked for two years the Gillespies challenged the right of Messrs Russell,
and argued that the valuable mineral Torbanite was not included among the
substances named in the agreement. The defendants maintained that it was a
coal, known as gas-, cannel- or parrot-coal. A verdict was given for the
defendants. Some of the scientific experts who gave evidence at the trial
considered that the Boghead afforded indications of organic structure, while
others regarded it as essentially mineral in origin.
The Torbanite or Boghead is a close-grained brown rock, of peculiar
toughness and having a subconchoidal fracture. It contains about 65%
carbon, with some hydrogen, oxygen, sulphur, and mineral substances. A
thin section examined under the microscope presents the appearance of a
dark and amorphous matrix, containing numerous oval, spherical and
irregularly shaped bright orange-yellow patches. Fig. 36, 1 shows the
Dr Renault and Prof. Bertrand, on the subject of the so-called Boghead of
France, Scotland, and other countries. They hold the view that the formation
of the extensive beds of this carbonaceous material was due to the
accumulation and preservation of enormous numbers of minute algae which
lived in Permo-Carboniferous lakes.
In an article contributed to Science-Progress in 1895 I ventured to
express doubts as to the correctness of the conclusions of MM. Renault and
Bertrand[339]. Since then Prof. Bertrand has very kindly demonstrated to me
many of his microscopic preparations of various Bogheads, and I am
indebted to Prof. Bayley Balfour of Edinburgh for an opportunity of
examining a series of sections of the Scotch Boghead. The examination of
these specimens has convinced me of the difficulties of the problems which
many investigators have tried to solve, but it has by no means led me to
entirely adopt the views expressed by MM. Bertrand and Renault.
BOGHEAD.
The Boghead or Torbanite of Scotland was rendered famous by a
protracted lawsuit tried in Edinburgh from July 29th to August 4th, 1853. A
lease had been granted by Mr and Mrs Gillespie, of Torbanehill, in
Fifeshire, to Messrs James Russell and Son, coal-masters of Falkirk, of “the
whole coal, ironstone, iron-ore, limestone, and fire-clay (but not to
comprehend copper, or any other minerals whatsoever, except those
specified) with lands of Torbanehill[340].” After the Boghead had been
worked for two years the Gillespies challenged the right of Messrs Russell,
and argued that the valuable mineral Torbanite was not included among the
substances named in the agreement. The defendants maintained that it was a
coal, known as gas-, cannel- or parrot-coal. A verdict was given for the
defendants. Some of the scientific experts who gave evidence at the trial
considered that the Boghead afforded indications of organic structure, while
others regarded it as essentially mineral in origin.
The Torbanite or Boghead is a close-grained brown rock, of peculiar
toughness and having a subconchoidal fracture. It contains about 65%
carbon, with some hydrogen, oxygen, sulphur, and mineral substances. A
thin section examined under the microscope presents the appearance of a
dark and amorphous matrix, containing numerous oval, spherical and
irregularly shaped bright orange-yellow patches. Fig. 36, 1 shows the
Page 198
manner of occurrence of the yellow bodies in a piece of Scotch Boghead, as
seen in a slightly magnified horizontal section. Under a higher power the
light patches in the figure reveal traces of a faint radial striation, which in
some cases suggests the occurrence of a number of oval or polygonal cells.
The Autun Boghead possesses practically the same structure. The yellow
bodies are often sufficiently abundant to impart a bright yellow colour to a
thin section. If the section is vertical the coloured bodies are seen to be
arranged in more or less regular layers parallel to the plane of bedding.
The Kerosene shale of New South Wales agrees closely with the Scotch
and French Boghead; it is approximately of the same geological age, and is
largely made up of orange or yellow bodies similar to those of the European
Boghead, but much more clearly preserved.
The nature and manner of formation of the various forms of coal should
be dealt with in a later chapter devoted to the subject of plants as rock-
builders, but in view of the recent statements as to the algal nature of these
bituminous deposits it may not be out of place to state briefly the main
conclusions of the French authors.
MM. Renault and Bertrand regard each of the yellow bodies in the
European and Australian Boghead as the thallus of an alga. To the form
which is most abundant in the Kerosene shale they have given the generic
name of Reinschia, while that in the Scotch and French Boghead is named
Pila.
Reinschia. Fig. 36, 3.
A section of a piece of Kerosene shale at right angles to the bedding
appears to be made up of fairly regular layers of flattened elliptical sacs of
an orange or yellow colour. Each sac or thallus is about 300µ in length and
150µ broad (fig. 36, 3). A single row of cells constitutes the wall
surrounding the central globular cavity. The cells are more or less pyriform
in shape, and the cell-cavities are filled with a dark substance, described by
Renault and Bertrand as protoplasm, and the cell-walls are fairly thick. In
some of the larger specimens there are often found a few smaller sacs
enclosed in the cavity of the partially disorganised mother-thallus. In the
larger specimens the wall is usually invaginated in several places, giving the
whole thallus a lobed or brain-like appearance. The supposed alga, which
seen in a slightly magnified horizontal section. Under a higher power the
light patches in the figure reveal traces of a faint radial striation, which in
some cases suggests the occurrence of a number of oval or polygonal cells.
The Autun Boghead possesses practically the same structure. The yellow
bodies are often sufficiently abundant to impart a bright yellow colour to a
thin section. If the section is vertical the coloured bodies are seen to be
arranged in more or less regular layers parallel to the plane of bedding.
The Kerosene shale of New South Wales agrees closely with the Scotch
and French Boghead; it is approximately of the same geological age, and is
largely made up of orange or yellow bodies similar to those of the European
Boghead, but much more clearly preserved.
The nature and manner of formation of the various forms of coal should
be dealt with in a later chapter devoted to the subject of plants as rock-
builders, but in view of the recent statements as to the algal nature of these
bituminous deposits it may not be out of place to state briefly the main
conclusions of the French authors.
MM. Renault and Bertrand regard each of the yellow bodies in the
European and Australian Boghead as the thallus of an alga. To the form
which is most abundant in the Kerosene shale they have given the generic
name of Reinschia, while that in the Scotch and French Boghead is named
Pila.
Reinschia. Fig. 36, 3.
A section of a piece of Kerosene shale at right angles to the bedding
appears to be made up of fairly regular layers of flattened elliptical sacs of
an orange or yellow colour. Each sac or thallus is about 300µ in length and
150µ broad (fig. 36, 3). A single row of cells constitutes the wall
surrounding the central globular cavity. The cells are more or less pyriform
in shape, and the cell-cavities are filled with a dark substance, described by
Renault and Bertrand as protoplasm, and the cell-walls are fairly thick. In
some of the larger specimens there are often found a few smaller sacs
enclosed in the cavity of the partially disorganised mother-thallus. In the
larger specimens the wall is usually invaginated in several places, giving the
whole thallus a lobed or brain-like appearance. The supposed alga, which
Page 199
makes up ⁹⁄₁₀ths of the contents of a block of Kerosene shale, is named
Reinschia Australis; it is regarded by the authors of the species as nearly
related to the Hydrodictyaceae or Volvocineae.
Fig. 36, 1. Section of a piece of Scotch Torbanite. Slightly enlarged. 2. Pila bibractensis from
the Autun Boghead, × 282 (after Bertrand). 3. Reinschia Australis, from the Kerosene
shale of New South Wales, × 592 (after Bertrand).
In the Kerosene shale from certain localities in New South Wales
Bertrand recognises a second form of thallus, which he refers to the genus
Pila, characteristic of the European Bogheads.
Pila. Fig. 36, 2.
The “thallus” characteristic of the Scotch Boghead has been named Pila
scotica, and that of the Autun Boghead, Pila bibractensis.
In the latter form, which has been studied in more detail by MM. Renault
and Bertrand, the thallus consists of about 6–700 cells, and is irregularly
ellipsoidal in form, from ·189–·225mm. in length, and ·136–·160mm.
broad. The surface-cells are radially disposed and pyramidal in shape, the
internal cells are polygonal in outline and less regularly arranged (fig. 36,
2). The Pila thalli make up ¾ths of the mass in an average sample of the
Autun Boghead. The Autun Boghead often contains siliceous nodules, and
sections of these occasionally include cells of a Pila in which the
protoplasmic contents and nuclei have been described by the French
Reinschia Australis; it is regarded by the authors of the species as nearly
related to the Hydrodictyaceae or Volvocineae.
Fig. 36, 1. Section of a piece of Scotch Torbanite. Slightly enlarged. 2. Pila bibractensis from
the Autun Boghead, × 282 (after Bertrand). 3. Reinschia Australis, from the Kerosene
shale of New South Wales, × 592 (after Bertrand).
In the Kerosene shale from certain localities in New South Wales
Bertrand recognises a second form of thallus, which he refers to the genus
Pila, characteristic of the European Bogheads.
Pila. Fig. 36, 2.
The “thallus” characteristic of the Scotch Boghead has been named Pila
scotica, and that of the Autun Boghead, Pila bibractensis.
In the latter form, which has been studied in more detail by MM. Renault
and Bertrand, the thallus consists of about 6–700 cells, and is irregularly
ellipsoidal in form, from ·189–·225mm. in length, and ·136–·160mm.
broad. The surface-cells are radially disposed and pyramidal in shape, the
internal cells are polygonal in outline and less regularly arranged (fig. 36,
2). The Pila thalli make up ¾ths of the mass in an average sample of the
Autun Boghead. The Autun Boghead often contains siliceous nodules, and
sections of these occasionally include cells of a Pila in which the
protoplasmic contents and nuclei have been described by the French
Page 200
authors. The evidence for the existence of these supposed nuclei is,
however, not entirely satisfactory; sections of silicified thalli which were
shown to me by Prof. Bertrand did not satisfy me as to the minute
histological details recognised by Bertrand and Renault.
The species of Pila are compared with the recent genus Celastrum, and
regarded as most nearly allied to the Chroococcaceae or Pleurococcaceae
among recent algae. Prof. Bornet[341] has suggested Gomphosphaeria as a
genus which presents a resemblance to the Autun Pila.
In addition to the Bogheads of Autun, Torbanehill, and New South Wales,
there are similar Palaeozoic deposits in Russia, America, and various other
parts of the world. Full details of the structure of Boghead and the supposed
algae referred to Reinschia, Pila, and other genera will be found in the
writings of Bertrand and Renault[342].
The Kerosene shale of New South Wales affords the most striking and
well-preserved examples of the cellular orange and yellow bodies referred
to as the globular thalli of algae. It is almost impossible to conceive a purely
inorganic material assuming such forms as those which occur in the
Australian Boghead. On the other hand, it is hardly less easy to understand
the possibility of such explanations as have been suggested of the organic
origin of these characteristic bodies.
The ground-mass or matrix of the Boghead is referred to a brown ulmic
precipitate thrown down on the floor of a Permian or Carboniferous lake,
probably under the action of calcareous water. In this material there
accumulated countless thalli of minute gelatinous algae, which probably at
certain seasons completely covered the surface of the waters, as the fleurs
d’eau in many of our fresh-water lakes. In addition to the thalli of Reinschia
and Pila the Bogheads contain a few remains of various plant fragments,
pollen-grains, and pieces of wood. Fish-scales and the coprolites of reptiles
and fishes occur in some of the beds. On a piece of Kerosene shale in the
Woodwardian Museum, Cambridge, there are two well-preserved graphitic
impressions of the tongue-shaped fronds of Glossopteris Browniana,
Brongn. There can be little doubt that the beds of Boghead were deposited
under water as members of a regular sequence of sedimentary strata. The
yellow bodies which form so great a part of the beds are practically all of
the same type. Reinschia and Pila cannot always be distinguished, and it
however, not entirely satisfactory; sections of silicified thalli which were
shown to me by Prof. Bertrand did not satisfy me as to the minute
histological details recognised by Bertrand and Renault.
The species of Pila are compared with the recent genus Celastrum, and
regarded as most nearly allied to the Chroococcaceae or Pleurococcaceae
among recent algae. Prof. Bornet[341] has suggested Gomphosphaeria as a
genus which presents a resemblance to the Autun Pila.
In addition to the Bogheads of Autun, Torbanehill, and New South Wales,
there are similar Palaeozoic deposits in Russia, America, and various other
parts of the world. Full details of the structure of Boghead and the supposed
algae referred to Reinschia, Pila, and other genera will be found in the
writings of Bertrand and Renault[342].
The Kerosene shale of New South Wales affords the most striking and
well-preserved examples of the cellular orange and yellow bodies referred
to as the globular thalli of algae. It is almost impossible to conceive a purely
inorganic material assuming such forms as those which occur in the
Australian Boghead. On the other hand, it is hardly less easy to understand
the possibility of such explanations as have been suggested of the organic
origin of these characteristic bodies.
The ground-mass or matrix of the Boghead is referred to a brown ulmic
precipitate thrown down on the floor of a Permian or Carboniferous lake,
probably under the action of calcareous water. In this material there
accumulated countless thalli of minute gelatinous algae, which probably at
certain seasons completely covered the surface of the waters, as the fleurs
d’eau in many of our fresh-water lakes. In addition to the thalli of Reinschia
and Pila the Bogheads contain a few remains of various plant fragments,
pollen-grains, and pieces of wood. Fish-scales and the coprolites of reptiles
and fishes occur in some of the beds. On a piece of Kerosene shale in the
Woodwardian Museum, Cambridge, there are two well-preserved graphitic
impressions of the tongue-shaped fronds of Glossopteris Browniana,
Brongn. There can be little doubt that the beds of Boghead were deposited
under water as members of a regular sequence of sedimentary strata. The
yellow bodies which form so great a part of the beds are practically all of
the same type. Reinschia and Pila cannot always be distinguished, and it
Page 201
would seem that there are no adequate grounds for instituting two distinct
genera and referring them to different families of recent algae.
Stated briefly, my conclusion is that the algae of the French authors may
be definite organic bodies, but it is unwise to attempt to determine their
affinities within such narrow limits as have been referred to in the above
résumé. The structure of the bituminous deposits is worthy of careful study,
and it is by no means impossible that further research might lead us to
accept the view of the earlier investigators, that the brightly coloured
organic-like bodies may be inorganic in origin.
D. RHODOPHYCEAE. (Florideae. Red Algae.)
The thallus of the members of this group assumes various forms, and
consists of branched cell-filaments of a more or less complex structure.
Cells of the thallus contain a red colouring matter in addition to the green
chlorophyll. The reproduction is asexual and sexual; the formation of
asexual reproductive cells (tetraspores) in groups of four in sporangia is a
characteristic method of reproduction. Sexual reproduction is effected by
means of distinct male and female cells.
With the exception of a few fresh-water genera all the red algae are
marine. The Rhodophyceae, like the Cyanophyceae and Chlorophyceae,
include a shell-boring form which has been found in the common razor-
shell[343]. Several genera live as endophytes in the tissues of other algae. The
recent species of this section of algae are characteristic of temperate and
tropical seas. One subdivision of the red algae, the Corallinaceae, is
extremely important from a geological point of view and must be dealt with
in some detail.
Corallinaceae.
The thallus is usually encrusted with carbonate of lime; it is of a
branched cylindrical form in the well-known Corallina officinalis, Linn. of
the British coasts, of an encrusting and foliaceous type, in the genus
Lithophyllum, and of a more coral-like form in the genus Lithothamnion.
The reproductive organs occur in conceptacles, having the form of small
depressed cavities in the thallus, or projecting as warty swellings above the
surface of the plant. Asexual reproduction is by means of tetraspores
genera and referring them to different families of recent algae.
Stated briefly, my conclusion is that the algae of the French authors may
be definite organic bodies, but it is unwise to attempt to determine their
affinities within such narrow limits as have been referred to in the above
résumé. The structure of the bituminous deposits is worthy of careful study,
and it is by no means impossible that further research might lead us to
accept the view of the earlier investigators, that the brightly coloured
organic-like bodies may be inorganic in origin.
D. RHODOPHYCEAE. (Florideae. Red Algae.)
The thallus of the members of this group assumes various forms, and
consists of branched cell-filaments of a more or less complex structure.
Cells of the thallus contain a red colouring matter in addition to the green
chlorophyll. The reproduction is asexual and sexual; the formation of
asexual reproductive cells (tetraspores) in groups of four in sporangia is a
characteristic method of reproduction. Sexual reproduction is effected by
means of distinct male and female cells.
With the exception of a few fresh-water genera all the red algae are
marine. The Rhodophyceae, like the Cyanophyceae and Chlorophyceae,
include a shell-boring form which has been found in the common razor-
shell[343]. Several genera live as endophytes in the tissues of other algae. The
recent species of this section of algae are characteristic of temperate and
tropical seas. One subdivision of the red algae, the Corallinaceae, is
extremely important from a geological point of view and must be dealt with
in some detail.
Corallinaceae.
The thallus is usually encrusted with carbonate of lime; it is of a
branched cylindrical form in the well-known Corallina officinalis, Linn. of
the British coasts, of an encrusting and foliaceous type, in the genus
Lithophyllum, and of a more coral-like form in the genus Lithothamnion.
The reproductive organs occur in conceptacles, having the form of small
depressed cavities in the thallus, or projecting as warty swellings above the
surface of the plant. Asexual reproduction is by means of tetraspores
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formed in conceptacles resembling those containing the sexual cells. The
Corallinaceae may be subdivided into the two families Melobesieae and
Corallineae[344].
Melobesieae. Thallus encrusting, leaf- or coral-like; unsegmented.
(Melobesia, Lithophyllum, Lithothamnion.)
Corallineae. Cylindrical filamentous and segmented thallus.
(Amphiroa and Corallina.)
The genus Corallina is the best known British representative of the
Corallinaceae. With other members of the group it was long regarded as a
coralline animal, and it is only comparatively recently that the plant-nature
of these forms has been generally admitted. Lithophyllum, Lithothamnion,
Melobesia, and other genera of the Corallinaceae and some of the
Siphoneae play a very important part in the building and cementing of
coral-reefs. The pink or rose-coloured calcareous thallus of some of these
calcareous algae or Nullipores imparts to coral-reefs a characteristic
appearance. In some cases, indeed, the coral-reefs are very largely
composed of algae. Saville Kent[345] describes the Corallines or Nullipores
of the Australian Barrier-reef as furnishing a considerable quota towards the
composition of the coral rock. Mr Stanley Gardiner, who accompanied the
coral-boring expedition to the island of Funafuti, has kindly allowed me to
quote the following extract from his notes, which affords an interesting
example of the importance of calcareous algae as reef-building organisms.
“It is quite a misnomer to speak of the outer edge of a reef like this (Rotuma
Island) as being formed of coral. It would be far better to call it a Nullipore
reef, as it is completely encrusted by these algae, while outside in the
perfectly clear water, 10 to 15 fathoms in depth, the bottom has a most
brilliant appearance from masses of red, white and pink Nullipores, with
only a stray coral here and there.”
Agassiz[346] has given an account of the occurrence of immense masses of
Nullipores (Udotea, Halimeda etc.) in the Florida reefs; his description is
illustrated by good figures of these algae.
In the Mediterranean there are true Nullipore reefs, which are interesting
geologically as well as botanically. Walther[347] has described one of these
limestone-banks in the Gulf of Naples which occurs about 1 kilometre from
the coast and 30 metres below the surface of the water. Every dredging, he
Corallinaceae may be subdivided into the two families Melobesieae and
Corallineae[344].
Melobesieae. Thallus encrusting, leaf- or coral-like; unsegmented.
(Melobesia, Lithophyllum, Lithothamnion.)
Corallineae. Cylindrical filamentous and segmented thallus.
(Amphiroa and Corallina.)
The genus Corallina is the best known British representative of the
Corallinaceae. With other members of the group it was long regarded as a
coralline animal, and it is only comparatively recently that the plant-nature
of these forms has been generally admitted. Lithophyllum, Lithothamnion,
Melobesia, and other genera of the Corallinaceae and some of the
Siphoneae play a very important part in the building and cementing of
coral-reefs. The pink or rose-coloured calcareous thallus of some of these
calcareous algae or Nullipores imparts to coral-reefs a characteristic
appearance. In some cases, indeed, the coral-reefs are very largely
composed of algae. Saville Kent[345] describes the Corallines or Nullipores
of the Australian Barrier-reef as furnishing a considerable quota towards the
composition of the coral rock. Mr Stanley Gardiner, who accompanied the
coral-boring expedition to the island of Funafuti, has kindly allowed me to
quote the following extract from his notes, which affords an interesting
example of the importance of calcareous algae as reef-building organisms.
“It is quite a misnomer to speak of the outer edge of a reef like this (Rotuma
Island) as being formed of coral. It would be far better to call it a Nullipore
reef, as it is completely encrusted by these algae, while outside in the
perfectly clear water, 10 to 15 fathoms in depth, the bottom has a most
brilliant appearance from masses of red, white and pink Nullipores, with
only a stray coral here and there.”
Agassiz[346] has given an account of the occurrence of immense masses of
Nullipores (Udotea, Halimeda etc.) in the Florida reefs; his description is
illustrated by good figures of these algae.
In the Mediterranean there are true Nullipore reefs, which are interesting
geologically as well as botanically. Walther[347] has described one of these
limestone-banks in the Gulf of Naples which occurs about 1 kilometre from
the coast and 30 metres below the surface of the water. Every dredging, he
Page 203
says, brings up numberless masses of Lithothamnion fasciculatum
(Lamarck), and L. crassum (Phil.). Between the branches of the algae,
gasteropods and other animals become completely enclosed by the growing
plants, while diatoms, foraminifera, and other forms of life are abundant.
Water percolating through the mass gradually destroys the structure of the
algal thalli, and in places reduces the whole bank to a compact structureless
limestone.
The same author[348] has also called attention to the importance of
Lithophyllum as a constructive element in the coral-reefs off the Sinai
peninsula.
Lithothamnion a typical genus of the Corallinaceae may be briefly
described.
Lithothamnion. Fig. 37.
Philippi[349] was the first writer to describe this and other genera as plants.
He gave the following definition of Lithothamnion:
“Stirps calcarea rigida, e ramis cylindricis vel compressiusculis dichotoma ramosis constans.”
The thallus of Lithothamnion grows attached to the face of a rock or
other foundation, and forms a hard, stony mass, assuming various coralline
shapes. The exposed face may have the form of numerous short branches or
of an irregular warty surface.
In section (fig. 37, A.) the lower part of the thallus is seen to be made up
of rows of cells radiating out from a central point, and the upper portion
consists of vertical and horizontal rows of cells. The whole body is divided
up into a large number of small cells by anticlinal and periclinal walls, and
possesses an evident cellular as distinct from a tubular structure.
Conceptacles containing reproductive organs are either sunk in the thallus
or project above the surface. The two types of structure in a single thallus
are shown in fig. 37, A, also a conceptacle containing tetraspores.
(Lamarck), and L. crassum (Phil.). Between the branches of the algae,
gasteropods and other animals become completely enclosed by the growing
plants, while diatoms, foraminifera, and other forms of life are abundant.
Water percolating through the mass gradually destroys the structure of the
algal thalli, and in places reduces the whole bank to a compact structureless
limestone.
The same author[348] has also called attention to the importance of
Lithophyllum as a constructive element in the coral-reefs off the Sinai
peninsula.
Lithothamnion a typical genus of the Corallinaceae may be briefly
described.
Lithothamnion. Fig. 37.
Philippi[349] was the first writer to describe this and other genera as plants.
He gave the following definition of Lithothamnion:
“Stirps calcarea rigida, e ramis cylindricis vel compressiusculis dichotoma ramosis constans.”
The thallus of Lithothamnion grows attached to the face of a rock or
other foundation, and forms a hard, stony mass, assuming various coralline
shapes. The exposed face may have the form of numerous short branches or
of an irregular warty surface.
In section (fig. 37, A.) the lower part of the thallus is seen to be made up
of rows of cells radiating out from a central point, and the upper portion
consists of vertical and horizontal rows of cells. The whole body is divided
up into a large number of small cells by anticlinal and periclinal walls, and
possesses an evident cellular as distinct from a tubular structure.
Conceptacles containing reproductive organs are either sunk in the thallus
or project above the surface. The two types of structure in a single thallus
are shown in fig. 37, A, also a conceptacle containing tetraspores.
Page 204
Fig. 37, A. Section of a recent Lithothamnion (after Rosanoff[350], × 200). B. Section of
Lithothamnion suganum, Roth (after Rothpletz[351], × 100). C. A conceptacle with
tetraspores from a Tertiary Lithothamnion (after Früh[352], × 300). D. Sphaerocodium
Bornemanni Roth, (after Rothpletz, × 150).
In the closely allied Lithophyllum the thallus is encrusting, and in section
it presents the same appearance as the lower part of a Lithothamnion
thallus.
Species of Lithothamnion occur in the Mediterranean Sea, and are
abundant in the arctic regions[353], while on the British coasts the genus is
represented by four species[354]. Some large specimens of Lithothamnion and
Lithophyllum are exhibited in one of the show-cases in the botanical
department of the British Museum. For the best figures and descriptions of
recent species reference should be made to the works of Hauck, Rosanoff,
Rosenvinge, Kjellman and Solms-Laubach[355].
It is to be expected that such calcareous algae as Lithothamnion should
be widely represented by fossil forms. In addition to the botanical
importance of the data furnished by the fossil species as to the past history
of the Corallinaceae, there is much of geological interest to be learnt from a
study of the manner of occurrence of both the fossil and recent
representatives. As agents of rock-building the coralline algae are especially
Lithothamnion suganum, Roth (after Rothpletz[351], × 100). C. A conceptacle with
tetraspores from a Tertiary Lithothamnion (after Früh[352], × 300). D. Sphaerocodium
Bornemanni Roth, (after Rothpletz, × 150).
In the closely allied Lithophyllum the thallus is encrusting, and in section
it presents the same appearance as the lower part of a Lithothamnion
thallus.
Species of Lithothamnion occur in the Mediterranean Sea, and are
abundant in the arctic regions[353], while on the British coasts the genus is
represented by four species[354]. Some large specimens of Lithothamnion and
Lithophyllum are exhibited in one of the show-cases in the botanical
department of the British Museum. For the best figures and descriptions of
recent species reference should be made to the works of Hauck, Rosanoff,
Rosenvinge, Kjellman and Solms-Laubach[355].
It is to be expected that such calcareous algae as Lithothamnion should
be widely represented by fossil forms. In addition to the botanical
importance of the data furnished by the fossil species as to the past history
of the Corallinaceae, there is much of geological interest to be learnt from a
study of the manner of occurrence of both the fossil and recent
representatives. As agents of rock-building the coralline algae are especially
Page 205
important. The late Prof. Unger[356] in 1858 gave an account of the so-called
Leithakalk of the Tertiary Vienna basin, and recognised the importance of
fossil algae as rock-forming organisms. The Miocene Leithakalk, which is
widely used in Vienna as a building stone[357], consists in part of limestone
rocks consisting to a large extent of Lithothamnion.
Since the publication of Unger’s work several writers have described
numerous fossil species of Lithothamnion from various geological horizons.
A few examples will suffice to illustrate the range and structure of this and
other genera of the Corallinaceae. In dealing with the fossil species it is
often impossible to make use of those characters which are of primary
importance in the recognition of recent species. The fossil thallus is usually
too intimately associated with the surrounding rock to admit of any use
being made of external form as a diagnostic feature. The size and form of
the cells must be taken as the chief basis on which to determine specific
differences. In the absence of conceptacles or reproductive organs it is not
always easy to distinguish calcareous algae from fossil Hydrozoa or
Bryozoa. In many instances, however, apart from the nature and size of the
elements composing the thallus, the conceptacles afford a valuable aid to
identification. An example of a fossil conceptacle containing tetraspores is
shown in fig. 37, C; it is from a Tertiary species of Lithothamnion,
described by Früh from Montévraz in Switzerland.
• • • • •
1. Lithothamnion mamillosum Gümb. Fig. 32, A (i) and (ii). (p. 155.) This
species was first recorded by Gümbel[358] from the Upper Cretaceous
(Danian) rocks of Petersbergs, near Maëstricht, on the Belgian frontier. It
was originally described as a Bryozoan. The thallus has the form of an
encrusting calcareous structure bearing on its upper surface thick nodular
branches, as shown in fig. 32, A (ii); in section, A (i), the thallus consists of
a regular series of rectangular cells.
The specific name mamillosum has also been given to a recent species by
Hauck[359], but probably in ignorance of the existence of Gümbel’s
Cretaceous species.
• • • • •
Leithakalk of the Tertiary Vienna basin, and recognised the importance of
fossil algae as rock-forming organisms. The Miocene Leithakalk, which is
widely used in Vienna as a building stone[357], consists in part of limestone
rocks consisting to a large extent of Lithothamnion.
Since the publication of Unger’s work several writers have described
numerous fossil species of Lithothamnion from various geological horizons.
A few examples will suffice to illustrate the range and structure of this and
other genera of the Corallinaceae. In dealing with the fossil species it is
often impossible to make use of those characters which are of primary
importance in the recognition of recent species. The fossil thallus is usually
too intimately associated with the surrounding rock to admit of any use
being made of external form as a diagnostic feature. The size and form of
the cells must be taken as the chief basis on which to determine specific
differences. In the absence of conceptacles or reproductive organs it is not
always easy to distinguish calcareous algae from fossil Hydrozoa or
Bryozoa. In many instances, however, apart from the nature and size of the
elements composing the thallus, the conceptacles afford a valuable aid to
identification. An example of a fossil conceptacle containing tetraspores is
shown in fig. 37, C; it is from a Tertiary species of Lithothamnion,
described by Früh from Montévraz in Switzerland.
• • • • •
1. Lithothamnion mamillosum Gümb. Fig. 32, A (i) and (ii). (p. 155.) This
species was first recorded by Gümbel[358] from the Upper Cretaceous
(Danian) rocks of Petersbergs, near Maëstricht, on the Belgian frontier. It
was originally described as a Bryozoan. The thallus has the form of an
encrusting calcareous structure bearing on its upper surface thick nodular
branches, as shown in fig. 32, A (ii); in section, A (i), the thallus consists of
a regular series of rectangular cells.
The specific name mamillosum has also been given to a recent species by
Hauck[359], but probably in ignorance of the existence of Gümbel’s
Cretaceous species.
• • • • •
Page 206
2. Lithothamnion suganum Roth. Fig. 37, B. The section of this form
given in fig. 37, B shows three oval conceptacles filled with crystalline
material. The two lower conceptacles originally communicated with the
surface of the thallus, but as in recent species the deeper portions of the
algal body became covered over by additions to the surface, forming merely
dead foundations for new and overlying living tissues.
The cells of the thallus have a breadth of 7–9µ, and a length of 9–12µ.
The specimen was obtained from a Lithothamnion bank, probably of
Upper Oligocene age, in Val Sugana[360], in the Austrian Tyrol.
Numerous other species of Jurassic, Cretaceous and Tertiary age might
be quoted, but the above may suffice to illustrate the general characters and
mode of occurrence of the genus. It is important that the student should
become familiar with the Lithothamnion and Lithophyllum types of thallus,
in view of their frequent occurrence in crystalline limestone rocks and in
such comparatively recent deposits as those of upraised coral-reefs. The
coral-rock of Barbados and other West-Indian islands affords a good
illustration of the manner of occurrence of fossil coralline algae in
association with corals and other organisms[361].
In the fossil species of Lithothamnion hitherto recorded there do not
appear to be any important features in which they differ from recent forms;
the geological history of the genus so far as it is known, favours the view
that the generic characters are of considerable antiquity.
Solenopora. Fig. 38.
Mr A. Brown[362], of Aberdeen, has recently brought forward good
evidence for including various calcareous fossils, described by several
authors under different names and referred to various genera of fossil
animals, in the genus Solenopora, which he places among the coralline
algae.
Species of this genus have been described from England, Scotland,
Esthonia, Russia, and other countries. The geological range of Solenopora
appears to be from Ordovician to Jurassic rocks; in some cases it is an
important constituent of beds of limestone.
• • • • •
given in fig. 37, B shows three oval conceptacles filled with crystalline
material. The two lower conceptacles originally communicated with the
surface of the thallus, but as in recent species the deeper portions of the
algal body became covered over by additions to the surface, forming merely
dead foundations for new and overlying living tissues.
The cells of the thallus have a breadth of 7–9µ, and a length of 9–12µ.
The specimen was obtained from a Lithothamnion bank, probably of
Upper Oligocene age, in Val Sugana[360], in the Austrian Tyrol.
Numerous other species of Jurassic, Cretaceous and Tertiary age might
be quoted, but the above may suffice to illustrate the general characters and
mode of occurrence of the genus. It is important that the student should
become familiar with the Lithothamnion and Lithophyllum types of thallus,
in view of their frequent occurrence in crystalline limestone rocks and in
such comparatively recent deposits as those of upraised coral-reefs. The
coral-rock of Barbados and other West-Indian islands affords a good
illustration of the manner of occurrence of fossil coralline algae in
association with corals and other organisms[361].
In the fossil species of Lithothamnion hitherto recorded there do not
appear to be any important features in which they differ from recent forms;
the geological history of the genus so far as it is known, favours the view
that the generic characters are of considerable antiquity.
Solenopora. Fig. 38.
Mr A. Brown[362], of Aberdeen, has recently brought forward good
evidence for including various calcareous fossils, described by several
authors under different names and referred to various genera of fossil
animals, in the genus Solenopora, which he places among the coralline
algae.
Species of this genus have been described from England, Scotland,
Esthonia, Russia, and other countries. The geological range of Solenopora
appears to be from Ordovician to Jurassic rocks; in some cases it is an
important constituent of beds of limestone.
• • • • •
Page 207
Solenopora compacta (Billings). Fig. 38. This species was originally
described by Billings as Stromatopora compacta, and afterwards defined by
Nicholson and Etheridge. The thallus forms sub-spheroidal masses, from
the size of a hemp-seed to that of an orange. The external surface is
lobulate; the fractured surface has a porcellaneous and sometimes a fibrous
appearance, and is usually white or light brown in colour. In vertical section
(fig. 38, B) the cells are elongated and arranged in a radiating and parallel
fashion; they often occur in concentric layers. The cells have a diameter of
about ¹⁄₁₇ mm. and possess distinctly undulating walls, as seen in a
tangential section (fig. 38, A). Brown describes certain larger cells in the
thallus (fig. 38, A) as sporangia[363], but it is difficult to recognise any
distinct sporangial cavities in the drawing. The example figured is from the
Trenton limestone of Canada; a variety of the same species has been
recorded from the Ordovician rocks of Girvan in Ayrshire. There appear to
be good reasons for accepting Brown’s conclusion that Solenopora belongs
to the Corallinaceae rather than to the Hydrozoa, among which it was
originally included. After comparing Solenopora with recent genera of
Florideae, Brown concludes that “the forms of the cells and cell-walls, the
method of increase, and the arrangement of the tissue cells in the various
species of Solenopora bear strong evidence of relationship between that
genus and the calcareous algae[364].”
Fig. 38. Solenopora compacta (Billings). A. Tangential section. × 100. B. Vertical section. ×
50. (After Brown.)
The importance of the calcareous Rhodophyceae has been frequently
emphasised by recent researches, and our knowledge of the rock-building
described by Billings as Stromatopora compacta, and afterwards defined by
Nicholson and Etheridge. The thallus forms sub-spheroidal masses, from
the size of a hemp-seed to that of an orange. The external surface is
lobulate; the fractured surface has a porcellaneous and sometimes a fibrous
appearance, and is usually white or light brown in colour. In vertical section
(fig. 38, B) the cells are elongated and arranged in a radiating and parallel
fashion; they often occur in concentric layers. The cells have a diameter of
about ¹⁄₁₇ mm. and possess distinctly undulating walls, as seen in a
tangential section (fig. 38, A). Brown describes certain larger cells in the
thallus (fig. 38, A) as sporangia[363], but it is difficult to recognise any
distinct sporangial cavities in the drawing. The example figured is from the
Trenton limestone of Canada; a variety of the same species has been
recorded from the Ordovician rocks of Girvan in Ayrshire. There appear to
be good reasons for accepting Brown’s conclusion that Solenopora belongs
to the Corallinaceae rather than to the Hydrozoa, among which it was
originally included. After comparing Solenopora with recent genera of
Florideae, Brown concludes that “the forms of the cells and cell-walls, the
method of increase, and the arrangement of the tissue cells in the various
species of Solenopora bear strong evidence of relationship between that
genus and the calcareous algae[364].”
Fig. 38. Solenopora compacta (Billings). A. Tangential section. × 100. B. Vertical section. ×
50. (After Brown.)
The importance of the calcareous Rhodophyceae has been frequently
emphasised by recent researches, and our knowledge of the rock-building
Page 208
forms is already fairly extensive. We possess evidence of the existence of
species of different genera in Ordovician seas, as well as in those of the
Silurian, Triassic, Jurassic, and more recent periods. It is reasonable to
prophesy that further researches into the structure of ancient limestones will
considerably extend our knowledge of the geological and botanical history
of the Corallinaceae.
Numerous fossils have been described as examples of other genera[365] of
Rhodophyceae than those included in the Corallinaceae, but these possess
little or no scientific value and need not be considered.
E. PHAEOPHYCEAE (Brown Algae).
Olive-brown algae, thallus often leathery in texture, composed of cell-
filaments or parenchymatous tissue, in some cases exhibiting a considerable
degree of internal differentiation. The sexual reproductive organs may be
either in the form of passive egg-cells and motile antherozoids or of motile
cells showing no external sexual difference.
With one or two exceptions all the genera are marine. They have a wide
distribution at the present day, and are especially characteristic of far
northern and extreme southern latitudes. The gigantic forms Lessonia,
Macrocystis and others already alluded to, belong to this group; also the
genus Sargassum, of which the numberless floating plants constitute the
characteristic vegetation of the Sargasso Sea.
Palaeobotanical literature is full of descriptions of supposed fossil
representatives of the brown algae, but only a few of the recorded species
possess more than a very doubtful value; most of them are worthless as
trustworthy botanical records. Many of the numerous impressions referred
to as species of Fucoides and other genera present a superficial resemblance
to the thallus of the common Bladder-wrack and other brown seaweeds.
Such similarity of form, however, in the case of flat and branched algal-like
fossils is of no scientific value. In many instances the impressions are
probably those of an alga, but they are of no botanical interest. The flat and
forked type of thallus of Fucus, Chondrus crispus (L.) and other members
of the Phaeophyceae is met with also among the red and green algae, to say
nothing of its occurrence in the group of thalloid Liverworts, or of the
almost identical form of various members of the animal kingdom. The
species of different genera in Ordovician seas, as well as in those of the
Silurian, Triassic, Jurassic, and more recent periods. It is reasonable to
prophesy that further researches into the structure of ancient limestones will
considerably extend our knowledge of the geological and botanical history
of the Corallinaceae.
Numerous fossils have been described as examples of other genera[365] of
Rhodophyceae than those included in the Corallinaceae, but these possess
little or no scientific value and need not be considered.
E. PHAEOPHYCEAE (Brown Algae).
Olive-brown algae, thallus often leathery in texture, composed of cell-
filaments or parenchymatous tissue, in some cases exhibiting a considerable
degree of internal differentiation. The sexual reproductive organs may be
either in the form of passive egg-cells and motile antherozoids or of motile
cells showing no external sexual difference.
With one or two exceptions all the genera are marine. They have a wide
distribution at the present day, and are especially characteristic of far
northern and extreme southern latitudes. The gigantic forms Lessonia,
Macrocystis and others already alluded to, belong to this group; also the
genus Sargassum, of which the numberless floating plants constitute the
characteristic vegetation of the Sargasso Sea.
Palaeobotanical literature is full of descriptions of supposed fossil
representatives of the brown algae, but only a few of the recorded species
possess more than a very doubtful value; most of them are worthless as
trustworthy botanical records. Many of the numerous impressions referred
to as species of Fucoides and other genera present a superficial resemblance
to the thallus of the common Bladder-wrack and other brown seaweeds.
Such similarity of form, however, in the case of flat and branched algal-like
fossils is of no scientific value. In many instances the impressions are
probably those of an alga, but they are of no botanical interest. The flat and
forked type of thallus of Fucus, Chondrus crispus (L.) and other members
of the Phaeophyceae is met with also among the red and green algae, to say
nothing of its occurrence in the group of thalloid Liverworts, or of the
almost identical form of various members of the animal kingdom. The
Page 209
variety of form of the thallus in one species is well illustrated by the
common Chondrus crispus (L.). This alga was described by Turner[366] in
his classic work on the Fuci under the name of Fucus crispus as “a marine
Proteus.” It affords an interesting example of the different appearance
presented by the same species under different conditions, and at the same
time it furnishes another proof of the futility of relying on imperfectly
preserved external features as taxonomic characters of primary importance.
An example of a supposed Jurassic Fucus is shown in fig. 49, and briefly
described in the Chapter dealing with fossil Bryophytes.
Several species of Flysch Algae have recently been referred by
Rothpletz[367] to the Phaeophyceae under the provisional generic name
Phycopsis, but they are of no special botanical interest.
The extremely interesting genus Nematophycus has lately been assigned
by a Canadian author[368] to a position in the Phaeophyceae. Although the
particular points on which he chiefly relies are not perhaps thoroughly
established, there are certain considerations which lead us to include
Nematophycus as a doubtful member of the present group of algae.
Nematophycus.
The stem attains a diameter of between 2 and 3 feet in the largest
specimens; it is made up either of comparatively wide and loosely arranged
tubes pursuing a slightly irregular vertical course accompanied by a plexus
of much narrower tubes, or of tubes varying in diameter but not divisible
into two distinct types. Rings of growth occur in some forms but not in
others. Radially elongated or isodiametric spaces occur in the stem tissues
in which the tubes are less abundant.
Reproductive organs unknown, with the possible exception of some very
doubtful bodies described as spores.
In 1856 Sir William Dawson proposed the generic name Prototaxites for
some large silicified trunks discovered in the Lower and Middle Devonian
rocks of Canada. A few years later the same writer[369] published a detailed
account of the new fossils and arrived at the conclusion that the Devonian
stem showed definite points of affinity with the recent genus Taxus, and the
generic name suggests that he regarded it as the type of Coniferous trees
common Chondrus crispus (L.). This alga was described by Turner[366] in
his classic work on the Fuci under the name of Fucus crispus as “a marine
Proteus.” It affords an interesting example of the different appearance
presented by the same species under different conditions, and at the same
time it furnishes another proof of the futility of relying on imperfectly
preserved external features as taxonomic characters of primary importance.
An example of a supposed Jurassic Fucus is shown in fig. 49, and briefly
described in the Chapter dealing with fossil Bryophytes.
Several species of Flysch Algae have recently been referred by
Rothpletz[367] to the Phaeophyceae under the provisional generic name
Phycopsis, but they are of no special botanical interest.
The extremely interesting genus Nematophycus has lately been assigned
by a Canadian author[368] to a position in the Phaeophyceae. Although the
particular points on which he chiefly relies are not perhaps thoroughly
established, there are certain considerations which lead us to include
Nematophycus as a doubtful member of the present group of algae.
Nematophycus.
The stem attains a diameter of between 2 and 3 feet in the largest
specimens; it is made up either of comparatively wide and loosely arranged
tubes pursuing a slightly irregular vertical course accompanied by a plexus
of much narrower tubes, or of tubes varying in diameter but not divisible
into two distinct types. Rings of growth occur in some forms but not in
others. Radially elongated or isodiametric spaces occur in the stem tissues
in which the tubes are less abundant.
Reproductive organs unknown, with the possible exception of some very
doubtful bodies described as spores.
In 1856 Sir William Dawson proposed the generic name Prototaxites for
some large silicified trunks discovered in the Lower and Middle Devonian
rocks of Canada. A few years later the same writer[369] published a detailed
account of the new fossils and arrived at the conclusion that the Devonian
stem showed definite points of affinity with the recent genus Taxus, and the
generic name suggests that he regarded it as the type of Coniferous trees
Page 210
belonging to the sub-family Taxineae. The reasons for this determination
were afterwards shown by Carruthers to be erroneous. Dawson thought he
recognised pits and spiral thickenings in the walls of the tubular elements,
as well as pointed ends in some of the latter. The spiral markings were in
reality small hyphal tubes passing obliquely across the face of the wider
tubes, and the apparent ends of the supposed tracheids were deceptive
appearances due to the fact that the tubes had in some cases been cut
through in an oblique direction. In 1870 Carruthers[370] expressed the
opinion that Dawson’s Prototaxites was a “colossal fossil seaweed” and not
a coniferous plant. The same author[371] in 1872 published a full and able
account of the genus, and conclusively proved that Prototaxites could not
be accepted as a Phanerogam; he brought forward almost convincing
evidence in favour of including the genus among the algae. The name
Prototaxites was now changed for that of Nematophycus. Carruthers
compares the rings of growth in the fossil stems with those in the large
Antarctic Lessonia stems, but he regards the histological characters as
pointing to the Siphoneae as the most likely group of recent algae in which
to include the Palaeozoic genus.
We may pass over various notes and additional contributions by Dawson,
who did not admit the corrections to his original descriptions which
Carruthers’ work supplied. In 1889 an important memoir appeared by
Penhallow[372] of Montreal in which he confirmed Carruthers’ decision as to
the algal nature of Prototaxites; he contributed some new facts to the
previous account by Carruthers, and expressed himself in favour of
regarding the fossil plant as a near ally of the recent Laminariae. The next
addition to our botanical knowledge of this genus was made by Barber[373]
who described a new specific type of Nematophycus—N. Storriei—found
by Storrie in beds of Wenlock limestone age near Cardiff. Solms-
Laubach[374], in a recent memoir on Devonian plants, recorded the
occurrence of another species of this genus in Middle Devonian rocks near
Gräfrath on the Lower Rhine. Lastly Penhallow[375], in describing a new
species, lays stress on the resemblance of some of the tubular elements in
the stem to the sieve-hyphae of the recent seaweeds Macrocystis and
Laminaria. He concludes that the new facts he records make it clear that
Nematophycus “is an alga, and of an alliance with the Laminarias.” The
recent evidence brought forward by Penhallow is not entirely satisfactory;
the drawings and descriptions of the supposed trumpet-shaped sieve-hyphae
were afterwards shown by Carruthers to be erroneous. Dawson thought he
recognised pits and spiral thickenings in the walls of the tubular elements,
as well as pointed ends in some of the latter. The spiral markings were in
reality small hyphal tubes passing obliquely across the face of the wider
tubes, and the apparent ends of the supposed tracheids were deceptive
appearances due to the fact that the tubes had in some cases been cut
through in an oblique direction. In 1870 Carruthers[370] expressed the
opinion that Dawson’s Prototaxites was a “colossal fossil seaweed” and not
a coniferous plant. The same author[371] in 1872 published a full and able
account of the genus, and conclusively proved that Prototaxites could not
be accepted as a Phanerogam; he brought forward almost convincing
evidence in favour of including the genus among the algae. The name
Prototaxites was now changed for that of Nematophycus. Carruthers
compares the rings of growth in the fossil stems with those in the large
Antarctic Lessonia stems, but he regards the histological characters as
pointing to the Siphoneae as the most likely group of recent algae in which
to include the Palaeozoic genus.
We may pass over various notes and additional contributions by Dawson,
who did not admit the corrections to his original descriptions which
Carruthers’ work supplied. In 1889 an important memoir appeared by
Penhallow[372] of Montreal in which he confirmed Carruthers’ decision as to
the algal nature of Prototaxites; he contributed some new facts to the
previous account by Carruthers, and expressed himself in favour of
regarding the fossil plant as a near ally of the recent Laminariae. The next
addition to our botanical knowledge of this genus was made by Barber[373]
who described a new specific type of Nematophycus—N. Storriei—found
by Storrie in beds of Wenlock limestone age near Cardiff. Solms-
Laubach[374], in a recent memoir on Devonian plants, recorded the
occurrence of another species of this genus in Middle Devonian rocks near
Gräfrath on the Lower Rhine. Lastly Penhallow[375], in describing a new
species, lays stress on the resemblance of some of the tubular elements in
the stem to the sieve-hyphae of the recent seaweeds Macrocystis and
Laminaria. He concludes that the new facts he records make it clear that
Nematophycus “is an alga, and of an alliance with the Laminarias.” The
recent evidence brought forward by Penhallow is not entirely satisfactory;
the drawings and descriptions of the supposed trumpet-shaped sieve-hyphae
Page 211
are not conclusive. On the whole it is probably the better course to speak of
Nematophycus as a possible ally of the brown algae rather than as an extinct
type of the Siphoneae, but until our knowledge is more complete it is
practically impossible to decide the exact position of this Siluro-Devonian
genus.
Solms-Laubach[376] has suggested that the generic name Nematophyton,
used by Penhallow in preference to Carruthers’ term Nematophycus, is the
more suitable as being a neutral designation and not one which assumes a
definite botanical position. In view of the nature of the evidence in favour
of the algal affinities of the fossil, the reasons for discarding Carruthers’
original name are hardly sufficient.
Before discussing more fully the distribution and botanical position of
Nematophycus we may describe at length one of the best known species,
and give a short account of some other forms.
• • • • •
1. Nematophycus Logani (Daws.). Fig. 39, A–E. The stem possesses well
marked concentric rings of growth due to a periodic difference in size of the
large tubular elements. The tissues consist of two distinct kinds of tubular
elements, the larger tubes loosely arranged and pursuing a fairly regular
longitudinal course, and having a diameter of 13–35µ; the smaller tubes,
with a diameter of 5–6µ, ramify in different directions and form a loose
plexus among the larger and more regularly disposed elements. Branching
occurs in both kinds of tubes; septa have been recognised only in the
smaller tubes. Irregular and discontinuous radial spaces traverse the stem
tissues, having a superficial resemblance in their manner of occurrence to
the medullary rays of the higher plants.
The best specimens of this species were obtained by Sir William Dawson
from the Devonian Sandstones of Gaspé in New Brunswick. The largest
stems had a diameter of 3 feet and reached a length of several feet[377]; in
some examples Dawson found lateral appendages attached to the stem
which he described as “spreading roots.” Externally the specimens were
occasionally covered with a layer of friable coal, and internally the tissues
were found to be more or less perfectly preserved by the infiltration of a
siliceous solution. Most of the examples of Nematophycus from Britain and
Germany are much smaller and less perfectly preserved than those from
Nematophycus as a possible ally of the brown algae rather than as an extinct
type of the Siphoneae, but until our knowledge is more complete it is
practically impossible to decide the exact position of this Siluro-Devonian
genus.
Solms-Laubach[376] has suggested that the generic name Nematophyton,
used by Penhallow in preference to Carruthers’ term Nematophycus, is the
more suitable as being a neutral designation and not one which assumes a
definite botanical position. In view of the nature of the evidence in favour
of the algal affinities of the fossil, the reasons for discarding Carruthers’
original name are hardly sufficient.
Before discussing more fully the distribution and botanical position of
Nematophycus we may describe at length one of the best known species,
and give a short account of some other forms.
• • • • •
1. Nematophycus Logani (Daws.). Fig. 39, A–E. The stem possesses well
marked concentric rings of growth due to a periodic difference in size of the
large tubular elements. The tissues consist of two distinct kinds of tubular
elements, the larger tubes loosely arranged and pursuing a fairly regular
longitudinal course, and having a diameter of 13–35µ; the smaller tubes,
with a diameter of 5–6µ, ramify in different directions and form a loose
plexus among the larger and more regularly disposed elements. Branching
occurs in both kinds of tubes; septa have been recognised only in the
smaller tubes. Irregular and discontinuous radial spaces traverse the stem
tissues, having a superficial resemblance in their manner of occurrence to
the medullary rays of the higher plants.
The best specimens of this species were obtained by Sir William Dawson
from the Devonian Sandstones of Gaspé in New Brunswick. The largest
stems had a diameter of 3 feet and reached a length of several feet[377]; in
some examples Dawson found lateral appendages attached to the stem
which he described as “spreading roots.” Externally the specimens were
occasionally covered with a layer of friable coal, and internally the tissues
were found to be more or less perfectly preserved by the infiltration of a
siliceous solution. Most of the examples of Nematophycus from Britain and
Germany are much smaller and less perfectly preserved than those from
Page 212
Canada. The Peter Redpath Museum, Montreal, contains several very large
blocks of Nematophycus, in many of which one sees the concentric rings of
growth clearly etched out by weathering agents in a cross section of a large
stem.
In fig. 39, A, a sketch is given of a thin transverse section of a stem,
drawn natural size. The lines of growth are clearly seen, and as in
coniferous stems the breadth of the concentric zones varies considerably.
The short lines traversing the tissues in a radial direction represent the
medullary-ray-like spaces referred to in the specific diagnosis. A transverse
section examined under a low-power objective presents the appearance of a
number of thick-walled and comparatively wide tubes loosely arranged;
they may be in contact or separated from one another. If the microscope be
carefully focussed through the thickness of the section the transversely-cut
tubes appear to move laterally, producing a curiously dazzling effect if the
objective is raised or lowered rapidly. This lateral movement is due to the
undulating vertical course of the tubes. Under a higher power the lighter-
coloured matrix in which the tubes are embedded shows a number of very
much smaller and thinner-walled hyphal elements; some of these are cut
across transversely, others more or less obliquely and others again
longitudinally. These smaller tubes constitute an irregular plexus
surrounding and ramifying between the larger elements. The diameter of the
larger tubes decreases for a certain distance in a radial direction as seen in a
transverse section, and this change in size gives rise to the appearance of
concentric lines indicating periodic changes in growth.
blocks of Nematophycus, in many of which one sees the concentric rings of
growth clearly etched out by weathering agents in a cross section of a large
stem.
In fig. 39, A, a sketch is given of a thin transverse section of a stem,
drawn natural size. The lines of growth are clearly seen, and as in
coniferous stems the breadth of the concentric zones varies considerably.
The short lines traversing the tissues in a radial direction represent the
medullary-ray-like spaces referred to in the specific diagnosis. A transverse
section examined under a low-power objective presents the appearance of a
number of thick-walled and comparatively wide tubes loosely arranged;
they may be in contact or separated from one another. If the microscope be
carefully focussed through the thickness of the section the transversely-cut
tubes appear to move laterally, producing a curiously dazzling effect if the
objective is raised or lowered rapidly. This lateral movement is due to the
undulating vertical course of the tubes. Under a higher power the lighter-
coloured matrix in which the tubes are embedded shows a number of very
much smaller and thinner-walled hyphal elements; some of these are cut
across transversely, others more or less obliquely and others again
longitudinally. These smaller tubes constitute an irregular plexus
surrounding and ramifying between the larger elements. The diameter of the
larger tubes decreases for a certain distance in a radial direction as seen in a
transverse section, and this change in size gives rise to the appearance of
concentric lines indicating periodic changes in growth.
Page 213
Fig. 39. Nematophycus Logani (Daws.). A. Part of a transverse section from a specimen in
the British Museum. (Nat. size.) B. Transverse section from specimens in Mr Barber’s
possession. C. Longitudinal section. (B and C × 160.) D. Transverse section showing a
radial space. E. Transverse section; a few ‘cells’ more highly magnified. D and E from a
specimen in the British Museum.
The radial spaces are characterised by the partial absence of the larger
tubes, and as seen in longitudinal sections these spaces constitute regions in
which the smaller tubes branch very freely. Fig. 39, B, represents a small
piece of a transverse section seen under a fairly high power. In fig. 39, C,
the tubes are seen in longitudinal section. The larger elements are unseptate
and not very regular in their vertical course through the stem; the smaller
the British Museum. (Nat. size.) B. Transverse section from specimens in Mr Barber’s
possession. C. Longitudinal section. (B and C × 160.) D. Transverse section showing a
radial space. E. Transverse section; a few ‘cells’ more highly magnified. D and E from a
specimen in the British Museum.
The radial spaces are characterised by the partial absence of the larger
tubes, and as seen in longitudinal sections these spaces constitute regions in
which the smaller tubes branch very freely. Fig. 39, B, represents a small
piece of a transverse section seen under a fairly high power. In fig. 39, C,
the tubes are seen in longitudinal section. The larger elements are unseptate
and not very regular in their vertical course through the stem; the smaller
Page 214
elements are seen as fine tubes lying between and across the larger tubes. In
the sections I have examined no undoubted transverse septa were detected
in any of the tubular elements.
The question as to the possible connection between the larger and smaller
elements is one which is not as yet satisfactorily disposed of. Penhallow[378]
regards the finer hyphal elements as branches of the larger tubes, but
Barber[379], who has carefully examined good material of Nematophycus
Logani, was unable to detect any organic connection between the two. My
own observations are in accord with those of Barber. Further details and
numerous figures of this species of Nematophycus will be found in the
memoirs of Carruthers, Penhallow and Barber.
• • • • •
Some specimens of silicified Nematophycus stems afford particularly
instructive examples of the state of preservation or method of
mineralisation as a source of error in histological work. The sketches
reproduced in fig. 39, D and E, were made from a section of a large
specimen of Nematophycus in the British Museum. In fig. D we have one of
the radial spaces containing some indistinct small elements, the tissue
surrounding the space appears to consist of polygonal cells suggesting
ordinary parenchymatous tissue. In fig. E a few of these ‘cells’ are seen
more clearly, they have black and ragged walls, and often contain very
small and faint circles of which the precise nature is uncertain. The true
interpretation of this form of structure was first supplied by Penhallow[380].
The black network simulating parenchymatous tissue consists of the
substance of Nematophycus tubes which has been completely redistributed
during fossilisation and collected along fairly regular lines, as seen in figs.
D and E. The original structure has been almost completely destroyed, and
the material composing the walls of the large tubes has finally been
rearranged as a network, interrupted here and there by the characteristic
radial spaces which remain as evidence of the original Nematophycus
characters. It is possible in some cases to trace every gradation from
sections exhibiting the normal structure through those having the
appearance shown in figs. D and E to others in which the structure is
completely lost. Penhallow describes this method of fossilisation in N.
crassus (Daws.); an examination of several specimens in the National
Collection leads me to entirely confirm his general conclusions, and also to
the sections I have examined no undoubted transverse septa were detected
in any of the tubular elements.
The question as to the possible connection between the larger and smaller
elements is one which is not as yet satisfactorily disposed of. Penhallow[378]
regards the finer hyphal elements as branches of the larger tubes, but
Barber[379], who has carefully examined good material of Nematophycus
Logani, was unable to detect any organic connection between the two. My
own observations are in accord with those of Barber. Further details and
numerous figures of this species of Nematophycus will be found in the
memoirs of Carruthers, Penhallow and Barber.
• • • • •
Some specimens of silicified Nematophycus stems afford particularly
instructive examples of the state of preservation or method of
mineralisation as a source of error in histological work. The sketches
reproduced in fig. 39, D and E, were made from a section of a large
specimen of Nematophycus in the British Museum. In fig. D we have one of
the radial spaces containing some indistinct small elements, the tissue
surrounding the space appears to consist of polygonal cells suggesting
ordinary parenchymatous tissue. In fig. E a few of these ‘cells’ are seen
more clearly, they have black and ragged walls, and often contain very
small and faint circles of which the precise nature is uncertain. The true
interpretation of this form of structure was first supplied by Penhallow[380].
The black network simulating parenchymatous tissue consists of the
substance of Nematophycus tubes which has been completely redistributed
during fossilisation and collected along fairly regular lines, as seen in figs.
D and E. The original structure has been almost completely destroyed, and
the material composing the walls of the large tubes has finally been
rearranged as a network, interrupted here and there by the characteristic
radial spaces which remain as evidence of the original Nematophycus
characters. It is possible in some cases to trace every gradation from
sections exhibiting the normal structure through those having the
appearance shown in figs. D and E to others in which the structure is
completely lost. Penhallow describes this method of fossilisation in N.
crassus (Daws.); an examination of several specimens in the National
Collection leads me to entirely confirm his general conclusions, and also to
Page 215
the opinion that N. Logani shows exactly the same manner of mineralisation
as N. crassus. The chief point of interest as regards this method of
preservation lies in the fact that a fossil described by Dawson[381] as
Celluloxylon primaevum, and referred to as a probable conifer, is
undoubtedly a badly preserved Nematophycus. Penhallow examined
Dawson’s specimens and obtained convincing evidence of their identity
with certain forms of highly altered Nematophycus stems.
• • • • •
2. Nematophycus Storriei Barber. Fig. 40. The specimens on which
Barber[382] founded this species were obtained by Mr Storrie from the
Tymawr quarry near Cardiff, in beds of Wenlock age. The fragmentary
nature of the material is largely compensated for by the excellence of the
preservation. We may briefly define the species as follows:
The stem consists of separate interlacing undivided and usually
unbranched tubes of varying diameter. Spaces more or less isodiametric in
dimensions are scattered through the tissue. The spaces constitute regions in
which the tubular elements branch freely.
The main distinguishing features of this British species are (i) the
absence of two distinct and well-defined forms of tubular elements. The
main part of the stem consists of thick walled tubes similar to those of N.
Logani, but the spaces between them are occupied by thinner-walled and
smaller tubes varying considerably in diameter; (ii) the form of the spaces
which are not radially elongated as in N. Logani.
as N. crassus. The chief point of interest as regards this method of
preservation lies in the fact that a fossil described by Dawson[381] as
Celluloxylon primaevum, and referred to as a probable conifer, is
undoubtedly a badly preserved Nematophycus. Penhallow examined
Dawson’s specimens and obtained convincing evidence of their identity
with certain forms of highly altered Nematophycus stems.
• • • • •
2. Nematophycus Storriei Barber. Fig. 40. The specimens on which
Barber[382] founded this species were obtained by Mr Storrie from the
Tymawr quarry near Cardiff, in beds of Wenlock age. The fragmentary
nature of the material is largely compensated for by the excellence of the
preservation. We may briefly define the species as follows:
The stem consists of separate interlacing undivided and usually
unbranched tubes of varying diameter. Spaces more or less isodiametric in
dimensions are scattered through the tissue. The spaces constitute regions in
which the tubular elements branch freely.
The main distinguishing features of this British species are (i) the
absence of two distinct and well-defined forms of tubular elements. The
main part of the stem consists of thick walled tubes similar to those of N.
Logani, but the spaces between them are occupied by thinner-walled and
smaller tubes varying considerably in diameter; (ii) the form of the spaces
which are not radially elongated as in N. Logani.
Page 216
Fig. 40. Nematophycus Storriei Barb. Longitudinal section, from a photograph by Mr C. A.
Barber. × 45.
Fig. 40 shows the undulating course of the tubes as seen in a longitudinal
section; the black colour of some of the elements is due to the fact that the
surface of the wall is seen, while in the lighter-coloured portions of the
tubes the wall has been cut through. The lighter patch about the middle of
the figure shows the form of one of the spaces in which the tubes are freely
branched.
In addition to the two species already described six others have been
recorded, but with these we need not concern ourselves in detail. One of
these species, N. Hicksi, was found by Dr Hicks[383] in the Denbighshire
grits quarry of Pen-y-Glog near Corwen in North Wales. The position of
these beds has recently been determined by Mr Lake[384] as corresponding to
that of the Wenlock limestone. This species and N. Storriei are both Silurian
examples of the genus. It is possible, as Barber has suggested, that the
specimens described under these two names should be referred to one
species. The specimens found by Hicks were small and imperfectly
preserved fragments; Etheridge has given a full description of their
structure, and Barber has subsequently examined the material. The
preservation is not such as will admit of any very precise specific diagnosis;
Barber. × 45.
Fig. 40 shows the undulating course of the tubes as seen in a longitudinal
section; the black colour of some of the elements is due to the fact that the
surface of the wall is seen, while in the lighter-coloured portions of the
tubes the wall has been cut through. The lighter patch about the middle of
the figure shows the form of one of the spaces in which the tubes are freely
branched.
In addition to the two species already described six others have been
recorded, but with these we need not concern ourselves in detail. One of
these species, N. Hicksi, was found by Dr Hicks[383] in the Denbighshire
grits quarry of Pen-y-Glog near Corwen in North Wales. The position of
these beds has recently been determined by Mr Lake[384] as corresponding to
that of the Wenlock limestone. This species and N. Storriei are both Silurian
examples of the genus. It is possible, as Barber has suggested, that the
specimens described under these two names should be referred to one
species. The specimens found by Hicks were small and imperfectly
preserved fragments; Etheridge has given a full description of their
structure, and Barber has subsequently examined the material. The
preservation is not such as will admit of any very precise specific diagnosis;
Page 217
the fragments are correctly referred to Nematophycus, but their specific
characters cannot be clearly determined.
Solms-Laubach[385] has described some fragments of another species of
Nematophycus from the Devonian rocks of the Lower Rhine. His specimens
are chiefly interesting as extending the geographical range of the genus, and
as affording examples of a curious method of preservation. The specimens
obtained were small fragments, flattened and very dark brown in colour.
The tubular elements consisted of an external membrane of black coal,
enclosing a central core of dark red iron-oxide. On burning the fragment on
a piece of platinum foil the coal composing the wall of the tubes was
removed and the deep-red casts of the tube-cavities remained[386]. The
investigation of the structural characters of this imperfect material was
conducted by reflected light. Under certain conditions, when it is
impossible to obtain thin sections for examination by transmitted light, it is
possible to accomplish much, as shown by Solms-Laubach’s work, by
means of observation with direct light.
The last species to be noticed is Nematophycus Ortoni recently described
by Penhallow. There are no concentric rings of growth, no radial spaces and
no smaller hyphae in the tissues of this type of stem. In longitudinal section,
the tubes show occasional local expansions of the lumen which Penhallow
compares with the ‘trumpet-hyphae’ of some recent brown algae. No actual
sieve-plates or transverse walls have been detected, but the general
appearance of the tubes is considered to afford distinct evidence of the
original existence of such walls. The figures accompanying the description
do not carry conviction as to the correctness of the reference of the tubes to
imperfectly preserved sieve-hyphae.
The following list, taken, with a few alterations, from Penhallow’s
memoir[387], shows the geographical and geological range of the species of
Nematophycus hitherto recorded.
Lower Devonian of Gaspé.
Nematophycus Logani (Daws.) Silurian [Wenlock] of England.
Silurian of New Brunswick.
N. Hicksi (Eth.) Silurian. (Wenlock) of N. Wales.
N. crassus (Daws.)[388] Middle Devonian of Gaspé and New York.
N. laxus (Daws.) Lower Devonian of Gaspé.
N. tenuis (Daws.) Lower Devonian of Gaspé.
characters cannot be clearly determined.
Solms-Laubach[385] has described some fragments of another species of
Nematophycus from the Devonian rocks of the Lower Rhine. His specimens
are chiefly interesting as extending the geographical range of the genus, and
as affording examples of a curious method of preservation. The specimens
obtained were small fragments, flattened and very dark brown in colour.
The tubular elements consisted of an external membrane of black coal,
enclosing a central core of dark red iron-oxide. On burning the fragment on
a piece of platinum foil the coal composing the wall of the tubes was
removed and the deep-red casts of the tube-cavities remained[386]. The
investigation of the structural characters of this imperfect material was
conducted by reflected light. Under certain conditions, when it is
impossible to obtain thin sections for examination by transmitted light, it is
possible to accomplish much, as shown by Solms-Laubach’s work, by
means of observation with direct light.
The last species to be noticed is Nematophycus Ortoni recently described
by Penhallow. There are no concentric rings of growth, no radial spaces and
no smaller hyphae in the tissues of this type of stem. In longitudinal section,
the tubes show occasional local expansions of the lumen which Penhallow
compares with the ‘trumpet-hyphae’ of some recent brown algae. No actual
sieve-plates or transverse walls have been detected, but the general
appearance of the tubes is considered to afford distinct evidence of the
original existence of such walls. The figures accompanying the description
do not carry conviction as to the correctness of the reference of the tubes to
imperfectly preserved sieve-hyphae.
The following list, taken, with a few alterations, from Penhallow’s
memoir[387], shows the geographical and geological range of the species of
Nematophycus hitherto recorded.
Lower Devonian of Gaspé.
Nematophycus Logani (Daws.) Silurian [Wenlock] of England.
Silurian of New Brunswick.
N. Hicksi (Eth.) Silurian. (Wenlock) of N. Wales.
N. crassus (Daws.)[388] Middle Devonian of Gaspé and New York.
N. laxus (Daws.) Lower Devonian of Gaspé.
N. tenuis (Daws.) Lower Devonian of Gaspé.
Page 218
N. Storriei (Barb.) Silurian (Wenlock) of Wales (Cardiff).
N. dechenianus (Pied.) Upper Devonian of Germany (Gräfrath).
N. Ortoni (Pen.) Upper Erian of Ohio.
In summing up our information as to the structure of Nematophycus we
find there are certain points not definitely settled, and which are of
considerable importance. The few recorded instances of spore-like bodies
by Penhallow and Barber are not satisfactory; we are still ignorant of the
nature of the reproductive organs. Such instances of lateral appendages as
have been referred to do not throw much light on the habit of the plant. So
far as we know at present the stem of Nematophycus was not differentiated
internally into a cortical and central region. It may be that the specimens
have been only partially preserved, and the coaly layer which occasionally
surrounds a stem may represent a carbonised cortex which has never been
petrified. The large and loosely arranged tubes constitute the chief
characteristic feature of the genus; in some cases (N. Logani) there is an
accompanying plexus of smaller hyphae, in others (N. Storriei) there is no
definite division of the tissue into two sets of tubes of uniform size, and in
N. Ortoni the tubular elements are all of the large type.
Penhallow has recognised the branching of large tubes in N. Logani and
N. crassus giving rise to the small hyphal elements. In most specimens,
however, no such mode of origin of the smaller tubes can be detected. The
spaces which interrupt the homogeneity of the tissues in some forms have
been described as branching depots, on account of the frequent occurrence
in these areas of much branched hyphae. The function of these spaces (fig.
39, D, and fig. 40) may be connected with aeration of the stem-tissues.
As Carruthers first pointed out the unseptate nature of the elements and
the occurrence of large and small tubes forming a comparatively lax tissue
suggested affinities with such recent genera as Penicillus, Halimeda,
Udotea and other members of the Siphoneae. In those fossil stems which
possess tubes of two distinct sizes, we cannot as a rule trace any organic
connection between the two sets of tubular elements. Transverse septa have
been detected in the tubes of some specimens of N. Logani. These
considerations and the large size and habit of growth of the stem leave one
sceptical as to the wisdom of assigning the fossil genus to the Siphoneae.
On the other hand, apart from the doubtful sieve-hyphae of Penhallow, the
manner of growth of the plant, the concentric rings, marked by a decrease in
N. dechenianus (Pied.) Upper Devonian of Germany (Gräfrath).
N. Ortoni (Pen.) Upper Erian of Ohio.
In summing up our information as to the structure of Nematophycus we
find there are certain points not definitely settled, and which are of
considerable importance. The few recorded instances of spore-like bodies
by Penhallow and Barber are not satisfactory; we are still ignorant of the
nature of the reproductive organs. Such instances of lateral appendages as
have been referred to do not throw much light on the habit of the plant. So
far as we know at present the stem of Nematophycus was not differentiated
internally into a cortical and central region. It may be that the specimens
have been only partially preserved, and the coaly layer which occasionally
surrounds a stem may represent a carbonised cortex which has never been
petrified. The large and loosely arranged tubes constitute the chief
characteristic feature of the genus; in some cases (N. Logani) there is an
accompanying plexus of smaller hyphae, in others (N. Storriei) there is no
definite division of the tissue into two sets of tubes of uniform size, and in
N. Ortoni the tubular elements are all of the large type.
Penhallow has recognised the branching of large tubes in N. Logani and
N. crassus giving rise to the small hyphal elements. In most specimens,
however, no such mode of origin of the smaller tubes can be detected. The
spaces which interrupt the homogeneity of the tissues in some forms have
been described as branching depots, on account of the frequent occurrence
in these areas of much branched hyphae. The function of these spaces (fig.
39, D, and fig. 40) may be connected with aeration of the stem-tissues.
As Carruthers first pointed out the unseptate nature of the elements and
the occurrence of large and small tubes forming a comparatively lax tissue
suggested affinities with such recent genera as Penicillus, Halimeda,
Udotea and other members of the Siphoneae. In those fossil stems which
possess tubes of two distinct sizes, we cannot as a rule trace any organic
connection between the two sets of tubular elements. Transverse septa have
been detected in the tubes of some specimens of N. Logani. These
considerations and the large size and habit of growth of the stem leave one
sceptical as to the wisdom of assigning the fossil genus to the Siphoneae.
On the other hand, apart from the doubtful sieve-hyphae of Penhallow, the
manner of growth of the plant, the concentric rings, marked by a decrease in
Page 219
the diameter of the tubes, the lax arrangement and irregular course of the
elements, afford points of agreement with some recent Phaeophyceae. The
stem of a Laminaria (fig. 29) or of a Lessonia are the most obvious
structures with which to compare Nematophycus. The medullary region of a
Laminaria or Fucus and of other genera presents a certain resemblance to
the tissues of the fossil stems. On the whole we may be content to leave
Nematophycus for the present as probably an extinct type of alga, more
closely allied to the large members of the Phaeophyceae than to any other
recent seaweeds.
Pachytheca.
(A fossil of uncertain affinity.)
There is another fossil occasionally associated with Nematophycus and
referred by many writers to the Algae, which calls for a brief notice.
Pachytheca is too doubtful a genus to justify a detailed treatment in the
present work. Although, as I have elsewhere suggested[389], we are hardly in
a position to speak with any degree of certainty as to its affinity, it is not
improbable that it may eventually be shown to be an alga.
Without attempting a full diagnosis of the genus, we may briefly refer to
its most striking characters.
Pachytheca usually occurs in the form of small spherical bodies, about ·5
cm. in diameter, in Old Red Sandstone or Silurian rocks. In section a single
sphere is found to consist of two well marked regions; in the centre, of a
number of ramifying and irregularly placed narrow tubes, and in the
peripheral or cortical region, of numerous regular and radially disposed
simple or forked septate tubes. The tubular elements of the two regions are
in organic connection.
The name was proposed by Sir Joseph Hooker for some specimens found
by Dr Strickland[390] in the Ludlow bone-bed (Silurian) of Woolhope and
May-Hill. Examples were subsequently recorded from the Wenlock
limestone of Malvern and from Silurian and Old Red Sandstone rocks of
other districts. Hicks[391] found Pachytheca in the Pen-y-Glog grits of
Corwen in association with Nematophycus, and the two fossils have been
found together elsewhere. This association led to the suggestion that
Pachytheca might be the sporangium of Nematophycus, and Dawson[392], in
elements, afford points of agreement with some recent Phaeophyceae. The
stem of a Laminaria (fig. 29) or of a Lessonia are the most obvious
structures with which to compare Nematophycus. The medullary region of a
Laminaria or Fucus and of other genera presents a certain resemblance to
the tissues of the fossil stems. On the whole we may be content to leave
Nematophycus for the present as probably an extinct type of alga, more
closely allied to the large members of the Phaeophyceae than to any other
recent seaweeds.
Pachytheca.
(A fossil of uncertain affinity.)
There is another fossil occasionally associated with Nematophycus and
referred by many writers to the Algae, which calls for a brief notice.
Pachytheca is too doubtful a genus to justify a detailed treatment in the
present work. Although, as I have elsewhere suggested[389], we are hardly in
a position to speak with any degree of certainty as to its affinity, it is not
improbable that it may eventually be shown to be an alga.
Without attempting a full diagnosis of the genus, we may briefly refer to
its most striking characters.
Pachytheca usually occurs in the form of small spherical bodies, about ·5
cm. in diameter, in Old Red Sandstone or Silurian rocks. In section a single
sphere is found to consist of two well marked regions; in the centre, of a
number of ramifying and irregularly placed narrow tubes, and in the
peripheral or cortical region, of numerous regular and radially disposed
simple or forked septate tubes. The tubular elements of the two regions are
in organic connection.
The name was proposed by Sir Joseph Hooker for some specimens found
by Dr Strickland[390] in the Ludlow bone-bed (Silurian) of Woolhope and
May-Hill. Examples were subsequently recorded from the Wenlock
limestone of Malvern and from Silurian and Old Red Sandstone rocks of
other districts. Hicks[391] found Pachytheca in the Pen-y-Glog grits of
Corwen in association with Nematophycus, and the two fossils have been
found together elsewhere. This association led to the suggestion that
Pachytheca might be the sporangium of Nematophycus, and Dawson[392], in
Page 220
conformity with his belief in the coniferous character of the latter plant,
referred to Pachytheca as a true seed.
The best sections of this fossil have been prepared with remarkable skill
by Mr Storrie of Cardiff; they were carefully examined and described by
Barber in two memoirs[393] published in the Annals of Botany, the account
being illustrated by several well executed drawings and microphotographs.
Among other difficulties to contend against in the interpretation of
Pachytheca there is that of mineralisation. The preservation is such as to
render the discrimination of original structure as distinct from structural
features of secondary origin, consequent on a particular manner of
crystallisation of the siliceous material, a matter of considerable difficulty.
Suggestions as to the nature of Pachytheca have been particularly
numerous; it has been referred to most classes of plants and relegated by
some writers to the animal kingdom. The most recent addition to our
knowledge of this problematic fossil was the discovery of a specimen by
Mr Storrie in which the Pachytheca sphere rested in a small cup, like an
acorn fruit in its cupule. This specimen was figured and described by Mr
George Murray[394] in 1895; he expresses the opinion that the discovery
makes the taxonomic position of the genus still more obscure. Solms-
Laubach briefly refers to Pachytheca in connection with Nematophycus,
and regards its precise nature almost as much an unsolved riddle now as it
was when first discovered. For a fuller account of this fossil reference must
be made to the contributions of Hooker[395], Barber[396] and others. The
literature is quoted by Barber and more recently by Solms-Laubach[397].
There are several specimens and microscopic sections of Pachytheca in the
geological and botanical departments of the British Museum. The genus has
been recorded from Shropshire, North Wales, Malvern, Herefordshire,
Perthshire and other British localities, as well as from Canada; it occurs in
both Silurian and Old Red Sandstone rocks.
Algites.
A generic name for those fossils which in all probability belong to the
class Algae, but which, by reason of the absence of reproductive organs,
internal structure, or characters of a trustworthy nature in the determination
referred to Pachytheca as a true seed.
The best sections of this fossil have been prepared with remarkable skill
by Mr Storrie of Cardiff; they were carefully examined and described by
Barber in two memoirs[393] published in the Annals of Botany, the account
being illustrated by several well executed drawings and microphotographs.
Among other difficulties to contend against in the interpretation of
Pachytheca there is that of mineralisation. The preservation is such as to
render the discrimination of original structure as distinct from structural
features of secondary origin, consequent on a particular manner of
crystallisation of the siliceous material, a matter of considerable difficulty.
Suggestions as to the nature of Pachytheca have been particularly
numerous; it has been referred to most classes of plants and relegated by
some writers to the animal kingdom. The most recent addition to our
knowledge of this problematic fossil was the discovery of a specimen by
Mr Storrie in which the Pachytheca sphere rested in a small cup, like an
acorn fruit in its cupule. This specimen was figured and described by Mr
George Murray[394] in 1895; he expresses the opinion that the discovery
makes the taxonomic position of the genus still more obscure. Solms-
Laubach briefly refers to Pachytheca in connection with Nematophycus,
and regards its precise nature almost as much an unsolved riddle now as it
was when first discovered. For a fuller account of this fossil reference must
be made to the contributions of Hooker[395], Barber[396] and others. The
literature is quoted by Barber and more recently by Solms-Laubach[397].
There are several specimens and microscopic sections of Pachytheca in the
geological and botanical departments of the British Museum. The genus has
been recorded from Shropshire, North Wales, Malvern, Herefordshire,
Perthshire and other British localities, as well as from Canada; it occurs in
both Silurian and Old Red Sandstone rocks.
Algites.
A generic name for those fossils which in all probability belong to the
class Algae, but which, by reason of the absence of reproductive organs,
internal structure, or characters of a trustworthy nature in the determination
Page 221
of affinity, cannot be referred with any degree of certainty to a particular
recent genus or family.
This term was suggested in 1894[398] as a provisional and comprehensive
designation under which might be included such impressions or casts as
might reasonably be referred to Algae. The practice of applying to alga-like
fossils names suggestive of a definite alliance with recent genera is as a rule
unsound. It would simplify nomenclature, and avoid the multiplication of
generic names, if the term Algites were applied to such algal fossils from
rocks of various ages as afford no trustworthy data by which their family or
generic affinity can be established.
V. MYXOMYCETES (MYCETOZOA).
This class of organisms affords an interesting example of the
impossibility of maintaining a hard and fast line between the animal and
plant kingdom. Zoologists and Botanists usually include the
Myxomycetes[399] in the text-books of their respective subjects, and the
name Animal-fungi which has been applied to these organisms expresses
their dual relationship. They constitute one of three groups which we may
include in that intermediate zone or ‘buffer-state’ between the two
kingdoms. From a palaeobotanical point of view the Myxomycetes are of
little interest, but a very brief reference may be made to them rather for the
sake of avoiding unnecessary incompleteness in our classification than from
their importance as possible fossils.
They are organisms without chlorophyll, consisting of a naked mass of
protoplasm, known as the plasmodium, which may attain a size of several
inches. Such plasmodia creep over the surface of decaying organic
substrata, and in forming their asexual reproductive cells they are converted
into somewhat complex fruits containing spores. The spores produce motile
swarm-cells, which eventually coalesce together to form a new
plasmodium.
A few examples of fossil Myxomycetes have been recorded from the
Palaeozoic and more recent formations, but none of them are entirely
beyond suspicion. We may mention three examples of fossils referred to
this group, but only one of these is entitled to serious consideration.
recent genus or family.
This term was suggested in 1894[398] as a provisional and comprehensive
designation under which might be included such impressions or casts as
might reasonably be referred to Algae. The practice of applying to alga-like
fossils names suggestive of a definite alliance with recent genera is as a rule
unsound. It would simplify nomenclature, and avoid the multiplication of
generic names, if the term Algites were applied to such algal fossils from
rocks of various ages as afford no trustworthy data by which their family or
generic affinity can be established.
V. MYXOMYCETES (MYCETOZOA).
This class of organisms affords an interesting example of the
impossibility of maintaining a hard and fast line between the animal and
plant kingdom. Zoologists and Botanists usually include the
Myxomycetes[399] in the text-books of their respective subjects, and the
name Animal-fungi which has been applied to these organisms expresses
their dual relationship. They constitute one of three groups which we may
include in that intermediate zone or ‘buffer-state’ between the two
kingdoms. From a palaeobotanical point of view the Myxomycetes are of
little interest, but a very brief reference may be made to them rather for the
sake of avoiding unnecessary incompleteness in our classification than from
their importance as possible fossils.
They are organisms without chlorophyll, consisting of a naked mass of
protoplasm, known as the plasmodium, which may attain a size of several
inches. Such plasmodia creep over the surface of decaying organic
substrata, and in forming their asexual reproductive cells they are converted
into somewhat complex fruits containing spores. The spores produce motile
swarm-cells, which eventually coalesce together to form a new
plasmodium.
A few examples of fossil Myxomycetes have been recorded from the
Palaeozoic and more recent formations, but none of them are entirely
beyond suspicion. We may mention three examples of fossils referred to
this group, but only one of these is entitled to serious consideration.
Page 222
Myxomycetes Mangini Ren.[400] It is not uncommon to find distinct traces
of original or secondary cell-contents in well preserved petrified plant-
tissues. There is often a difficulty, however, in distinguishing between the
true cell-contents and the cells of some parasitic or saprophytic intruder. In
some petrified corky tissue in a silicified nodule from the Permo-
Carboniferous beds of Autun, Renault has recently discovered what he
believes to be traces of a Myxomycetous plasmodium. The cork-cells would
be without protoplasmic contents of their own, and their cavities contain a
number of fine strands stretching from the cell-walls in different directions
and uniting in places as irregular or more or less spherical masses. The
drawings given by Renault of these irregular reticulated structures with
scattered patches of what may possibly be petrified plasmodial protoplasm
bear a striking resemblance to the plasmodium of a Myxomycete. A figure
of the capillitium of a species of Leocarpus figured by Schröter[401] in his
account of the Myxomycetes in Engler and Prantl’s work is very similar to
that of Renault’s ‘plasmodium.’
It is by no means inconceivable that the Myxomycetes Mangini may be
correctly referred to this group, but the wisdom of assigning a name to such
structures may well be questioned.
• • • • •
The other two examples call for little notice. Messrs Cash and Hick[402] in
a paper on fossil fungi from the Coal-Measures refer to some small
spherical bodies as possibly the spores of a Myxomycete. They might be
referred equally well to numerous other organisms.
Göppert and Menge[403] in their monograph on plants in the Baltic
Tertiary Amber, express the opinion that an ill-defined tangle of threads
which they figure may be a Myxomycete.
It would serve no useful purpose to quote other instances of possible
representatives of fossil Mycetozoa; but the consideration of the above
examples may serve to emphasize the desirability of refraining from
converting a possibility into an apparently recognised fact by the
application of definite generic and specific names.
VI. FUNGI.
of original or secondary cell-contents in well preserved petrified plant-
tissues. There is often a difficulty, however, in distinguishing between the
true cell-contents and the cells of some parasitic or saprophytic intruder. In
some petrified corky tissue in a silicified nodule from the Permo-
Carboniferous beds of Autun, Renault has recently discovered what he
believes to be traces of a Myxomycetous plasmodium. The cork-cells would
be without protoplasmic contents of their own, and their cavities contain a
number of fine strands stretching from the cell-walls in different directions
and uniting in places as irregular or more or less spherical masses. The
drawings given by Renault of these irregular reticulated structures with
scattered patches of what may possibly be petrified plasmodial protoplasm
bear a striking resemblance to the plasmodium of a Myxomycete. A figure
of the capillitium of a species of Leocarpus figured by Schröter[401] in his
account of the Myxomycetes in Engler and Prantl’s work is very similar to
that of Renault’s ‘plasmodium.’
It is by no means inconceivable that the Myxomycetes Mangini may be
correctly referred to this group, but the wisdom of assigning a name to such
structures may well be questioned.
• • • • •
The other two examples call for little notice. Messrs Cash and Hick[402] in
a paper on fossil fungi from the Coal-Measures refer to some small
spherical bodies as possibly the spores of a Myxomycete. They might be
referred equally well to numerous other organisms.
Göppert and Menge[403] in their monograph on plants in the Baltic
Tertiary Amber, express the opinion that an ill-defined tangle of threads
which they figure may be a Myxomycete.
It would serve no useful purpose to quote other instances of possible
representatives of fossil Mycetozoa; but the consideration of the above
examples may serve to emphasize the desirability of refraining from
converting a possibility into an apparently recognised fact by the
application of definite generic and specific names.
VI. FUNGI.
Page 223
The most striking difference between the fungi and algae is the absence
of chlorophyll in the former, and the consequent inability of fungi to
manufacture their organic compounds from inorganic material. Fungi live
therefore either as parasites or saprophytes, and as the same species may
pass part of its life in a living host to occur at another stage of its
development as a saprophyte, it is impossible to distinguish definitely
between parasitic and saprophytic forms. The vegetative body of a fungus,
that is the portion which is concerned with providing nourishment and
preparing the plastic food-substance for the reproductive organs, is known
as the mycelium. It consists either of a single and branched tubular cell
known as a hypha, or of several hyphae or thread-like elements
(filamentous fungi). The hyphal filaments may be closely packed together
and form a felted mass of compact tissue, which in cross section closely
simulates the parenchyma of the higher plants. This pseudoparenchymatous
form of thallus is particularly well illustrated by the so-called sclerotia;
these are sharply defined and often tuberous masses of hyphal tissue
covered by a firm rind and containing supplies of food in the inner hyphae.
They are able to remain in a quiescent state for some time, and to resist
unfavourable conditions until germination and the formation of a new
individual take place. The reproductive structures assume various forms; in
some of the simpler fungi (Phycomycetes) sexual organs occur, as in the
parallel group of Siphoneae among the algae, but in the higher fungi the
reproduction is usually entirely asexual. An interesting case has recently
been recorded among the more highly differentiated fungi in which distinct
sexuality has been established[404]. In addition to the reproductive organs,
such as oogonia and antheridia, the asexual cells or spores are borne either
in special sporangia, or they occur as exposed conidia on supporting hyphae
or conidiophores. Thick-walled and resistant resting-spores of various
forms are also met with.
Without going into further details we may very briefly refer to the larger
subdivisions of this group of Thallophytes.
PHYCOMYCETES. Mycelium usually consisting of a single cell. Reproduction by means
ZYGOMYCETES, of conidia, and in many cases also by the conjugation of two similar
OOMYCETES, hyphae or by the fertilisation of an egg-cell contained in an oogonium.
including
Chytridiaceae, &c.
of chlorophyll in the former, and the consequent inability of fungi to
manufacture their organic compounds from inorganic material. Fungi live
therefore either as parasites or saprophytes, and as the same species may
pass part of its life in a living host to occur at another stage of its
development as a saprophyte, it is impossible to distinguish definitely
between parasitic and saprophytic forms. The vegetative body of a fungus,
that is the portion which is concerned with providing nourishment and
preparing the plastic food-substance for the reproductive organs, is known
as the mycelium. It consists either of a single and branched tubular cell
known as a hypha, or of several hyphae or thread-like elements
(filamentous fungi). The hyphal filaments may be closely packed together
and form a felted mass of compact tissue, which in cross section closely
simulates the parenchyma of the higher plants. This pseudoparenchymatous
form of thallus is particularly well illustrated by the so-called sclerotia;
these are sharply defined and often tuberous masses of hyphal tissue
covered by a firm rind and containing supplies of food in the inner hyphae.
They are able to remain in a quiescent state for some time, and to resist
unfavourable conditions until germination and the formation of a new
individual take place. The reproductive structures assume various forms; in
some of the simpler fungi (Phycomycetes) sexual organs occur, as in the
parallel group of Siphoneae among the algae, but in the higher fungi the
reproduction is usually entirely asexual. An interesting case has recently
been recorded among the more highly differentiated fungi in which distinct
sexuality has been established[404]. In addition to the reproductive organs,
such as oogonia and antheridia, the asexual cells or spores are borne either
in special sporangia, or they occur as exposed conidia on supporting hyphae
or conidiophores. Thick-walled and resistant resting-spores of various
forms are also met with.
Without going into further details we may very briefly refer to the larger
subdivisions of this group of Thallophytes.
PHYCOMYCETES. Mycelium usually consisting of a single cell. Reproduction by means
ZYGOMYCETES, of conidia, and in many cases also by the conjugation of two similar
OOMYCETES, hyphae or by the fertilisation of an egg-cell contained in an oogonium.
including
Chytridiaceae, &c.
Page 224
MESOMYCETES, Intermediate between the Phycomycetes and the higher fungi.
including the Multicellular hyphae. No sexual organs.
Sub-classes
HEMIASCI and
HEMIBASIDII.
MYCOMYCETES. Septate vegetative mycelium. No sexual reproduction—as a general
including the rule. Asexual conidia and other forms of spores. In the Ascomycetes the
Sub-classes spores are found in characteristic club-shaped cases or asci; in the
ASCOMYCETES and Basidiomycetes the spores are borne on special branches from swollen
BASIDIOMYCETES. cells known as basidia. The sporophore or spore-bearing body in this
group may attain a considerable size (e.g. Agaricus, Polyporus, &c.)
and exhibit a distinct internal differentiation.
Before describing a few examples of fossil fungi, it is important to
consider the general question of their manner of occurrence and
determination. Considering the small size and delicate nature of most fungi,
it is not surprising that we have but few satisfactory records of well-defined
fossil forms. The large leathery sporophores of Polyporus and other genera
of the Basidiomycetes, which are familiar objects as yellow or brown
brackets projecting from the trunks of diseased forest trees, have been
found in a fairly perfect condition in the Cambridgeshire peat-beds, and
examples have been described also by continental writers[405]. As a general
rule, however, we have to depend on the chance mineralisation or
petrifaction of the hyphae of a fungus-mycelium which has invaded the
living or dead tissues of some higher plant. In the literature on fossil plants
there are numerous recorded species of fungi founded on dark coloured
spots and blotches on the impression of a leaf. Most of such records are
worthless; the external features being usually too imperfect to allow of
accurate identification. The occurrence of recent fungi as discolourations on
leaves is exceedingly common, and the characteristic perithecia or compact
and more or less spherical cases enclosing a group of sporangia in certain
Ascomycetous species, might be readily preserved in a fossil condition.
Ascomycetes.
Some examples of possible Ascomycetous fungi have been recently
recorded by Potonié from leaves and other portions of plants of Permian
age. There is a distinct superficial resemblance between the specimens he
figures and the fructifications of recent Ascomycetes, but in the absence of
internal structure, it would be rash to do more than suggest the probable
including the Multicellular hyphae. No sexual organs.
Sub-classes
HEMIASCI and
HEMIBASIDII.
MYCOMYCETES. Septate vegetative mycelium. No sexual reproduction—as a general
including the rule. Asexual conidia and other forms of spores. In the Ascomycetes the
Sub-classes spores are found in characteristic club-shaped cases or asci; in the
ASCOMYCETES and Basidiomycetes the spores are borne on special branches from swollen
BASIDIOMYCETES. cells known as basidia. The sporophore or spore-bearing body in this
group may attain a considerable size (e.g. Agaricus, Polyporus, &c.)
and exhibit a distinct internal differentiation.
Before describing a few examples of fossil fungi, it is important to
consider the general question of their manner of occurrence and
determination. Considering the small size and delicate nature of most fungi,
it is not surprising that we have but few satisfactory records of well-defined
fossil forms. The large leathery sporophores of Polyporus and other genera
of the Basidiomycetes, which are familiar objects as yellow or brown
brackets projecting from the trunks of diseased forest trees, have been
found in a fairly perfect condition in the Cambridgeshire peat-beds, and
examples have been described also by continental writers[405]. As a general
rule, however, we have to depend on the chance mineralisation or
petrifaction of the hyphae of a fungus-mycelium which has invaded the
living or dead tissues of some higher plant. In the literature on fossil plants
there are numerous recorded species of fungi founded on dark coloured
spots and blotches on the impression of a leaf. Most of such records are
worthless; the external features being usually too imperfect to allow of
accurate identification. The occurrence of recent fungi as discolourations on
leaves is exceedingly common, and the characteristic perithecia or compact
and more or less spherical cases enclosing a group of sporangia in certain
Ascomycetous species, might be readily preserved in a fossil condition.
Ascomycetes.
Some examples of possible Ascomycetous fungi have been recently
recorded by Potonié from leaves and other portions of plants of Permian
age. There is a distinct superficial resemblance between the specimens he
figures and the fructifications of recent Ascomycetes, but in the absence of
internal structure, it would be rash to do more than suggest the probable
Page 225
nature of the markings he describes. For one of the fungus-like impressions
Potonié proposes the generic name Rosellinites; he compares certain
irregularly shaped projections on a piece of Permian wood with the
perithecia of Rosellinia, a member of the Sphaeriaceae, and describes them
as Rosellinites Beyschlagii Pot.[406] Various other records of similar
Ascomycetes-like fossils may be found in palaeobotanical literature[407], but
it is unnecessary to examine these in detail. Unless we are able to determine
the nature of the supposed fungus by microscopical methods our
identifications cannot in most cases be of any great value.
An example of the perithecia of a fungus (Rosellinia congregata [Beck])
[408]
has been recorded from the Oligocene of Saxony, which would appear
to rest on a more satisfactory basis than is often the case. In this particular
instance the small projections on a piece of fossil coniferous stem present a
form which naturally suggests a fungus perithecium. In cases where the
black spots on a fossil stem or leaf possess a definite form and structure, it
is perfectly legitimate to refer them to a group of fungi; but in very many
instances the forms referred to such genera as Sphaerites and others are of
little or no value. Many forms of scale-insects and galls on leaves present
an obvious superficial resemblance to epiphyllous fungi, and might readily
be mistaken for the fructifications of certain Ascomycetous species. As
examples of scale-insects simulating fungi, reference may be made to such
genera of the Coccineae as Aspidiotus, Diaspis, Lecanium, Coccus, and
others. The female insects lying on the surface of a leaf, if preserved as a
fossil impression, might easily be mistaken for perithecia[409].
Another pitfall in fossil mycology may be illustrated by a description of a
supposed fungus, Sclerotites Salisburiae[410], Mass. on a Tertiary Ginkgo
leaf. The figure given by Massalongo represents a Ginkgo leaf with well
marked veins, the lamina between the veins being traversed by short
discontinuous and longitudinally-running lines; the latter are referred to as
the fungus. In a recent Ginkgo leaf one may easily detect with the naked eye
a number of short lines between and parallel to the veins, which if
examined in section are found to be secretory canals. There can be little
doubt that Sclerotites Salisburiae owes its existence to the preservation of
these canals.
The list of fossil fungi given by Meschinelli in Saccardo’s Sylloge
Fungorum[411] includes certain species which are of no botanical value, and
Potonié proposes the generic name Rosellinites; he compares certain
irregularly shaped projections on a piece of Permian wood with the
perithecia of Rosellinia, a member of the Sphaeriaceae, and describes them
as Rosellinites Beyschlagii Pot.[406] Various other records of similar
Ascomycetes-like fossils may be found in palaeobotanical literature[407], but
it is unnecessary to examine these in detail. Unless we are able to determine
the nature of the supposed fungus by microscopical methods our
identifications cannot in most cases be of any great value.
An example of the perithecia of a fungus (Rosellinia congregata [Beck])
[408]
has been recorded from the Oligocene of Saxony, which would appear
to rest on a more satisfactory basis than is often the case. In this particular
instance the small projections on a piece of fossil coniferous stem present a
form which naturally suggests a fungus perithecium. In cases where the
black spots on a fossil stem or leaf possess a definite form and structure, it
is perfectly legitimate to refer them to a group of fungi; but in very many
instances the forms referred to such genera as Sphaerites and others are of
little or no value. Many forms of scale-insects and galls on leaves present
an obvious superficial resemblance to epiphyllous fungi, and might readily
be mistaken for the fructifications of certain Ascomycetous species. As
examples of scale-insects simulating fungi, reference may be made to such
genera of the Coccineae as Aspidiotus, Diaspis, Lecanium, Coccus, and
others. The female insects lying on the surface of a leaf, if preserved as a
fossil impression, might easily be mistaken for perithecia[409].
Another pitfall in fossil mycology may be illustrated by a description of a
supposed fungus, Sclerotites Salisburiae[410], Mass. on a Tertiary Ginkgo
leaf. The figure given by Massalongo represents a Ginkgo leaf with well
marked veins, the lamina between the veins being traversed by short
discontinuous and longitudinally-running lines; the latter are referred to as
the fungus. In a recent Ginkgo leaf one may easily detect with the naked eye
a number of short lines between and parallel to the veins, which if
examined in section are found to be secretory canals. There can be little
doubt that Sclerotites Salisburiae owes its existence to the preservation of
these canals.
The list of fossil fungi given by Meschinelli in Saccardo’s Sylloge
Fungorum[411] includes certain species which are of no botanical value, and
Page 226
should have no place in any list which claims to be authentic.
Among the numerous examples of fossil ‘fungi’ which have no claim to
be classed with plants, there are some which are in all probability the
galleries of wood-eating animals. The radiating grooves frequently found on
the inner face of the bark of a pine tree made by species of the beetle
Bostrychus might be mistaken for the impressions of the firm strands of
mycelial tissue of some Basidiomycetous fungus.
In some notes on fossil fungi by J. F. James[412] contributed to the
American Journal of Mycology in 1893, it is pointed out that a supposed
fungus described by Lesquereux from the Lower Coal-Measures as
Rhizomorpha Sigillariae[413], bears a strong likeness to some insect-burrows,
such as those of Bostrychus.
“A new fungus from the Coal-Measures” described by Herzer in 1893[414]
may probably be referred to animal agency. In any case there is no evidence
as to the fungoid nature of the object represented in the figure
accompanying Herzer’s description.
Basidiomycetes.
More trustworthy evidence of fossil fungi is afforded by the marks of
disease in petrified tissue and by the presence of true mycelia. In examining
closely the calcareous and siliceous plant-tissues from the Coal-Measures
and other geological horizons, one occasionally sees fine thread-like hyphae
ramifying through the cells or tracheal cavities; in many cases the hyphae
bear no reproductive organs and cannot as a rule be referred to a particular
type of fungus. If the hyphal filaments are unseptate, they most likely
belong to some Phycomycetous species; or if they are obviously septate the
Mesomycetes or the Mycomycetes are the more probable groups.
Occasionally there may be found indications of the characteristic clamp-
connections in the septate filaments; a small semicircular branch, which is
given off from a mycelium immediately above a transverse wall, bends
round to fuse with the filament just below the septum, thus serving as a
small loop-line connecting the cell-cavity above and below a cross wall.
Such clamp-connections are usually confined to the hyphae of
Basidiomycetes and thus serve as a useful aid in identification. A good
example of a clamp-connection in a fossil mycelium is figured by
Among the numerous examples of fossil ‘fungi’ which have no claim to
be classed with plants, there are some which are in all probability the
galleries of wood-eating animals. The radiating grooves frequently found on
the inner face of the bark of a pine tree made by species of the beetle
Bostrychus might be mistaken for the impressions of the firm strands of
mycelial tissue of some Basidiomycetous fungus.
In some notes on fossil fungi by J. F. James[412] contributed to the
American Journal of Mycology in 1893, it is pointed out that a supposed
fungus described by Lesquereux from the Lower Coal-Measures as
Rhizomorpha Sigillariae[413], bears a strong likeness to some insect-burrows,
such as those of Bostrychus.
“A new fungus from the Coal-Measures” described by Herzer in 1893[414]
may probably be referred to animal agency. In any case there is no evidence
as to the fungoid nature of the object represented in the figure
accompanying Herzer’s description.
Basidiomycetes.
More trustworthy evidence of fossil fungi is afforded by the marks of
disease in petrified tissue and by the presence of true mycelia. In examining
closely the calcareous and siliceous plant-tissues from the Coal-Measures
and other geological horizons, one occasionally sees fine thread-like hyphae
ramifying through the cells or tracheal cavities; in many cases the hyphae
bear no reproductive organs and cannot as a rule be referred to a particular
type of fungus. If the hyphal filaments are unseptate, they most likely
belong to some Phycomycetous species; or if they are obviously septate the
Mesomycetes or the Mycomycetes are the more probable groups.
Occasionally there may be found indications of the characteristic clamp-
connections in the septate filaments; a small semicircular branch, which is
given off from a mycelium immediately above a transverse wall, bends
round to fuse with the filament just below the septum, thus serving as a
small loop-line connecting the cell-cavity above and below a cross wall.
Such clamp-connections are usually confined to the hyphae of
Basidiomycetes and thus serve as a useful aid in identification. A good
example of a clamp-connection in a fossil mycelium is figured by
Page 227
Conwentz[415] in his monograph on the Baltic amber-trees of Oligocene age.
The stout and thick type of hypha found in some fossil woods agrees
closely with that of Polyporus, Agaricus melleus and other well-known
recent Basidiomycetes.
In a section of a piece of lignified coniferous wood recently brought by
Col. Feilden from Kolguev island[416], the brown and stout hyphae of a
fungus are clearly seen as distinct dark lines traversing the tracheal tissue.
The occurrence of septa and the large diameter of the mycelial branches at
once suggest a comparison with such recent forms as Agaricus melleus,
Polyporus and other Basidiomycetes. The age of the Kolguev wood is not
known with any certainty.
The vesicular swellings such as those represented in fig. 41, A, B, D and
E, may easily be misinterpreted. Such spherical expansions in a mycelium,
either terminal or intercalary, may be sporangia, oogonia or large resting-
spores, or non-fungal cell-contents, and it is usually impossible in the
absence of the contents to determine their precise nature. Hartig[417] and
others have drawn attention to the occurrence of such bladder-like swellings
in the mycelia of recent fungi, which have nothing to do with reproductive
purposes; under certain conditions the hyphae of a fungus growing in the
cavity of a cell or trachea may form such vesicles, and these, as in fig. 42,
D, m may completely fill up the cavity of a large tracheid.
Some good examples of bladder-like swellings, such as occur in the
mycelium of Agaricus melleus and other recent fungi, have been figured by
Conwentz[418] in fossil wood of Tertiary age from Karlsdorf. The swellings
in this fossil fungus might easily be mistaken for oogonia or sporangia;
especially as they are few in number and spherical in form.
A similar appearance is presented by a mass of tyloses in the cavity of an
old vessel or tracheid; and vesicular cell-contents, as in the cells of fig. 41,
A, 2–5, may closely simulate a number of thin-walled fungal spores or
sporangia.
A good example of such a vesicular tissue, in addition to that already
quoted, is afforded by a specimen of an Eocene fern, Osmundites Dowkeri
Carr.[419] described by Carruthers in 1870. The ground-tissue cells contain
traces of distinct fungal hyphae (fig. 41, B), and in many of the
parenchymatous elements the cavity is completely filled with spherical
The stout and thick type of hypha found in some fossil woods agrees
closely with that of Polyporus, Agaricus melleus and other well-known
recent Basidiomycetes.
In a section of a piece of lignified coniferous wood recently brought by
Col. Feilden from Kolguev island[416], the brown and stout hyphae of a
fungus are clearly seen as distinct dark lines traversing the tracheal tissue.
The occurrence of septa and the large diameter of the mycelial branches at
once suggest a comparison with such recent forms as Agaricus melleus,
Polyporus and other Basidiomycetes. The age of the Kolguev wood is not
known with any certainty.
The vesicular swellings such as those represented in fig. 41, A, B, D and
E, may easily be misinterpreted. Such spherical expansions in a mycelium,
either terminal or intercalary, may be sporangia, oogonia or large resting-
spores, or non-fungal cell-contents, and it is usually impossible in the
absence of the contents to determine their precise nature. Hartig[417] and
others have drawn attention to the occurrence of such bladder-like swellings
in the mycelia of recent fungi, which have nothing to do with reproductive
purposes; under certain conditions the hyphae of a fungus growing in the
cavity of a cell or trachea may form such vesicles, and these, as in fig. 42,
D, m may completely fill up the cavity of a large tracheid.
Some good examples of bladder-like swellings, such as occur in the
mycelium of Agaricus melleus and other recent fungi, have been figured by
Conwentz[418] in fossil wood of Tertiary age from Karlsdorf. The swellings
in this fossil fungus might easily be mistaken for oogonia or sporangia;
especially as they are few in number and spherical in form.
A similar appearance is presented by a mass of tyloses in the cavity of an
old vessel or tracheid; and vesicular cell-contents, as in the cells of fig. 41,
A, 2–5, may closely simulate a number of thin-walled fungal spores or
sporangia.
A good example of such a vesicular tissue, in addition to that already
quoted, is afforded by a specimen of an Eocene fern, Osmundites Dowkeri
Carr.[419] described by Carruthers in 1870. The ground-tissue cells contain
traces of distinct fungal hyphae (fig. 41, B), and in many of the
parenchymatous elements the cavity is completely filled with spherical
Page 228
vesicles; in other cases one finds hyphae in the centre of the cell while
vesicles line the wall, as shewn in fig. 41, B. Carruthers refers to these
bladders as starch grains, and this may be their true nature; their appearance
and abundant occurrence in the parenchyma certainly suggest vesicular cell-
contents rather than fungal cells. I could detect no proof of any connection
between the hyphae and bladders, and the absence of the latter in the
cavities of the tracheids, fig. 41, C, favoured the view of their being either
starch-grains or other vacuolated contents similar to that in the cells of the
Portland Cycad (fig. 41, A) referred to on p. 88.
PATHOLOGY OF FOSSIL TISSUES.
The vacuolated cell-contents partially filling the cells in fig. 41, D,
present a striking resemblance to the contents of the cells 2–5 in fig. 41, A.
In fig. D the frothy and contracted substance might be easily mistaken for a
parasitic or saprophytic fungus, but this resemblance is entirely misleading.
It is by no means uncommon to find the cells of recent plants occupied by
such vacuolated contents, especially in diseased tissues in which a
pathological effect produces an appearance which has more than once
misled the most practised observers.
In the important work recently published by Renault on the Permo-
Carboniferous flora of Autun, there is a small spore-like body described as a
teleutospore, and classed with the Puccineae[420]. We have as yet no
satisfactory evidence of the existence of this section of Fungi in Palaeozoic
times, and Renault’s description of Teleutospora Milloti from Autun might
be seriously misleading if accepted without reference to his figure. The
fragment he describes cannot be accepted as sufficient evidence for the
existence of a Palaeozoic Puccinia.
The same author refers another Palaeozoic fungus to the Mucorineae
under the name of Mucor Combrensis[421]; this identification is based on a
mycelium having a resemblance to the branched thallus of Mucor, but in the
absence of reproductive organs such resemblance is hardly adequate as a
means of recognition.
The occurrence of hyphal cells in calcareous shells and corals has already
been alluded to.[422] In addition to the examples referred to above, there is
one which has been described by Etheridge[423] from a Permo-Carboniferous
coral. This observer records the occurrence of tubular cavities in the calices
vesicles line the wall, as shewn in fig. 41, B. Carruthers refers to these
bladders as starch grains, and this may be their true nature; their appearance
and abundant occurrence in the parenchyma certainly suggest vesicular cell-
contents rather than fungal cells. I could detect no proof of any connection
between the hyphae and bladders, and the absence of the latter in the
cavities of the tracheids, fig. 41, C, favoured the view of their being either
starch-grains or other vacuolated contents similar to that in the cells of the
Portland Cycad (fig. 41, A) referred to on p. 88.
PATHOLOGY OF FOSSIL TISSUES.
The vacuolated cell-contents partially filling the cells in fig. 41, D,
present a striking resemblance to the contents of the cells 2–5 in fig. 41, A.
In fig. D the frothy and contracted substance might be easily mistaken for a
parasitic or saprophytic fungus, but this resemblance is entirely misleading.
It is by no means uncommon to find the cells of recent plants occupied by
such vacuolated contents, especially in diseased tissues in which a
pathological effect produces an appearance which has more than once
misled the most practised observers.
In the important work recently published by Renault on the Permo-
Carboniferous flora of Autun, there is a small spore-like body described as a
teleutospore, and classed with the Puccineae[420]. We have as yet no
satisfactory evidence of the existence of this section of Fungi in Palaeozoic
times, and Renault’s description of Teleutospora Milloti from Autun might
be seriously misleading if accepted without reference to his figure. The
fragment he describes cannot be accepted as sufficient evidence for the
existence of a Palaeozoic Puccinia.
The same author refers another Palaeozoic fungus to the Mucorineae
under the name of Mucor Combrensis[421]; this identification is based on a
mycelium having a resemblance to the branched thallus of Mucor, but in the
absence of reproductive organs such resemblance is hardly adequate as a
means of recognition.
The occurrence of hyphal cells in calcareous shells and corals has already
been alluded to.[422] In addition to the examples referred to above, there is
one which has been described by Etheridge[423] from a Permo-Carboniferous
coral. This observer records the occurrence of tubular cavities in the calices
Page 229
of Stenopora crinita Lonsd., and attributes their origin to a fungus which he
names Palaeoperone endophytica; he mentions one case in which a tube
contains fine spherical spore-like bodies which he compares with the spores
of a Saprolegnia. As pointed out above (p. 128), it is almost impossible to
decide how far these tubes in shells and corals should be attributed to fungi,
and how far to algae.
names Palaeoperone endophytica; he mentions one case in which a tube
contains fine spherical spore-like bodies which he compares with the spores
of a Saprolegnia. As pointed out above (p. 128), it is almost impossible to
decide how far these tubes in shells and corals should be attributed to fungi,
and how far to algae.
Page 230
Fig. 41. A. Cells of Cycadeoidea gigantea Sew. × 355. B and C. Parenchymatous cells and
scalariform tracheids of Osmundites Dowkeri Carr. × 230. D. Epidermal cells of
Memecylon (Melastomaceae) with vacuolated contents. E. Peronosporites antiquarius
Smith, (No. 1923 in the Williamson collection). × 230. F. Zygosporites. × 230. (A, B, C and
E drawn from specimens in the British Museum; D from a drawing by Prof. Marshall
Ward; F from a specimen in the Botanical Laboratory Collection, Cambridge.)
scalariform tracheids of Osmundites Dowkeri Carr. × 230. D. Epidermal cells of
Memecylon (Melastomaceae) with vacuolated contents. E. Peronosporites antiquarius
Smith, (No. 1923 in the Williamson collection). × 230. F. Zygosporites. × 230. (A, B, C and
E drawn from specimens in the British Museum; D from a drawing by Prof. Marshall
Ward; F from a specimen in the Botanical Laboratory Collection, Cambridge.)
Page 231
Fig. 42. A, B, C. Tracheids of coniferous wood attacked by Trametes radiciperda Hart.
(Polyporus annosus Fr.) D and E. Tracheids attacked by Agaricus melleus Vahl. A, × 650,
B–E, × 360. (After Hartig.)
Passing from the direct evidence obtained from the presence of fungal
hyphae in petrified tissues, we must draw attention to the indirect evidence
of fungal action afforded by many fossil plants. It is important to be familiar
with at least the more striking effects of fungal ravages in recent wood in
order that we may escape some of the mistakes to which pathological
phenomena may lead us in the case of fossils[424].
The gradual dissociation of the elements in a piece of fossil wood owing
to the destruction of the middle lamellae, the occurrence of various forms of
slit-like apertures in the walls of tracheids (fig. 42, E) and the production of
a system of fine parallel striation on the walls of a vessel are among the
results produced by parasitic and saprophytic fungi. With the help of a
ferment secreted by its hyphae, a fungus is able to eat away either the
thickening cell layers or the middle lamellae or both, and if, as in fig. 42, A,
only the middle lamellae are left one might easily regard such tissue in a
fossil condition as consisting of delicate thin-walled elements. The oblique
striae on the walls of a tracheid may often be due to the action of a ferment
(Polyporus annosus Fr.) D and E. Tracheids attacked by Agaricus melleus Vahl. A, × 650,
B–E, × 360. (After Hartig.)
Passing from the direct evidence obtained from the presence of fungal
hyphae in petrified tissues, we must draw attention to the indirect evidence
of fungal action afforded by many fossil plants. It is important to be familiar
with at least the more striking effects of fungal ravages in recent wood in
order that we may escape some of the mistakes to which pathological
phenomena may lead us in the case of fossils[424].
The gradual dissociation of the elements in a piece of fossil wood owing
to the destruction of the middle lamellae, the occurrence of various forms of
slit-like apertures in the walls of tracheids (fig. 42, E) and the production of
a system of fine parallel striation on the walls of a vessel are among the
results produced by parasitic and saprophytic fungi. With the help of a
ferment secreted by its hyphae, a fungus is able to eat away either the
thickening cell layers or the middle lamellae or both, and if, as in fig. 42, A,
only the middle lamellae are left one might easily regard such tissue in a
fossil condition as consisting of delicate thin-walled elements. The oblique
striae on the walls of a tracheid may often be due to the action of a ferment
Page 232
which has dissolved the membrane in such a manner as to etch out a system
of spiral lines, probably as a consequence of the original structure of the
tracheids. In distinguishing between the woods of Conifers the presence of
spiral thickening layers in the wood element is an important diagnostic
character, and it is necessary to guard against the confusion of purely
secondary structures, due to fungal action, with original features which may
be of value in determining the generic affinity of a piece of fossil wood.
Oochytrium Lepidodendri, Ren. Fig. 43, 1.
Under this name Renault has recently described a filamentous fungus
endophytic in the cavities of the scalariform tracheids of a
Lepidodendron[425]. The mycelium has the form of slender branched hyphae
with transverse septa. Numerous ovoid and more or less spherical sporangia
occur as terminal swellings of the mycelial threads. The long axis of the
ovoid forms measures 12–15 µ, and the shorter axis 9–10 µ; the contents
may be seen as a slightly contracted mass in the sporangial cavity. In some
of the sporangia one sees a short apical prolongation in the form of a small
elongated papilla, as shown in fig. 43, 1. Renault refers this fungus to the
Chytridineae, and compares it with Cladochytrium, Woronina, Olpidium,
and other recent genera.
In the immediate neighbourhood of two of the sporangia shown in the
uppermost tracheid of fig. 43, 1, there are seen a few minute dark dots
which are described as spores petrified in the act of escaping from a lateral
pore. This interpretation strikes one as lacking in scientific caution.
The sporangia of Hyphochytrium infestans[426], as figured by Fischer in
Rabenhorst’s work bear a close resemblance to those of the fossil. It would
seem very probable that Renault’s species may be reasonably referred to the
Chytridineae, as he proposes.
of spiral lines, probably as a consequence of the original structure of the
tracheids. In distinguishing between the woods of Conifers the presence of
spiral thickening layers in the wood element is an important diagnostic
character, and it is necessary to guard against the confusion of purely
secondary structures, due to fungal action, with original features which may
be of value in determining the generic affinity of a piece of fossil wood.
Oochytrium Lepidodendri, Ren. Fig. 43, 1.
Under this name Renault has recently described a filamentous fungus
endophytic in the cavities of the scalariform tracheids of a
Lepidodendron[425]. The mycelium has the form of slender branched hyphae
with transverse septa. Numerous ovoid and more or less spherical sporangia
occur as terminal swellings of the mycelial threads. The long axis of the
ovoid forms measures 12–15 µ, and the shorter axis 9–10 µ; the contents
may be seen as a slightly contracted mass in the sporangial cavity. In some
of the sporangia one sees a short apical prolongation in the form of a small
elongated papilla, as shown in fig. 43, 1. Renault refers this fungus to the
Chytridineae, and compares it with Cladochytrium, Woronina, Olpidium,
and other recent genera.
In the immediate neighbourhood of two of the sporangia shown in the
uppermost tracheid of fig. 43, 1, there are seen a few minute dark dots
which are described as spores petrified in the act of escaping from a lateral
pore. This interpretation strikes one as lacking in scientific caution.
The sporangia of Hyphochytrium infestans[426], as figured by Fischer in
Rabenhorst’s work bear a close resemblance to those of the fossil. It would
seem very probable that Renault’s species may be reasonably referred to the
Chytridineae, as he proposes.
Page 233
Fig. 43. 1. Oochytrium Lepidodendri, Ren. (After Renault.) 2. Polyporus vaporarius Fr. var.
succinea. (After Conwentz.) 3. Cladosporites bipartitus Fel. (After Felix.) 4.
Haplographites cateniger Fel. (After Felix.)
Peronosporites antiquarius W. Smith. Fig. 41, E.
In an address to the Geologists’ Association delivered by Mr Carruthers
in 1876 a brief reference, accompanied by a small-scale drawing, is made to
the discovery of a fungus in the scalariform tracheids of a Lepidodendron
from the English Coal-Measures[427]. In the following year Worthington
Smith published a fuller account of the fungus, and proposed for it the
above name[428], which he chose on the ground of a close similarity between
the mycelium and reproductive organs of the fossil form and recent
members of the Peronosporeae. In Smith’s description the mycelium is
described as bearing spherical swellings containing zoospores. These
spherical organs are fairly abundant and not infrequently met with in
sections of petrified plant-tissues from the English Coal-Measures; they
may be oogonia or sporangia, or in some cases mere vesicular expansions
of a purely vegetative hypha. No confirmation has been given to the
supposed spores referred to by Smith. Prof. Williamson and others have
carefully examined the specimens, but they have failed to detect any trace
of reproductive cells enclosed in the spherical sacs[429]. The mycelium does
succinea. (After Conwentz.) 3. Cladosporites bipartitus Fel. (After Felix.) 4.
Haplographites cateniger Fel. (After Felix.)
Peronosporites antiquarius W. Smith. Fig. 41, E.
In an address to the Geologists’ Association delivered by Mr Carruthers
in 1876 a brief reference, accompanied by a small-scale drawing, is made to
the discovery of a fungus in the scalariform tracheids of a Lepidodendron
from the English Coal-Measures[427]. In the following year Worthington
Smith published a fuller account of the fungus, and proposed for it the
above name[428], which he chose on the ground of a close similarity between
the mycelium and reproductive organs of the fossil form and recent
members of the Peronosporeae. In Smith’s description the mycelium is
described as bearing spherical swellings containing zoospores. These
spherical organs are fairly abundant and not infrequently met with in
sections of petrified plant-tissues from the English Coal-Measures; they
may be oogonia or sporangia, or in some cases mere vesicular expansions
of a purely vegetative hypha. No confirmation has been given to the
supposed spores referred to by Smith. Prof. Williamson and others have
carefully examined the specimens, but they have failed to detect any trace
of reproductive cells enclosed in the spherical sacs[429]. The mycelium does
Page 234
not appear to show any satisfactory evidence of its being septate as figured
by Smith.
The example shown in fig. 41 E has been drawn from one of the
Williamson specimens: it illustrates the form and manner of occurrence of
the characteristic swellings. It is probable that some at least of the vesicles
are either sporangia or oogonia, but we cannot speak with absolute
confidence as to their precise nature. The general habit and structure of the
fungus favour its inclusion in the class of Phycomycetes. The occurrence of
several of the vesicles close together on short hyphal branches, as shown in
Williamson’s figures, suggests the spherical swellings on vegetative
hyphae, but it is impossible to speak with absolute confidence. There is a
close resemblance between this English form and one recently described by
Renault as Palaeomyces gracilis Ren.[430]; the two fossils should probably
be placed in the same genus.
The examples referred to below and originally recorded by Cash and
Hick no doubt belong to the same type as Smith’s Peronosporites.
The sketches reproduced in fig. 44 have been drawn from specimens
originally described by Cash and Hick in 1878[431]. The sections were cut
from a calcareous nodule from the Halifax Coal-Measures containing
fragments of various plants and among others a piece of cortical tissue,
probably of a Lepidodendron or Stigmaria. In a transverse section of this
tissue one sees under a moderately high power that the cells have become
partially separated from one another by the destruction of the middle
lamellae (fig. 44 A). The cell-cavities and the spaces between the isolated
cells contain numerous fine fungal hyphae, which here and there terminate
in spherical swellings. One such swelling is shown under a low power in
fig. 44 A, in the middle uppermost cell, and more highly magnified in fig.
44 B. In fig. C there are two such swellings (the larger one having a
diameter of ·003 mm.) in contact, but the connection does not appear to be
organic. The cell-walls of the infected tissue present a ragged and untidy
appearance, and in places (e.g. fig. 44 D) the membrane has been pierced by
some of the mycelial branches.
by Smith.
The example shown in fig. 41 E has been drawn from one of the
Williamson specimens: it illustrates the form and manner of occurrence of
the characteristic swellings. It is probable that some at least of the vesicles
are either sporangia or oogonia, but we cannot speak with absolute
confidence as to their precise nature. The general habit and structure of the
fungus favour its inclusion in the class of Phycomycetes. The occurrence of
several of the vesicles close together on short hyphal branches, as shown in
Williamson’s figures, suggests the spherical swellings on vegetative
hyphae, but it is impossible to speak with absolute confidence. There is a
close resemblance between this English form and one recently described by
Renault as Palaeomyces gracilis Ren.[430]; the two fossils should probably
be placed in the same genus.
The examples referred to below and originally recorded by Cash and
Hick no doubt belong to the same type as Smith’s Peronosporites.
The sketches reproduced in fig. 44 have been drawn from specimens
originally described by Cash and Hick in 1878[431]. The sections were cut
from a calcareous nodule from the Halifax Coal-Measures containing
fragments of various plants and among others a piece of cortical tissue,
probably of a Lepidodendron or Stigmaria. In a transverse section of this
tissue one sees under a moderately high power that the cells have become
partially separated from one another by the destruction of the middle
lamellae (fig. 44 A). The cell-cavities and the spaces between the isolated
cells contain numerous fine fungal hyphae, which here and there terminate
in spherical swellings. One such swelling is shown under a low power in
fig. 44 A, in the middle uppermost cell, and more highly magnified in fig.
44 B. In fig. C there are two such swellings (the larger one having a
diameter of ·003 mm.) in contact, but the connection does not appear to be
organic. The cell-walls of the infected tissue present a ragged and untidy
appearance, and in places (e.g. fig. 44 D) the membrane has been pierced by
some of the mycelial branches.
Page 235
Fig. 44. Cells with fungal hyphae. A. A piece of disorganised tissue, showing the separation
of the cells. B. Part of A more highly magnified. C. A single cell containing two swollen
hyphae. D. Partially destroyed cell-membranes pierced by fungal hyphae. (Drawn from
sections in the Edinburgh Botanical Museum, originally described by Cash and Hick.)
This fungus bears a close resemblance to Peronosporites antiquarius, but
it is impossible to determine its precise botanical position without further
data. In Cash and Hick’s paper in which the above fungus is briefly dealt
with, some small spore-like bodies are figured which the authors speak of
as possibly a Myxomycetous fungus[432]. There is however no sound reason
for such a supposition.
As examples of Ascomycetous fungi found in silicified wood of Tertiary
age, two species may be quoted from Felix.
Cladosporites bipartitus Felix[433], fig. 43, 3.
The mycelium and conidia of this form were discovered in some Eocene
silicified wood from Perekeschkul near Baku, on the shores of the Caspian.
The conidia are elliptical or pyriform in shape and divided by a transverse
septum into two cells. No traces were found of any special conidiophores.
The mycelium consists of septate branched hyphae, rendered conspicuous
of the cells. B. Part of A more highly magnified. C. A single cell containing two swollen
hyphae. D. Partially destroyed cell-membranes pierced by fungal hyphae. (Drawn from
sections in the Edinburgh Botanical Museum, originally described by Cash and Hick.)
This fungus bears a close resemblance to Peronosporites antiquarius, but
it is impossible to determine its precise botanical position without further
data. In Cash and Hick’s paper in which the above fungus is briefly dealt
with, some small spore-like bodies are figured which the authors speak of
as possibly a Myxomycetous fungus[432]. There is however no sound reason
for such a supposition.
As examples of Ascomycetous fungi found in silicified wood of Tertiary
age, two species may be quoted from Felix.
Cladosporites bipartitus Felix[433], fig. 43, 3.
The mycelium and conidia of this form were discovered in some Eocene
silicified wood from Perekeschkul near Baku, on the shores of the Caspian.
The conidia are elliptical or pyriform in shape and divided by a transverse
septum into two cells. No traces were found of any special conidiophores.
The mycelium consists of septate branched hyphae, rendered conspicuous
Page 236
by a brown colouration. Felix compares the fossil with the recent genera
Cephalothecium and Cladosporium.
Haplographites cateniger Felix[434], fig. 43, 4.
The conidia of this form were found to be fairly abundant in the silicified
tissue investigated by Felix; they occur usually in chains of 2 to 6 conidia
having an ovoid or flask-shaped form, with a thick membrane (fig. 43, 4).
The mycelium consists of branched hyphae divided into long cylindrical
cells by transverse septa; occasional instances were found of an H-shaped
fusion between lateral branches of parallel hyphae.
Felix compares this species with examples of the genera Haptographium
and Dematium of the family Sphaeriaceae; it was found in the woody tissue
of a dicotyledonous stem from Perekeschkul.
Zygosporites sp.
The object represented in fig. 41 F consists of a stalked spherical sac
bearing a number of radiating arms which are divided distally into delicate
terminations. We find similar bodies figured by Williamson[435] in his IXth
and Xth Memoirs on the Coal-Measure plants; he includes some of them
under the generic term Zygosporites, and compares them with the
zygospores of the freshwater algae Desmideae. Hitherto these spore-like
fossils have only been recorded as isolated spheres, but in the example
shown in fig. 41 F there is a distinct tubular and thin-walled stalk attached
to the Zygosporites. The specimen was found in the partially disorganised
cortical tissue of a Lyginodendron stem from the English Coal-Measures. It
is difficult to decide as to the precise nature of the fossil, but the presence of
the hyphal stalk points to a fungus rather than an alga as the most probable
type of plant with which to connect it. It may possibly be a sporangium of a
fungus comparable with the common mould Mucor, or it may be a
zygospore formed by the conjugation of two hyphae of which only one has
been preserved.
POLYPORUS.
Cephalothecium and Cladosporium.
Haplographites cateniger Felix[434], fig. 43, 4.
The conidia of this form were found to be fairly abundant in the silicified
tissue investigated by Felix; they occur usually in chains of 2 to 6 conidia
having an ovoid or flask-shaped form, with a thick membrane (fig. 43, 4).
The mycelium consists of branched hyphae divided into long cylindrical
cells by transverse septa; occasional instances were found of an H-shaped
fusion between lateral branches of parallel hyphae.
Felix compares this species with examples of the genera Haptographium
and Dematium of the family Sphaeriaceae; it was found in the woody tissue
of a dicotyledonous stem from Perekeschkul.
Zygosporites sp.
The object represented in fig. 41 F consists of a stalked spherical sac
bearing a number of radiating arms which are divided distally into delicate
terminations. We find similar bodies figured by Williamson[435] in his IXth
and Xth Memoirs on the Coal-Measure plants; he includes some of them
under the generic term Zygosporites, and compares them with the
zygospores of the freshwater algae Desmideae. Hitherto these spore-like
fossils have only been recorded as isolated spheres, but in the example
shown in fig. 41 F there is a distinct tubular and thin-walled stalk attached
to the Zygosporites. The specimen was found in the partially disorganised
cortical tissue of a Lyginodendron stem from the English Coal-Measures. It
is difficult to decide as to the precise nature of the fossil, but the presence of
the hyphal stalk points to a fungus rather than an alga as the most probable
type of plant with which to connect it. It may possibly be a sporangium of a
fungus comparable with the common mould Mucor, or it may be a
zygospore formed by the conjugation of two hyphae of which only one has
been preserved.
POLYPORUS.
Page 237
For an example of a fossil representative of the Basidiomycetes we may
turn to the excellent monograph by Conwentz on the Baltic amber trees, and
quote one of the forms which he has described.
Polyporus vaporarius Fr. f. succinea[436], fig. 43, 2.
In several preparations of the wood preserved by petrifaction in amber
Conwentz found distinct indications of the ravages of a fungus, which
suggested the presence of the recent species Polyporus vaporarius Fr. With
the help of the indirect evidence afforded by the pathological effects as seen
in the tissues of the host-plant, and the direct evidence of the fungal
mycelium Conwentz was led to this identification.
The mycelium is brown in colour, in part thick-walled, and in part with
thin walls, transversely septate and not much branched. In the portion of
one of Conwentz’ figures reproduced in fig. 43, 2, the rents and holes in the
tracheid walls are clearly shown; they afford the indirect evidence of fungal
attacks, and are of the same nature as those shown in fig. 42, B, C and E.
• • • • •
Enough has been said to call attention to the paucity of exact data on
which to generalise as to the geological history of fungi. The types selected
for description or passing allusion have not been chosen in each case
because of their special intrinsic value, but rather as convenient examples
by which to illustrate authentic records or to serve as warnings against
possible sources of error.
It would seem that we have fairly good and conclusive evidence of the
existence in Permo-Carboniferous times of Phycomycetous fungi, but it is
not until we pass to post-Palaeozoic or even Tertiary plants that we discover
satisfactory representatives of the higher fungi or Mycomycetes. If special
attention were paid to the investigation of fossil fungi, it is quite possible
that our knowledge of the past history of the group might be considerably
extended. It is essential that the greatest caution should be exercised in the
identification of forms and in their reference to definite families; otherwise
our lists of fossil species will serve to mislead, and to emphasize the
untrustworthy character of palaeobotanical data. Unless we feel satisfied as
to the position of a fossil fungus it is unwise to use a generic term
suggestive of a definite family or recent genus. Such a name as Renault has
turn to the excellent monograph by Conwentz on the Baltic amber trees, and
quote one of the forms which he has described.
Polyporus vaporarius Fr. f. succinea[436], fig. 43, 2.
In several preparations of the wood preserved by petrifaction in amber
Conwentz found distinct indications of the ravages of a fungus, which
suggested the presence of the recent species Polyporus vaporarius Fr. With
the help of the indirect evidence afforded by the pathological effects as seen
in the tissues of the host-plant, and the direct evidence of the fungal
mycelium Conwentz was led to this identification.
The mycelium is brown in colour, in part thick-walled, and in part with
thin walls, transversely septate and not much branched. In the portion of
one of Conwentz’ figures reproduced in fig. 43, 2, the rents and holes in the
tracheid walls are clearly shown; they afford the indirect evidence of fungal
attacks, and are of the same nature as those shown in fig. 42, B, C and E.
• • • • •
Enough has been said to call attention to the paucity of exact data on
which to generalise as to the geological history of fungi. The types selected
for description or passing allusion have not been chosen in each case
because of their special intrinsic value, but rather as convenient examples
by which to illustrate authentic records or to serve as warnings against
possible sources of error.
It would seem that we have fairly good and conclusive evidence of the
existence in Permo-Carboniferous times of Phycomycetous fungi, but it is
not until we pass to post-Palaeozoic or even Tertiary plants that we discover
satisfactory representatives of the higher fungi or Mycomycetes. If special
attention were paid to the investigation of fossil fungi, it is quite possible
that our knowledge of the past history of the group might be considerably
extended. It is essential that the greatest caution should be exercised in the
identification of forms and in their reference to definite families; otherwise
our lists of fossil species will serve to mislead, and to emphasize the
untrustworthy character of palaeobotanical data. Unless we feel satisfied as
to the position of a fossil fungus it is unwise to use a generic term
suggestive of a definite family or recent genus. Such a name as Renault has
Page 238
used in one instance, Palaeomyces, might be employed as a useful and
comprehensive designation.
VII. CHAROPHYTA.
CHARACEÆ. NITELLEÆ.
It has been the general custom to include the Characeæ or Stoneworts
among the Chlorophyceae (green algae), of which they form a distinctly
isolated family. On the whole, it would seem better to follow the course
lately adopted by Migula[437] and allow the Characeæ to rank as a family of
a distinct group, Charophyta. While agreeing in many respects with plants
higher in the scale than Thallophytes, the Stoneworts do not sufficiently
resemble the Bryophyta to be included in that group.
The Charophyta are plants containing chlorophyll, living in fresh and
brackish water; the stem is jointed, and bears at the nodes whorls of leaves,
on which are borne the reproductive organs. The antheridia are spherical in
shape and of complex structure, containing numerous biciliate antherozoids.
The oogonia are oval in form and contain a single large egg-cell. The
Chara-plant is developed from a protonema formed from the germinating
oospore. Vegetative reproduction is effected by means of bulbils, accessory
shoots, etc.
The Nitelleæ have not been recognised in a fossil condition. The absence
or feeble development of a calcareous incrustation renders the genera of this
family less likely to be preserved than such a genus as Chara.
Chareae.
Leaves and stems with or without a cortical investment. Fruit with a five-
celled corona. The envelope of the ‘fruit’ and other parts of the plant are
frequently encrusted with carbonate of lime.
In the genus Chara, the best known member of the family, the plant as a
whole resembles in its general habit and external differentiation of parts the
higher plants. The stem consists of long internodes separated by short nodes
bearing whorls of leaves. Each internode consists of a long cylindrical cell,
which becomes enclosed by a cortical sheath composed of rows of cells
comprehensive designation.
VII. CHAROPHYTA.
CHARACEÆ. NITELLEÆ.
It has been the general custom to include the Characeæ or Stoneworts
among the Chlorophyceae (green algae), of which they form a distinctly
isolated family. On the whole, it would seem better to follow the course
lately adopted by Migula[437] and allow the Characeæ to rank as a family of
a distinct group, Charophyta. While agreeing in many respects with plants
higher in the scale than Thallophytes, the Stoneworts do not sufficiently
resemble the Bryophyta to be included in that group.
The Charophyta are plants containing chlorophyll, living in fresh and
brackish water; the stem is jointed, and bears at the nodes whorls of leaves,
on which are borne the reproductive organs. The antheridia are spherical in
shape and of complex structure, containing numerous biciliate antherozoids.
The oogonia are oval in form and contain a single large egg-cell. The
Chara-plant is developed from a protonema formed from the germinating
oospore. Vegetative reproduction is effected by means of bulbils, accessory
shoots, etc.
The Nitelleæ have not been recognised in a fossil condition. The absence
or feeble development of a calcareous incrustation renders the genera of this
family less likely to be preserved than such a genus as Chara.
Chareae.
Leaves and stems with or without a cortical investment. Fruit with a five-
celled corona. The envelope of the ‘fruit’ and other parts of the plant are
frequently encrusted with carbonate of lime.
In the genus Chara, the best known member of the family, the plant as a
whole resembles in its general habit and external differentiation of parts the
higher plants. The stem consists of long internodes separated by short nodes
bearing whorls of leaves. Each internode consists of a long cylindrical cell,
which becomes enclosed by a cortical sheath composed of rows of cells
Page 239
which have grown upwards and downwards from the peripheral nodal cells.
The cortical cells are usually spirally twisted and impart to the stem a
characteristic appearance; they are divided by transverse walls into
numerous cells some of which occasionally grow out into short processes
(fig. 45 c). The leaves repeat on a smaller scale the structural features of the
stem, but possess a limited growth, whereas the stem has an unlimited
power of growth by means of a large hemispherical apical cell. Branches
arise in the axils of the leaves. The plants are either monoecious or
dioecious. The oogonium is elliptical in shape, and is borne on a short stalk-
cell, it contains a single oosphere. The wall of the oogonium is formed of
five spirally twisted cells which have grown over it from the five peripheral
cells of a leaf-node. The tips of the investing cells project at the apex in the
form of a terminal crown or corona (fig. 45, E, c). The antheridia have a
complex structure, and produce a very large number of motile antherozoids.
The cortical cells are usually spirally twisted and impart to the stem a
characteristic appearance; they are divided by transverse walls into
numerous cells some of which occasionally grow out into short processes
(fig. 45 c). The leaves repeat on a smaller scale the structural features of the
stem, but possess a limited growth, whereas the stem has an unlimited
power of growth by means of a large hemispherical apical cell. Branches
arise in the axils of the leaves. The plants are either monoecious or
dioecious. The oogonium is elliptical in shape, and is borne on a short stalk-
cell, it contains a single oosphere. The wall of the oogonium is formed of
five spirally twisted cells which have grown over it from the five peripheral
cells of a leaf-node. The tips of the investing cells project at the apex in the
form of a terminal crown or corona (fig. 45, E, c). The antheridia have a
complex structure, and produce a very large number of motile antherozoids.
Page 240
Fig. 45. A and B. Chara Knowltoni Sew. From a section in the British Museum. C. Stem of
Chara foetida A. Br. in transverse section (after Migula. × 18). D. Interior of oogonium of
C. foetida. E. Oogonium of C. foetida (D and E after Migula. × 50).
After fertilisation, the egg-cell becomes surrounded by a membrane, at
first colourless, but afterwards yellow or brown. The inner cell-walls of the
cells surrounding the oospore become thicker and darker in colour; the
outer walls remain thin and eventually fall away. The lateral walls may or
may not become thickened. In most of the Chareae a calcareous deposit is
formed between the hard shell and the outer walls of the cells enveloping
the oospore. This calcareous shell is developed subsequently to the
thickening and hardening of the inner walls of the fruit-case. The cells of
the corona and stalk do not become calcareous. In the fossil Charas, it is
this calcareous shell that is preserved. In the members of the Chareae the
Chara foetida A. Br. in transverse section (after Migula. × 18). D. Interior of oogonium of
C. foetida. E. Oogonium of C. foetida (D and E after Migula. × 50).
After fertilisation, the egg-cell becomes surrounded by a membrane, at
first colourless, but afterwards yellow or brown. The inner cell-walls of the
cells surrounding the oospore become thicker and darker in colour; the
outer walls remain thin and eventually fall away. The lateral walls may or
may not become thickened. In most of the Chareae a calcareous deposit is
formed between the hard shell and the outer walls of the cells enveloping
the oospore. This calcareous shell is developed subsequently to the
thickening and hardening of the inner walls of the fruit-case. The cells of
the corona and stalk do not become calcareous. In the fossil Charas, it is
this calcareous shell that is preserved. In the members of the Chareae the
Page 241
stems are usually encrusted with carbonate of lime, and thus have a much
better chance of preservation than the slightly calcareous Nitelleæ.
Chara.
The generic characters have already been described in the brief account
of the family Chareae.
The generic name was proposed by Vaillant in 1719[438], and adopted by
Linnaeus, who classed the Stoneworts with aquatic phanerogams. As long
ago as 1623[439] a figure of Chara was published by Caspar Bauhin as a
form of Equisetum. The generic name Chara has usually been applied to
recent and fossil species alike. The existing species have a wide
distribution; Chara foetida, A. Br., a common British form, occurs in
practically all parts of the world. Stems and calcareous ‘fruit-cases’ occur
fairly commonly in a fossil state, and differ but little from recent species, at
least as regards essential features.
It is difficult to say at what geological horizon the Stoneworts are first
represented. The first certain traces of Chara occur in Jurassic rocks, but
certain spirally marked subspherical bodies have been recorded from
Devonian and Carboniferous strata, which closely resemble Chara oogonia,
and may be Palaeozoic representatives of the genus.
In 1889 Mr Knowlton[440] of the American Geological Survey described
some ‘problematic organisms’ found in Devonian rocks at the falls of the
Ohio. Examples of these fossils are shown in fig. 46 b and c; the spirally
grooved body measures from 1·50 to 1·80 mm. in diameter, and about 1·70
mm. in length. The Chara-like character of the fossils had been previously
suggested by Meek[441] in 1873. Without going into the arguments for or
against placing these fossils in the Chareae, they may at least be mentioned
as possible but not certain Palaeozoic forms of Chara or an allied genus.
better chance of preservation than the slightly calcareous Nitelleæ.
Chara.
The generic characters have already been described in the brief account
of the family Chareae.
The generic name was proposed by Vaillant in 1719[438], and adopted by
Linnaeus, who classed the Stoneworts with aquatic phanerogams. As long
ago as 1623[439] a figure of Chara was published by Caspar Bauhin as a
form of Equisetum. The generic name Chara has usually been applied to
recent and fossil species alike. The existing species have a wide
distribution; Chara foetida, A. Br., a common British form, occurs in
practically all parts of the world. Stems and calcareous ‘fruit-cases’ occur
fairly commonly in a fossil state, and differ but little from recent species, at
least as regards essential features.
It is difficult to say at what geological horizon the Stoneworts are first
represented. The first certain traces of Chara occur in Jurassic rocks, but
certain spirally marked subspherical bodies have been recorded from
Devonian and Carboniferous strata, which closely resemble Chara oogonia,
and may be Palaeozoic representatives of the genus.
In 1889 Mr Knowlton[440] of the American Geological Survey described
some ‘problematic organisms’ found in Devonian rocks at the falls of the
Ohio. Examples of these fossils are shown in fig. 46 b and c; the spirally
grooved body measures from 1·50 to 1·80 mm. in diameter, and about 1·70
mm. in length. The Chara-like character of the fossils had been previously
suggested by Meek[441] in 1873. Without going into the arguments for or
against placing these fossils in the Chareae, they may at least be mentioned
as possible but not certain Palaeozoic forms of Chara or an allied genus.
Page 242
Fig. 46. a. Chara Bleicheri Sap. × 30. b and c. Devonian Chara? sp. circa × 12. d and e.
Chara Wrighti Forbes. circa × 12.
1. Chara Bleicheri, Saporta. Fig. 46, a.
In this form the ‘fruits’ are minute and subspherical, ·39-·44 mm. long,
and ·35-·40 mm. broad, showing in side view 5–6 slightly oblique spiral
bands. Each spiral band bears a row of slightly projecting tubercles.
This species was first described by Saporta[442] from the Oxfordian
(Jurassic) rocks of the Department of Lot in France; it is compared by the
author of the species with Chara Jaccardi Heer, described by Heer from the
Upper Jurassic rocks of Switzerland.
2. C. Knowltoni, Seward. Fig. 45, a and b, and Fig. 47.
The Oogonia are broadly oval, about ·5mm. in length, and at the broadest
part of about the same breadth. The surface is marked by eleven or twelve
bands in the form of a flattened spiral. The stems possess investing cortical
cells.
This species was founded on specimens from the Wealden beds of
Sussex[443], but numerous examples of Chara ‘fruits’ and stems have long
been known from the uppermost Jurassic rocks of the Dorset coast and the
Isle of Wight, which may probably be included in this species. These fossil
Charas are abundant[444] in the Chert beds of Purbeck age seen in the cliffs
near Swanage. Pieces of corticated stems from this locality are represented
in fig. 45 A and B.
Chara Wrighti Forbes. circa × 12.
1. Chara Bleicheri, Saporta. Fig. 46, a.
In this form the ‘fruits’ are minute and subspherical, ·39-·44 mm. long,
and ·35-·40 mm. broad, showing in side view 5–6 slightly oblique spiral
bands. Each spiral band bears a row of slightly projecting tubercles.
This species was first described by Saporta[442] from the Oxfordian
(Jurassic) rocks of the Department of Lot in France; it is compared by the
author of the species with Chara Jaccardi Heer, described by Heer from the
Upper Jurassic rocks of Switzerland.
2. C. Knowltoni, Seward. Fig. 45, a and b, and Fig. 47.
The Oogonia are broadly oval, about ·5mm. in length, and at the broadest
part of about the same breadth. The surface is marked by eleven or twelve
bands in the form of a flattened spiral. The stems possess investing cortical
cells.
This species was founded on specimens from the Wealden beds of
Sussex[443], but numerous examples of Chara ‘fruits’ and stems have long
been known from the uppermost Jurassic rocks of the Dorset coast and the
Isle of Wight, which may probably be included in this species. These fossil
Charas are abundant[444] in the Chert beds of Purbeck age seen in the cliffs
near Swanage. Pieces of corticated stems from this locality are represented
in fig. 45 A and B.
Page 243
The cortical cells surrounding a large internodal cell are very clearly seen
in the section shown in fig. 45 B, and in the longitudinal view in fig. 45 A.
The resemblance of these specimens to the stems of recent Stoneworts is
very striking.
Fig. 47. Chara Knowltoni, Sew. × 30.
The single oogonium of fig. 47 was found in the Wealden beds near
Hastings.
3. Chara Wrighti, Forbes. Fig. 46, d and e.
This species is characterised by globular or somewhat elliptical oogonia,
with six or seven spiral bands.
It is very abundant in the Lower Headon beds of Hordwell Cliffs on the
Hampshire coast[445]. Various species of Chara are commonly met with in
the Oligocene beds of the Isle of Wight and Hampshire, as well as in the
Paris basin beds, and elsewhere. Well preserved ‘fruits’ and stem fragments
are met with in a siliceous rock of Upper Oligocene age imported from
Montmorency in the Paris basin, and used as a stone for grinding
phosphates at some chemical works near Upware, a few miles from
Cambridge.
Many other species of fossil Charas are known from various horizons and
localities, but the above examples suffice as illustrative types. In Post-
Tertiary deposits masses of Chara and plant fragments occasionally occur
forming blocks of Travertine. Examples of such Chara beds have been
recorded by Sharpe from Northampton[446], by Lyell[447] from Forfarshire,
and by other writers from several other districts. Beds of calcareous marl
are occasionally seen as whitish streaks in the peat of the Fenland[448]; these
often consist in great part of Charas. A season’s growth of Chara in a
shallow lake or mere in the Fens may appear as a white line in a section of
in the section shown in fig. 45 B, and in the longitudinal view in fig. 45 A.
The resemblance of these specimens to the stems of recent Stoneworts is
very striking.
Fig. 47. Chara Knowltoni, Sew. × 30.
The single oogonium of fig. 47 was found in the Wealden beds near
Hastings.
3. Chara Wrighti, Forbes. Fig. 46, d and e.
This species is characterised by globular or somewhat elliptical oogonia,
with six or seven spiral bands.
It is very abundant in the Lower Headon beds of Hordwell Cliffs on the
Hampshire coast[445]. Various species of Chara are commonly met with in
the Oligocene beds of the Isle of Wight and Hampshire, as well as in the
Paris basin beds, and elsewhere. Well preserved ‘fruits’ and stem fragments
are met with in a siliceous rock of Upper Oligocene age imported from
Montmorency in the Paris basin, and used as a stone for grinding
phosphates at some chemical works near Upware, a few miles from
Cambridge.
Many other species of fossil Charas are known from various horizons and
localities, but the above examples suffice as illustrative types. In Post-
Tertiary deposits masses of Chara and plant fragments occasionally occur
forming blocks of Travertine. Examples of such Chara beds have been
recorded by Sharpe from Northampton[446], by Lyell[447] from Forfarshire,
and by other writers from several other districts. Beds of calcareous marl
are occasionally seen as whitish streaks in the peat of the Fenland[448]; these
often consist in great part of Charas. A season’s growth of Chara in a
shallow lake or mere in the Fens may appear as a white line in a section of
Page 244
peaty and other material which has been formed on the site of old pools or
lakes.
The recognition of specific characters in the isolated Chara ‘fruits’
usually met with in a fossil state is exceedingly unsatisfactory; the features
usually relied on in the living species are not preserved, and great care
should be taken in the separation of the various forms.
lakes.
The recognition of specific characters in the isolated Chara ‘fruits’
usually met with in a fossil state is exceedingly unsatisfactory; the features
usually relied on in the living species are not preserved, and great care
should be taken in the separation of the various forms.
Page 245
Page 246
CHAPTER VIII.
BRYOPHYTA (Muscineae).
I. HEPATICAE (Liverworts). II. MUSCI (Mosses).
The Bryophyta are small plants, varying in size from 1 mm. to about 30
cm., creeping or erect, having a thalloid, or more usually a foliose body,
consisting of a cell-mass exhibiting in most cases a distinct internal
differentiation. They possess no true roots and no true vascular tissue. The
life-history of the members of the group is characterised by a well-marked
and definite alternation of generations. The Moss or Liverwort plant is the
sexual generation (gametophyte), and as a result of the fertilisation of an
egg-cell the asexual or spore-bearing generation (sporophyte) is produced.
The sporophyte never exhibits a differentiation into stem and leaves.
Asexual and vegetative reproduction are effected by means of spores,
bulbils, or detached portions of the plant-body. Sexual reproduction is by
means of biciliate antherozoids produced in antheridia and egg-cells
formed singly in archegonia.
In the Bryophytes the distinguishing characteristics are more constant
and well-defined than in the Thallophytes. In the former the plant never
consists of a single cell or coenocyte, but is always multicellular, and
exhibits in most cases a definite physiological division of labour as
expressed in the histological differentiation of distinct tissue-systems. In the
Thallophytes there is no true alternation of generation in the same sense as
in the Mosses and Liverworts and in the higher plants. In the Bryophytes
the sexual reproduction has reached a higher stage of development and a
much greater constancy as regards the nature of the reproductive organs. On
the germination of the spore there is usually formed a fairly distinct
structure known as the protonema, from which the Moss or Liverwort
developes as a bud[449].
MARCHANTIALES.
I. HEPATICAE. ANTHOCEROTALES.
BRYOPHYTA (Muscineae).
I. HEPATICAE (Liverworts). II. MUSCI (Mosses).
The Bryophyta are small plants, varying in size from 1 mm. to about 30
cm., creeping or erect, having a thalloid, or more usually a foliose body,
consisting of a cell-mass exhibiting in most cases a distinct internal
differentiation. They possess no true roots and no true vascular tissue. The
life-history of the members of the group is characterised by a well-marked
and definite alternation of generations. The Moss or Liverwort plant is the
sexual generation (gametophyte), and as a result of the fertilisation of an
egg-cell the asexual or spore-bearing generation (sporophyte) is produced.
The sporophyte never exhibits a differentiation into stem and leaves.
Asexual and vegetative reproduction are effected by means of spores,
bulbils, or detached portions of the plant-body. Sexual reproduction is by
means of biciliate antherozoids produced in antheridia and egg-cells
formed singly in archegonia.
In the Bryophytes the distinguishing characteristics are more constant
and well-defined than in the Thallophytes. In the former the plant never
consists of a single cell or coenocyte, but is always multicellular, and
exhibits in most cases a definite physiological division of labour as
expressed in the histological differentiation of distinct tissue-systems. In the
Thallophytes there is no true alternation of generation in the same sense as
in the Mosses and Liverworts and in the higher plants. In the Bryophytes
the sexual reproduction has reached a higher stage of development and a
much greater constancy as regards the nature of the reproductive organs. On
the germination of the spore there is usually formed a fairly distinct
structure known as the protonema, from which the Moss or Liverwort
developes as a bud[449].
MARCHANTIALES.
I. HEPATICAE. ANTHOCEROTALES.
Page 247
JUNGERMANNIALES.
The vegetative plant-body possesses a different organisation on the
ventral and dorsal side; it has the form of a thalloid creeping plant (Thalloid
Liverworts), or of a delicate stem with thin appendages or leaves without a
midrib (Foliose Liverworts). In most cases the body of the plant is made up
of parenchymatous tissue, showing but little internal differentiation; in one
or two genera a few strengthening or mechanical fibres occur among the
thinner walled ground-tissue. On the germination of the spore, a feebly
developed protonema is produced, which gives rise to the Liverwort plant.
Reproduction as in the group Bryophyta.
DETERMINATION OF LIVERWORTS.
The Liverworts have a very wide geographical distribution, and are
specially abundant in moist shady situations; they grow on stones or damp
soil, and occur as epiphytes on other plants. Marchantia, Pellia, and
Jungermannia are among the better known British representatives of the
class.
Considering the soft nature of the body of recent Liverworts, it is not
surprising that they are poorly represented in a fossil state. In the absence of
the sexual reproductive organs, or of the sporophytes, which have scarcely
ever been preserved, exact identification is almost hopeless. The difficulties
already referred to in dealing with the algae, as regards the misleading
similarity between the form of the thallus and the bodies of other plants,
have to be faced in the case of the Liverworts. Many of the thalloid
Liverworts, if preserved in the form of a cast or impression without internal
structure or reproductive organs, could hardly be distinguished from various
genera of algae in which the thallus has the form of a forked plate-like
body. Such genera as Pellia, Marchantia, Lunularia, Reboulia, and others
bear a striking resemblance to Fucus, Chondrus and many other algae.
Imperfect specimens of certain Lichens, not to mention some of the
Polyzoa, might easily be mistaken for Liverworts. Among the higher plants,
there are some forms of the Podostemaceae which simulate in habit both
thalloid and foliose Liverworts as well as Mosses[450]. The members of this
Dicotyledonous family are described as water-plants with a Moss- or
Liverwort-like form; they occur on rocks in quickly-flowing water in the
tropics. In one instance a recent Podostemaceous genus has been described
The vegetative plant-body possesses a different organisation on the
ventral and dorsal side; it has the form of a thalloid creeping plant (Thalloid
Liverworts), or of a delicate stem with thin appendages or leaves without a
midrib (Foliose Liverworts). In most cases the body of the plant is made up
of parenchymatous tissue, showing but little internal differentiation; in one
or two genera a few strengthening or mechanical fibres occur among the
thinner walled ground-tissue. On the germination of the spore, a feebly
developed protonema is produced, which gives rise to the Liverwort plant.
Reproduction as in the group Bryophyta.
DETERMINATION OF LIVERWORTS.
The Liverworts have a very wide geographical distribution, and are
specially abundant in moist shady situations; they grow on stones or damp
soil, and occur as epiphytes on other plants. Marchantia, Pellia, and
Jungermannia are among the better known British representatives of the
class.
Considering the soft nature of the body of recent Liverworts, it is not
surprising that they are poorly represented in a fossil state. In the absence of
the sexual reproductive organs, or of the sporophytes, which have scarcely
ever been preserved, exact identification is almost hopeless. The difficulties
already referred to in dealing with the algae, as regards the misleading
similarity between the form of the thallus and the bodies of other plants,
have to be faced in the case of the Liverworts. Many of the thalloid
Liverworts, if preserved in the form of a cast or impression without internal
structure or reproductive organs, could hardly be distinguished from various
genera of algae in which the thallus has the form of a forked plate-like
body. Such genera as Pellia, Marchantia, Lunularia, Reboulia, and others
bear a striking resemblance to Fucus, Chondrus and many other algae.
Imperfect specimens of certain Lichens, not to mention some of the
Polyzoa, might easily be mistaken for Liverworts. Among the higher plants,
there are some forms of the Podostemaceae which simulate in habit both
thalloid and foliose Liverworts as well as Mosses[450]. The members of this
Dicotyledonous family are described as water-plants with a Moss- or
Liverwort-like form; they occur on rocks in quickly-flowing water in the
tropics. In one instance a recent Podostemaceous genus has been described
Page 248
as a member of the Anthocerotales; the genus Blandowia[451], referred to by
Willdenow as a Liverwort, has since been recognised as one of the
Podostemaceae. The resemblance between some of the foliose Hepaticae
and genera of Mosses is often very close. In certain Mosses, such as
Hookeria pennata[452], the large two-ranked leaves suggest the branches of a
Selaginella.
Fig. 48. A. Tristichia hypnoides Spreng. From a specimen in the British Museum. B.
Podocarpus cupressina Br. and Ben. (After Brown and Bennett[453].) C. Selaginella
Oregana Eat. From a plant in the Cambridge Botanic Garden. A, B and C very slightly
reduced.
The plant reproduced in fig. 48 A (Tristichia), one of the Podostemaceae,
might easily be mistaken for a foliose Liverwort if found as a fragmentary
fossil. Such species of Selaginella as S. Oregana Eat. and S. rupestris
Spring (fig. 48 C) have a distinctly moss-like habit and do not present a
very obvious resemblance to the more typical and better known
Selaginellas. The twig of a Podocarpus (P. cupressina)[454] in fig. 48 B
affords an instance of a conifer which simulates to some extent certain of
the larger-leaved Liverworts; it bears a resemblance also to some fossil
fragments referred to Selaginellites or Lycopodites. A small fossil specimen
figured by Nathorst[455] from Japan as possibly a Lycopodites may be
compared with a coniferous twig, and with some of the larger Liverworts,
Willdenow as a Liverwort, has since been recognised as one of the
Podostemaceae. The resemblance between some of the foliose Hepaticae
and genera of Mosses is often very close. In certain Mosses, such as
Hookeria pennata[452], the large two-ranked leaves suggest the branches of a
Selaginella.
Fig. 48. A. Tristichia hypnoides Spreng. From a specimen in the British Museum. B.
Podocarpus cupressina Br. and Ben. (After Brown and Bennett[453].) C. Selaginella
Oregana Eat. From a plant in the Cambridge Botanic Garden. A, B and C very slightly
reduced.
The plant reproduced in fig. 48 A (Tristichia), one of the Podostemaceae,
might easily be mistaken for a foliose Liverwort if found as a fragmentary
fossil. Such species of Selaginella as S. Oregana Eat. and S. rupestris
Spring (fig. 48 C) have a distinctly moss-like habit and do not present a
very obvious resemblance to the more typical and better known
Selaginellas. The twig of a Podocarpus (P. cupressina)[454] in fig. 48 B
affords an instance of a conifer which simulates to some extent certain of
the larger-leaved Liverworts; it bears a resemblance also to some fossil
fragments referred to Selaginellites or Lycopodites. A small fossil specimen
figured by Nathorst[455] from Japan as possibly a Lycopodites may be
compared with a coniferous twig, and with some of the larger Liverworts,
Page 249
e.g. species of Plagiochila[456]. Podocarpus cupressina is, however, chiefly
instructive as an example of the striking differences which are met with
among species of the same genus; it differs considerably from the ordinary
species of Podocarpus, and might well be identified as a member of some
other group than that of the Coniferae.
We have no records of Palaeozoic Hepaticae. The fossils which Zeiller
has figured in his Flore de Brive as Schizopteris dichotoma Gümb.[457] and
S. trichomanoides Göpp. bear a resemblance to some forms of hepatics, but
there is no satisfactory evidence for removing them from the position
assigned to them by the French writer. In Mesozoic rocks a few specimens
are known which bear a close resemblance as regards the form of the
thalloid body to recent Liverworts, but the identification of such fossils
cannot be absolutely trusted. Two French authors, MM. Fliche and
Bleicher[458], have described a plant from Lower Oolite rocks near Nancy as
a species of Marchantia, M. oolithus, but they point out the close agreement
of such forked laminar structures to algae and lichens. From Tertiary and
Post-Tertiary beds a certain number of fossil species have been recorded,
but they possess no special botanical interest.
Order Marchantiales.
The plant-body is always thalloid, bearing rhizoids on the lower surface,
and having an epidermis with pores limiting the upper or dorsal surface.
Marchantites.
This convenient generic name was proposed by Brongniart in 1849[459]; it
may be briefly defined as follows:
Vegetative body of laminar form, with apparently dichotomous branches, and agreeing in habit
with the recent thalloid Hepaticae, as represented by such a genus as Marchantia.
The name Marchantites is preferable to Marchantia, as the latter implies
identity with the recent genus, whereas the former is used in a wide sense
and refers rather to a definite form of vegetative body than to a particular
generic type.
1. Marchantites erectus (Leckenby). Fig. 49. This species may be
described as follows: The thalloid body is divided into spreading
instructive as an example of the striking differences which are met with
among species of the same genus; it differs considerably from the ordinary
species of Podocarpus, and might well be identified as a member of some
other group than that of the Coniferae.
We have no records of Palaeozoic Hepaticae. The fossils which Zeiller
has figured in his Flore de Brive as Schizopteris dichotoma Gümb.[457] and
S. trichomanoides Göpp. bear a resemblance to some forms of hepatics, but
there is no satisfactory evidence for removing them from the position
assigned to them by the French writer. In Mesozoic rocks a few specimens
are known which bear a close resemblance as regards the form of the
thalloid body to recent Liverworts, but the identification of such fossils
cannot be absolutely trusted. Two French authors, MM. Fliche and
Bleicher[458], have described a plant from Lower Oolite rocks near Nancy as
a species of Marchantia, M. oolithus, but they point out the close agreement
of such forked laminar structures to algae and lichens. From Tertiary and
Post-Tertiary beds a certain number of fossil species have been recorded,
but they possess no special botanical interest.
Order Marchantiales.
The plant-body is always thalloid, bearing rhizoids on the lower surface,
and having an epidermis with pores limiting the upper or dorsal surface.
Marchantites.
This convenient generic name was proposed by Brongniart in 1849[459]; it
may be briefly defined as follows:
Vegetative body of laminar form, with apparently dichotomous branches, and agreeing in habit
with the recent thalloid Hepaticae, as represented by such a genus as Marchantia.
The name Marchantites is preferable to Marchantia, as the latter implies
identity with the recent genus, whereas the former is used in a wide sense
and refers rather to a definite form of vegetative body than to a particular
generic type.
1. Marchantites erectus (Leckenby). Fig. 49. This species may be
described as follows: The thalloid body is divided into spreading
Page 250
dichotomously branched segments, obtusely pointed apically. The slightly
wrinkled surface shows a distinct and comparatively broad darker and
shorter median band, with lighter coloured and thinner margins.
Fig. 49. Marchantites erectus (Leck.). From the type-specimen in the Woodwardian
Museum. Nat. size.
In 1864 Leckenby described this plant from the Lower Oolite beds of the
Yorkshire coast near Scarborough, as Fucoides erectus, regarding it as a
fossil alga. I recently pointed out that the general appearance and mode of
occurrence of the specimens suggest a liverwort rather than an alga, and
proposed the substitution of the genus Marchantites[460]. It would, however,
be unwise to speak with any great confidence as to the real affinities of the
fossil.
The example shown in the figure is the type-specimen of Leckenby[461]:
the breadth of the branches is about 3 mm. Under a low magnifying power
the surface shows distinct and somewhat oblique wrinklings, the general
appearance being very similar to that of some recent forms of the genus
Marchantia.
A closely allied species has recently been described from the Wealden
beds of Ecclesbourne, near Hastings, on the Sussex coast, as Marchantites
Zeilleri Sew.[462].
In a recent monograph on Jurassic plants from Poland, apparently
containing much that is of the greatest value, but which is unfortunately
written in the Polish language, Raciborski[463] describes a new species of
thalloid Liverwort under the name of Paleohepatica Rostafinski. The
specimens are barren plants larger than any Jurassic species hitherto
wrinkled surface shows a distinct and comparatively broad darker and
shorter median band, with lighter coloured and thinner margins.
Fig. 49. Marchantites erectus (Leck.). From the type-specimen in the Woodwardian
Museum. Nat. size.
In 1864 Leckenby described this plant from the Lower Oolite beds of the
Yorkshire coast near Scarborough, as Fucoides erectus, regarding it as a
fossil alga. I recently pointed out that the general appearance and mode of
occurrence of the specimens suggest a liverwort rather than an alga, and
proposed the substitution of the genus Marchantites[460]. It would, however,
be unwise to speak with any great confidence as to the real affinities of the
fossil.
The example shown in the figure is the type-specimen of Leckenby[461]:
the breadth of the branches is about 3 mm. Under a low magnifying power
the surface shows distinct and somewhat oblique wrinklings, the general
appearance being very similar to that of some recent forms of the genus
Marchantia.
A closely allied species has recently been described from the Wealden
beds of Ecclesbourne, near Hastings, on the Sussex coast, as Marchantites
Zeilleri Sew.[462].
In a recent monograph on Jurassic plants from Poland, apparently
containing much that is of the greatest value, but which is unfortunately
written in the Polish language, Raciborski[463] describes a new species of
thalloid Liverwort under the name of Paleohepatica Rostafinski. The
specimens are barren plants larger than any Jurassic species hitherto
Page 251
described; they agree closely in habit with Saporta’s Tertiary species
Marchantites Sezannensis.
2. Marchantites Sezannensis Saporta. Fig. 50. The body is broadly linear
and dichotomously branched, with a somewhat undulating margin. Midrib
on the dorsal surface depressed, but more prominent on the ventral surface.
The upper surface is divided into hexagonal areas, in each of which occurs
a central pore. There are two rows of scales along the median line on the
lower surface. Stalked male receptacles.
Brongniart[464] first mentioned this fossil hepatic, which was found in the
calcareous travertine of Sézanne of Oligocene age in the Province of
Marne. The specimens figured by Saporta[465] show very clearly the
characters of one of the Marchantiaceae, and in this case we have the
additional evidence of the characteristic male receptacles which are given
off from a point towards the apex of the lobes, and arise from a slight
median depression. In one of Saporta’s figures (reproduced in fig. 50 A)
there are represented some median scars which may mark the position of
cups similar to those which occur on recent species of Marchantia, and in
which gemmæ or bulbils are produced.
Marchantites Sezannensis.
2. Marchantites Sezannensis Saporta. Fig. 50. The body is broadly linear
and dichotomously branched, with a somewhat undulating margin. Midrib
on the dorsal surface depressed, but more prominent on the ventral surface.
The upper surface is divided into hexagonal areas, in each of which occurs
a central pore. There are two rows of scales along the median line on the
lower surface. Stalked male receptacles.
Brongniart[464] first mentioned this fossil hepatic, which was found in the
calcareous travertine of Sézanne of Oligocene age in the Province of
Marne. The specimens figured by Saporta[465] show very clearly the
characters of one of the Marchantiaceae, and in this case we have the
additional evidence of the characteristic male receptacles which are given
off from a point towards the apex of the lobes, and arise from a slight
median depression. In one of Saporta’s figures (reproduced in fig. 50 A)
there are represented some median scars which may mark the position of
cups similar to those which occur on recent species of Marchantia, and in
which gemmæ or bulbils are produced.
Page 252
Fig. 50. Marchantites Sezannensis Sap. A. Surface view of the thallus; g, ? cups with
gemmæ. B. A male branch. C. A portion of A magnified to show the surface features.
(After Saporta.)
The collection of Sézanne fossils in the Sorbonne includes some very
beautiful casts of Marchantites in which the structural details are preserved
much more perfectly than in the examples described by Saporta. In a few
specimens which Prof. Munier-Chalmas recently showed me the
reproductive branches were exceedingly well shown. The fossils occur as
moulds in the travertine, and the museum specimens are in the form of
plaster-casts taken from the natural moulds.
Several species of Liverworts belonging to the Marchantiales and
Jungermanniales have been recorded from the amber of North Germany, of
Oligocene age. These appear to be represented by small fragments, such as
are figured by Göppert and Berendt[466] in their monograph on the amber
plants, published in 1845. The determinations have since been revised by
Gottsche[467], who recognises species of Frullania, Jungermannia, and other
genera.
SPHAGNALES.
II. MUSCI. ANDREAEALES.
BRYALES.
gemmæ. B. A male branch. C. A portion of A magnified to show the surface features.
(After Saporta.)
The collection of Sézanne fossils in the Sorbonne includes some very
beautiful casts of Marchantites in which the structural details are preserved
much more perfectly than in the examples described by Saporta. In a few
specimens which Prof. Munier-Chalmas recently showed me the
reproductive branches were exceedingly well shown. The fossils occur as
moulds in the travertine, and the museum specimens are in the form of
plaster-casts taken from the natural moulds.
Several species of Liverworts belonging to the Marchantiales and
Jungermanniales have been recorded from the amber of North Germany, of
Oligocene age. These appear to be represented by small fragments, such as
are figured by Göppert and Berendt[466] in their monograph on the amber
plants, published in 1845. The determinations have since been revised by
Gottsche[467], who recognises species of Frullania, Jungermannia, and other
genera.
SPHAGNALES.
II. MUSCI. ANDREAEALES.
BRYALES.
Page 253
The plant-body (gametophyte) in the Musci consists of a stem bearing
thin leaves, usually spirally disposed, rarely in two rows. The internal
differentiation of the stem is generally well marked, and in some cases is
comparable in complexity with the structure of the higher plants. A
protonema arises from the spore, having the form of a branched
filamentous, or more rarely a thalloid structure. Reproduction as in the
group Bryophyta.
Mosses like Liverworts have an extremely wide distribution, and occur in
various habitats. In many districts vast tracts of country are practically
monopolised by peat-forming genera, such as Sphagnum and other Mosses.
Some genera are found on rocks at high altitudes in dry regions, a few grow
as saprophytes, and many occur either as epiphytes on the leaves and stems
of other plants, or carpeting the ground under the shade of forest trees.
DETERMINATION OF MOSSES.
In the simpler Mosses, the stem consists of a parenchymatous ground-
tissue with a few outer layers of thicker-walled and smaller cells. In others
there is a distinct central cylinder which occupies the axis of the stem, and
consists of long and narrow cells; in the more complex forms the structure
of the axial tissues suggests the central cylinder or stele of higher plants.
The genus Polytrichum, so abundant on English moors, illustrates this
higher type of stem differentiation. In a transverse section of the stem the
peripheral tissue is seen to be composed of thick-walled cells, passing
internally into large parenchymatous tissue. The axial part is occupied by a
definite central cylinder consisting in the centre of elongated elements with
dark-coloured and thick walls having thin transverse septa; surrounding this
central tissue there are thinner walled elements, of which some closely
agree in form with the sieve-tubes of the higher plants. The central tissue
may be regarded as a rudimentary type of xylem, and the surrounding tissue
as a rudimentary phloem. Each leaf is traversed by a median conducting
strand which passes into the stem and eventually becomes connected with
the axial cylinder.
The fertilisation of the egg-cell gives rise to the development of a long
slender stalk terminating distally in a large spore-capsule. In section the
stalk or seta closely resembles the leafy axis of the moss plant. Considering
the fairly close approach of some of the mosses to the higher plants as
thin leaves, usually spirally disposed, rarely in two rows. The internal
differentiation of the stem is generally well marked, and in some cases is
comparable in complexity with the structure of the higher plants. A
protonema arises from the spore, having the form of a branched
filamentous, or more rarely a thalloid structure. Reproduction as in the
group Bryophyta.
Mosses like Liverworts have an extremely wide distribution, and occur in
various habitats. In many districts vast tracts of country are practically
monopolised by peat-forming genera, such as Sphagnum and other Mosses.
Some genera are found on rocks at high altitudes in dry regions, a few grow
as saprophytes, and many occur either as epiphytes on the leaves and stems
of other plants, or carpeting the ground under the shade of forest trees.
DETERMINATION OF MOSSES.
In the simpler Mosses, the stem consists of a parenchymatous ground-
tissue with a few outer layers of thicker-walled and smaller cells. In others
there is a distinct central cylinder which occupies the axis of the stem, and
consists of long and narrow cells; in the more complex forms the structure
of the axial tissues suggests the central cylinder or stele of higher plants.
The genus Polytrichum, so abundant on English moors, illustrates this
higher type of stem differentiation. In a transverse section of the stem the
peripheral tissue is seen to be composed of thick-walled cells, passing
internally into large parenchymatous tissue. The axial part is occupied by a
definite central cylinder consisting in the centre of elongated elements with
dark-coloured and thick walls having thin transverse septa; surrounding this
central tissue there are thinner walled elements, of which some closely
agree in form with the sieve-tubes of the higher plants. The central tissue
may be regarded as a rudimentary type of xylem, and the surrounding tissue
as a rudimentary phloem. Each leaf is traversed by a median conducting
strand which passes into the stem and eventually becomes connected with
the axial cylinder.
The fertilisation of the egg-cell gives rise to the development of a long
slender stalk terminating distally in a large spore-capsule. In section the
stalk or seta closely resembles the leafy axis of the moss plant. Considering
the fairly close approach of some of the mosses to the higher plants as
Page 254
regards histological characters, it is conceivable that imperfectly petrified
stems of fossil mosses might be mistaken for twigs of Vascular Cryptogams.
Like Liverworts, Mosses have left very few traces of their existence in
plant-bearing rocks. Without the aid of the characteristic moss-‘fruit’ or
sporogonium it is almost impossible to recognise fossil moss-plant
fragments. In species of the tropical genera Spiridens and Dawsonia, e.g. S.
longifolius[468] Lind. or D. superba[469] Grev. and D. polytrichoides[470] R. Br.,
the plant reaches a considerable length, and resembles twigs of plants
higher in the scale than the Bryophytes. The finer branches of species of the
extinct genus Lepidodendron are extremely moss-like in appearance. Again,
Cyathophyllum bulbosum Muell[471], with its two kinds of leaves arranged in
rows, is not at all unlike species of Selaginella or the hepatic genus
Gottschea. It is by no means improbable that some of the Palaeozoic
specimens described as twigs of Lycopodites, Selaginites, or
Lepidodendron, may be portions of mosses. The fertile branches of
Lycopodium phlegmaria in a fossil condition might be easily mistaken for
fragments of a moss. In some conifers with small and crowded scale-leaves
there is a certain resemblance to the stouter forms of moss stems. Such
possible sources of error should be prominently kept in view when we are
considering the value of negative evidence as regards the geological history
of the Musci.
A recent writer[472] on mosses has expressed the opinion that no doubt the
Musci played an exceedingly important rôle in past time. Although we have
no proof that this was so, yet it is far from improbable, and the absence of
fossil mosses must no doubt be attributed in part to their failure to be
preserved in a fossil state.
In the numerous samples of Coal-Measure vegetation preserved in
extraordinary perfection in the calcareous nodules of England, no certain
trace of a moss has so far been discovered. The most delicate tissue in the
larger Palaeozoic plants has often been preserved, and in view of such
possibilities of petrifaction it might appear strange that if moss-like plants
existed no fragments had been preserved. Their absence is, however, no
proof of the non-existence of Palaeozoic mosses, but it is a fact which
certainly tends towards the assumption that mosses were probably not very
abundant in the Coal Period forests. Epiphytic mosses frequently occur on
the stems and leaves of ferns and other plants in tropical forests. Such small
stems of fossil mosses might be mistaken for twigs of Vascular Cryptogams.
Like Liverworts, Mosses have left very few traces of their existence in
plant-bearing rocks. Without the aid of the characteristic moss-‘fruit’ or
sporogonium it is almost impossible to recognise fossil moss-plant
fragments. In species of the tropical genera Spiridens and Dawsonia, e.g. S.
longifolius[468] Lind. or D. superba[469] Grev. and D. polytrichoides[470] R. Br.,
the plant reaches a considerable length, and resembles twigs of plants
higher in the scale than the Bryophytes. The finer branches of species of the
extinct genus Lepidodendron are extremely moss-like in appearance. Again,
Cyathophyllum bulbosum Muell[471], with its two kinds of leaves arranged in
rows, is not at all unlike species of Selaginella or the hepatic genus
Gottschea. It is by no means improbable that some of the Palaeozoic
specimens described as twigs of Lycopodites, Selaginites, or
Lepidodendron, may be portions of mosses. The fertile branches of
Lycopodium phlegmaria in a fossil condition might be easily mistaken for
fragments of a moss. In some conifers with small and crowded scale-leaves
there is a certain resemblance to the stouter forms of moss stems. Such
possible sources of error should be prominently kept in view when we are
considering the value of negative evidence as regards the geological history
of the Musci.
A recent writer[472] on mosses has expressed the opinion that no doubt the
Musci played an exceedingly important rôle in past time. Although we have
no proof that this was so, yet it is far from improbable, and the absence of
fossil mosses must no doubt be attributed in part to their failure to be
preserved in a fossil state.
In the numerous samples of Coal-Measure vegetation preserved in
extraordinary perfection in the calcareous nodules of England, no certain
trace of a moss has so far been discovered. The most delicate tissue in the
larger Palaeozoic plants has often been preserved, and in view of such
possibilities of petrifaction it might appear strange that if moss-like plants
existed no fragments had been preserved. Their absence is, however, no
proof of the non-existence of Palaeozoic mosses, but it is a fact which
certainly tends towards the assumption that mosses were probably not very
abundant in the Coal Period forests. Epiphytic mosses frequently occur on
the stems and leaves of ferns and other plants in tropical forests. Such small
Page 255
and comparatively delicate plants would, however, be easily rubbed off or
destroyed in the process of fossilisation, and it is extremely rare to find
among petrified Palaeozoic plants the external features well preserved. It is
probable that the forests extended over low lying and swampy regions, and
that, in part, the trees were rooted in a submerged surface. Under such
conditions of growth there would not be the same abundance of Bryophytes
as in most of our modern forests.
To whatever cause the absence of mosses may be best attributed, it is a
fact that should not be too strongly emphasised in discussions on plant-
evolution.
Muscites.
This comprehensive genus may be defined as follows:—
Stem filiform, simple or branched, bearing small sessile leaves, with a
delicate lamina, without veins or with a single median vein, arranged in a
spiral manner on the stem.
Muscites[473] is one of those convenient generic designations which
limited knowledge and incomplete data render necessary in palaeontology.
Fossil plants which in their general habit bear a sufficiently striking
resemblance to recent mosses, may be included under this generic name.
Fig. 51. Muscites polytrichaceus Ren. and Zeill. (after Renault and Zeiller).
1. Muscites polytrichaceus Renault and Zeiller. In this species the stems
are about 3–4 cm. long and 1·3 m. broad, usually simple, but sometimes
giving off a few branches, and marked externally by very delicate
destroyed in the process of fossilisation, and it is extremely rare to find
among petrified Palaeozoic plants the external features well preserved. It is
probable that the forests extended over low lying and swampy regions, and
that, in part, the trees were rooted in a submerged surface. Under such
conditions of growth there would not be the same abundance of Bryophytes
as in most of our modern forests.
To whatever cause the absence of mosses may be best attributed, it is a
fact that should not be too strongly emphasised in discussions on plant-
evolution.
Muscites.
This comprehensive genus may be defined as follows:—
Stem filiform, simple or branched, bearing small sessile leaves, with a
delicate lamina, without veins or with a single median vein, arranged in a
spiral manner on the stem.
Muscites[473] is one of those convenient generic designations which
limited knowledge and incomplete data render necessary in palaeontology.
Fossil plants which in their general habit bear a sufficiently striking
resemblance to recent mosses, may be included under this generic name.
Fig. 51. Muscites polytrichaceus Ren. and Zeill. (after Renault and Zeiller).
1. Muscites polytrichaceus Renault and Zeiller. In this species the stems
are about 3–4 cm. long and 1·3 m. broad, usually simple, but sometimes
giving off a few branches, and marked externally by very delicate
Page 256
longitudinal grooves. The leaves are alternate, closely arranged, lanceolate,
with an acute apex, gradually narrowed towards the base, 1–2 mm. long,
traversed by a single median vein.
One of the French specimens, on which the species was founded[474], is
shown in fig. 51, and the form of the leaves is more clearly seen in the
small enlarged piece of stem. The authors of the species point out that the
tufted habit of the specimens, their small size, and the membranous
character of the leaves, all point to the Musci as the Class to which the plant
should be referred in spite of the absence of reproductive organs.
Among recent mosses, the genus Rhizogonium,—one of the Mniaceae,—
and Polytrichum are spoken of as offering a close resemblance to the fossil
form. The type-specimen was found in the Coal-Measures of Commentry,
and is now in the Museum of the École des Mines in Paris; the figure given
by MM. Renault and Zeiller faithfully represents the appearance of the
plant.
• • • • •
It has been suggested[475] that some small twigs figured by Lesquereux[476]
from the Coal-Measures of North America as Lycopodites Meeki Lesq., may
possibly be mosses. The specimens do not appear to be at all convincing,
and cannot well be included as probable representatives of Palaeozoic
Musci. Lycopodites Meeki Lesq. bears a close resemblance to the recent
Selaginella Oregana shown in fig. 48, C.
From Mesozoic rocks we have no absolutely trustworthy fossil mosses.
The late Prof. Heer[477] has quoted the occurrence of certain fossil
Caterpillars in Liassic beds as indicative of the existence of mosses, but
evidence of this kind cannot be accepted as scientifically sound. In 1850
Buckman[478] described and figured a few fragments of plants from a
freshwater limestone at the base of the Lias series near Bristol. Among
others he described certain specimens as examples of a fossil
Monocotyledon, under the generic name Najadita. Mr Starkie Gardner[479]
subsequently examined the specimens, and suggested that the Lias
fragments referred to Najadita should be compared with the recent
freshwater moss Fontinalis. In this opinion he was supported by Mr
Carruthers and Mr Murray of the British Museum. In a footnote to the
memoir in which this suggestion is made, Gardner refers to a moss-capsule
with an acute apex, gradually narrowed towards the base, 1–2 mm. long,
traversed by a single median vein.
One of the French specimens, on which the species was founded[474], is
shown in fig. 51, and the form of the leaves is more clearly seen in the
small enlarged piece of stem. The authors of the species point out that the
tufted habit of the specimens, their small size, and the membranous
character of the leaves, all point to the Musci as the Class to which the plant
should be referred in spite of the absence of reproductive organs.
Among recent mosses, the genus Rhizogonium,—one of the Mniaceae,—
and Polytrichum are spoken of as offering a close resemblance to the fossil
form. The type-specimen was found in the Coal-Measures of Commentry,
and is now in the Museum of the École des Mines in Paris; the figure given
by MM. Renault and Zeiller faithfully represents the appearance of the
plant.
• • • • •
It has been suggested[475] that some small twigs figured by Lesquereux[476]
from the Coal-Measures of North America as Lycopodites Meeki Lesq., may
possibly be mosses. The specimens do not appear to be at all convincing,
and cannot well be included as probable representatives of Palaeozoic
Musci. Lycopodites Meeki Lesq. bears a close resemblance to the recent
Selaginella Oregana shown in fig. 48, C.
From Mesozoic rocks we have no absolutely trustworthy fossil mosses.
The late Prof. Heer[477] has quoted the occurrence of certain fossil
Caterpillars in Liassic beds as indicative of the existence of mosses, but
evidence of this kind cannot be accepted as scientifically sound. In 1850
Buckman[478] described and figured a few fragments of plants from a
freshwater limestone at the base of the Lias series near Bristol. Among
others he described certain specimens as examples of a fossil
Monocotyledon, under the generic name Najadita. Mr Starkie Gardner[479]
subsequently examined the specimens, and suggested that the Lias
fragments referred to Najadita should be compared with the recent
freshwater moss Fontinalis. In this opinion he was supported by Mr
Carruthers and Mr Murray of the British Museum. In a footnote to the
memoir in which this suggestion is made, Gardner refers to a moss-capsule
Page 257
from the same beds, which he had received from Mr Brodie. Through the
kindness of the latter gentleman, I have had an opportunity of examining
the supposed capsule, and have no hesitation in describing it as absolutely
indeterminable. It is in the form of an irregularly oval brown stain on the
surface of the rock, with the suggestion of a stalk at one end, but there are
no grounds for describing the specimen as a moss-capsule, or indeed
anything else. The type-specimens figured by Brodie and subsequently
referred to a moss are now in the British Museum; they are small and
imperfect fragments of slender stems bearing rather long oval leaves which
might well have belonged to a moss. The material is however too
fragmentary to allow of accurate diagnosis or determination.
2. Muscites ferrugineus (Ludg.). This species possesses a slender stem
bearing crowded ovate-acuminate leaves. The capsules are cup-shaped,
borne on a short stalk, with a circular opening without marginal teeth. This
fossil was first figured and described by Ludwig[480] from a brown ironstone
of Miocene age at Dernbach in Nassau. The author of the species placed it
in the recent genus Gymnostomum, and Schimper[481] afterwards changed
the generic name to Sphagnum, at the same time altering the specific name
to Ludwigi. The evidence is hardly strong enough to justify a generic
designation which implies identity with a particular recent genus, and it is a
much safer plan to adopt the non-committal term Muscites, at the same time
retaining Ludwig’s original specific name. Without having examined the
type-specimen it is impossible to express a definite opinion as to the
accuracy of the description given by Ludwig; if the capsule is correctly
identified it is the oldest example hitherto recorded of a fossil moss-
sporogonium.
kindness of the latter gentleman, I have had an opportunity of examining
the supposed capsule, and have no hesitation in describing it as absolutely
indeterminable. It is in the form of an irregularly oval brown stain on the
surface of the rock, with the suggestion of a stalk at one end, but there are
no grounds for describing the specimen as a moss-capsule, or indeed
anything else. The type-specimens figured by Brodie and subsequently
referred to a moss are now in the British Museum; they are small and
imperfect fragments of slender stems bearing rather long oval leaves which
might well have belonged to a moss. The material is however too
fragmentary to allow of accurate diagnosis or determination.
2. Muscites ferrugineus (Ludg.). This species possesses a slender stem
bearing crowded ovate-acuminate leaves. The capsules are cup-shaped,
borne on a short stalk, with a circular opening without marginal teeth. This
fossil was first figured and described by Ludwig[480] from a brown ironstone
of Miocene age at Dernbach in Nassau. The author of the species placed it
in the recent genus Gymnostomum, and Schimper[481] afterwards changed
the generic name to Sphagnum, at the same time altering the specific name
to Ludwigi. The evidence is hardly strong enough to justify a generic
designation which implies identity with a particular recent genus, and it is a
much safer plan to adopt the non-committal term Muscites, at the same time
retaining Ludwig’s original specific name. Without having examined the
type-specimen it is impossible to express a definite opinion as to the
accuracy of the description given by Ludwig; if the capsule is correctly
identified it is the oldest example hitherto recorded of a fossil moss-
sporogonium.
Page 258
Page 259
CHAPTER IX.
PTERIDOPHYTA (Vascular Cryptogams).
The Pteridophytes include plants which vary in size from a few
millimetres[482] to several metres in height. The spore on germination gives
rise to a small thalloid structure, the prothallium, on which the sexual
organs are developed; this is the gametophyte or sexual generation. The
sexual organs have the form of typical archegonia and antheridia. From the
fertilised egg-cell there is developed the Pteridophyte plant or sporophyte,
which bears the spores. This asexual generation shows a well-marked
external differentiation into stem and leaves, and bears true roots. Internally
the tissues exhibit a high degree of differentiation into distinct tissue-
systems. True vascular bundles occur, which may or may not be capable of
secondary thickening by means of a cambium, i.e. a definitely localised
zone of meristematic tissue. The sporangia are borne either on the ordinary
foliage leaves or on special spore-bearing leaves called sporophylls, which
differ in a greater or less degree from the sterile leaves.
The majority of the best known and most important Palaeozoic genera
are either true Vascular Cryptogams, or possess certain of the pteridophytic
characteristics combined with those of higher plants. It is not merely the
commoner and more familiar recent genera with which the student of
extinct types must be acquainted, but it is extremely important that he
should make himself familiar with the rarer, less known and more isolated
recent forms, which often throw most light on the affinities of the older
representatives of the group. It is often the case, the more isolated living
plants are, the more likely are they to afford valuable assistance in the
interpretation of genera representing a class, which reached its maximum
development in the earlier periods of the earth’s history. The importance of
paying special attention to such recent plants as may be looked upon as
survivals of a class now tending towards extinction, will be more
thoroughly realised after the extinct vascular cryptogams have been dealt
with.
PTERIDOPHYTA (Vascular Cryptogams).
The Pteridophytes include plants which vary in size from a few
millimetres[482] to several metres in height. The spore on germination gives
rise to a small thalloid structure, the prothallium, on which the sexual
organs are developed; this is the gametophyte or sexual generation. The
sexual organs have the form of typical archegonia and antheridia. From the
fertilised egg-cell there is developed the Pteridophyte plant or sporophyte,
which bears the spores. This asexual generation shows a well-marked
external differentiation into stem and leaves, and bears true roots. Internally
the tissues exhibit a high degree of differentiation into distinct tissue-
systems. True vascular bundles occur, which may or may not be capable of
secondary thickening by means of a cambium, i.e. a definitely localised
zone of meristematic tissue. The sporangia are borne either on the ordinary
foliage leaves or on special spore-bearing leaves called sporophylls, which
differ in a greater or less degree from the sterile leaves.
The majority of the best known and most important Palaeozoic genera
are either true Vascular Cryptogams, or possess certain of the pteridophytic
characteristics combined with those of higher plants. It is not merely the
commoner and more familiar recent genera with which the student of
extinct types must be acquainted, but it is extremely important that he
should make himself familiar with the rarer, less known and more isolated
recent forms, which often throw most light on the affinities of the older
representatives of the group. It is often the case, the more isolated living
plants are, the more likely are they to afford valuable assistance in the
interpretation of genera representing a class, which reached its maximum
development in the earlier periods of the earth’s history. The importance of
paying special attention to such recent plants as may be looked upon as
survivals of a class now tending towards extinction, will be more
thoroughly realised after the extinct vascular cryptogams have been dealt
with.
Page 260
A comparison of the Pteridophyta and Bryophyta brings out certain
points of divergence. In the first place, the sporophyte assumes in the
former class a much more prominent rôle, and the gametophyte has suffered
very considerable reduction. The gametophyte, i.e. the structure which is
formed on the germination of the asexually-produced spore, is usually
short-lived, small, and more or less dependent on the sporophyte for its
nutrition. In a few cases only is it capable of providing itself with the
essential elements of food. On the other hand, the sporophyte, at a very
early stage of its development becomes free from the gametophyte and is
entirely self-supporting. Reproduction is effected as in the Bryophyta by
sexual reproductive organs and by asexual methods. Not only have we in
the Pteridophytes a much more complete external division of the plant-body
into definite members, which subserve distinct functions, and behave as
well-defined physiological organs adapted for taking a certain share in the
life-functions of the individual, but the internal differentiation has reached a
much higher stage. True vascular tissue, consisting of xylem and phloem,
occurs for the first time in this class. The whole plant is traversed by one or
more vascular strands composed of xylem and phloem elements, which are
respectively concerned with the distribution of inorganic and organic food
substances.
The Pteridophyta include the most important fossil plants. It is from a
study of the internal structure of various extinct representatives of this class,
that palaeobotanists have been able to contribute facts of the greatest
interest and importance towards the advancement of botanical science.
The botanist’s chief aim in the anatomical investigation of Palaeozoic
genera is to discover data which point the way to a solution of the problems
of plant-evolution. In the abundant material afforded by the petrified
remnants of ancient floras we have the means of tracing the past history of
existing groups or individual forms, and it is from the Palaeozoic
Pteridophytes that our most valuable results have been so far obtained.
In this and the following chapters of Volume I. two divisions of the
Pteridophyta are dealt with in such detail as the nature of the book allows.
In the earlier chapters of Volume II. the remaining representatives of this
class will be described. As in the preceding chapters such recent plants will
be described as are most essential for the correct interpretation of the fossil
forms.
points of divergence. In the first place, the sporophyte assumes in the
former class a much more prominent rôle, and the gametophyte has suffered
very considerable reduction. The gametophyte, i.e. the structure which is
formed on the germination of the asexually-produced spore, is usually
short-lived, small, and more or less dependent on the sporophyte for its
nutrition. In a few cases only is it capable of providing itself with the
essential elements of food. On the other hand, the sporophyte, at a very
early stage of its development becomes free from the gametophyte and is
entirely self-supporting. Reproduction is effected as in the Bryophyta by
sexual reproductive organs and by asexual methods. Not only have we in
the Pteridophytes a much more complete external division of the plant-body
into definite members, which subserve distinct functions, and behave as
well-defined physiological organs adapted for taking a certain share in the
life-functions of the individual, but the internal differentiation has reached a
much higher stage. True vascular tissue, consisting of xylem and phloem,
occurs for the first time in this class. The whole plant is traversed by one or
more vascular strands composed of xylem and phloem elements, which are
respectively concerned with the distribution of inorganic and organic food
substances.
The Pteridophyta include the most important fossil plants. It is from a
study of the internal structure of various extinct representatives of this class,
that palaeobotanists have been able to contribute facts of the greatest
interest and importance towards the advancement of botanical science.
The botanist’s chief aim in the anatomical investigation of Palaeozoic
genera is to discover data which point the way to a solution of the problems
of plant-evolution. In the abundant material afforded by the petrified
remnants of ancient floras we have the means of tracing the past history of
existing groups or individual forms, and it is from the Palaeozoic
Pteridophytes that our most valuable results have been so far obtained.
In this and the following chapters of Volume I. two divisions of the
Pteridophyta are dealt with in such detail as the nature of the book allows.
In the earlier chapters of Volume II. the remaining representatives of this
class will be described. As in the preceding chapters such recent plants will
be described as are most essential for the correct interpretation of the fossil
forms.
Page 261
It is impossible to do more than confine our attention to a few only of the
genera of living plants which directly concern us; some acquaintance with
the general facts of plant morphology must be assumed. Among the most
useful text-books or books of reference on the Pteridophyta the student may
consult those mentioned in the footnote[483].
I. EQUISETALES.
Leaves usually small in proportion to the size of the whole plant,
arranged in whorls at the nodes. Sporangia borne on specially modified
sporophylls or sporangiophores, which are aggregated to form a definite
strobilus or spore-bearing cone.
Equisetaceae. (Recent Species.)
The leaves are in whorls, coherent in the form of a sheath, and traversed
by longitudinal veins which do not fork or anastomose. The stem is divided
into comparatively long internodes separated by the leaf-bearing nodes, and
the branches arise in the leaf-axils at the nodes. The fertile leaves or
sporophylls differ from the sterile leaves, and usually occur in definite
aggregations or strobili containing spores of one kind (isosporous). In the
single living genus Equisetum, the outer coat of the mature spore forms two
hygroscopically sensitive filamentous structures or elaters. On the
germination of the spore the gametophyte is developed in the form of a
small lobed prothallium 1–2 cm. in length. In most cases there are distinct
male and female prothallia.
The genus Equisetum L., the common Horse-tail, is the sole living
representative of this Family. It occurs as a common native plant in Britain,
and has a wide geographical distribution. Species of Equisetum are
abundant in the temperate zones of both hemispheres, and occur in arctic as
well as tropical latitudes. Wallace[484] speaks of Horse-tails, “very like our
own species,” growing at a height of 5000 feet on the Pangerango mountain
in Java. In favourable situations the large British Horse-tail, Equisetum
maximum Lam. (= E. Telmateia Erhb.), occasionally reaches a height of
about six feet, and growing in thick clusters forms miniature forests of trees
with slender erect stems and regular circles of long and thin branches. A
tropical species, Equisetum giganteum Linn.[2] living in the marshes of
genera of living plants which directly concern us; some acquaintance with
the general facts of plant morphology must be assumed. Among the most
useful text-books or books of reference on the Pteridophyta the student may
consult those mentioned in the footnote[483].
I. EQUISETALES.
Leaves usually small in proportion to the size of the whole plant,
arranged in whorls at the nodes. Sporangia borne on specially modified
sporophylls or sporangiophores, which are aggregated to form a definite
strobilus or spore-bearing cone.
Equisetaceae. (Recent Species.)
The leaves are in whorls, coherent in the form of a sheath, and traversed
by longitudinal veins which do not fork or anastomose. The stem is divided
into comparatively long internodes separated by the leaf-bearing nodes, and
the branches arise in the leaf-axils at the nodes. The fertile leaves or
sporophylls differ from the sterile leaves, and usually occur in definite
aggregations or strobili containing spores of one kind (isosporous). In the
single living genus Equisetum, the outer coat of the mature spore forms two
hygroscopically sensitive filamentous structures or elaters. On the
germination of the spore the gametophyte is developed in the form of a
small lobed prothallium 1–2 cm. in length. In most cases there are distinct
male and female prothallia.
The genus Equisetum L., the common Horse-tail, is the sole living
representative of this Family. It occurs as a common native plant in Britain,
and has a wide geographical distribution. Species of Equisetum are
abundant in the temperate zones of both hemispheres, and occur in arctic as
well as tropical latitudes. Wallace[484] speaks of Horse-tails, “very like our
own species,” growing at a height of 5000 feet on the Pangerango mountain
in Java. In favourable situations the large British Horse-tail, Equisetum
maximum Lam. (= E. Telmateia Erhb.), occasionally reaches a height of
about six feet, and growing in thick clusters forms miniature forests of trees
with slender erect stems and regular circles of long and thin branches. A
tropical species, Equisetum giganteum Linn.[2] living in the marshes of
Page 262
Mexico and Cuba[485], and extending southward to Buenos Ayres and Chili,
reaches a height of twenty to forty feet, but the stem always remains
slender, and does not exceed an inch in diameter. Groves of such tall slender
plants on the eastern slopes of the Andes[486] suggest to the palaeobotanist an
enfeebled forest-growth recalling the arborescent Calamites of a Palaeozoic
vegetation. The twenty-five existing species of Equisetum are remnants of
various generic types of former epochs, and possess a special interest from
the point of view of the geological history of plants. A brief description of
the main characters of the recent genus will enable the student to appreciate
the points of difference and agreement between the extinct and present
representatives of the Equisetales.
reaches a height of twenty to forty feet, but the stem always remains
slender, and does not exceed an inch in diameter. Groves of such tall slender
plants on the eastern slopes of the Andes[486] suggest to the palaeobotanist an
enfeebled forest-growth recalling the arborescent Calamites of a Palaeozoic
vegetation. The twenty-five existing species of Equisetum are remnants of
various generic types of former epochs, and possess a special interest from
the point of view of the geological history of plants. A brief description of
the main characters of the recent genus will enable the student to appreciate
the points of difference and agreement between the extinct and present
representatives of the Equisetales.
Page 263
Fig. 52. Equisetum maximum Lam. A. Fertile shoot with strobilus and sterile leaf-sheaths
[after Luerssen (89); slightly less than nat. size]. B. Sporophyll bearing open sporangia
(after Luerssen; slightly enlarged). C. Part of a transverse section (diagrammatic); v,
vallecular canals, e, endodermis, c, carinal canals (after Luerssen; × 20). D. Equisetum
arvense L. Part of a transverse section of an internode of a sterile shoot. v, cortex, e,
endodermis, x, xylem tracheids, a remains of annular tracheids of the protoxylem, c,
carinal canal (after Strasburger; × 90).
Equisetum.
The plant consists of a perennial underground creeping rhizome,
branching into secondary rhizomes, divided into well-marked nodes and
internodes. From the nodes are given off two sets of buds, which may
develope into ascending aerial shoots or descending roots. At each node is a
leaf-sheath more or less deeply divided along the upper margin into teeth
representing the tips of coherent leaves (fig. 52, A).
In some species one or more internodes of underground branches become
considerably swollen and assume the form of ovate or elliptical starch-
storing tubers, which are capable of giving rise to new plants by vegetative
[after Luerssen (89); slightly less than nat. size]. B. Sporophyll bearing open sporangia
(after Luerssen; slightly enlarged). C. Part of a transverse section (diagrammatic); v,
vallecular canals, e, endodermis, c, carinal canals (after Luerssen; × 20). D. Equisetum
arvense L. Part of a transverse section of an internode of a sterile shoot. v, cortex, e,
endodermis, x, xylem tracheids, a remains of annular tracheids of the protoxylem, c,
carinal canal (after Strasburger; × 90).
Equisetum.
The plant consists of a perennial underground creeping rhizome,
branching into secondary rhizomes, divided into well-marked nodes and
internodes. From the nodes are given off two sets of buds, which may
develope into ascending aerial shoots or descending roots. At each node is a
leaf-sheath more or less deeply divided along the upper margin into teeth
representing the tips of coherent leaves (fig. 52, A).
In some species one or more internodes of underground branches become
considerably swollen and assume the form of ovate or elliptical starch-
storing tubers, which are capable of giving rise to new plants by vegetative
Page 264
reproduction. Tubers, either singly or in chains, occur in E. arvense Linn.,
E. sylvaticum Linn., E. maximum Lam., among British species.
Fig. 53. Rhizome (R) of Equisetum palustre L. with a thin shoot giving off roots and
tuberous branches from a node [after Duval-Jouve (64)].
In the example shown in fig. 53 (Equisetum palustre L.[487]) the stout
rhizome R gives off from its node, marked by a small and irregular leaf-
sheath, two thin roots and a single shoot. The latter has a leaf-sheath at its
base, and from the second node, with a larger leaf-sheath, there have been
developed branches with tuberous internodes; the constrictions between the
tubers and the tips of the terminal tubers bear small leaf-sheaths. Branched
roots are also given off from the upper node of the erect shoot.
Near the surface of the ground the buds on the rhizome nodes develope
into green erect shoots. The shoot axis is marked out into long internodes
separated by nodes bearing the leaf-sheaths. The surface of each internode
is traversed by regular and more or less prominent longitudinal ridges and
grooves; each ridge marking the position of an internal longitudinal
vascular strand. In the axil of each leaf, that is in the axil of each portion of
a leaf-sheath corresponding to a marginal uni-nerved tooth, there is
E. sylvaticum Linn., E. maximum Lam., among British species.
Fig. 53. Rhizome (R) of Equisetum palustre L. with a thin shoot giving off roots and
tuberous branches from a node [after Duval-Jouve (64)].
In the example shown in fig. 53 (Equisetum palustre L.[487]) the stout
rhizome R gives off from its node, marked by a small and irregular leaf-
sheath, two thin roots and a single shoot. The latter has a leaf-sheath at its
base, and from the second node, with a larger leaf-sheath, there have been
developed branches with tuberous internodes; the constrictions between the
tubers and the tips of the terminal tubers bear small leaf-sheaths. Branched
roots are also given off from the upper node of the erect shoot.
Near the surface of the ground the buds on the rhizome nodes develope
into green erect shoots. The shoot axis is marked out into long internodes
separated by nodes bearing the leaf-sheaths. The surface of each internode
is traversed by regular and more or less prominent longitudinal ridges and
grooves; each ridge marking the position of an internal longitudinal
vascular strand. In the axil of each leaf, that is in the axil of each portion of
a leaf-sheath corresponding to a marginal uni-nerved tooth, there is
Page 265
produced a lateral bud which may either remain dormant or break through
the leaf-sheath and emerge as a lateral branch. At the base of each branch an
adventitious root may be formed from a cell immediately below the first
leaf-sheath, but in aerial shoots the roots usually remain undeveloped. The
lateral branches repeat on a smaller scale the general features of the main
axis. In some species, the shoots are unbranched, and in others the slender
branches arise in crowded whorls from each node. Leaves, roots and
branches are given off in whorls, and the whorls from each node alternate
with those from the node next above and next below.
ANATOMY OF EQUISETUM.
In some species of Equisetum the aerial stem terminates in a conical
group of sporophylls, while in others the strobilus is formed at the apex of a
pale-coloured fertile shoot, which never attains any considerable length and
dies down early in the season of growth (fig. 52, A). Below the terminal
cone or strobilus there occur one or two modified leaf-sheaths. Such a ring
of incompletely developed leaves intervening between the cone of
sporangiophores and the normal leaves, is known as the annulus. The
annulus is seen in fig. 52, A, immediately below the lowest whorl of
sporophylls; it has the form of a low sheath with a ragged margin. In the
region of the cone the internodes remain shorter, and the whorls of
appendages, known as sporophylls or sporangiophores, have the form of
stalked structures terminating distally in a hexagonal peltate disc, which
bears on its inner face a ring of five to ten oval sporangia (fig. 52, B). Each
sporangium contains numerous spores which eventually escape by the
longitudinal dehiscence of the sporangial wall. The opening of the
sporangia is probably assisted by the movements of the characteristic
elaters formed from the outer wall of each spore.
The spores, which are capable of living only a short time, grow into
aerial green prothallia, 1–2 cm. in length; these have the form of irregularly
and more or less deeply lobed structures. On the larger and more deeply
lobed prothallia the archegonia or female reproductive organs are borne,
and the smaller or male prothallia bear the antheridia. On the fertilisation of
an egg-cell, the Equisetum plant is gradually developed. For a short time
parasitic on the female prothallium or gametophyte, the young plant soon
takes root in the ground and becomes completely independent.
the leaf-sheath and emerge as a lateral branch. At the base of each branch an
adventitious root may be formed from a cell immediately below the first
leaf-sheath, but in aerial shoots the roots usually remain undeveloped. The
lateral branches repeat on a smaller scale the general features of the main
axis. In some species, the shoots are unbranched, and in others the slender
branches arise in crowded whorls from each node. Leaves, roots and
branches are given off in whorls, and the whorls from each node alternate
with those from the node next above and next below.
ANATOMY OF EQUISETUM.
In some species of Equisetum the aerial stem terminates in a conical
group of sporophylls, while in others the strobilus is formed at the apex of a
pale-coloured fertile shoot, which never attains any considerable length and
dies down early in the season of growth (fig. 52, A). Below the terminal
cone or strobilus there occur one or two modified leaf-sheaths. Such a ring
of incompletely developed leaves intervening between the cone of
sporangiophores and the normal leaves, is known as the annulus. The
annulus is seen in fig. 52, A, immediately below the lowest whorl of
sporophylls; it has the form of a low sheath with a ragged margin. In the
region of the cone the internodes remain shorter, and the whorls of
appendages, known as sporophylls or sporangiophores, have the form of
stalked structures terminating distally in a hexagonal peltate disc, which
bears on its inner face a ring of five to ten oval sporangia (fig. 52, B). Each
sporangium contains numerous spores which eventually escape by the
longitudinal dehiscence of the sporangial wall. The opening of the
sporangia is probably assisted by the movements of the characteristic
elaters formed from the outer wall of each spore.
The spores, which are capable of living only a short time, grow into
aerial green prothallia, 1–2 cm. in length; these have the form of irregularly
and more or less deeply lobed structures. On the larger and more deeply
lobed prothallia the archegonia or female reproductive organs are borne,
and the smaller or male prothallia bear the antheridia. On the fertilisation of
an egg-cell, the Equisetum plant is gradually developed. For a short time
parasitic on the female prothallium or gametophyte, the young plant soon
takes root in the ground and becomes completely independent.
Page 266
As seen in transverse section through a young stem near the apex, the
axis consists of a mass of parenchyma, in which may be distinguished a
central larger-celled tissue, surrounded by a ring of smaller-celled groups
marking the position of a circle of embryonic vascular strands. In each
young vascular strand, a few of the cells next the pith may be seen to have
thicker walls and to be provided with a ring-like internal thickening; these
have passed over into the condition of annular tracheids and represent the
protoxylem elements. At a later stage, a transverse section through the stem
shows a central hollow pith, formed by the tearing apart and subsequent
disappearance of the medullary parenchymatous cells, which were unable to
keep pace with the growth in thickness of the stem. The pith cavity is
bridged across at each node by a multi-layered plate of parenchyma, which
forms the so-called nodal diaphragm. The inner edge of each vascular
strand is now found to be occupied by a small irregularly circular canal (fig.
52, C, c, and D, c) in which may be seen some of the rings of protoxylem
tracheids (D, a) which have been torn apart and almost completely
destroyed. These canals, known as carinal canals, have arisen by the
tearing and disruption of the thin-walled cells in the immediate
neighbourhood of the protoxylem. Each carinal canal is bounded by a layer
of elongated parenchymatous cells which form part of the xylem of the
vascular bundle, and is succeeded internally by the general ground-tissue of
the stem. The xylem parenchyma next a carinal canal is succeeded
externally by phloem tissue, consisting of short protoplasmic cells and
longer elements, without nuclei and poor in contents; the latter may be
regarded as sieve-tubes. On either side of the phloem, the xylem occurs in
two separate bands or groups of annular and reticulately thickened
tracheids. In some species, e.g. Equisetum xylochaetum Metten.[488] and E.
giganteum[489] L. a native of South America, the xylem has the form of two
bands composed of fairly numerous tracheids, but in most species the
xylem tracheids occur in small groups, as shown in the figure of E.
maximum (fig. 52, D). In the shape of the vascular bundle, and in the
formation of the carinal canal, there is a distinct resemblance between the
vascular bundles of Equisetum and those of a monocotyledonous stem.
These collateral stem-bundles of xylem and phloem traverse each internode
as distinct strands, and at the nodes each strand forks into two branches (fig.
54, A), which anastomose with the alternating bundles passing into the stem
axis consists of a mass of parenchyma, in which may be distinguished a
central larger-celled tissue, surrounded by a ring of smaller-celled groups
marking the position of a circle of embryonic vascular strands. In each
young vascular strand, a few of the cells next the pith may be seen to have
thicker walls and to be provided with a ring-like internal thickening; these
have passed over into the condition of annular tracheids and represent the
protoxylem elements. At a later stage, a transverse section through the stem
shows a central hollow pith, formed by the tearing apart and subsequent
disappearance of the medullary parenchymatous cells, which were unable to
keep pace with the growth in thickness of the stem. The pith cavity is
bridged across at each node by a multi-layered plate of parenchyma, which
forms the so-called nodal diaphragm. The inner edge of each vascular
strand is now found to be occupied by a small irregularly circular canal (fig.
52, C, c, and D, c) in which may be seen some of the rings of protoxylem
tracheids (D, a) which have been torn apart and almost completely
destroyed. These canals, known as carinal canals, have arisen by the
tearing and disruption of the thin-walled cells in the immediate
neighbourhood of the protoxylem. Each carinal canal is bounded by a layer
of elongated parenchymatous cells which form part of the xylem of the
vascular bundle, and is succeeded internally by the general ground-tissue of
the stem. The xylem parenchyma next a carinal canal is succeeded
externally by phloem tissue, consisting of short protoplasmic cells and
longer elements, without nuclei and poor in contents; the latter may be
regarded as sieve-tubes. On either side of the phloem, the xylem occurs in
two separate bands or groups of annular and reticulately thickened
tracheids. In some species, e.g. Equisetum xylochaetum Metten.[488] and E.
giganteum[489] L. a native of South America, the xylem has the form of two
bands composed of fairly numerous tracheids, but in most species the
xylem tracheids occur in small groups, as shown in the figure of E.
maximum (fig. 52, D). In the shape of the vascular bundle, and in the
formation of the carinal canal, there is a distinct resemblance between the
vascular bundles of Equisetum and those of a monocotyledonous stem.
These collateral stem-bundles of xylem and phloem traverse each internode
as distinct strands, and at the nodes each strand forks into two branches (fig.
54, A), which anastomose with the alternating bundles passing into the stem
Page 267
from the leaf-sheath. Thus the vascular strands of each internode alternate
in position with those of the next internode.
Fig. 54. A. Plan of the vascular bundles in the stem of an Equisetum; b, branches passing
out to buds (after Strasburger); l, vascular strands passing to the leaf-segments. B.
Longitudinal section through a node of E. arvense L. (after Duval-Jouve; × 20).
Explanation in the text.
There are certain points connected with the vascular bundles in the nodal
region of a shoot, which have an important bearing on the structure of fossil
equisetaceous stems. Fig. 54 B represents a diagrammatic longitudinal
section through the node of a rhizome of Equisetum arvense from which a
root h is passing off in a downward direction, and a branch in an upward
direction. The black band c in the parent stem shows the position of the
vascular strands; in the region of the node the vascular tissue attains a
considerable thickness, as seen at d in the figure. The bands passing out to
the left from d go to supply the branch and root respectively. The increased
breadth of the xylem strands at the node is due to the intercalation of a
number of short tracheids. Fig. 55, 4 shows a transverse section through a
mature node of Equisetum maximum; px marks the position of the
protoxylem and e that of the endodermis. On comparing this section with
that of the internodal vascular bundle in fig. 52, D, the much greater
development of wood in the former is obvious; the carinal canal of the
internodal bundle is absent in the section through a node. The disposition of
in position with those of the next internode.
Fig. 54. A. Plan of the vascular bundles in the stem of an Equisetum; b, branches passing
out to buds (after Strasburger); l, vascular strands passing to the leaf-segments. B.
Longitudinal section through a node of E. arvense L. (after Duval-Jouve; × 20).
Explanation in the text.
There are certain points connected with the vascular bundles in the nodal
region of a shoot, which have an important bearing on the structure of fossil
equisetaceous stems. Fig. 54 B represents a diagrammatic longitudinal
section through the node of a rhizome of Equisetum arvense from which a
root h is passing off in a downward direction, and a branch in an upward
direction. The black band c in the parent stem shows the position of the
vascular strands; in the region of the node the vascular tissue attains a
considerable thickness, as seen at d in the figure. The bands passing out to
the left from d go to supply the branch and root respectively. The increased
breadth of the xylem strands at the node is due to the intercalation of a
number of short tracheids. Fig. 55, 4 shows a transverse section through a
mature node of Equisetum maximum; px marks the position of the
protoxylem and e that of the endodermis. On comparing this section with
that of the internodal vascular bundle in fig. 52, D, the much greater
development of wood in the former is obvious; the carinal canal of the
internodal bundle is absent in the section through a node. The disposition of
Page 268
the xylem tracheids in fig. 55, 4 shows a certain regularity which, though
not very well marked, suggests the development of wood elements as the
result of cambial activity. Longitudinal sections through the nodal region
demonstrate the existence of “cells similar to those of an ordinary cambium,
and a cell-formation resulting from their division which is similar to that in
an ordinary secondary thickening.”[490] The short tracheids which make up
this nodal mass of xylem differ from those in the internodal bundle in their
smaller size, and in being reticulately thickened. There is, therefore,
evidence that in the nodes of some Equisetum stems additional xylem
elements are produced by a method of growth comparable with the cambial
activity which brings about the growth in thickness of a forest-tree[491]. The
significance of these statements will be realised when the structure of the
extinct genus Calamites is described and compared with that of Equisetum.
The small drawing in fig. 55, 3 shows part of the ring of thick nodal
wood; the section cuts through two bundles about their point of bifurcation,
the strand x is passing out in a radial direction to a lateral branch, the strand
to the right of x and the separate fragment of a strand to the left of x are
portions of leaf-trace bundles on their way to the leaf-sheath. Reverting to
fig. 54, B, the other structures seen in the section are the leaf-sheaths (l and
m), the vallecular canal (f), the epidermis, cortex and pith (k, e and a) of the
stem. The epidermis which has been ruptured by the root and branch is
indicated at i, i; the dotted lines traversing the upper part of the pith of the
lateral branch mark the position of a nodal diaphragm.
not very well marked, suggests the development of wood elements as the
result of cambial activity. Longitudinal sections through the nodal region
demonstrate the existence of “cells similar to those of an ordinary cambium,
and a cell-formation resulting from their division which is similar to that in
an ordinary secondary thickening.”[490] The short tracheids which make up
this nodal mass of xylem differ from those in the internodal bundle in their
smaller size, and in being reticulately thickened. There is, therefore,
evidence that in the nodes of some Equisetum stems additional xylem
elements are produced by a method of growth comparable with the cambial
activity which brings about the growth in thickness of a forest-tree[491]. The
significance of these statements will be realised when the structure of the
extinct genus Calamites is described and compared with that of Equisetum.
The small drawing in fig. 55, 3 shows part of the ring of thick nodal
wood; the section cuts through two bundles about their point of bifurcation,
the strand x is passing out in a radial direction to a lateral branch, the strand
to the right of x and the separate fragment of a strand to the left of x are
portions of leaf-trace bundles on their way to the leaf-sheath. Reverting to
fig. 54, B, the other structures seen in the section are the leaf-sheaths (l and
m), the vallecular canal (f), the epidermis, cortex and pith (k, e and a) of the
stem. The epidermis which has been ruptured by the root and branch is
indicated at i, i; the dotted lines traversing the upper part of the pith of the
lateral branch mark the position of a nodal diaphragm.
Page 269
Fig. 55. 1. Transverse section of a root of Equisetum variegatum Schl., e endodermis, or
outer layer of the phloeoterma (after Pfitzer; × 160). 2. Transverse section of rhizome of
E. maximum, slightly enlarged. 3. Transverse section through a node of E. maximum, x,
branch of vascular strand (slightly enlarged). 4. Transverse section through a node of E.
maximum showing the mass of xylem, px protoxylem (× 175). (Figs. 3 and 4 after
Cormack.)
Immediately external to each vascular strand, as seen in transverse
section, there is a layer of cells containing starch, and this is followed by a
distinct endodermis, of which the cells show the characteristic black dot in
the cuticularised radial walls (fig. 52, D). Beyond the endodermis there is
the large-celled parenchyma of the rest of the cortex. Tannin cells occur
here and there scattered among the ground tissue. On the same radius on
which each vascular strand occurs, the cortical parenchyma passes into a
mass of sub-epidermal thick-walled mechanical tissue or stereome.
Alternating with the ridges of stereome, the grooves are occupied by thin-
walled chlorophyll-containing tissue which carries on most of the
assimilating functions, and communicates with the external atmosphere by
means of stomata arranged in vertical rows down each internode. The
continuity of the cortical tissue is interrupted by the occurrence of large
longitudinal vallecular canals alternating in position with the stem ridges
and vascular strands (fig. 52, C, v). The epidermis consists of a single layer
outer layer of the phloeoterma (after Pfitzer; × 160). 2. Transverse section of rhizome of
E. maximum, slightly enlarged. 3. Transverse section through a node of E. maximum, x,
branch of vascular strand (slightly enlarged). 4. Transverse section through a node of E.
maximum showing the mass of xylem, px protoxylem (× 175). (Figs. 3 and 4 after
Cormack.)
Immediately external to each vascular strand, as seen in transverse
section, there is a layer of cells containing starch, and this is followed by a
distinct endodermis, of which the cells show the characteristic black dot in
the cuticularised radial walls (fig. 52, D). Beyond the endodermis there is
the large-celled parenchyma of the rest of the cortex. Tannin cells occur
here and there scattered among the ground tissue. On the same radius on
which each vascular strand occurs, the cortical parenchyma passes into a
mass of sub-epidermal thick-walled mechanical tissue or stereome.
Alternating with the ridges of stereome, the grooves are occupied by thin-
walled chlorophyll-containing tissue which carries on most of the
assimilating functions, and communicates with the external atmosphere by
means of stomata arranged in vertical rows down each internode. The
continuity of the cortical tissue is interrupted by the occurrence of large
longitudinal vallecular canals alternating in position with the stem ridges
and vascular strands (fig. 52, C, v). The epidermis consists of a single layer
Page 270
of cells, containing stomata, and with the outer cell-walls impregnated with
silica.
In certain species of Equisetum, e.g. E. palustre L., the whole circle of
vascular strands is enclosed by an endodermis, and has the structure typical
of a monostelic stem. In others e.g. E. litorale Kühl. each vascular strand is
surrounded by a separate endodermis, and in some forms e.g. E. sylvaticum
L. there is an inner as well as an outer endodermal layer[492]. Without
discussing the explanation given to this variation in the occurrence of the
endodermis, it may be stated that in all species of Equisetum the stem may
be regarded as monostelic[493].
In the rhizome the structure agrees in the main with that of the green
shoots, but the vallecular canals attain a larger size, and the pith is solid. A
slightly enlarged transverse section of a rhizome of Equisetum maximum is
shown in fig. 55, 2, the small circles surrounding the pith mark the position
of the vascular bundles and carinal canals; the much larger spaces between
the central cylinder and the surface of the stem are the vallecular canals.
The central cylinder or stele of the root is of the diarch, triarch or tetrarch
type; i.e. there may be 2, 3 or 4 groups of protoxylem in the xylem of the
root stele. The axial portion is occupied by large tracheids, and the smaller
tracheids of the xylem occur as radially disposed groups, alternating with
groups of phloem. External to the xylem and phloem strands there occur
two layers of cells, usually spoken of as a double endodermis, but it has
been suggested that it is preferable to describe the double layer as the
phloeoterma[494], of which the inner layer has the functions of a pericycle,
and the outer that of an endodermis. A transverse section of a root is seen in
fig. 55, 1, the dark cells on the left are part of a thick band of sclerenchyma
in the cortex of the root, the layer e is the outer layer of the phloeoterma.
Without describing in detail the development[495] of the sporangia, it
should be noted that the sporangial wall is at first 3 to 4 cells thick, but it
eventually consists of a single layer. The cells have spiral thickening bands
on the ventral surface, and rings on the cells where the longitudinal splitting
takes place. Each sporangium is supplied by a vascular bundle which is
given off from that of the sporangiophore axis. The strobili are isosporous.
A. EQUISETITES.
II. FOSSIL EQUISETALES. B. PHYLLOTHECA.
silica.
In certain species of Equisetum, e.g. E. palustre L., the whole circle of
vascular strands is enclosed by an endodermis, and has the structure typical
of a monostelic stem. In others e.g. E. litorale Kühl. each vascular strand is
surrounded by a separate endodermis, and in some forms e.g. E. sylvaticum
L. there is an inner as well as an outer endodermal layer[492]. Without
discussing the explanation given to this variation in the occurrence of the
endodermis, it may be stated that in all species of Equisetum the stem may
be regarded as monostelic[493].
In the rhizome the structure agrees in the main with that of the green
shoots, but the vallecular canals attain a larger size, and the pith is solid. A
slightly enlarged transverse section of a rhizome of Equisetum maximum is
shown in fig. 55, 2, the small circles surrounding the pith mark the position
of the vascular bundles and carinal canals; the much larger spaces between
the central cylinder and the surface of the stem are the vallecular canals.
The central cylinder or stele of the root is of the diarch, triarch or tetrarch
type; i.e. there may be 2, 3 or 4 groups of protoxylem in the xylem of the
root stele. The axial portion is occupied by large tracheids, and the smaller
tracheids of the xylem occur as radially disposed groups, alternating with
groups of phloem. External to the xylem and phloem strands there occur
two layers of cells, usually spoken of as a double endodermis, but it has
been suggested that it is preferable to describe the double layer as the
phloeoterma[494], of which the inner layer has the functions of a pericycle,
and the outer that of an endodermis. A transverse section of a root is seen in
fig. 55, 1, the dark cells on the left are part of a thick band of sclerenchyma
in the cortex of the root, the layer e is the outer layer of the phloeoterma.
Without describing in detail the development[495] of the sporangia, it
should be noted that the sporangial wall is at first 3 to 4 cells thick, but it
eventually consists of a single layer. The cells have spiral thickening bands
on the ventral surface, and rings on the cells where the longitudinal splitting
takes place. Each sporangium is supplied by a vascular bundle which is
given off from that of the sporangiophore axis. The strobili are isosporous.
A. EQUISETITES.
II. FOSSIL EQUISETALES. B. PHYLLOTHECA.
Page 271
C. SCHIZONEURA.
D. CALAMITES.
E. ARCHAEOCALAMITES.
In dealing with the fossil Equisetales, we will first consider the genera
Equisetites, Phyllotheca and Schizoneura, and afterwards describe the older
and better known genera Calamites and Archaeocalamites. A thoroughly
satisfactory classification of the members of the Equisetales is practically
impossible without more data than we at present possess. It has been the
custom to include Equisetites, Phyllotheca and Schizoneura in the family
Equisetaceae, and to refer Calamites and Archaeocalamites to the
Calamarieae; such a division rests in part on assumption, and cannot be
considered final. When we attempt to define the Equisetales and the two
families Equisetaceae and Calamarieae, we find ourselves seriously
hampered by lack of knowledge of certain important characters, which
should be taken into account in framing diagnoses. There is little harm in
retaining provisionally the two families already referred to, if we do not
allow a purely arbitrary classification to prejudice our opinions as to the
affinities of the several members of the Equisetales.
The Equisetaceae might be defined as a family including plants which
were usually herbaceous but in some cases arborescent, bearing verticils of
leaves in the form of sheaths more or less deeply divided into segments or
teeth. The strobili were isosporous and consisted of a central axis bearing
verticils of distally expanded sporophylls with sporangia, as in Equisetum.
The genus Equisetites might be included in this family, but it must be
admitted that we know next to nothing as to its anatomy, and we cannot be
sure that the strobili were always isosporous.
The genus Schizoneura is too imperfectly known to be defined with any
approach to completeness, or to be assigned to a family defined within
certain prescribed limits. Phyllotheca is another genus about which we
possess but little satisfactory knowledge; we are still without evidence as to
its structure, and the descriptions of the few strobili that are known are not
consistent. Recent work points to a probability of Phyllotheca being closely
allied to Annularia, a genus included in the Calamarieae, and standing for a
certain type of Calamitean foliage-shoots.
In comparing the Calamarieae with the Equisetaceae, the alternation of
sterile and fertile whorls in the strobilus, and the free linear leaves at the
D. CALAMITES.
E. ARCHAEOCALAMITES.
In dealing with the fossil Equisetales, we will first consider the genera
Equisetites, Phyllotheca and Schizoneura, and afterwards describe the older
and better known genera Calamites and Archaeocalamites. A thoroughly
satisfactory classification of the members of the Equisetales is practically
impossible without more data than we at present possess. It has been the
custom to include Equisetites, Phyllotheca and Schizoneura in the family
Equisetaceae, and to refer Calamites and Archaeocalamites to the
Calamarieae; such a division rests in part on assumption, and cannot be
considered final. When we attempt to define the Equisetales and the two
families Equisetaceae and Calamarieae, we find ourselves seriously
hampered by lack of knowledge of certain important characters, which
should be taken into account in framing diagnoses. There is little harm in
retaining provisionally the two families already referred to, if we do not
allow a purely arbitrary classification to prejudice our opinions as to the
affinities of the several members of the Equisetales.
The Equisetaceae might be defined as a family including plants which
were usually herbaceous but in some cases arborescent, bearing verticils of
leaves in the form of sheaths more or less deeply divided into segments or
teeth. The strobili were isosporous and consisted of a central axis bearing
verticils of distally expanded sporophylls with sporangia, as in Equisetum.
The genus Equisetites might be included in this family, but it must be
admitted that we know next to nothing as to its anatomy, and we cannot be
sure that the strobili were always isosporous.
The genus Schizoneura is too imperfectly known to be defined with any
approach to completeness, or to be assigned to a family defined within
certain prescribed limits. Phyllotheca is another genus about which we
possess but little satisfactory knowledge; we are still without evidence as to
its structure, and the descriptions of the few strobili that are known are not
consistent. Recent work points to a probability of Phyllotheca being closely
allied to Annularia, a genus included in the Calamarieae, and standing for a
certain type of Calamitean foliage-shoots.
In comparing the Calamarieae with the Equisetaceae, the alternation of
sterile and fertile whorls in the strobilus, and the free linear leaves at the
Page 272
nodes instead of leaf-sheaths are two characters made use of as
distinguishing features of the genus Calamites as the type of the
Calamarieae. On the other hand, the strobili of Phyllotheca appear to agree
with those of Calamites rather than with those of Equisetum, and strobili of
Archaeocalamites have been found exhibiting the typical Equisetum
characters. The sheath-like form of the leaves is not necessarily peculiar to
the Equisetaceae, and we have evidence that leaf-sheaths occurred on the
nodes of Calamitean plants. In Archaeocalamites the leaves possess
characteristic features, and can hardly be said to agree more closely with
those of Calamites than with the leaves of Phyllotheca or Sphenophyllum, a
genus belonging to another class of Pteridophytes.
On the whole, then, without discussing further the possibilities of a
subdivision of the Equisetales, we may regard the genera Calamites,
Archaeocalamites, Equisetites, Equisetum, Phyllotheca and Schizoneura as
so many members of the Equisetales, without insisting on a classification
which cannot be supported by satisfactory evidence.
Our knowledge of Calamites is fairly complete. Abundant and well-
preserved material from the Coal-Measures of England, and from Permo-
Carboniferous rocks of France, Germany and elsewhere, has enabled
palaeobotanists to investigate the anatomical characters of both the
vegetative and reproductive structures of this genus. We are in a position to
give a detailed diagnosis of Calamitean stems, roots and strobili, and to
determine the place of this type of plant in a system of classification.
Calamites not only illustrates the possibilities of palaeobotanical research,
but it demonstrates the importance of fossil forms as foundations on which
to construct the most rational classification of existing plants. The close
alliance between Calamites and the recent Equisetaceae has been clearly
established, and certain characteristics of the former genus render necessary
an extension and modification of the definition of the class to which both
Calamites and Equisetites belong. The Calamites broaden our conception of
the Equisetaceous alliance, and by their resemblance to other extinct
Palaeozoic types they furnish us with important links towards a
phylogenetic series, which the other members of the Equisetales do not
supply.
From the Upper Devonian to the Permian epoch Calamites and other
closely related types played a prominent part in the vegetation of the world.
distinguishing features of the genus Calamites as the type of the
Calamarieae. On the other hand, the strobili of Phyllotheca appear to agree
with those of Calamites rather than with those of Equisetum, and strobili of
Archaeocalamites have been found exhibiting the typical Equisetum
characters. The sheath-like form of the leaves is not necessarily peculiar to
the Equisetaceae, and we have evidence that leaf-sheaths occurred on the
nodes of Calamitean plants. In Archaeocalamites the leaves possess
characteristic features, and can hardly be said to agree more closely with
those of Calamites than with the leaves of Phyllotheca or Sphenophyllum, a
genus belonging to another class of Pteridophytes.
On the whole, then, without discussing further the possibilities of a
subdivision of the Equisetales, we may regard the genera Calamites,
Archaeocalamites, Equisetites, Equisetum, Phyllotheca and Schizoneura as
so many members of the Equisetales, without insisting on a classification
which cannot be supported by satisfactory evidence.
Our knowledge of Calamites is fairly complete. Abundant and well-
preserved material from the Coal-Measures of England, and from Permo-
Carboniferous rocks of France, Germany and elsewhere, has enabled
palaeobotanists to investigate the anatomical characters of both the
vegetative and reproductive structures of this genus. We are in a position to
give a detailed diagnosis of Calamitean stems, roots and strobili, and to
determine the place of this type of plant in a system of classification.
Calamites not only illustrates the possibilities of palaeobotanical research,
but it demonstrates the importance of fossil forms as foundations on which
to construct the most rational classification of existing plants. The close
alliance between Calamites and the recent Equisetaceae has been clearly
established, and certain characteristics of the former genus render necessary
an extension and modification of the definition of the class to which both
Calamites and Equisetites belong. The Calamites broaden our conception of
the Equisetaceous alliance, and by their resemblance to other extinct
Palaeozoic types they furnish us with important links towards a
phylogenetic series, which the other members of the Equisetales do not
supply.
From the Upper Devonian to the Permian epoch Calamites and other
closely related types played a prominent part in the vegetation of the world.
Page 273
We have no good evidence for the existence of Calamites in Triassic times;
in its place there were gigantic Equisetums which resembled modern Horse-
tails in a remarkable degree. In the succeeding Jurassic period tree-like
Equisetums were still in existence, and species of Equisetites are met with
in rocks of this age in nearly all parts of the world. A few widely distributed
species are known from Wealden rocks, but as we ascend the geologic
series from the Jurassic strata, the Equisetums become less numerous and
the individual plants gradually assume proportions practically identical with
those of existing forms.
A. Equisetites.
The generic name Equisetites was proposed by Sternberg in 1838[496] as a
convenient designation for fossil stems bearing a close resemblance to
recent species of Equisetum. Some authors have preferred to apply the
name Equisetum to fossil and recent species alike, but in spite of the
apparent identity in the external characters of the fossil stems with those of
existing Horse-tails, and a close similarity as regards the cones, there are
certain reasons for retaining Sternberg’s generic name. It is important to
avoid such nomenclature as might appear to express more than the facts
admit. If the custom of adding the termination -ites to the root of a recent
generic term is generally followed, it at once serves to show that the plants
so named are fossil and not recent species. Moreover, in the case of fossil
Equisetums we know nothing of their internal structure, and our
comparisons are limited to external characters. Stems, cones, tubers, and
leaves are often very well preserved as sandstone casts with distinct
surface-markings, but we are still in want of petrified specimens. There is
indeed evidence that some of the Triassic and Jurassic species of
Equisetites, like the older Calamites, possessed the power of secondary
growth in thickness, but our deductions are based solely on external
characters.
In the following pages a few of the better known species of Equisetites
are briefly described, the examples being chosen partly with a view to
illustrate the geological history of the genus, and partly to contribute
something towards a fuller knowledge of particular species. One of the
most striking facts to be gleaned from a general survey of the past history of
the Equisetaceae is the persistence since the latter part of the Palaeozoic
in its place there were gigantic Equisetums which resembled modern Horse-
tails in a remarkable degree. In the succeeding Jurassic period tree-like
Equisetums were still in existence, and species of Equisetites are met with
in rocks of this age in nearly all parts of the world. A few widely distributed
species are known from Wealden rocks, but as we ascend the geologic
series from the Jurassic strata, the Equisetums become less numerous and
the individual plants gradually assume proportions practically identical with
those of existing forms.
A. Equisetites.
The generic name Equisetites was proposed by Sternberg in 1838[496] as a
convenient designation for fossil stems bearing a close resemblance to
recent species of Equisetum. Some authors have preferred to apply the
name Equisetum to fossil and recent species alike, but in spite of the
apparent identity in the external characters of the fossil stems with those of
existing Horse-tails, and a close similarity as regards the cones, there are
certain reasons for retaining Sternberg’s generic name. It is important to
avoid such nomenclature as might appear to express more than the facts
admit. If the custom of adding the termination -ites to the root of a recent
generic term is generally followed, it at once serves to show that the plants
so named are fossil and not recent species. Moreover, in the case of fossil
Equisetums we know nothing of their internal structure, and our
comparisons are limited to external characters. Stems, cones, tubers, and
leaves are often very well preserved as sandstone casts with distinct
surface-markings, but we are still in want of petrified specimens. There is
indeed evidence that some of the Triassic and Jurassic species of
Equisetites, like the older Calamites, possessed the power of secondary
growth in thickness, but our deductions are based solely on external
characters.
In the following pages a few of the better known species of Equisetites
are briefly described, the examples being chosen partly with a view to
illustrate the geological history of the genus, and partly to contribute
something towards a fuller knowledge of particular species. One of the
most striking facts to be gleaned from a general survey of the past history of
the Equisetaceae is the persistence since the latter part of the Palaeozoic
Page 274
period of that type of plant which is represented by existing Equisetums.
There is perhaps no genus in existence which illustrates more vividly than
Equisetum the survival of an extremely ancient group, which is represented
to-day by numerous and widely spread species. The Equisetaceous
characteristics mark an isolated division of existing Vascular Cryptogams,
and without reference to extinct types it is practically impossible to do more
than vaguely guess at the genealogical connections of the family. When we
go back to Palaeozoic plants there are indications of guiding lines which
point the way to connecting branches between the older Equisetales and
other classes of Pteridophytes. The recently discovered genus
Cheirostrobus[497] is especially important from this point of view.
LEAF-SHEATHS OF EQUISETITES.
The accurate description of species, and the determination of the value of
such differences as are exhibited in the surface characters of structureless
casts, are practically impossible in many of the fossil forms. In certain
living Horse-tails we find striking differences between fertile and sterile
shoots, and between branches of different orders. The isolated occurrence of
fragments of fossil stems often leads to an artificial separation of ‘species’
largely founded on differences in diameter, or on slight variations in the
form of the leaf-sheaths. It is wiser to admit that in many cases we are
without the means of accurate diagnosis, and that the specific names
applied to fossil Equisetums do not always possess much value as criteria of
taxonomic differences.
The specimens of fossil Equisetums are usually readily recognised by the
coherent leaf-segments in the form of nodal sheaths resembling those of
recent species. The tissues of the cortex and central cylinder are
occasionally represented by a thin layer of coal pressed on to the surface of
a sandstone cast, or covering a flattened stem-impression on a piece of
shale. It is sometimes possible under the microscope to recognise on the
carbonised epidermal tissues the remains of a surface-ornamentation similar
to that in recent species, which is due to the occurrence of siliceous patches
on the superficial cells. Longitudinal rows of stomata may also be detected
under favourable conditions of preservation. The nodal diaphragms of stems
have occasionally been preserved apart, but such circular and radially-
striated bodies may be misleading if found as isolated objects. Casts of the
wide hollow pith of Equisetites, with longitudinal ridges and grooves, and
There is perhaps no genus in existence which illustrates more vividly than
Equisetum the survival of an extremely ancient group, which is represented
to-day by numerous and widely spread species. The Equisetaceous
characteristics mark an isolated division of existing Vascular Cryptogams,
and without reference to extinct types it is practically impossible to do more
than vaguely guess at the genealogical connections of the family. When we
go back to Palaeozoic plants there are indications of guiding lines which
point the way to connecting branches between the older Equisetales and
other classes of Pteridophytes. The recently discovered genus
Cheirostrobus[497] is especially important from this point of view.
LEAF-SHEATHS OF EQUISETITES.
The accurate description of species, and the determination of the value of
such differences as are exhibited in the surface characters of structureless
casts, are practically impossible in many of the fossil forms. In certain
living Horse-tails we find striking differences between fertile and sterile
shoots, and between branches of different orders. The isolated occurrence of
fragments of fossil stems often leads to an artificial separation of ‘species’
largely founded on differences in diameter, or on slight variations in the
form of the leaf-sheaths. It is wiser to admit that in many cases we are
without the means of accurate diagnosis, and that the specific names
applied to fossil Equisetums do not always possess much value as criteria of
taxonomic differences.
The specimens of fossil Equisetums are usually readily recognised by the
coherent leaf-segments in the form of nodal sheaths resembling those of
recent species. The tissues of the cortex and central cylinder are
occasionally represented by a thin layer of coal pressed on to the surface of
a sandstone cast, or covering a flattened stem-impression on a piece of
shale. It is sometimes possible under the microscope to recognise on the
carbonised epidermal tissues the remains of a surface-ornamentation similar
to that in recent species, which is due to the occurrence of siliceous patches
on the superficial cells. Longitudinal rows of stomata may also be detected
under favourable conditions of preservation. The nodal diaphragms of stems
have occasionally been preserved apart, but such circular and radially-
striated bodies may be misleading if found as isolated objects. Casts of the
wide hollow pith of Equisetites, with longitudinal ridges and grooves, and
Page 275
fairly deep nodal constrictions, have often been mistaken for the medullary
casts of Calamites.
Several species of Equisetites have been recorded from the Upper Coal-
Measures and overlying Permian rocks, but these present special
difficulties. In one instance described below, (Equisetites Hemingwayi
Kidst.), the species was founded on a cast of what appeared to be a strobilus
made up of sporophylls similar to those in an Equisetum cone. In other
Permo-Carboniferous species the choice of the generic name Equisetites has
been determined by the occurrence of leaf-sheaths either isolated or
attached to the node of a stem. The question to consider is, how far may the
Equisetum-like leaf-sheath be regarded as a characteristic feature of
Equisetites as distinct from Calamites? In the genus Calamites the leaves
are generally described as simple linear leaves arranged in a whorl at the
nodes, but not coherent in the form of a sheath (fig. 85). The fusion of the
segments into a continuous sheath or collar is regarded as a distinguishing
characteristic of Equisetites and Equisetum. The typical leaf-sheath of a
recent Horse-tail has already been described. In some species we have fairly
large and persistent free teeth on the upper margin of the leaf-sheath, but in
other Equisetums the rim of the sheath is practically straight and has a
truncated appearance, the distal ends of the segments being separated from
one another by very slight depressions, as in a portion of the sheath of
Equisetum ramosissimum Desf. of fig. 58, C. In other leaf-sheaths of this
species there are delicate and pointed teeth adherent to the margin of the
coherent segments; the teeth are deciduous, and after they have fallen the
sheath presents a truncated appearance. This difference between the sheaths
to which the teeth are still attached and those from which they have fallen is
illustrated by fig. 58, B and C; it is one which should be borne in mind in
the description of fossil species, and has probably been responsible for
erroneous specific diagnoses. In some recent Horse-tails the sheath is
occasionally divided in one or two places by a slit reaching to the base of
the coherent segments[498]; this shows a tendency of the segments towards
the free manner of occurrence which is usually considered a Calamitean
character. In certain fossils referred to the genus Annularia, the nodes bear
whorls of long and narrow leaves which are fused basally into a collar (fig.
58, D). There are good grounds for believing that at least some Annularias
were the foliage shoots of true Calamites. Again, in some species of
Calamitina, a sub-genus of Calamites, the leaves appear to have been
casts of Calamites.
Several species of Equisetites have been recorded from the Upper Coal-
Measures and overlying Permian rocks, but these present special
difficulties. In one instance described below, (Equisetites Hemingwayi
Kidst.), the species was founded on a cast of what appeared to be a strobilus
made up of sporophylls similar to those in an Equisetum cone. In other
Permo-Carboniferous species the choice of the generic name Equisetites has
been determined by the occurrence of leaf-sheaths either isolated or
attached to the node of a stem. The question to consider is, how far may the
Equisetum-like leaf-sheath be regarded as a characteristic feature of
Equisetites as distinct from Calamites? In the genus Calamites the leaves
are generally described as simple linear leaves arranged in a whorl at the
nodes, but not coherent in the form of a sheath (fig. 85). The fusion of the
segments into a continuous sheath or collar is regarded as a distinguishing
characteristic of Equisetites and Equisetum. The typical leaf-sheath of a
recent Horse-tail has already been described. In some species we have fairly
large and persistent free teeth on the upper margin of the leaf-sheath, but in
other Equisetums the rim of the sheath is practically straight and has a
truncated appearance, the distal ends of the segments being separated from
one another by very slight depressions, as in a portion of the sheath of
Equisetum ramosissimum Desf. of fig. 58, C. In other leaf-sheaths of this
species there are delicate and pointed teeth adherent to the margin of the
coherent segments; the teeth are deciduous, and after they have fallen the
sheath presents a truncated appearance. This difference between the sheaths
to which the teeth are still attached and those from which they have fallen is
illustrated by fig. 58, B and C; it is one which should be borne in mind in
the description of fossil species, and has probably been responsible for
erroneous specific diagnoses. In some recent Horse-tails the sheath is
occasionally divided in one or two places by a slit reaching to the base of
the coherent segments[498]; this shows a tendency of the segments towards
the free manner of occurrence which is usually considered a Calamitean
character. In certain fossils referred to the genus Annularia, the nodes bear
whorls of long and narrow leaves which are fused basally into a collar (fig.
58, D). There are good grounds for believing that at least some Annularias
were the foliage shoots of true Calamites. Again, in some species of
Calamitina, a sub-genus of Calamites, the leaves appear to have been
Page 276
united basally into a narrow sheath. We see, then, that it is a mistake to
attach great importance to the separate or coherent character of leaf-
segments in attempting to draw a line between the true Calamites and
Equisetites. Potonié[499] while pointing out that this distinction does not
possess much value as a generic character, retains the genus Equisetites for
certain Palaeozoic Equisetum-like leaf-sheaths.
Fig. 56. Calamitean leaf-sheath. From a specimen in the Woodwardian Museum. a, base of
leaf-sheath; (very slightly reduced).
Fig. 56 represents a rather faint impression of a leaf-sheath and nodal
diaphragm. The specimen is from the Coal-Measures of Ardwick,
Manchester. The letter a probably points to the attachment of the sheath to
the node of the stem. The flattened sheath is indistinctly divided into
segments, and at the middle of the free margin there appears to be a single
free tooth. The lower part of the specimen, as seen in the figure, shows the
position of the nodal diaphragm. Between the diaphragm and the sheath
there are several slight ridges converging towards the nodal line; these
agree with the characteristic ridges and grooves of Calamite casts which are
described in detail in Chapter X. There is another specimen in the British
Museum which illustrates, rather more clearly than that shown in fig. 56,
the association of a fused leaf-sheath with a type of cast usually regarded as
belonging to a Calamitean stem. Some leaf-sheaths of Permian age
described by Zeiller[500] as Equisetites Vaujolyi bear a close resemblance to
attach great importance to the separate or coherent character of leaf-
segments in attempting to draw a line between the true Calamites and
Equisetites. Potonié[499] while pointing out that this distinction does not
possess much value as a generic character, retains the genus Equisetites for
certain Palaeozoic Equisetum-like leaf-sheaths.
Fig. 56. Calamitean leaf-sheath. From a specimen in the Woodwardian Museum. a, base of
leaf-sheath; (very slightly reduced).
Fig. 56 represents a rather faint impression of a leaf-sheath and nodal
diaphragm. The specimen is from the Coal-Measures of Ardwick,
Manchester. The letter a probably points to the attachment of the sheath to
the node of the stem. The flattened sheath is indistinctly divided into
segments, and at the middle of the free margin there appears to be a single
free tooth. The lower part of the specimen, as seen in the figure, shows the
position of the nodal diaphragm. Between the diaphragm and the sheath
there are several slight ridges converging towards the nodal line; these
agree with the characteristic ridges and grooves of Calamite casts which are
described in detail in Chapter X. There is another specimen in the British
Museum which illustrates, rather more clearly than that shown in fig. 56,
the association of a fused leaf-sheath with a type of cast usually regarded as
belonging to a Calamitean stem. Some leaf-sheaths of Permian age
described by Zeiller[500] as Equisetites Vaujolyi bear a close resemblance to
Page 277
the sheath in fig. 58 E. The nature of the true Calamite leaves is considered
more fully on a later page.
PALAEOZOIC EQUISETITES.
The examples of supposed Equisetites sheaths referred to below may
serve to illustrate the kind of evidence on which this genus has been
recorded from Upper Palaeozoic rocks. I have retained the name Equisetites
in the description of the species, but it would probably be better to speak of
such specimens as ‘Calamitean leaf-sheaths’ rather than to describe them as
definite species of Equisetites. We have not as yet any thoroughly
satisfactory evidence that the Equisetites of Triassic and post-Triassic times
existed in the vegetation of earlier periods.
In Grand’Eury’s Flore du Gard[501] a fossil strobilus is figured under the
name Calamostachys tenuissima Grand’Eury, which consists of a slender
axis bearing series of sporophylls and sporangia apparently resembling
those of an Equisetum. There are no sterile appendages or bracts alternating
with the sporophylls; and the absence of the former suggests a comparison
with Equisetites rather than Calamites. Grand’Eury refers to the fossil as
“parfois à peine perceptible,” and a recent examination of the specimen
leads me to thoroughly endorse this description. It was impossible to
recognise the features represented in Grand’Eury’s drawing. Setting aside
this fossil, there are other strobili recorded by Renault[502] and referred by
him to the genus Bornia (Archaeocalamites), which also exhibit the
Equisetum-like character; the axis bears sporophylls only and no sterile
bracts. It would appear then that in the Palaeozoic period the Equisetaceous
strobilus, as we know it in Equisetum, was represented in some of the
members of the Equisetales.
more fully on a later page.
PALAEOZOIC EQUISETITES.
The examples of supposed Equisetites sheaths referred to below may
serve to illustrate the kind of evidence on which this genus has been
recorded from Upper Palaeozoic rocks. I have retained the name Equisetites
in the description of the species, but it would probably be better to speak of
such specimens as ‘Calamitean leaf-sheaths’ rather than to describe them as
definite species of Equisetites. We have not as yet any thoroughly
satisfactory evidence that the Equisetites of Triassic and post-Triassic times
existed in the vegetation of earlier periods.
In Grand’Eury’s Flore du Gard[501] a fossil strobilus is figured under the
name Calamostachys tenuissima Grand’Eury, which consists of a slender
axis bearing series of sporophylls and sporangia apparently resembling
those of an Equisetum. There are no sterile appendages or bracts alternating
with the sporophylls; and the absence of the former suggests a comparison
with Equisetites rather than Calamites. Grand’Eury refers to the fossil as
“parfois à peine perceptible,” and a recent examination of the specimen
leads me to thoroughly endorse this description. It was impossible to
recognise the features represented in Grand’Eury’s drawing. Setting aside
this fossil, there are other strobili recorded by Renault[502] and referred by
him to the genus Bornia (Archaeocalamites), which also exhibit the
Equisetum-like character; the axis bears sporophylls only and no sterile
bracts. It would appear then that in the Palaeozoic period the Equisetaceous
strobilus, as we know it in Equisetum, was represented in some of the
members of the Equisetales.
Page 278
Fig. 57. A. Equisetites Hemingwayi Kidst. From a specimen in the British Museum. ⅔ nat.
size. B. Diaphragm and sheath of an Equisetaceous plant, from the Coal-Measures. ⅔
nat. size. From a specimen in the British Museum.
1. Equisetites Hemingwayi Kidst. Fig. 57, A.
Mr Kidston[503] founded this species on a few specimens of cones found
in the Middle Coal-Measures of Barnsley in Yorkshire. The best example of
the cone described by Kidston has a length of 2·5 cm., and a breadth of 1·5
cm.; the surface is divided up into several hexagonal areas 4 mm. high and
5 mm. wide. Each of these plates shows a fairly prominent projecting point
in its centre; this is regarded as the point of attachment of the
size. B. Diaphragm and sheath of an Equisetaceous plant, from the Coal-Measures. ⅔
nat. size. From a specimen in the British Museum.
1. Equisetites Hemingwayi Kidst. Fig. 57, A.
Mr Kidston[503] founded this species on a few specimens of cones found
in the Middle Coal-Measures of Barnsley in Yorkshire. The best example of
the cone described by Kidston has a length of 2·5 cm., and a breadth of 1·5
cm.; the surface is divided up into several hexagonal areas 4 mm. high and
5 mm. wide. Each of these plates shows a fairly prominent projecting point
in its centre; this is regarded as the point of attachment of the
Page 279
sporangiophore axis which expanded distally into a hexagonal plate bearing
sporangia. An examination of Mr Kidston’s specimens enabled me to
recognise the close resemblance which he insists on between the fossils and
such a recent Equisetaceous strobilus as that of Equisetum limosum Sm.
Nothing is known of the structure of the fossils beyond the character of the
superficial pattern of the impressions, and it is impossible to speak with
absolute confidence as to their nature. The author of the species makes use
of the generic name Equisetum; but in view of our ignorance of structural
features it is better to adopt the more usual term Equisetites.
Since Kidston’s description was published I noticed a specimen in the
British Museum collection which throws some further light on this doubtful
fossil. Part of this specimen is shown in fig. 57, A. The stem is 21 cm. in
length and about 5 mm. broad; it is divided into distinct nodes and
internodes; the former being a little exaggerated in the drawing. The surface
is marked by fine and irregular striations, and in one or two places there
occur broken pieces of narrow linear leaves in the neighbourhood of a node.
Portions of four cones occurring in contact with the stem, appear to be
sessile on the nodes, but the preservation is not sufficiently good to enable
one to speak with certainty as to the manner of attachment. Each cone
consists of regular hexagonal depressions, which agree exactly with the
surface characters of Kidston’s type-specimen. The manner of occurrence of
the cones points to a lateral and not a terminal attachment. The stem does
not show any traces of Equisetaceous leaf-sheaths at the nodes, and such
fragments of leaves as occur appear to have the form of separate linear
segments; they are not such as are met with on Equisetites. It agrees with
some of the slender foliage-shoots of Calamitean plants often described
under the generic name Asterophyllites. As regards the cones; they differ
from the known Calamitean strobili in the absence of sterile bracts, and
appear to consist entirely of distally expanded sporophylls as in Equisetum.
The general impression afforded by the fossil is that we have not sufficient
evidence for definitely associating this stem and cones with a true
Equisetites. We may, however, adhere to this generic title until more
satisfactory data are available.
2. Equisetites spatulatus Zeill. Fig. 58, A.
sporangia. An examination of Mr Kidston’s specimens enabled me to
recognise the close resemblance which he insists on between the fossils and
such a recent Equisetaceous strobilus as that of Equisetum limosum Sm.
Nothing is known of the structure of the fossils beyond the character of the
superficial pattern of the impressions, and it is impossible to speak with
absolute confidence as to their nature. The author of the species makes use
of the generic name Equisetum; but in view of our ignorance of structural
features it is better to adopt the more usual term Equisetites.
Since Kidston’s description was published I noticed a specimen in the
British Museum collection which throws some further light on this doubtful
fossil. Part of this specimen is shown in fig. 57, A. The stem is 21 cm. in
length and about 5 mm. broad; it is divided into distinct nodes and
internodes; the former being a little exaggerated in the drawing. The surface
is marked by fine and irregular striations, and in one or two places there
occur broken pieces of narrow linear leaves in the neighbourhood of a node.
Portions of four cones occurring in contact with the stem, appear to be
sessile on the nodes, but the preservation is not sufficiently good to enable
one to speak with certainty as to the manner of attachment. Each cone
consists of regular hexagonal depressions, which agree exactly with the
surface characters of Kidston’s type-specimen. The manner of occurrence of
the cones points to a lateral and not a terminal attachment. The stem does
not show any traces of Equisetaceous leaf-sheaths at the nodes, and such
fragments of leaves as occur appear to have the form of separate linear
segments; they are not such as are met with on Equisetites. It agrees with
some of the slender foliage-shoots of Calamitean plants often described
under the generic name Asterophyllites. As regards the cones; they differ
from the known Calamitean strobili in the absence of sterile bracts, and
appear to consist entirely of distally expanded sporophylls as in Equisetum.
The general impression afforded by the fossil is that we have not sufficient
evidence for definitely associating this stem and cones with a true
Equisetites. We may, however, adhere to this generic title until more
satisfactory data are available.
2. Equisetites spatulatus Zeill. Fig. 58, A.
Page 280
This species is chosen as an example of a French Equisetites of Permian
age. It was recently founded by Zeiller[504] on some specimens of imperfect
leaf-sheaths, and defined as follows:—
Sheaths spreading, erect, formed of numerous uninerved coherent leaves, convex on the dorsal
surface, spatulate in form, 5–6 cm. in length and 2–3 mm. broad at the base, and 5–10 mm. broad
at the apex, rounded at the distal end.
The specimen shown in fig. 58, A, represents part of a flattened sheath,
the narrower crenulated end being the base of the sheath. The limits of the
coherent segments and the position of the veins are clearly marked. Zeiller’s
description accurately represents the character of the sheaths. They agree
closely with an Equisetaceous leaf-sheath, but as I have already pointed out,
we cannot feel certain that sheaths of this kind were not originally attached
to a Calamite stem.
The portion of a leaf-sheath and a diaphragm represented in fig. 57, B,
agrees closely with Zeiller’s examples. This specimen is from the English
Coal-Measures, but it is not advisable to attempt any specific diagnosis on
such fragmentary material. It is questionable, indeed, if these detached
fossil leaf-sheaths should be designated by specific names. Another similar
form of sheath, hardly distinguishable from Zeiller’s species, has recently
been described by Potonié from the Permian (Rothliegende) of Thuringia.
age. It was recently founded by Zeiller[504] on some specimens of imperfect
leaf-sheaths, and defined as follows:—
Sheaths spreading, erect, formed of numerous uninerved coherent leaves, convex on the dorsal
surface, spatulate in form, 5–6 cm. in length and 2–3 mm. broad at the base, and 5–10 mm. broad
at the apex, rounded at the distal end.
The specimen shown in fig. 58, A, represents part of a flattened sheath,
the narrower crenulated end being the base of the sheath. The limits of the
coherent segments and the position of the veins are clearly marked. Zeiller’s
description accurately represents the character of the sheaths. They agree
closely with an Equisetaceous leaf-sheath, but as I have already pointed out,
we cannot feel certain that sheaths of this kind were not originally attached
to a Calamite stem.
The portion of a leaf-sheath and a diaphragm represented in fig. 57, B,
agrees closely with Zeiller’s examples. This specimen is from the English
Coal-Measures, but it is not advisable to attempt any specific diagnosis on
such fragmentary material. It is questionable, indeed, if these detached
fossil leaf-sheaths should be designated by specific names. Another similar
form of sheath, hardly distinguishable from Zeiller’s species, has recently
been described by Potonié from the Permian (Rothliegende) of Thuringia.
Page 281
Fig. 58.
A. Equisetites spatulatus, Zeill. Leaf-sheath. ⅘ nat. size. (After Zeiller.)
B. E. columnaris, Brongn. From a specimen in the British Museum. ¾ nat. size.
C. Equisetum ramosissimum, Desf. × 2.
D. Annularia stellata (Schloth.). Leaf-sheath. Slightly enlarged. (After Potonié.)
E. Equisetites zeaeformis (Schloth.). Leaf-sheath. ⅘ nat. size. (After Potonié.)
F. E. lateralis, Phill. From a specimen in the Scarborough Museum. Nat. size.
3. Equisetites zeaeformis (Schloth.)[505] Fig. 58, E.
The sheaths consist of linear segments fused laterally as in Equisetum. In
some specimens the component parts of the sheath are more or less separate
A. Equisetites spatulatus, Zeill. Leaf-sheath. ⅘ nat. size. (After Zeiller.)
B. E. columnaris, Brongn. From a specimen in the British Museum. ¾ nat. size.
C. Equisetum ramosissimum, Desf. × 2.
D. Annularia stellata (Schloth.). Leaf-sheath. Slightly enlarged. (After Potonié.)
E. Equisetites zeaeformis (Schloth.). Leaf-sheath. ⅘ nat. size. (After Potonié.)
F. E. lateralis, Phill. From a specimen in the Scarborough Museum. Nat. size.
3. Equisetites zeaeformis (Schloth.)[505] Fig. 58, E.
The sheaths consist of linear segments fused laterally as in Equisetum. In
some specimens the component parts of the sheath are more or less separate
Page 282
from one another, and in this form they are apparently identical with the
leaves of Calamites (Calamitina) varians, Sternb. The example shown in
fig. 58, E is probably a young leaf-sheath; the segments are fused, and each
is traversed by a single vein represented by a dark line in the figure. The
regular crenulated lower margin is the base of the sheath, and corresponds
to the upper portion of fig. 58, A. This species affords, therefore, an
interesting illustration of the difficulty of separating Equisetites leaves from
those of true Calamites. Potonié has suggested that the leaf-sheath of a
young Calamite might well be split up into distinct linear segments as the
result of the increase in girth of the stem.
• • • • •
Other Palaeozoic species of Equisetites have been recorded, but with one
exception these need not be dealt with, as they do not add anything to our
knowledge of botanical importance. The specimen described in the Flore de
Commentry as Equisetites Monyi, by Renault and Zeiller[506], differs from
most of the other Palaeozoic species of Equisetites, in the fact that we have
a stem with short internodes bearing a leaf-sheath at each node divided into
comparatively long and distinct teeth. This species presents a close
agreement with specimens of Calamitina, but Renault and Zeiller consider
that it is generically distinct. They suggest that the English species,
originally described and figured by Lindley and Hutton[507] as Hippurites
gigantea, and now usually spoken of as Calamitina, should be named
Equisetites. It would probably be better to adopt the name Calamitina for
the French species. The type-specimen of this species is in the Natural
History Museum, Paris.
EQUISETITES PLATYODON.
leaves of Calamites (Calamitina) varians, Sternb. The example shown in
fig. 58, E is probably a young leaf-sheath; the segments are fused, and each
is traversed by a single vein represented by a dark line in the figure. The
regular crenulated lower margin is the base of the sheath, and corresponds
to the upper portion of fig. 58, A. This species affords, therefore, an
interesting illustration of the difficulty of separating Equisetites leaves from
those of true Calamites. Potonié has suggested that the leaf-sheath of a
young Calamite might well be split up into distinct linear segments as the
result of the increase in girth of the stem.
• • • • •
Other Palaeozoic species of Equisetites have been recorded, but with one
exception these need not be dealt with, as they do not add anything to our
knowledge of botanical importance. The specimen described in the Flore de
Commentry as Equisetites Monyi, by Renault and Zeiller[506], differs from
most of the other Palaeozoic species of Equisetites, in the fact that we have
a stem with short internodes bearing a leaf-sheath at each node divided into
comparatively long and distinct teeth. This species presents a close
agreement with specimens of Calamitina, but Renault and Zeiller consider
that it is generically distinct. They suggest that the English species,
originally described and figured by Lindley and Hutton[507] as Hippurites
gigantea, and now usually spoken of as Calamitina, should be named
Equisetites. It would probably be better to adopt the name Calamitina for
the French species. The type-specimen of this species is in the Natural
History Museum, Paris.
EQUISETITES PLATYODON.
Page 283
Fig. 59. Equisetites platyodon Brongn. (After Schoenlein, slightly reduced.)
When we pass from the Permian to the Triassic period, we find large
casts of very modern-looking Equisetaceous stems which must clearly be
referred to the genus Equisetites. The portion of a stem represented in fig.
59 known as Equisetites platyodon Brongn.[508] affords an example of a
Triassic Equisetaceous stem with a clearly preserved leaf-sheath. The stem
measures about 6 cm. in diameter. One of the oldest known Triassic species
is Equisetites Mougeoti[509] (Brongn.) from the Bunter series of the Vosges.
The Keuper species E. arenaceus is, however, more completely known.
The specimens referred to this species are very striking fossils; they agree
in all external characters with recent Horse-tails but greatly exceed them in
dimensions.
4. Equisetites arenaceus Bronn.
When we pass from the Permian to the Triassic period, we find large
casts of very modern-looking Equisetaceous stems which must clearly be
referred to the genus Equisetites. The portion of a stem represented in fig.
59 known as Equisetites platyodon Brongn.[508] affords an example of a
Triassic Equisetaceous stem with a clearly preserved leaf-sheath. The stem
measures about 6 cm. in diameter. One of the oldest known Triassic species
is Equisetites Mougeoti[509] (Brongn.) from the Bunter series of the Vosges.
The Keuper species E. arenaceus is, however, more completely known.
The specimens referred to this species are very striking fossils; they agree
in all external characters with recent Horse-tails but greatly exceed them in
dimensions.
4. Equisetites arenaceus Bronn.
Page 284
This plant has been found in the Triassic rocks of various parts of
Germany and France; it occurs in the Lettenkohl group (Lower Keuper), as
well as in the Middle Keuper of Stuttgart and elsewhere. The species may
be defined as follows:—
Rhizome from 8–14 cm. in diameter, with short internodes, bearing lateral ovate tubers. Aerial
shoots from 4–12 cm. in diameter, bearing whorls of branches, and leaf-sheaths made up of 110–
120 coherent uni-nerved linear segments terminating in an apical lanceolate tooth. Strobili oval,
consisting of crowded sporangiophores with pentagonal and hexagonal peltate terminations.
The casts of branches, rhizomes, tubers, buds and cones enable us to
form a fairly exact estimate of the size and general appearance of this
largest fossil Horse-tail. The Strassburg Museum contains many good
examples of this species, and a few specimens may be seen in the British
Museum. In the École des Mines, Paris, there are some exceptionally clear
impressions of cones of this species from a lignite mine in the Vosges.
It is estimated that the plant reached a height of 8 to 10 meters, about
equal to that of the tallest recent species of Equisetum, but in the diameter
of the stems the Triassic plant far exceeded any existing species.
It is interesting to determine as far as possible, in the absence of petrified
specimens, if this Keuper species increased in girth by means of a
cambium. There are occasionally found sandstone casts of the pith-cavity
which present an appearance very similar to that of Calamitean medullary
casts[510]. The nodes are marked by comparatively deep constrictions, which
probably represent the projecting nodal wood. The surface of the casts is
traversed by regular ridges and grooves as in an ordinary Calamite, and it is
probable that in Equisetites arenaceus, as in Calamites, these surface-
features are the impression of the inner face of a cylinder of secondary
wood (cf. p. 310). Excellent figures of this species of Equisetites are given
by Schimper in his Atlas of fossil plants[511], also by Schimper and
Koechlin-Schlumberger[512], and by Schoenlein and Schenk[513].
5. Equisetites columnaris Brongn. Figs. 11 and 58, B.
This species, which is by far the best known British Equisetites, was
founded by Brongniart[514] on some specimens from the Lower Oolite beds
of the Yorkshire coast. Casts of stems are familiar to those who have
collected fossils on the coast between Whitby and Scarborough; they are
Germany and France; it occurs in the Lettenkohl group (Lower Keuper), as
well as in the Middle Keuper of Stuttgart and elsewhere. The species may
be defined as follows:—
Rhizome from 8–14 cm. in diameter, with short internodes, bearing lateral ovate tubers. Aerial
shoots from 4–12 cm. in diameter, bearing whorls of branches, and leaf-sheaths made up of 110–
120 coherent uni-nerved linear segments terminating in an apical lanceolate tooth. Strobili oval,
consisting of crowded sporangiophores with pentagonal and hexagonal peltate terminations.
The casts of branches, rhizomes, tubers, buds and cones enable us to
form a fairly exact estimate of the size and general appearance of this
largest fossil Horse-tail. The Strassburg Museum contains many good
examples of this species, and a few specimens may be seen in the British
Museum. In the École des Mines, Paris, there are some exceptionally clear
impressions of cones of this species from a lignite mine in the Vosges.
It is estimated that the plant reached a height of 8 to 10 meters, about
equal to that of the tallest recent species of Equisetum, but in the diameter
of the stems the Triassic plant far exceeded any existing species.
It is interesting to determine as far as possible, in the absence of petrified
specimens, if this Keuper species increased in girth by means of a
cambium. There are occasionally found sandstone casts of the pith-cavity
which present an appearance very similar to that of Calamitean medullary
casts[510]. The nodes are marked by comparatively deep constrictions, which
probably represent the projecting nodal wood. The surface of the casts is
traversed by regular ridges and grooves as in an ordinary Calamite, and it is
probable that in Equisetites arenaceus, as in Calamites, these surface-
features are the impression of the inner face of a cylinder of secondary
wood (cf. p. 310). Excellent figures of this species of Equisetites are given
by Schimper in his Atlas of fossil plants[511], also by Schimper and
Koechlin-Schlumberger[512], and by Schoenlein and Schenk[513].
5. Equisetites columnaris Brongn. Figs. 11 and 58, B.
This species, which is by far the best known British Equisetites, was
founded by Brongniart[514] on some specimens from the Lower Oolite beds
of the Yorkshire coast. Casts of stems are familiar to those who have
collected fossils on the coast between Whitby and Scarborough; they are
Page 285
often found in an erect position in the sandstone, and are usually described
as occurring in the actual place of growth. As previously pointed out (p.
72), such stems have generally been deposited by water, and have assumed
a vertical position (fig. 11). Young and Bird[515] figured a specimen of this
species in 1822, and in view of its striking resemblance to the sugar-cane,
they regarded the fossil as being of the same family as Saccharum
officinarum, if not specifically identical.
A specimen was described by König[516] in 1829, from the Lower Oolite
rocks of Brora in the north of Scotland under the name of Oncylogonatum
carbonarium, but Brongniart[517] pointed out its identity with the English
species Equisetites columnaris.
Our acquaintance with this species is practically limited to the casts of
stems. A typical stem of E. columnaris measures 3 to 6 cm. in diameter and
has fairly long internodes. The largest stem in the British Museum
collection has internodes about 14 cm. long and a diameter of about 5 cm.
In some cases the stem casts show irregular lateral projections in the
neighbourhood of a node, but there is no evidence that the aerial shoots of
this species gave off verticils of branches. In habit E. columnaris probably
closely resembled such recent species as Equisetum hiemale L., E.
trachyodon A. Br. and others.
The stems often show a distinct swelling at the nodes; this may be due, at
least in part, to the existence of transverse nodal diaphragms which enabled
the dead shoots to resist contraction in the region of the nodes. The leaf-
sheaths consist of numerous long and narrow segments often truncated
distally, as in fig. 58, B, and as in the sheath of such a recent Horse-tail as
E. ramosissimum shown in fig. 58, C. In some specimens one occasionally
finds indications of delicate acuminate teeth extending above the limits of a
truncated sheath. Brongniart speaks of the existence of caducous acuminate
teeth in his diagnosis of the species, and the example represented in fig. 58,
B, demonstrates the existence of such deciduous appendages. There is a
very close resemblance between the fossil sheath of fig. 58, B, with and
without the teeth, and the leaf-sheath of the recent Equisetum in fig. 58, C.
In some specimens of E. columnaris in which the cast is covered with a
carbonaceous film, each segment in a leaf-sheath is seen to be slightly
depressed in the median portion, which is often distinctly marked by
numerous small dots, the edges of the segment being flat and smooth. The
as occurring in the actual place of growth. As previously pointed out (p.
72), such stems have generally been deposited by water, and have assumed
a vertical position (fig. 11). Young and Bird[515] figured a specimen of this
species in 1822, and in view of its striking resemblance to the sugar-cane,
they regarded the fossil as being of the same family as Saccharum
officinarum, if not specifically identical.
A specimen was described by König[516] in 1829, from the Lower Oolite
rocks of Brora in the north of Scotland under the name of Oncylogonatum
carbonarium, but Brongniart[517] pointed out its identity with the English
species Equisetites columnaris.
Our acquaintance with this species is practically limited to the casts of
stems. A typical stem of E. columnaris measures 3 to 6 cm. in diameter and
has fairly long internodes. The largest stem in the British Museum
collection has internodes about 14 cm. long and a diameter of about 5 cm.
In some cases the stem casts show irregular lateral projections in the
neighbourhood of a node, but there is no evidence that the aerial shoots of
this species gave off verticils of branches. In habit E. columnaris probably
closely resembled such recent species as Equisetum hiemale L., E.
trachyodon A. Br. and others.
The stems often show a distinct swelling at the nodes; this may be due, at
least in part, to the existence of transverse nodal diaphragms which enabled
the dead shoots to resist contraction in the region of the nodes. The leaf-
sheaths consist of numerous long and narrow segments often truncated
distally, as in fig. 58, B, and as in the sheath of such a recent Horse-tail as
E. ramosissimum shown in fig. 58, C. In some specimens one occasionally
finds indications of delicate acuminate teeth extending above the limits of a
truncated sheath. Brongniart speaks of the existence of caducous acuminate
teeth in his diagnosis of the species, and the example represented in fig. 58,
B, demonstrates the existence of such deciduous appendages. There is a
very close resemblance between the fossil sheath of fig. 58, B, with and
without the teeth, and the leaf-sheath of the recent Equisetum in fig. 58, C.
In some specimens of E. columnaris in which the cast is covered with a
carbonaceous film, each segment in a leaf-sheath is seen to be slightly
depressed in the median portion, which is often distinctly marked by
numerous small dots, the edges of the segment being flat and smooth. The
Page 286
median region is that in which the stomata are found and on which deposits
of silica occur.
6. Equisetites Beani (Bunb.). Figs. 60–62.
Bunbury[518] proposed the name Calamites Beani for some fossil stems
from the Lower Oolite beds of the Yorkshire coast, which Bean had
previously referred to in unpublished notes as C. giganteus. The latter name
was not adopted by Bunbury on account of the possible confusion between
this species and the Palaeozoic species Calamites gigas Brongn. The
generic name Calamites must be replaced by Equisetites now that we are
familiar with more perfect specimens which demonstrate the Equisetean
characters of the plant.
Fig. 60. Equisetites Beani (Bunb.). ⅔ nat. size. [After Starkie Gardner (86) Pl. ix. fig. 2.]
of silica occur.
6. Equisetites Beani (Bunb.). Figs. 60–62.
Bunbury[518] proposed the name Calamites Beani for some fossil stems
from the Lower Oolite beds of the Yorkshire coast, which Bean had
previously referred to in unpublished notes as C. giganteus. The latter name
was not adopted by Bunbury on account of the possible confusion between
this species and the Palaeozoic species Calamites gigas Brongn. The
generic name Calamites must be replaced by Equisetites now that we are
familiar with more perfect specimens which demonstrate the Equisetean
characters of the plant.
Fig. 60. Equisetites Beani (Bunb.). ⅔ nat. size. [After Starkie Gardner (86) Pl. ix. fig. 2.]
Page 287
Schimper[519] speaks of this species as possibly the pith-cast of Equisetites
columnaris, but his opinion cannot be maintained; the species first
described by Bunbury has considerably larger stems than those of E.
columnaris. It is not impossible, however, that E. columnaris and E. Beani
may be portions of the same species. The chief difference between these
forms is that of size; but we have not sufficient data to justify the inclusion
of both forms under one name. Zigno[520], in his work on the Oolitic Flora,
figures an imperfect stem cast of E. Beani under the name of Calamites
Beani, but the species has received little attention at the hands of recent
writers. In 1886 Starkie Gardner[521] figured a specimen which was
identified by Williamson as an example of Bunbury’s species; but the latter
pointed out the greater resemblance, as regards the external appearance of
the Jurassic stem, to some of the recent arborescent Gramineae[522] than to
the Equisetaceae. Williamson, with his usual caution, adds that such
appearances have very little taxonomic value. Fig. 60 is reproduced from
the block used by Gardner in his memoir on Mesozoic Angiosperms; he
quotes the specimen as possibly a Monocotyledonous stem. The fossil is an
imperfect cast of a stem showing two clearly marked nodal regions, but no
trace of leaf-sheaths. A recent examination of specimens in the museums of
Whitby, Scarborough, York and London has convinced me that the plant
named by Bunbury Calamites Beani is a large Equisetites. As a rule the
specimens do not show any indications of the leaf-sheaths, but in a few
cases the sheaths have left fairly distinct impressions.
columnaris, but his opinion cannot be maintained; the species first
described by Bunbury has considerably larger stems than those of E.
columnaris. It is not impossible, however, that E. columnaris and E. Beani
may be portions of the same species. The chief difference between these
forms is that of size; but we have not sufficient data to justify the inclusion
of both forms under one name. Zigno[520], in his work on the Oolitic Flora,
figures an imperfect stem cast of E. Beani under the name of Calamites
Beani, but the species has received little attention at the hands of recent
writers. In 1886 Starkie Gardner[521] figured a specimen which was
identified by Williamson as an example of Bunbury’s species; but the latter
pointed out the greater resemblance, as regards the external appearance of
the Jurassic stem, to some of the recent arborescent Gramineae[522] than to
the Equisetaceae. Williamson, with his usual caution, adds that such
appearances have very little taxonomic value. Fig. 60 is reproduced from
the block used by Gardner in his memoir on Mesozoic Angiosperms; he
quotes the specimen as possibly a Monocotyledonous stem. The fossil is an
imperfect cast of a stem showing two clearly marked nodal regions, but no
trace of leaf-sheaths. A recent examination of specimens in the museums of
Whitby, Scarborough, York and London has convinced me that the plant
named by Bunbury Calamites Beani is a large Equisetites. As a rule the
specimens do not show any indications of the leaf-sheaths, but in a few
cases the sheaths have left fairly distinct impressions.
Page 288
Fig. 61. Equisetites Beani (Bunb.). From a specimen in the British Museum, ⅔ nat. size. (No.
V. 2725.)
In the portion of stem shown in fig. 61 the impressions of the leaf
segments are clearly marked. This specimen affords much better evidence
of the Equisetaceous character of the plant than those which are simply
internal casts. The narrow projecting lines extending upwards from the
nodes in the figured specimen probably represent the divisions between the
several segments of each leaf-sheath.
In the museums of Whitby and Scarborough there are some long
specimens, in one case 44 cm. in length, and 33 cm. in circumference,
V. 2725.)
In the portion of stem shown in fig. 61 the impressions of the leaf
segments are clearly marked. This specimen affords much better evidence
of the Equisetaceous character of the plant than those which are simply
internal casts. The narrow projecting lines extending upwards from the
nodes in the figured specimen probably represent the divisions between the
several segments of each leaf-sheath.
In the museums of Whitby and Scarborough there are some long
specimens, in one case 44 cm. in length, and 33 cm. in circumference,
Page 289
which are probably casts of the broad pith-cavity. These casts are often
transversely broken across at the nodes, so that they consist of three or four
separate pieces which fit together by clean-cut faces. This manner of
occurrence is most probably due to the existence of large and resistant nodal
diaphragms which separated the sand-casts of adjacent internodes. In the
York museum there are some large diaphragms, 10 cm. in diameter,
preserved separately in a piece of rock containing a cast of Equisetites
Beani. The nodal diaphragms of some of the Carboniferous Calamites were
the seat of cork development[523], and it may be that the frequent
preservation of Equisetaceous diaphragms in Triassic and Jurassic rocks is
due to the protection afforded by a corky investment.
The stem shown in fig. 62 appears to be a portion of a shoot of E. Beani
not far from its apical region. From the lower nodes there extend clearly
marked and regular lines or slight grooves tapering gradually towards the
next higher node; these are no doubt the impressions of segments of leaf-
sheaths. The sheaths themselves have been detached and only their
impressions remain. The flattened bands at the node of the stem in fig. 60,
and shown also in fig. 61, mark the place of attachment of the leaf-sheaths.
On some of these nodal bands one is able to recognise small scars which are
most likely the casts of outgoing leaf-trace bundles.
Some of the internal casts of this species are marked by numerous closely
arranged longitudinal lines, which are probably the impressions of the inner
face of a central woody cylinder. In the smaller specimen shown in fig. 62
we have the apical portion of a shoot in which the uppermost internodes are
in an unexpanded condition.
transversely broken across at the nodes, so that they consist of three or four
separate pieces which fit together by clean-cut faces. This manner of
occurrence is most probably due to the existence of large and resistant nodal
diaphragms which separated the sand-casts of adjacent internodes. In the
York museum there are some large diaphragms, 10 cm. in diameter,
preserved separately in a piece of rock containing a cast of Equisetites
Beani. The nodal diaphragms of some of the Carboniferous Calamites were
the seat of cork development[523], and it may be that the frequent
preservation of Equisetaceous diaphragms in Triassic and Jurassic rocks is
due to the protection afforded by a corky investment.
The stem shown in fig. 62 appears to be a portion of a shoot of E. Beani
not far from its apical region. From the lower nodes there extend clearly
marked and regular lines or slight grooves tapering gradually towards the
next higher node; these are no doubt the impressions of segments of leaf-
sheaths. The sheaths themselves have been detached and only their
impressions remain. The flattened bands at the node of the stem in fig. 60,
and shown also in fig. 61, mark the place of attachment of the leaf-sheaths.
On some of these nodal bands one is able to recognise small scars which are
most likely the casts of outgoing leaf-trace bundles.
Some of the internal casts of this species are marked by numerous closely
arranged longitudinal lines, which are probably the impressions of the inner
face of a central woody cylinder. In the smaller specimen shown in fig. 62
we have the apical portion of a shoot in which the uppermost internodes are
in an unexpanded condition.
Page 290
Fig. 62. Equisetites Beani (Bunb.). From a specimen in the Scarborough Museum. Very
slightly reduced.
It is impossible to give a satisfactory diagnosis of this species without
better material. The plant is characterised chiefly by the great breadth of the
stem, and by the possession of leaf-sheaths consisting of numerous long and
narrow segments. Equisetites Beani must have almost equalled in size the
Triassic species, E. arenaceus, described above.
7. Equisetites lateralis Phill. Figs. 58, F, 63, and 64.
This species is described at some length as affording a useful illustration
of the misleading character of certain features which are entirely due to
methods of preservation. The specific name was proposed by Phillips in his
first edition of the Geology of the Yorkshire Coast for some very imperfect
stems from the Lower Oolite rocks near Whitby[524]. The choice of the term
lateralis illustrates a misconception; it was given to the plant in the belief
that certain characteristic wheel-like marks on the stems were the scars of
branches. Lindley and Hutton[525] figured a specimen of this species in their
Fossil Flora, and quoted a remark by “Mr Williamson junior” (afterwards
slightly reduced.
It is impossible to give a satisfactory diagnosis of this species without
better material. The plant is characterised chiefly by the great breadth of the
stem, and by the possession of leaf-sheaths consisting of numerous long and
narrow segments. Equisetites Beani must have almost equalled in size the
Triassic species, E. arenaceus, described above.
7. Equisetites lateralis Phill. Figs. 58, F, 63, and 64.
This species is described at some length as affording a useful illustration
of the misleading character of certain features which are entirely due to
methods of preservation. The specific name was proposed by Phillips in his
first edition of the Geology of the Yorkshire Coast for some very imperfect
stems from the Lower Oolite rocks near Whitby[524]. The choice of the term
lateralis illustrates a misconception; it was given to the plant in the belief
that certain characteristic wheel-like marks on the stems were the scars of
branches. Lindley and Hutton[525] figured a specimen of this species in their
Fossil Flora, and quoted a remark by “Mr Williamson junior” (afterwards
Page 291
Prof. Williamson) that the so-called scars often occur as isolated discs in the
neighbourhood of the stems. Bunbury[526] described an example of the same
species with narrow spreading leaves like those of a Palaeozoic
Asterophyllites, and proposed this generic name as more appropriate than
Equisetites. In all probability the example shown in fig. 63 is that which
Bunbury described. It is certainly the same as one figured by Zigno[527] as
Calamites lateralis in his Flora fossilis formationis Oolithicae.
Fig. 63. Equisetites lateralis Phill. From a specimen in the British Museum. Slightly
reduced.
This specimen illustrates a further misconception in the diagnosis of the
species. The long linear appendages spreading from the nodes are, I believe,
neighbourhood of the stems. Bunbury[526] described an example of the same
species with narrow spreading leaves like those of a Palaeozoic
Asterophyllites, and proposed this generic name as more appropriate than
Equisetites. In all probability the example shown in fig. 63 is that which
Bunbury described. It is certainly the same as one figured by Zigno[527] as
Calamites lateralis in his Flora fossilis formationis Oolithicae.
Fig. 63. Equisetites lateralis Phill. From a specimen in the British Museum. Slightly
reduced.
This specimen illustrates a further misconception in the diagnosis of the
species. The long linear appendages spreading from the nodes are, I believe,
Page 292
slender branches and not leaves; they have not the form of delicate filmy
markings on the rock face, but are comparatively thick and almost woody in
appearance. The true leaves are distinctly indicated at the nodes, and exhibit
the ordinary features of toothed sheaths.
Heer[528] proposed to transfer Phillips’ species to the genus Phyllotheca,
and Schimper[529] preferred the generic term Schizoneura. The suggestion
for the use of these two names would probably not have been made had the
presence of the Equisetum sheaths been recognised.
The circular depressions a short distance above each node are the ‘branch
scars’ of various writers. Schimper suggested that these radially marked
circles might be displaced nodal diaphragms. Andrae[530] figured the same
objects in 1853 but regarded them as branch scars, although in the specimen
he describes, there are several of them lying apart from the stems, and to
one of them is attached a portion of a leaf-sheath. Solms-Laubach[531] points
out that the internodal position of these supposed scars is an obvious
difficulty; we should not expect to find branches arising from an internode.
After referring to some specimens in the Oxford museum, he adds—“In
presence of these facts the usual explanation of these structures appears to
me, as to Heer, very doubtful.... We are driven to the very arbitrary
assumption that they represent the lowest nodes of the lateral branches
which were inserted above the line of the nodes of the stem.” Circular discs
similar to those of E. lateralis have been found in the Jurassic rocks of
Siberia[532] and elsewhere. There are one or two examples of such discs from
Siberia in the British Museum. If the nodal diaphragms were fairly hard and
stout, it is easy to conceive that they might have been pressed out of their
original position when the stems were flattened in the process of
fossilisation. It is not quite clear what the radial spoke-like lines of the discs
are due to; possibly they mark the position of bands of more resistant tissue
or of outgoing strands of vascular bundles. A detached diaphragm is seen in
fig. 64 C; in the centre it consists of a flat plate of tissue, and the peripheral
region is traversed by the radiating lines. In the stem of fig. 64, A the deeply
divided leaf-sheaths are clearly seen, and an imperfect impression of a
diaphragm is preserved on the face of the middle internode. In fig. 64 B a
flattened leaf-sheath is shown with the free acuminate teeth fused basally
into a continuous collar[533]. The short piece of stem of Equisetites lateralis
shown in fig. 58, F, shows how the free teeth may be outspread in a manner
markings on the rock face, but are comparatively thick and almost woody in
appearance. The true leaves are distinctly indicated at the nodes, and exhibit
the ordinary features of toothed sheaths.
Heer[528] proposed to transfer Phillips’ species to the genus Phyllotheca,
and Schimper[529] preferred the generic term Schizoneura. The suggestion
for the use of these two names would probably not have been made had the
presence of the Equisetum sheaths been recognised.
The circular depressions a short distance above each node are the ‘branch
scars’ of various writers. Schimper suggested that these radially marked
circles might be displaced nodal diaphragms. Andrae[530] figured the same
objects in 1853 but regarded them as branch scars, although in the specimen
he describes, there are several of them lying apart from the stems, and to
one of them is attached a portion of a leaf-sheath. Solms-Laubach[531] points
out that the internodal position of these supposed scars is an obvious
difficulty; we should not expect to find branches arising from an internode.
After referring to some specimens in the Oxford museum, he adds—“In
presence of these facts the usual explanation of these structures appears to
me, as to Heer, very doubtful.... We are driven to the very arbitrary
assumption that they represent the lowest nodes of the lateral branches
which were inserted above the line of the nodes of the stem.” Circular discs
similar to those of E. lateralis have been found in the Jurassic rocks of
Siberia[532] and elsewhere. There are one or two examples of such discs from
Siberia in the British Museum. If the nodal diaphragms were fairly hard and
stout, it is easy to conceive that they might have been pressed out of their
original position when the stems were flattened in the process of
fossilisation. It is not quite clear what the radial spoke-like lines of the discs
are due to; possibly they mark the position of bands of more resistant tissue
or of outgoing strands of vascular bundles. A detached diaphragm is seen in
fig. 64 C; in the centre it consists of a flat plate of tissue, and the peripheral
region is traversed by the radiating lines. In the stem of fig. 64, A the deeply
divided leaf-sheaths are clearly seen, and an imperfect impression of a
diaphragm is preserved on the face of the middle internode. In fig. 64 B a
flattened leaf-sheath is shown with the free acuminate teeth fused basally
into a continuous collar[533]. The short piece of stem of Equisetites lateralis
shown in fig. 58, F, shows how the free teeth may be outspread in a manner
Page 293
which bears some resemblance to the leaves of Phyllotheca, but a
comparison with the specimens already described, and a careful
examination of this specimen itself, demonstrate the generic identity of the
species with Equisetites. The carbonaceous film on the surface of such
stems as those of fig. 58, F, and 64, A, shows a characteristic shagreen
texture which may possibly be due to the presence of silica in the epidermis
as in recent Horse-tails.
There is another species of Equisetites, E. Münsteri, Schk., from a lower
geological horizon which has been compared with E. lateralis, and lends
support to the view that the so-called branch-scars are nodal diaphragms[534].
This species also affords additional evidence in favour of retaining the
generic name Equisetites for Phillips’ species. Equisetites Münsteri is a
typical Rhaetic plant; it has been found at Beyreuth and Kuhnbach, as well
as in Switzerland, Hungary and elsewhere. A specimen of Equisetites
originally described by Buckman as E. Brodii[535], from the Lower Lias of
Worcestershire, may possibly be identical with E. Münsteri. The leaf-
sheaths of this Rhaetic species consist of broad segments prolonged into
acuminate teeth; some of the examples figured by Schenk[536] show clearly
marked impressions of displaced nodal diaphragms exactly as in E.
lateralis. Another form, Equisetum rotiferum described by Tenison-
Woods[537] from Australia, is closely allied to, or possibly identical with E.
lateralis.
comparison with the specimens already described, and a careful
examination of this specimen itself, demonstrate the generic identity of the
species with Equisetites. The carbonaceous film on the surface of such
stems as those of fig. 58, F, and 64, A, shows a characteristic shagreen
texture which may possibly be due to the presence of silica in the epidermis
as in recent Horse-tails.
There is another species of Equisetites, E. Münsteri, Schk., from a lower
geological horizon which has been compared with E. lateralis, and lends
support to the view that the so-called branch-scars are nodal diaphragms[534].
This species also affords additional evidence in favour of retaining the
generic name Equisetites for Phillips’ species. Equisetites Münsteri is a
typical Rhaetic plant; it has been found at Beyreuth and Kuhnbach, as well
as in Switzerland, Hungary and elsewhere. A specimen of Equisetites
originally described by Buckman as E. Brodii[535], from the Lower Lias of
Worcestershire, may possibly be identical with E. Münsteri. The leaf-
sheaths of this Rhaetic species consist of broad segments prolonged into
acuminate teeth; some of the examples figured by Schenk[536] show clearly
marked impressions of displaced nodal diaphragms exactly as in E.
lateralis. Another form, Equisetum rotiferum described by Tenison-
Woods[537] from Australia, is closely allied to, or possibly identical with E.
lateralis.
Page 294
Fig. 64. Equisetites lateralis Phill. A. Part of a stem showing leaf-sheaths and an imperfect
diaphragm. B. A single flattened leaf-sheath. C. A detached nodal diaphragm. From a
specimen in the York Museum. Slightly reduced.
8. Equisetites Burchardti Dunker[538]. Fig. 65.
This species of Equisetites is fairly common in the Wealden beds of the
Sussex coast near Hastings, and also in Westphalia.
diaphragm. B. A single flattened leaf-sheath. C. A detached nodal diaphragm. From a
specimen in the York Museum. Slightly reduced.
8. Equisetites Burchardti Dunker[538]. Fig. 65.
This species of Equisetites is fairly common in the Wealden beds of the
Sussex coast near Hastings, and also in Westphalia.
Page 295
Fig. 65. Equisetites Burchardti Dunk. Showing a node with two tubers and a root. From a
specimen in the British Museum. Nat. size.
It is characterised by having long and slender internodes, bearing at the
nodes leaf-sheaths with five or six pointed segments, and by the frequent
formation of branch-tubers. These tuberous branches closely resemble those
which are formed on the underground shoots of Equisetum arvense L., E.
sylvaticum L. and others; they occur either singly or in chains[539]. In the
specimen shown in the figure the left-hand tuber is remarkably well
preserved, its surface is somewhat sunk and shrivelled, and the apex is
surrounded by a nodal leaf-sheath. A thin branched root is given off just
below the point of insertion of the oval tuber.
No other species of Equisetites affords such numerous examples of tubers
as this Wealden plant. By some of the earlier writers the detached tubers of
E. Burchardti were described as fossil seeds under the name Carpolithus.
specimen in the British Museum. Nat. size.
It is characterised by having long and slender internodes, bearing at the
nodes leaf-sheaths with five or six pointed segments, and by the frequent
formation of branch-tubers. These tuberous branches closely resemble those
which are formed on the underground shoots of Equisetum arvense L., E.
sylvaticum L. and others; they occur either singly or in chains[539]. In the
specimen shown in the figure the left-hand tuber is remarkably well
preserved, its surface is somewhat sunk and shrivelled, and the apex is
surrounded by a nodal leaf-sheath. A thin branched root is given off just
below the point of insertion of the oval tuber.
No other species of Equisetites affords such numerous examples of tubers
as this Wealden plant. By some of the earlier writers the detached tubers of
E. Burchardti were described as fossil seeds under the name Carpolithus.
Page 296
Fig. 66. Equisetites Yokoyamae Sew. From specimens in the British Museum. Nat. size.
The specimens shown in fig. 66 have been referred to another species, E.
Yokoyamae Sew.[540]; they were obtained from the Wealden beds of Sussex,
but according to Mr Rufford, who discovered them, the smaller tubers of
this species are not found in association with those of E. Burchardti. The
stems are very narrow and the tubers have a characteristic elliptical form;
the species is of little value botanically, but it affords another instance of the
common occurrence of these tuberous branches in the Wealden Equisetums.
Similar fossil tubers, on a much larger scale, have been found in
association with the Triassic Equisetites arenaceus; with E. Parlatori
Heer[541], a Tertiary species from Switzerland, and with other Mesozoic and
Tertiary stems. E. Burejensis[542], described by Heer from the Jurassic rocks
of Siberia, bears a close resemblance to the Wealden species.
• • • • •
The description of the above species by no means exhausts the material
which is available towards a history of fossil Equisetums. The examples
which have been selected may serve to illustrate the kind of specimens that
are usually met with, as well as some of the possible sources of error which
have to be borne in mind in the description of species.
Such Tertiary species as have been recorded need not be considered; they
furnish us with no facts of particular interest from a morphological point of
view. The wide distribution of Equisetites, especially during the Jurassic
period, is one of the most interesting lessons to be learnt from a review of
The specimens shown in fig. 66 have been referred to another species, E.
Yokoyamae Sew.[540]; they were obtained from the Wealden beds of Sussex,
but according to Mr Rufford, who discovered them, the smaller tubers of
this species are not found in association with those of E. Burchardti. The
stems are very narrow and the tubers have a characteristic elliptical form;
the species is of little value botanically, but it affords another instance of the
common occurrence of these tuberous branches in the Wealden Equisetums.
Similar fossil tubers, on a much larger scale, have been found in
association with the Triassic Equisetites arenaceus; with E. Parlatori
Heer[541], a Tertiary species from Switzerland, and with other Mesozoic and
Tertiary stems. E. Burejensis[542], described by Heer from the Jurassic rocks
of Siberia, bears a close resemblance to the Wealden species.
• • • • •
The description of the above species by no means exhausts the material
which is available towards a history of fossil Equisetums. The examples
which have been selected may serve to illustrate the kind of specimens that
are usually met with, as well as some of the possible sources of error which
have to be borne in mind in the description of species.
Such Tertiary species as have been recorded need not be considered; they
furnish us with no facts of particular interest from a morphological point of
view. The wide distribution of Equisetites, especially during the Jurassic
period, is one of the most interesting lessons to be learnt from a review of
Page 297
the fossil forms. No doubt a detailed comparison of the several species from
different parts of the world would lead us to reduce the number of specific
names; and at the same time it would emphasize the apparent identity of
fossils which have been described from widely separated latitudes under
different names.
Specimens of Equisetites are occasionally found in plant-bearing beds
apart from the other members of a Flora; this isolated manner of occurrence
suggests that the plant grew in a different station from that occupied by
Cycads and other elements of the vegetation[543].
A selection of Triassic and Jurassic species arranged in a tabular form
demonstrates the world-wide distribution of this persistent type of plant[544].
B. Phyllotheca.
The generic name Phyllotheca was proposed by Brongniart[545] in 1828
for some small fossil stems from the Hawkesbury river, near Port Jackson,
Australia. The stems of this genus are divided into nodes and internodes and
possess leaf-sheaths as in Equisetum, but Phyllotheca differs from other
Equisetaceous plants in the form of the leaves and in the character of its
sporophylls. We may define the genus as follows:—
Plants resembling in habit the recent Equisetums. Stems simple or
branched, divided into distinct nodes and internodes, the latter marked by
longitudinal ridges and grooves; from the nodes are given off leaf-sheaths
consisting of linear-lanceolate uninerved segments coherent basally, but
having the form of free narrow teeth for the greater part of their length. The
long free teeth are usually spread out in the form of a cup and not adpressed
to the stem, the tips of the teeth are often incurved.
The sporangia are borne on peltate sporangiophores attached to the stem
between whorls of sterile leaves.
Our knowledge of Phyllotheca is unfortunately far from complete. The
chief characteristic of the vegetative shoots consists in the cup-like leaf-
sheaths; these are divided up into several linear segments, which differ from
the teeth of an Equisetum leaf-sheath in their greater length and in their
more open and spreading habit of growth. The large loose sheaths of the
fertile shoots of some recent Horse-tails bear a certain resemblance to the
different parts of the world would lead us to reduce the number of specific
names; and at the same time it would emphasize the apparent identity of
fossils which have been described from widely separated latitudes under
different names.
Specimens of Equisetites are occasionally found in plant-bearing beds
apart from the other members of a Flora; this isolated manner of occurrence
suggests that the plant grew in a different station from that occupied by
Cycads and other elements of the vegetation[543].
A selection of Triassic and Jurassic species arranged in a tabular form
demonstrates the world-wide distribution of this persistent type of plant[544].
B. Phyllotheca.
The generic name Phyllotheca was proposed by Brongniart[545] in 1828
for some small fossil stems from the Hawkesbury river, near Port Jackson,
Australia. The stems of this genus are divided into nodes and internodes and
possess leaf-sheaths as in Equisetum, but Phyllotheca differs from other
Equisetaceous plants in the form of the leaves and in the character of its
sporophylls. We may define the genus as follows:—
Plants resembling in habit the recent Equisetums. Stems simple or
branched, divided into distinct nodes and internodes, the latter marked by
longitudinal ridges and grooves; from the nodes are given off leaf-sheaths
consisting of linear-lanceolate uninerved segments coherent basally, but
having the form of free narrow teeth for the greater part of their length. The
long free teeth are usually spread out in the form of a cup and not adpressed
to the stem, the tips of the teeth are often incurved.
The sporangia are borne on peltate sporangiophores attached to the stem
between whorls of sterile leaves.
Our knowledge of Phyllotheca is unfortunately far from complete. The
chief characteristic of the vegetative shoots consists in the cup-like leaf-
sheaths; these are divided up into several linear segments, which differ from
the teeth of an Equisetum leaf-sheath in their greater length and in their
more open and spreading habit of growth. The large loose sheaths of the
fertile shoots of some recent Horse-tails bear a certain resemblance to the
Page 298
sheaths of Phyllotheca. The diagnosis of the fertile shoots is founded
principally on some Permian specimens of the genus described by
Schmalhausen from Russia[546] and redescribed more recently by Solms-
Laubach[547]. Prof. Zeiller[548] has, however, lately received some examples
of Phyllotheca from the Coal-Measures of Asia Minor which bear strobili
like those of the genus Annularia, a type which is dealt with in the
succeeding chapter. A description of a few species will serve to illustrate the
features usually associated with this generic type, as well as to emphasize
the unsatisfactory state of our knowledge as to the real significance of such
supposed generic characteristics.
There are a few fossil stems from Permian rocks of Siberia, from Jurassic
strata in Italy, and from Lower Mesozoic and Permo-Carboniferous beds in
South America, South Africa, India and Australia which do not conform in
all points to the usually accepted definition of Equisetites, and so justify
their inclusion in an allied genus. On the other hand there are numerous
instances of stems or branches which have been referred to Phyllotheca on
insufficient grounds. Our knowledge of this Equisetaceous plant has
recently been extended by Zeiller[549], who has recorded its occurrence in the
Coal-Measures of Asia Minor associated with typical Upper Carboniferous
plants. The same author[550] has also brought forward good evidence for the
Permian age of the beds in Siberia and Altai, where Phyllotheca has long
been known. It is true that Zigno’s species of the genus occurs in Italian
Jurassic rocks, but on the whole it would seem that this genus is rather a
Permian than a Jurassic type. The species which Zeiller describes under the
name Phyllotheca Rallii from the Coal-Measures of Herakleion (Asia
Minor) shows some points of contact with Annularia. It is much to be
desired, however, that we might learn more as to the reproductive organs of
this member of the Equisetales; until we possess a closer acquaintance with
the fructification we cannot hope to arrive at any satisfactory conclusion as
to the exact position of the genus among the Calamarian and Equisetaceous
forms. M. Zeiller[551] informs me that his specimens of P. Rallii, which are
to be fully described in a forthcoming work, include fossil strobili
resembling those of Annularia radiata. The verticils of linear leaves fused
basally into a sheath agree in appearance with the star-like leaves of
principally on some Permian specimens of the genus described by
Schmalhausen from Russia[546] and redescribed more recently by Solms-
Laubach[547]. Prof. Zeiller[548] has, however, lately received some examples
of Phyllotheca from the Coal-Measures of Asia Minor which bear strobili
like those of the genus Annularia, a type which is dealt with in the
succeeding chapter. A description of a few species will serve to illustrate the
features usually associated with this generic type, as well as to emphasize
the unsatisfactory state of our knowledge as to the real significance of such
supposed generic characteristics.
There are a few fossil stems from Permian rocks of Siberia, from Jurassic
strata in Italy, and from Lower Mesozoic and Permo-Carboniferous beds in
South America, South Africa, India and Australia which do not conform in
all points to the usually accepted definition of Equisetites, and so justify
their inclusion in an allied genus. On the other hand there are numerous
instances of stems or branches which have been referred to Phyllotheca on
insufficient grounds. Our knowledge of this Equisetaceous plant has
recently been extended by Zeiller[549], who has recorded its occurrence in the
Coal-Measures of Asia Minor associated with typical Upper Carboniferous
plants. The same author[550] has also brought forward good evidence for the
Permian age of the beds in Siberia and Altai, where Phyllotheca has long
been known. It is true that Zigno’s species of the genus occurs in Italian
Jurassic rocks, but on the whole it would seem that this genus is rather a
Permian than a Jurassic type. The species which Zeiller describes under the
name Phyllotheca Rallii from the Coal-Measures of Herakleion (Asia
Minor) shows some points of contact with Annularia. It is much to be
desired, however, that we might learn more as to the reproductive organs of
this member of the Equisetales; until we possess a closer acquaintance with
the fructification we cannot hope to arrive at any satisfactory conclusion as
to the exact position of the genus among the Calamarian and Equisetaceous
forms. M. Zeiller[551] informs me that his specimens of P. Rallii, which are
to be fully described in a forthcoming work, include fossil strobili
resembling those of Annularia radiata. The verticils of linear leaves fused
basally into a sheath agree in appearance with the star-like leaves of
Page 299
Annularia, but in Phyllotheca Rallii the segments appear to spread in all
directions and are not extended in one plane as in the typical Annularia[552].
1. Phyllotheca deliquescens (Göpp.).
In an account of some fossil plants collected by Tchikatcheff in Altai,
Göppert[553] describes and figures two imperfect stems of an Equisetum-like
plant. Owing to the apparent absence of nodal lines on the surface of the
stem the generic name Anarthrocanna is proposed for the fossils; and the
manner in which the main axis appears to break up into slender branches
suggested the specific name deliquescens. Schmalhausen[554] afterwards
recognised the generic identity of Göppert’s fragments with the Indian and
Australian stems referred to the genus Phyllotheca by McCoy[555] and
Bunbury[556].
We may define the species as follows:—
Stem reaching a diameter of 2–3 cm. with internodes as much as 4 cm.
long, the surface of which is traversed by longitudinal ridges and grooves
which are continuous and not alternate at the nodes. Branches arise in
verticils from the nodes. The leaves have the form of funnel-shaped sheaths
split up into narrow and spreading linear segments, each of which is
traversed by a median vein. The fertile shoot terminates in a loose strobilus
bearing alternating whorls of sterile bracts and sporangiophores.
The specimens on which this diagnosis is founded are for the most part
fragments of sterile branches. Some of these present the appearance of
Calamitean stems in which the ridges and grooves continue in straight lines
from one internode to the next. Similar stem-casts have been referred by
some writers to the allied genus Schizoneura, and it would appear to be a
hopeless task to decide with certainty under which generic designation such
specimens should be described. The portion of stem shown in fig. 67
affords an example of an Equisetaceous plant, probably in the form of a cast
of a hollow pith, which might be referred to either Phyllotheca or
Schizoneura. The specimen was found in certain South African rocks which
are probably of Permo-Carboniferous age[557]. It agrees closely with some
stems from India described by Feistmantel[558] as Schizoneura
gondwanensis, and it also resembles equally closely the Australian
directions and are not extended in one plane as in the typical Annularia[552].
1. Phyllotheca deliquescens (Göpp.).
In an account of some fossil plants collected by Tchikatcheff in Altai,
Göppert[553] describes and figures two imperfect stems of an Equisetum-like
plant. Owing to the apparent absence of nodal lines on the surface of the
stem the generic name Anarthrocanna is proposed for the fossils; and the
manner in which the main axis appears to break up into slender branches
suggested the specific name deliquescens. Schmalhausen[554] afterwards
recognised the generic identity of Göppert’s fragments with the Indian and
Australian stems referred to the genus Phyllotheca by McCoy[555] and
Bunbury[556].
We may define the species as follows:—
Stem reaching a diameter of 2–3 cm. with internodes as much as 4 cm.
long, the surface of which is traversed by longitudinal ridges and grooves
which are continuous and not alternate at the nodes. Branches arise in
verticils from the nodes. The leaves have the form of funnel-shaped sheaths
split up into narrow and spreading linear segments, each of which is
traversed by a median vein. The fertile shoot terminates in a loose strobilus
bearing alternating whorls of sterile bracts and sporangiophores.
The specimens on which this diagnosis is founded are for the most part
fragments of sterile branches. Some of these present the appearance of
Calamitean stems in which the ridges and grooves continue in straight lines
from one internode to the next. Similar stem-casts have been referred by
some writers to the allied genus Schizoneura, and it would appear to be a
hopeless task to decide with certainty under which generic designation such
specimens should be described. The portion of stem shown in fig. 67
affords an example of an Equisetaceous plant, probably in the form of a cast
of a hollow pith, which might be referred to either Phyllotheca or
Schizoneura. The specimen was found in certain South African rocks which
are probably of Permo-Carboniferous age[557]. It agrees closely with some
stems from India described by Feistmantel[558] as Schizoneura
gondwanensis, and it also resembles equally closely the Australian
Page 300
specimens referred by Feistmantel[559] to Phyllotheca australis and some
stems of Phyllotheca indica figured by Bunbury[560].
The longitudinal ridges and grooves shown in fig. 67 probably represent
the broad medullary rays and the projecting wedges of secondary wood
surrounding a large hollow pith, as in Calamites. In the Calamitean casts the
ridges and grooves of each internode usually alternate in position with those
of the next, as in Equisetum (fig. 54, A), but in Phyllotheca, Schizoneura
and Archaeocalamites there is no such regular alternation at the nodes of
the internodal vascular strands.
stems of Phyllotheca indica figured by Bunbury[560].
The longitudinal ridges and grooves shown in fig. 67 probably represent
the broad medullary rays and the projecting wedges of secondary wood
surrounding a large hollow pith, as in Calamites. In the Calamitean casts the
ridges and grooves of each internode usually alternate in position with those
of the next, as in Equisetum (fig. 54, A), but in Phyllotheca, Schizoneura
and Archaeocalamites there is no such regular alternation at the nodes of
the internodal vascular strands.
Page 301
Fig. 67. Phyllotheca? ¾ nat. size. From a South African specimen of Permo-Carboniferous
age in the British Museum.
In Phyllotheca and Schizoneura there are no casts of ‘infranodal canals’
below each nodal line, but these are by no means always found in true
Calamites. It is therefore practically impossible to determine the generic
position of such fossils as that shown in fig. 67 without further evidence
than is afforded by leafless casts.
A few examples of Phyllotheca deliquescens have been described by
Schmalhausen in which a branch bears clusters of sporangiophores,
alternating with verticils of sterile bracts. The sporangiophores appear to
age in the British Museum.
In Phyllotheca and Schizoneura there are no casts of ‘infranodal canals’
below each nodal line, but these are by no means always found in true
Calamites. It is therefore practically impossible to determine the generic
position of such fossils as that shown in fig. 67 without further evidence
than is afforded by leafless casts.
A few examples of Phyllotheca deliquescens have been described by
Schmalhausen in which a branch bears clusters of sporangiophores,
alternating with verticils of sterile bracts. The sporangiophores appear to
Page 302
have the form of stalked peltate appendages bearing sporangia, very similar
to the sporangiophores of Equisetum. Solms-Laubach[561] has examined the
best of Schmalhausen’s specimens, and a carefully drawn figure of one of
the fertile branches is given in his Fossil Botany.
The significance of this manner of occurrence of sporangiophores and
whorls of sterile bracts on the fertile branch will be better understood after a
description of the strobilus of Calamites. In Phyllotheca the
sporangiophores appear to have been given off in whorls, which were
separated from one another by whorls of sterile bracts, whereas in
Equisetum there are no sterile appendages associated with the
sporangiophores of the strobilus, with the exception of the annulus at the
base of the cone. Heer[562] first drew attention to the fact that in Phyllotheca
we have a form of strobilus or fertile shoot to a certain extent intermediate
in character between Equisetum and Calamites.
In abnormal fertile shoots of Equisetum, sporophylls occasionally occur
above and below a sterile leaf-sheath. Potonié[563] has figured such an
example in which an apical strobilus is succeeded at a lower level by a
sterile leaf-sheath, and this again by a second cluster of sporophylls. As
Potonié points out, this alternation of fertile and sterile members affords an
interesting resemblance between Phyllotheca and Equisetum. It suggests a
partial reversion towards the Calamitean type of strobilus.
2. Phyllotheca Brongniarti Zigno. Fig. 68, A.
This species of Phyllotheca from the Lower Oolite rocks of Italy is
known only in the form of sterile branches. The leaves are fused basally
into an open cup-like sheath which is dissected into several spreading and
incurved linear segments. The internodes are striated longitudinally; they
are about 2 mm. in diameter and 10 mm. in length.
The specimen represented in fig. 68, A, was originally described by the
Italian palaeobotanist Zigno[564]; it serves to illustrate the points of
difference between this genus and the ordinary Equisetum. The open and
spreading sheaths clasping the nodes and the erect solitary branches give
the plant a distinctive appearance.
to the sporangiophores of Equisetum. Solms-Laubach[561] has examined the
best of Schmalhausen’s specimens, and a carefully drawn figure of one of
the fertile branches is given in his Fossil Botany.
The significance of this manner of occurrence of sporangiophores and
whorls of sterile bracts on the fertile branch will be better understood after a
description of the strobilus of Calamites. In Phyllotheca the
sporangiophores appear to have been given off in whorls, which were
separated from one another by whorls of sterile bracts, whereas in
Equisetum there are no sterile appendages associated with the
sporangiophores of the strobilus, with the exception of the annulus at the
base of the cone. Heer[562] first drew attention to the fact that in Phyllotheca
we have a form of strobilus or fertile shoot to a certain extent intermediate
in character between Equisetum and Calamites.
In abnormal fertile shoots of Equisetum, sporophylls occasionally occur
above and below a sterile leaf-sheath. Potonié[563] has figured such an
example in which an apical strobilus is succeeded at a lower level by a
sterile leaf-sheath, and this again by a second cluster of sporophylls. As
Potonié points out, this alternation of fertile and sterile members affords an
interesting resemblance between Phyllotheca and Equisetum. It suggests a
partial reversion towards the Calamitean type of strobilus.
2. Phyllotheca Brongniarti Zigno. Fig. 68, A.
This species of Phyllotheca from the Lower Oolite rocks of Italy is
known only in the form of sterile branches. The leaves are fused basally
into an open cup-like sheath which is dissected into several spreading and
incurved linear segments. The internodes are striated longitudinally; they
are about 2 mm. in diameter and 10 mm. in length.
The specimen represented in fig. 68, A, was originally described by the
Italian palaeobotanist Zigno[564]; it serves to illustrate the points of
difference between this genus and the ordinary Equisetum. The open and
spreading sheaths clasping the nodes and the erect solitary branches give
the plant a distinctive appearance.
Page 303
Fig. 68.
A. Phyllotheca Brongniarti, Zigno. Nat. size. (After Zigno.)
B. Calamocladus frondosus, Grand’Eury. (After Grand’Eury.) Slightly enlarged.
C. Phyllotheca indica, Bunb. Part of a leaf-sheath. From a specimen in the Museum of the
Geological Society. Slightly enlarged.
3. Phyllotheca indica Bunb. and P. australis Brongn. Fig. 68, C.
Sir Charles Bunbury[565] described several imperfect specimens from the
Nagpur district of India under this name, but he expressed the opinion that
it was not clear to him if the plant was specifically distinct from the
Phyllotheca australis Brongn. previously recorded from New South Wales.
A. Phyllotheca Brongniarti, Zigno. Nat. size. (After Zigno.)
B. Calamocladus frondosus, Grand’Eury. (After Grand’Eury.) Slightly enlarged.
C. Phyllotheca indica, Bunb. Part of a leaf-sheath. From a specimen in the Museum of the
Geological Society. Slightly enlarged.
3. Phyllotheca indica Bunb. and P. australis Brongn. Fig. 68, C.
Sir Charles Bunbury[565] described several imperfect specimens from the
Nagpur district of India under this name, but he expressed the opinion that
it was not clear to him if the plant was specifically distinct from the
Phyllotheca australis Brongn. previously recorded from New South Wales.
Page 304
Feistmantel[566] subsequently described a few other Indian specimens, but
did not materially add to our knowledge of the genus. Bunbury’s specimens
were obtained from Bharatwádá in Nagpur, in beds belonging to the
Damuda series of the Lower Gondwana rocks, usually regarded as of about
the same age as the Permian rocks of Europe.
Phyllotheca indica is represented by broken and imperfect fragments of
leaf-bearing stems. The species is thus diagnosed by Bunbury:—“Stem
branched, furrowed; sheaths lax, somewhat bell-shaped, distinctly striated;
leaves narrow linear, with a strong and distinct midrib, widely spreading
and often recurved, nearly twice as long as the sheaths.” An examination of
the specimens in the Museum of the Geological Society of London, on
which this account was based, has led me to the opinion that it is practically
impossible to distinguish the Indian examples from P. australis described
by Brongniart[567] from New South Wales. The few specimens of the latter
species which I have had an opportunity of examining bear out this view. In
the smaller branches the axis of P. indica is divided into rather short
internodes on which the ridges and grooves are faintly marked. In the larger
stems the ridges and grooves are much more prominent, and continuous in
direction from one internode to the next; a few branches are given off from
the nodes of some of the specimens. The leaves are not very well preserved;
they consist of a narrow collar-like basal sheath divided up into numerous,
long and narrow segments, which are several times as long as the breadth of
the sheath, and not merely twice as long as Bunbury described them. Each
leaf-sheath has the form of a very shallow cup-like rim clasping the stem at
a node, with long free spreading segments which are often bent back in
their distal region. The general habit of the leafy branches appears to be
identical with that of P. australis as figured by McCoy.
Prof. Zeiller informs me that in the type-specimen on which Brongniart
founded the species, P. australis, the sheath appears to be closely applied to
the stem with a verticil of narrow spreading segments radiating from its
margin. It may be, therefore, that in the Australian form there was not such
an open and cup-like sheath as in P. indica; but it would be difficult,
without better material before us, to feel confidence in any well marked
specific distinctions between the Indian and Australian Phyllothecas.
On the broader stems, such as that of fig. 67, we have clearly marked
narrow grooves and broader and slightly convex ridges, which present an
did not materially add to our knowledge of the genus. Bunbury’s specimens
were obtained from Bharatwádá in Nagpur, in beds belonging to the
Damuda series of the Lower Gondwana rocks, usually regarded as of about
the same age as the Permian rocks of Europe.
Phyllotheca indica is represented by broken and imperfect fragments of
leaf-bearing stems. The species is thus diagnosed by Bunbury:—“Stem
branched, furrowed; sheaths lax, somewhat bell-shaped, distinctly striated;
leaves narrow linear, with a strong and distinct midrib, widely spreading
and often recurved, nearly twice as long as the sheaths.” An examination of
the specimens in the Museum of the Geological Society of London, on
which this account was based, has led me to the opinion that it is practically
impossible to distinguish the Indian examples from P. australis described
by Brongniart[567] from New South Wales. The few specimens of the latter
species which I have had an opportunity of examining bear out this view. In
the smaller branches the axis of P. indica is divided into rather short
internodes on which the ridges and grooves are faintly marked. In the larger
stems the ridges and grooves are much more prominent, and continuous in
direction from one internode to the next; a few branches are given off from
the nodes of some of the specimens. The leaves are not very well preserved;
they consist of a narrow collar-like basal sheath divided up into numerous,
long and narrow segments, which are several times as long as the breadth of
the sheath, and not merely twice as long as Bunbury described them. Each
leaf-sheath has the form of a very shallow cup-like rim clasping the stem at
a node, with long free spreading segments which are often bent back in
their distal region. The general habit of the leafy branches appears to be
identical with that of P. australis as figured by McCoy.
Prof. Zeiller informs me that in the type-specimen on which Brongniart
founded the species, P. australis, the sheath appears to be closely applied to
the stem with a verticil of narrow spreading segments radiating from its
margin. It may be, therefore, that in the Australian form there was not such
an open and cup-like sheath as in P. indica; but it would be difficult,
without better material before us, to feel confidence in any well marked
specific distinctions between the Indian and Australian Phyllothecas.
On the broader stems, such as that of fig. 67, we have clearly marked
narrow grooves and broader and slightly convex ridges, which present an
Page 305
appearance identical with that of some Calamitean stems. In the specimen
figured by Bunbury[568] in his Pl. X, fig. 6, there is a circular depression on
the line of the node which represents the impression of the basal end of a
branch; on the edges of the node there are indications of two other lateral
branches. The nature of this stem-cast points umnistakeably to a woody
stem like that of Calamites. The precise meaning of the ridges and grooves
on the cast is described in the Chapter dealing with Calamitean plants.
CALAMOCLADUS.
Grand’Eury[569] in his monograph on the coal-basin of Gard, has recently
described under the name of Calamocladus frondosus what he believes to
be the leaf-bearing axes of a Calamitean plant. The thicker branches are
almost exactly identical in appearance with the broader specimens of
Phyllotheca. The finer branches of Calamocladus bear cup-like leaf-sheaths
which are divided into long and narrow recurved segments (fig. 67, B),
precisely as in Phyllotheca. These comparisons lead one to the opinion that
the Phyllotheca of Australia and India may be a close ally of the Permo-
Carboniferous Calamitean plants. The form of the leaf-whorls of Annularia
(Calamarian leaf-bearing branches) and of Calamocladus is of the same
type as in Phyllotheca; the character of the medullary casts is also the same.
The nature of the fertile shoot of Phyllotheca described by Schmalhausen
from Siberia, with its alternating whorls of sterile and fertile leaves, is
another point of agreement between this genus and Calamitean plants. An
Equisetaceous species has been described from the Newcastle Coal-
Measures of Australia by Etheridge[570] in which there are two forms of
leaves, some of which closely resemble those of Phyllotheca indica, while
others are compared with the sterile bracts of Cingularia, a Calamitean
genus instituted by Weiss[571].
When we turn to other recorded forms of Phyllotheca many of them
appear on examination to have been placed in this genus on unsatisfactory
grounds. Heer figures several stem fragments from the Jurassic rocks of
Siberia as P. Sibirica Heer[572], and it was the resemblance between this form
and the English Equisetites lateralis which led to the substitution of
Phyllotheca for Equisetites in the latter species. Without examining Heer’s
material it is impossible to criticise his conclusions with any completeness,
but several of his specimens, appear to possess leaf-sheaths more like those
of Equisetum than of Phyllotheca.
figured by Bunbury[568] in his Pl. X, fig. 6, there is a circular depression on
the line of the node which represents the impression of the basal end of a
branch; on the edges of the node there are indications of two other lateral
branches. The nature of this stem-cast points umnistakeably to a woody
stem like that of Calamites. The precise meaning of the ridges and grooves
on the cast is described in the Chapter dealing with Calamitean plants.
CALAMOCLADUS.
Grand’Eury[569] in his monograph on the coal-basin of Gard, has recently
described under the name of Calamocladus frondosus what he believes to
be the leaf-bearing axes of a Calamitean plant. The thicker branches are
almost exactly identical in appearance with the broader specimens of
Phyllotheca. The finer branches of Calamocladus bear cup-like leaf-sheaths
which are divided into long and narrow recurved segments (fig. 67, B),
precisely as in Phyllotheca. These comparisons lead one to the opinion that
the Phyllotheca of Australia and India may be a close ally of the Permo-
Carboniferous Calamitean plants. The form of the leaf-whorls of Annularia
(Calamarian leaf-bearing branches) and of Calamocladus is of the same
type as in Phyllotheca; the character of the medullary casts is also the same.
The nature of the fertile shoot of Phyllotheca described by Schmalhausen
from Siberia, with its alternating whorls of sterile and fertile leaves, is
another point of agreement between this genus and Calamitean plants. An
Equisetaceous species has been described from the Newcastle Coal-
Measures of Australia by Etheridge[570] in which there are two forms of
leaves, some of which closely resemble those of Phyllotheca indica, while
others are compared with the sterile bracts of Cingularia, a Calamitean
genus instituted by Weiss[571].
When we turn to other recorded forms of Phyllotheca many of them
appear on examination to have been placed in this genus on unsatisfactory
grounds. Heer figures several stem fragments from the Jurassic rocks of
Siberia as P. Sibirica Heer[572], and it was the resemblance between this form
and the English Equisetites lateralis which led to the substitution of
Phyllotheca for Equisetites in the latter species. Without examining Heer’s
material it is impossible to criticise his conclusions with any completeness,
but several of his specimens, appear to possess leaf-sheaths more like those
of Equisetum than of Phyllotheca.
Page 306
The frequent occurrence of isolated diaphragms and the comparatively
long acuminate teeth of the leaf-sheath afford obvious points of
resemblance to Equisetites lateralis. Some of the examples figured by Heer
appear to be stem fragments, with numerous long and narrow filiform
leaves different in appearance from those of other specimens which he
figures. It may be that some of the less distinct pieces of stems are badly
torn specimens in which the internodes have been divided into filiform
threads. Heer also figures a fertile axis associated with the sterile stems, and
this does not, as Heer admits, show the alternating sterile bracts such as
Schmalhausen has described. So far as it is possible to judge from an
examination of Heer’s figures and a few specimens from Siberia in the
British Museum—and this is by no means a safe basis on which to found
definite opinions—there appears to be little evidence in favour of separating
the fossils described as Phyllotheca Sibirica from Equisetites. This Siberian
form may indeed be specifically identical with Equisetites lateralis Phill.
Various species of Phyllotheca have been described from Jurassic and
Upper Palaeozoic rocks in Australia. Some of these possess cup-like leaf-
sheaths, and in the case of the thicker specimens they show continuous
ridges and grooves on the internodes, as well as a habit of branching similar
to that in some of the Italian Phyllothecas. In some of the stems it is
however difficult to recognise any characters which justify the use of the
term Phyllotheca. A fragment figured by Tenison-Woods[573] as a new
species of Phyllotheca, P. carnosa, from Ipswich, Queensland, affords an
example of the worthless material on which species have not infrequently
been founded. The author of the species describes his single specimen as a
“faint impression”; the figure accompanying his description suggests a
fragment of some coniferous branch, as Feistmantel has pointed out in his
monograph on Australian plants.
It is important that a thorough comparative examination should be made
of the various fossil Phyllothecas with a view to determine their scientific
value, and to discover how far the separation of Phyllotheca and Equisetites
is legitimate in each case. There is too often a tendency to allow
geographical distribution to decide the adoption of a particular generic
name, and this seems to have been especially the case as regards several
Mesozoic and Palaeozoic Southern Hemisphere plants.
long acuminate teeth of the leaf-sheath afford obvious points of
resemblance to Equisetites lateralis. Some of the examples figured by Heer
appear to be stem fragments, with numerous long and narrow filiform
leaves different in appearance from those of other specimens which he
figures. It may be that some of the less distinct pieces of stems are badly
torn specimens in which the internodes have been divided into filiform
threads. Heer also figures a fertile axis associated with the sterile stems, and
this does not, as Heer admits, show the alternating sterile bracts such as
Schmalhausen has described. So far as it is possible to judge from an
examination of Heer’s figures and a few specimens from Siberia in the
British Museum—and this is by no means a safe basis on which to found
definite opinions—there appears to be little evidence in favour of separating
the fossils described as Phyllotheca Sibirica from Equisetites. This Siberian
form may indeed be specifically identical with Equisetites lateralis Phill.
Various species of Phyllotheca have been described from Jurassic and
Upper Palaeozoic rocks in Australia. Some of these possess cup-like leaf-
sheaths, and in the case of the thicker specimens they show continuous
ridges and grooves on the internodes, as well as a habit of branching similar
to that in some of the Italian Phyllothecas. In some of the stems it is
however difficult to recognise any characters which justify the use of the
term Phyllotheca. A fragment figured by Tenison-Woods[573] as a new
species of Phyllotheca, P. carnosa, from Ipswich, Queensland, affords an
example of the worthless material on which species have not infrequently
been founded. The author of the species describes his single specimen as a
“faint impression”; the figure accompanying his description suggests a
fragment of some coniferous branch, as Feistmantel has pointed out in his
monograph on Australian plants.
It is important that a thorough comparative examination should be made
of the various fossil Phyllothecas with a view to determine their scientific
value, and to discover how far the separation of Phyllotheca and Equisetites
is legitimate in each case. There is too often a tendency to allow
geographical distribution to decide the adoption of a particular generic
name, and this seems to have been especially the case as regards several
Mesozoic and Palaeozoic Southern Hemisphere plants.
Page 307
The geological and geographical range of Phyllotheca is a question of
considerable interest, but as already pointed out it is desirable to carefully
examine the various records of the genus before attempting to generalise as
to the range of the species. Phyllotheca is often spoken of as a characteristic
member of the Glossopteris Flora of the Southern Hemisphere, and its
geological age is usually considered to be Mesozoic rather than Palaeozoic.
C. Schizoneura.
The plants included under this genus were originally designated by
Brongniart[574] Convallarites and classed as Monocotyledons. Some years
later Schimper and Mougeot[575] had the opportunity of examining more
perfect material from the Bunter beds of the Vosges, and proposed the new
name Schizoneura in place of Brongniart’s term, on the grounds that the
specimens were in all probability portions of Equisetaceous stems, and not
Monocotyledons. Our knowledge of this genus is very limited, but the
characteristics are on the whole better defined than in the case of
Phyllotheca. The following diagnosis illustrates the chief features of
Schizoneura.
Hollow stems with nodes and internodes as in Equisetum; the surface of
the internodes is traversed by regular ridges and grooves, which are
continuous and not alternate in their course from one internode to the next.
The leaf-sheaths are large and consist of several coherent segments; the
sheaths are usually split into two or more elongate ovate lobes, and each
lobe contains more than one vein. Fertile shoots are unknown.
Two of the best known and most satisfactory species are Schizoneura
gondwanensis Feist. and S. paradoxa Schimp. and Moug.
Schizoneura gondwanensis Feist. Fig. 69, A and B.
This species is represented by numerous specimens from the Lower
Gondwana rocks of India[576]; it is characterised by narrow articulated stems
which bear large leaf-sheaths at the nodes. The sheaths may have the form
of two large and spreading elongate-oval lobes, each of which is traversed
by several veins (fig. 69, B), or the lobes may be further dissected into long
linear single-veined segments, as in fig. 69, A. It is supposed that in the
young condition each node bears a leaf-sheath consisting of laterally
considerable interest, but as already pointed out it is desirable to carefully
examine the various records of the genus before attempting to generalise as
to the range of the species. Phyllotheca is often spoken of as a characteristic
member of the Glossopteris Flora of the Southern Hemisphere, and its
geological age is usually considered to be Mesozoic rather than Palaeozoic.
C. Schizoneura.
The plants included under this genus were originally designated by
Brongniart[574] Convallarites and classed as Monocotyledons. Some years
later Schimper and Mougeot[575] had the opportunity of examining more
perfect material from the Bunter beds of the Vosges, and proposed the new
name Schizoneura in place of Brongniart’s term, on the grounds that the
specimens were in all probability portions of Equisetaceous stems, and not
Monocotyledons. Our knowledge of this genus is very limited, but the
characteristics are on the whole better defined than in the case of
Phyllotheca. The following diagnosis illustrates the chief features of
Schizoneura.
Hollow stems with nodes and internodes as in Equisetum; the surface of
the internodes is traversed by regular ridges and grooves, which are
continuous and not alternate in their course from one internode to the next.
The leaf-sheaths are large and consist of several coherent segments; the
sheaths are usually split into two or more elongate ovate lobes, and each
lobe contains more than one vein. Fertile shoots are unknown.
Two of the best known and most satisfactory species are Schizoneura
gondwanensis Feist. and S. paradoxa Schimp. and Moug.
Schizoneura gondwanensis Feist. Fig. 69, A and B.
This species is represented by numerous specimens from the Lower
Gondwana rocks of India[576]; it is characterised by narrow articulated stems
which bear large leaf-sheaths at the nodes. The sheaths may have the form
of two large and spreading elongate-oval lobes, each of which is traversed
by several veins (fig. 69, B), or the lobes may be further dissected into long
linear single-veined segments, as in fig. 69, A. It is supposed that in the
young condition each node bears a leaf-sheath consisting of laterally
Page 308
coherent segments which, as development proceeds, split into two or more
lobes. Feistmantel records this species from the Talchir, Damuda and
Panchet divisions of the Lower Gondwana series of India; these divisions
are regarded as equivalent to the Permo-Carboniferous and Triassic rocks of
Europe. The two specimens shown in fig. 69 are from the Lower Gondwana
rocks of the Raniganj Coal-field, India.
As already pointed out[577], some of the specimens of flat and broader
stems referred by Feistmantel to Schizoneura are identical in appearance
with stems which have been described from India and elsewhere as species
of Phyllotheca.
Fig. 69. Schizoneura gondwanensis Feist. (After Feistmantel; slightly reduced.)
lobes. Feistmantel records this species from the Talchir, Damuda and
Panchet divisions of the Lower Gondwana series of India; these divisions
are regarded as equivalent to the Permo-Carboniferous and Triassic rocks of
Europe. The two specimens shown in fig. 69 are from the Lower Gondwana
rocks of the Raniganj Coal-field, India.
As already pointed out[577], some of the specimens of flat and broader
stems referred by Feistmantel to Schizoneura are identical in appearance
with stems which have been described from India and elsewhere as species
of Phyllotheca.
Fig. 69. Schizoneura gondwanensis Feist. (After Feistmantel; slightly reduced.)
Page 309
There are a few specimens of S. gondwanensis in the British Museum,
but the genus is poorly represented in European collections.
A similar plant was described in 1844 by Schimper and Mougeot[578] from
the Bunter rocks of the Vosges as Schizoneura paradoxa. This species bears
a very close resemblance to the Indian forms, and indeed it is difficult to
point to any distinction of taxonomic importance. Feistmantel considers that
the European plant has rather fewer segments in the leaf-sheaths, and that
the Indian plant had somewhat stronger stems. Both of these differences are
such as might easily be found on branches of the same species. It is,
however, interesting to notice the very close resemblance between the
Lower Trias European plant and the somewhat older member of the
Glossopteris flora recorded from India and other regions, which probably
once formed part of that Southern Hemisphere Continent which is known as
Gondwana Land[579].
but the genus is poorly represented in European collections.
A similar plant was described in 1844 by Schimper and Mougeot[578] from
the Bunter rocks of the Vosges as Schizoneura paradoxa. This species bears
a very close resemblance to the Indian forms, and indeed it is difficult to
point to any distinction of taxonomic importance. Feistmantel considers that
the European plant has rather fewer segments in the leaf-sheaths, and that
the Indian plant had somewhat stronger stems. Both of these differences are
such as might easily be found on branches of the same species. It is,
however, interesting to notice the very close resemblance between the
Lower Trias European plant and the somewhat older member of the
Glossopteris flora recorded from India and other regions, which probably
once formed part of that Southern Hemisphere Continent which is known as
Gondwana Land[579].
Page 310
Page 311
CHAPTER X.
I. EQUISETALES (continued).
(CALAMARIEAE.)
In order to minimise repetition and digression the following account of
the Calamarieae is divided into sections, under each of which a certain part
of the subject is more particularly dealt with. After a brief sketch of the
history of our knowledge of Calamites, and a short description of the
characteristics of the genus, the morphological features are more fully
considered. A description of the most striking features of the better known
Calamitean types is followed by a short discussion on the question of
nomenclature and classification, and reference is made to the manner of
occurrence of Calamites and to some of the possible sources of error in
identification.
D. Calamites.
I. Historical Sketch.
In the following account of the Calamarieae the generic name Calamites
is used in a somewhat comprehensive sense. As previous writers have
pointed out, it is probable that under this generic name there may be
included more than one type of plant worthy of generic designation. Owing
to the various opinions which have been held by different authors, as to the
relationship and botanical position of plants now generally included in the
Calamarieae, there has been no little confusion in nomenclature. Facts as to
the nature of the genus Calamites have occasionally to be selected from
writings containing many speculative and erroneous views, but the data at
our disposal enable us to give a fairly complete account of the morphology
of this Palaeozoic plant.
I. EQUISETALES (continued).
(CALAMARIEAE.)
In order to minimise repetition and digression the following account of
the Calamarieae is divided into sections, under each of which a certain part
of the subject is more particularly dealt with. After a brief sketch of the
history of our knowledge of Calamites, and a short description of the
characteristics of the genus, the morphological features are more fully
considered. A description of the most striking features of the better known
Calamitean types is followed by a short discussion on the question of
nomenclature and classification, and reference is made to the manner of
occurrence of Calamites and to some of the possible sources of error in
identification.
D. Calamites.
I. Historical Sketch.
In the following account of the Calamarieae the generic name Calamites
is used in a somewhat comprehensive sense. As previous writers have
pointed out, it is probable that under this generic name there may be
included more than one type of plant worthy of generic designation. Owing
to the various opinions which have been held by different authors, as to the
relationship and botanical position of plants now generally included in the
Calamarieae, there has been no little confusion in nomenclature. Facts as to
the nature of the genus Calamites have occasionally to be selected from
writings containing many speculative and erroneous views, but the data at
our disposal enable us to give a fairly complete account of the morphology
of this Palaeozoic plant.
Page 312
In the earliest works on fossil plants we find several figures of Calamites,
which are in most cases described as those of fossil reeds or grasses. The
Herbarium diluvianum of Scheuchzer[580] contains a figure of a Calamitean
cast which is described as probably a reed. Another specimen is figured by
Volkmann[581] in his Silesia subterranea and compared with a piece of
sugar-cane. A similar flattened cast in the old Woodwardian collection at
Cambridge is described by Woodward[582] as “part of a broad long flat leaf,
appearing to be of some Iris, or rather an Aloe, but ’tis striated without.”
Schulze[583], one of the earlier German writers, figured a Calamitean branch
bearing verticils of leaves, and described the fossil as probably the
impression of an Equisetaceous plant. It has been pointed out by another
German writer that the Equisetaceous character of Calamites was
recognised by laymen many years before specialists shared this view.
One of the most interesting and important of all the older records of
Calamites is that published by Suckow[584] in 1784. Suckow is usually
quoted as the author of the generic name Calamites; he does not attempt
any diagnosis of the plant, but merely speaks of the specimens he is
describing as “Calamiten.” The examples figured in this classic paper are
characteristic casts from the Coal-Measures of Western Germany. Suckow
describes them as ribbed stems, which were found in an oblique position in
the strata and termed by the workmen Jupiter’s nails (“Nägel”). Previous
writers had regarded the fossils as casts of reeds, but Suckow correctly
points out that the ribbed character is hardly consistent with the view that
the casts are those of reeds or grasses. He goes on to say that the material
filling up the hollow pith of a reed would not have impressed upon it a
number of ribs and grooves such as occur on the Calamites. He considers it
more probable that the casts are those of some well-developed tree,
probably a foreign plant. Equisetum giganteum L. is mentioned as a species
with which Calamites may be compared, although the stem of the
Palaeozoic genus was much larger than that of the recent Horse-tail. The
tree of which the Calamites are the casts must, he adds, have possessed a
ribbed stem, and the bark must also have been marked by vertical ribs and
grooves on its inner face. It is clear, therefore, that Suckow inclined to the
view that Calamites should be regarded as an internal cast of a woody
plant. Such an interpretation of the fossils was generally accepted by
palaeobotanists only a comparatively few years ago, and the first suggestion
which are in most cases described as those of fossil reeds or grasses. The
Herbarium diluvianum of Scheuchzer[580] contains a figure of a Calamitean
cast which is described as probably a reed. Another specimen is figured by
Volkmann[581] in his Silesia subterranea and compared with a piece of
sugar-cane. A similar flattened cast in the old Woodwardian collection at
Cambridge is described by Woodward[582] as “part of a broad long flat leaf,
appearing to be of some Iris, or rather an Aloe, but ’tis striated without.”
Schulze[583], one of the earlier German writers, figured a Calamitean branch
bearing verticils of leaves, and described the fossil as probably the
impression of an Equisetaceous plant. It has been pointed out by another
German writer that the Equisetaceous character of Calamites was
recognised by laymen many years before specialists shared this view.
One of the most interesting and important of all the older records of
Calamites is that published by Suckow[584] in 1784. Suckow is usually
quoted as the author of the generic name Calamites; he does not attempt
any diagnosis of the plant, but merely speaks of the specimens he is
describing as “Calamiten.” The examples figured in this classic paper are
characteristic casts from the Coal-Measures of Western Germany. Suckow
describes them as ribbed stems, which were found in an oblique position in
the strata and termed by the workmen Jupiter’s nails (“Nägel”). Previous
writers had regarded the fossils as casts of reeds, but Suckow correctly
points out that the ribbed character is hardly consistent with the view that
the casts are those of reeds or grasses. He goes on to say that the material
filling up the hollow pith of a reed would not have impressed upon it a
number of ribs and grooves such as occur on the Calamites. He considers it
more probable that the casts are those of some well-developed tree,
probably a foreign plant. Equisetum giganteum L. is mentioned as a species
with which Calamites may be compared, although the stem of the
Palaeozoic genus was much larger than that of the recent Horse-tail. The
tree of which the Calamites are the casts must, he adds, have possessed a
ribbed stem, and the bark must also have been marked by vertical ribs and
grooves on its inner face. It is clear, therefore, that Suckow inclined to the
view that Calamites should be regarded as an internal cast of a woody
plant. Such an interpretation of the fossils was generally accepted by
palaeobotanists only a comparatively few years ago, and the first suggestion
Page 313
of this view is usually attributed to Germar, Dawes, and other authors who
wrote more than fifty years later than Suckow.
One of the earliest notices of Calamites in the present century is by
Steinhauer[585], who published a memoir in the Transactions of the American
Philosophical Society in 1818 on Fossil reliquia of unknown vegetables in
the Carboniferous rocks. He gives some good figures of Calamitean casts
under the generic name of Phytolithus, one of those general terms often
used by the older writers on fossils. Among English authors, Martin[586] may
be mentioned as figuring casts of Calamites, which he describes as
probably grass stems. By far the best of the earlier figures are those by
Artis[587] in his Antediluvian Phytology. This writer does not discuss the
botanical nature of the specimens beyond a brief reference to the views of
earlier authors. Adolphe Brongniart[588], writing in 1822, expresses the
opinion that the Calamites are related to the genus Equisetum, and refers to
M. de Candolle as having first suggested this view. In a later work
Brongniart[589] includes species of Calamites as figured by Suckow,
Schlotheim, Sternberg and Artis in the family Equisetaceae. Lindley and
Hutton[590] give several figures of Calamites in their Fossil flora, but do not
commit themselves to an Equisetaceous affinity.
An important advance was made in 1835 by Cotta[591], a German writer,
who gave a short account of the internal structure of some Calamite stems,
which he referred to a new genus Calamitea. The British Museum
collection includes some silicified fragments of the stems figured and
described by Cotta in his Dendrolithen. Some of the specimens described
by this author as examples of Calamitea have since been recognised as
members of another family.
PETZHOLDT AND UNGER.
In 1840 Unger[592] published a note on the structure and affinities of
Calamites, and expressed his belief in the close relationship of the
Palaeozoic plant and recent Horse-tails.
An important contribution to our knowledge of Calamites was supplied
by Petzholdt[593] in 1841. His main contention was the Equisetaceous
character of this Palaeozoic genus. The external resemblance between
Calamite casts and Equisetum stems had long been recognised, but after
Cotta’s account of the internal structure it was believed that the apparent
wrote more than fifty years later than Suckow.
One of the earliest notices of Calamites in the present century is by
Steinhauer[585], who published a memoir in the Transactions of the American
Philosophical Society in 1818 on Fossil reliquia of unknown vegetables in
the Carboniferous rocks. He gives some good figures of Calamitean casts
under the generic name of Phytolithus, one of those general terms often
used by the older writers on fossils. Among English authors, Martin[586] may
be mentioned as figuring casts of Calamites, which he describes as
probably grass stems. By far the best of the earlier figures are those by
Artis[587] in his Antediluvian Phytology. This writer does not discuss the
botanical nature of the specimens beyond a brief reference to the views of
earlier authors. Adolphe Brongniart[588], writing in 1822, expresses the
opinion that the Calamites are related to the genus Equisetum, and refers to
M. de Candolle as having first suggested this view. In a later work
Brongniart[589] includes species of Calamites as figured by Suckow,
Schlotheim, Sternberg and Artis in the family Equisetaceae. Lindley and
Hutton[590] give several figures of Calamites in their Fossil flora, but do not
commit themselves to an Equisetaceous affinity.
An important advance was made in 1835 by Cotta[591], a German writer,
who gave a short account of the internal structure of some Calamite stems,
which he referred to a new genus Calamitea. The British Museum
collection includes some silicified fragments of the stems figured and
described by Cotta in his Dendrolithen. Some of the specimens described
by this author as examples of Calamitea have since been recognised as
members of another family.
PETZHOLDT AND UNGER.
In 1840 Unger[592] published a note on the structure and affinities of
Calamites, and expressed his belief in the close relationship of the
Palaeozoic plant and recent Horse-tails.
An important contribution to our knowledge of Calamites was supplied
by Petzholdt[593] in 1841. His main contention was the Equisetaceous
character of this Palaeozoic genus. The external resemblance between
Calamite casts and Equisetum stems had long been recognised, but after
Cotta’s account of the internal structure it was believed that the apparent
Page 314
relation between Equisetum and Calamites was not confirmed by the facts
of anatomy. Petzholdt based his conclusions on certain partially preserved
Permian stems from Plauenscher Grund, near Dresden. Although his
account of the fossils is not accurate his general conclusions are correct.
The specimens described by Petzholdt differ from the common Calamite
casts in having some carbonised remnants of cortical and woody tissue. A
transverse section of one of the Plauenscher Grund fossils is shown in fig.
70. The irregular black patches were described by Petzholdt as portions of
cortical tissue, while he regarded the spaces as marking the position of
canals like the vallecular canals in an Equisetum. Our more complete
knowledge of the structure of a Calamite stem enables us to correlate the
patches in which no tissue has been preserved with the broad medullary
rays, which separated the wedge-shaped groups of xylem elements; the
latter being more resistant were converted into a black coaly substance,
while the cells of the medullary rays left little or no trace in the sandstone
matrix. The thin black line, which forms the limit of the drawing in fig. 70,
external to the carbonised wood, no doubt marks the limit of the cortex, and
the appendage indicated in the lower part of the figure may possibly be an
adventitious root. It is interesting to note that Unger[594] in 1844 expressed
the opinion, which we now know to be correct, that the coaly mass in the
specimens described by Petzholdt represented the wood, and that there was
no proof of the existence of canals in the cortex as Petzholdt believed.
of anatomy. Petzholdt based his conclusions on certain partially preserved
Permian stems from Plauenscher Grund, near Dresden. Although his
account of the fossils is not accurate his general conclusions are correct.
The specimens described by Petzholdt differ from the common Calamite
casts in having some carbonised remnants of cortical and woody tissue. A
transverse section of one of the Plauenscher Grund fossils is shown in fig.
70. The irregular black patches were described by Petzholdt as portions of
cortical tissue, while he regarded the spaces as marking the position of
canals like the vallecular canals in an Equisetum. Our more complete
knowledge of the structure of a Calamite stem enables us to correlate the
patches in which no tissue has been preserved with the broad medullary
rays, which separated the wedge-shaped groups of xylem elements; the
latter being more resistant were converted into a black coaly substance,
while the cells of the medullary rays left little or no trace in the sandstone
matrix. The thin black line, which forms the limit of the drawing in fig. 70,
external to the carbonised wood, no doubt marks the limit of the cortex, and
the appendage indicated in the lower part of the figure may possibly be an
adventitious root. It is interesting to note that Unger[594] in 1844 expressed
the opinion, which we now know to be correct, that the coaly mass in the
specimens described by Petzholdt represented the wood, and that there was
no proof of the existence of canals in the cortex as Petzholdt believed.
Page 315
Fig. 70. Transverse section of a Calamite stem, showing carbonised remnants of secondary
wood. From a specimen (no. 40934), presented to the British Museum by Dr Petzholdt
from Plauenscher Grund, Dresden. ½ nat. size.
Turning to Brongniart’s later work[595] we find an important proposal
which led to no little controversy. While retaining the genus Calamites for
such specimens as possess a thin bark and a ribbed external surface,
showing occasional branch-scars at the nodes, and having such characters
as warrant their inclusion in the Equisetaceae, he proposes a second generic
name for other specimens which had hitherto been included in Calamites.
The fossils assigned to his new genus Calamodendron are described as
having a thick woody stem, and as differing from Equisetum in their
arborescent nature. Brongniart’s genus Calamodendron is made to include
the plants for which Cotta instituted the name Calamitea, and it is placed
among the Gymnosperms. This distinction between the Vascular Cryptogam
Calamites and the supposed Gymnosperm Calamodendron is based on the
presence of secondary wood in the latter type of stem. The prominence
formerly assigned to the power of secondary thickening possessed by a
wood. From a specimen (no. 40934), presented to the British Museum by Dr Petzholdt
from Plauenscher Grund, Dresden. ½ nat. size.
Turning to Brongniart’s later work[595] we find an important proposal
which led to no little controversy. While retaining the genus Calamites for
such specimens as possess a thin bark and a ribbed external surface,
showing occasional branch-scars at the nodes, and having such characters
as warrant their inclusion in the Equisetaceae, he proposes a second generic
name for other specimens which had hitherto been included in Calamites.
The fossils assigned to his new genus Calamodendron are described as
having a thick woody stem, and as differing from Equisetum in their
arborescent nature. Brongniart’s genus Calamodendron is made to include
the plants for which Cotta instituted the name Calamitea, and it is placed
among the Gymnosperms. This distinction between the Vascular Cryptogam
Calamites and the supposed Gymnosperm Calamodendron is based on the
presence of secondary wood in the latter type of stem. The prominence
formerly assigned to the power of secondary thickening possessed by a
Page 316
plant as a taxonomic feature, is now known to have been the result of
imperfect knowledge. The occurrence of a cambium layer and the ability of
a plant to increase in girth by the activity of a definite meristem, is a feature
which some recent Vascular Cryptogams[596] share with the higher plants;
and in former ages many of the Pteridophytes possessed this method of
growth in a striking degree.
Although Brongniart’s distinction between Calamites and
Calamodendron has not been borne out by subsequent researches, the latter
term is still used as a convenient designation for a special type of
Calamitean structure. One of the earliest accounts of the anatomy of
Calamodendron stems is by Mougeot[597], who published figures and
descriptions of two species, Calamodendron striatum and C. bistriatum.
Some years later Göppert[598], who was one of the greatest of the older
palaeobotanists, instituted another genus, Arthropitys[599], for certain
specimens of silicified stems from the Permian rocks of Chemnitz in
Saxony, which Cotta had previously placed in his genus Calamitea under
the name of Calamitea bistriata[600]. Göppert rightly decided that the plants
so named by Cotta differed in important histological characters from other
species of Calamitea. The generic name Arthropitys has been widely
adopted for a type of Calamitean stem characterised by definite structural
features. The great majority of the petrified Calamite stems found in the
English Coal-Measures belong to Göppert’s Arthropitys.
WILLIAMSON.
The next proposal to be noticed is one by Williamson[601] in 1868; he
instituted the generic name Calamopitys for a few examples of English
stems, which differed in the structure of the wood and primary medullary
rays from previously recorded types. We have thus four names which all
stand for generic types of Calamitean stems. Of these Calamodendron and
Arthropitys are still used as convenient designations for stems with well-
defined anatomical characters. The genus Calamitea is no longer in use, and
Williamson’s name Calamopitys had previously been made use of by
Unger[602] for plants which do not belong to the Calamarieae. As it is
convenient to have some term to apply to such stems as those which
Williamson made the type of Calamopitys, the name Arthrodendron is
suggested by my friend Dr Scott[603] as a substitute for Williamson’s genus.
imperfect knowledge. The occurrence of a cambium layer and the ability of
a plant to increase in girth by the activity of a definite meristem, is a feature
which some recent Vascular Cryptogams[596] share with the higher plants;
and in former ages many of the Pteridophytes possessed this method of
growth in a striking degree.
Although Brongniart’s distinction between Calamites and
Calamodendron has not been borne out by subsequent researches, the latter
term is still used as a convenient designation for a special type of
Calamitean structure. One of the earliest accounts of the anatomy of
Calamodendron stems is by Mougeot[597], who published figures and
descriptions of two species, Calamodendron striatum and C. bistriatum.
Some years later Göppert[598], who was one of the greatest of the older
palaeobotanists, instituted another genus, Arthropitys[599], for certain
specimens of silicified stems from the Permian rocks of Chemnitz in
Saxony, which Cotta had previously placed in his genus Calamitea under
the name of Calamitea bistriata[600]. Göppert rightly decided that the plants
so named by Cotta differed in important histological characters from other
species of Calamitea. The generic name Arthropitys has been widely
adopted for a type of Calamitean stem characterised by definite structural
features. The great majority of the petrified Calamite stems found in the
English Coal-Measures belong to Göppert’s Arthropitys.
WILLIAMSON.
The next proposal to be noticed is one by Williamson[601] in 1868; he
instituted the generic name Calamopitys for a few examples of English
stems, which differed in the structure of the wood and primary medullary
rays from previously recorded types. We have thus four names which all
stand for generic types of Calamitean stems. Of these Calamodendron and
Arthropitys are still used as convenient designations for stems with well-
defined anatomical characters. The genus Calamitea is no longer in use, and
Williamson’s name Calamopitys had previously been made use of by
Unger[602] for plants which do not belong to the Calamarieae. As it is
convenient to have some term to apply to such stems as those which
Williamson made the type of Calamopitys, the name Arthrodendron is
suggested by my friend Dr Scott[603] as a substitute for Williamson’s genus.
Page 317
The twofold division of the Calamites instituted by Brongniart has
already been alluded to, and for many years it was generally agreed that
both Pteridophytes and Gymnosperms were represented among the
Palaeozoic fossils known as Calamites. The work of Prof. Williamson was
largely instrumental in proving the unsound basis for this artificial
separation; he insisted on the inclusion of all Calamites in the Vascular
Cryptogams, irrespective of the presence or absence of secondary wood. By
degrees the adherents of Brongniart’s views acknowledged the force of the
English botanist’s contention. It is one of the many signs of the value of
Williamson’s work that there is now almost complete accord among
palaeobotanical writers as to the affinities of Calamitean plants.
In the following account of the Calamites, the generic name Calamites is
used in a wide sense as including stems possessing different types of
internal structure; when it is possible to recognise any of these structural
types the terms Calamodendron, Arthropitys or Arthrodendron are used as
subgenera. The reasons for this nomenclature are discussed in a later part of
the Chapter.
Genus Calamites, This term was originally applied to the common pith-casts of
Suckow, 1714 Calamitean stems, without reference to internal structure.
Subgenera Calamodendron, Brongniart, 1849
Arthropitys Göppert, 1864 These names have primarily reference to
Arthrodendron Scott 1897 internal structure.
(= Calamopitys Williamson, 1871
II. Description of the anatomy of Calamites.
a. Stems. b. Leaves. c. Roots. d. Cones.
No fossils are better known to collectors of Coal-Measure plants than the
casts and impressions of the numerous species of Calamites. In sandstone
quarries of Upper Carboniferous rocks there are frequently found
cylindrical or somewhat flattened fossils, varying from one to several
inches in diameter, marked on the surface by longitudinal ridges and
grooves, and at more or less regular intervals by regular transverse
constrictions. Similar specimens are still more abundant as flattened casts in
the blocks of shale found on the rubbish heaps of collieries. The sandstone
casts are often separated from the surrounding rock by a loose brown or
already been alluded to, and for many years it was generally agreed that
both Pteridophytes and Gymnosperms were represented among the
Palaeozoic fossils known as Calamites. The work of Prof. Williamson was
largely instrumental in proving the unsound basis for this artificial
separation; he insisted on the inclusion of all Calamites in the Vascular
Cryptogams, irrespective of the presence or absence of secondary wood. By
degrees the adherents of Brongniart’s views acknowledged the force of the
English botanist’s contention. It is one of the many signs of the value of
Williamson’s work that there is now almost complete accord among
palaeobotanical writers as to the affinities of Calamitean plants.
In the following account of the Calamites, the generic name Calamites is
used in a wide sense as including stems possessing different types of
internal structure; when it is possible to recognise any of these structural
types the terms Calamodendron, Arthropitys or Arthrodendron are used as
subgenera. The reasons for this nomenclature are discussed in a later part of
the Chapter.
Genus Calamites, This term was originally applied to the common pith-casts of
Suckow, 1714 Calamitean stems, without reference to internal structure.
Subgenera Calamodendron, Brongniart, 1849
Arthropitys Göppert, 1864 These names have primarily reference to
Arthrodendron Scott 1897 internal structure.
(= Calamopitys Williamson, 1871
II. Description of the anatomy of Calamites.
a. Stems. b. Leaves. c. Roots. d. Cones.
No fossils are better known to collectors of Coal-Measure plants than the
casts and impressions of the numerous species of Calamites. In sandstone
quarries of Upper Carboniferous rocks there are frequently found
cylindrical or somewhat flattened fossils, varying from one to several
inches in diameter, marked on the surface by longitudinal ridges and
grooves, and at more or less regular intervals by regular transverse
constrictions. Similar specimens are still more abundant as flattened casts in
the blocks of shale found on the rubbish heaps of collieries. The sandstone
casts are often separated from the surrounding rock by a loose brown or
Page 318
black crumbling material, and the specimens in the shale are frequently
covered by a thin layer of coal.
Most of the earlier writers regarded such specimens as the impressions of
the ribbed stems of plants similar to or identical with reeds or grasses.
Suckow, and afterwards Dawes and others, expressed the opinion that the
ordinary Calamite cast represented a hardened mass of sand or marl, which
had filled up the pith of a stem either originally fistular or rendered hollow
by decay. The investigation of the internal structure confirmed this view,
and proved that the surface-features of a Calamite stem do not represent the
external markings of the original plant, but the form of the inner face of the
cylinder of wood. The ribs represent the medullary rays of the original stem
or branch, and the intervening grooves mark the position of the strands of
xylem which are arranged in a ring round a large hollow pith[604].
With this brief preliminary account we may pass to a detailed description
of the anatomical characters of Calamites.
The genus Calamites may be briefly defined as follows:—
Arborescent plants reaching a height of several meters, and having a
diameter of proportional size. In habit of growth the Calamites bore a close
resemblance to Equisetum; an underground rhizome giving off lateral
branches and erect aerial shoots bearing branches, either in whorls from
regularly recurring branch-bearing nodes, or two or three from each node;
and in some cases the stems bore occasional branches from widely
separated nodes. The leaves were disposed in whorls either as star-shaped
verticils on slender foliage shoots, or in the form of a circle of long narrow
leaves on the node of a thicker branch. Adventitious roots were developed
from the nodal regions of underground and aerial stems. The cones had the
form of long and narrow strobili consisting of a central axis bearing whorls
of sterile and fertile appendages; the latter in the form of sporangiophores
bearing groups of sporangia. The strobili were heterosporous in some cases,
isosporous in others. The stems had a large hollow pith bridged across by a
transverse diaphragm at the nodes in the centre of the single stele; the latter
consisted of a ring of collateral bundles separated from one another by
primary medullary rays. Each group of xylem was composed of spiral,
annular, scalariform and occasionally reticulate tracheids, the position of the
protoxylem being marked by a longitudinal carinal canal. The shoots and
covered by a thin layer of coal.
Most of the earlier writers regarded such specimens as the impressions of
the ribbed stems of plants similar to or identical with reeds or grasses.
Suckow, and afterwards Dawes and others, expressed the opinion that the
ordinary Calamite cast represented a hardened mass of sand or marl, which
had filled up the pith of a stem either originally fistular or rendered hollow
by decay. The investigation of the internal structure confirmed this view,
and proved that the surface-features of a Calamite stem do not represent the
external markings of the original plant, but the form of the inner face of the
cylinder of wood. The ribs represent the medullary rays of the original stem
or branch, and the intervening grooves mark the position of the strands of
xylem which are arranged in a ring round a large hollow pith[604].
With this brief preliminary account we may pass to a detailed description
of the anatomical characters of Calamites.
The genus Calamites may be briefly defined as follows:—
Arborescent plants reaching a height of several meters, and having a
diameter of proportional size. In habit of growth the Calamites bore a close
resemblance to Equisetum; an underground rhizome giving off lateral
branches and erect aerial shoots bearing branches, either in whorls from
regularly recurring branch-bearing nodes, or two or three from each node;
and in some cases the stems bore occasional branches from widely
separated nodes. The leaves were disposed in whorls either as star-shaped
verticils on slender foliage shoots, or in the form of a circle of long narrow
leaves on the node of a thicker branch. Adventitious roots were developed
from the nodal regions of underground and aerial stems. The cones had the
form of long and narrow strobili consisting of a central axis bearing whorls
of sterile and fertile appendages; the latter in the form of sporangiophores
bearing groups of sporangia. The strobili were heterosporous in some cases,
isosporous in others. The stems had a large hollow pith bridged across by a
transverse diaphragm at the nodes in the centre of the single stele; the latter
consisted of a ring of collateral bundles separated from one another by
primary medullary rays. Each group of xylem was composed of spiral,
annular, scalariform and occasionally reticulate tracheids, the position of the
protoxylem being marked by a longitudinal carinal canal. The shoots and
Page 319
roots grew in thickness by means of a regular cambium layer. The cortex
consisted of parenchymatous and sclerenchymatous cells, with scattered
secretory sacs. The increase in girth of the central cylinder was often
accompanied by a considerable development of cortical periderm. The roots
differed from the shoots in having no carinal canals, and in the possession
of a solid pith and centripetally developed primary xylem groups alternating
with strands of phloem.
The above incomplete diagnosis includes only some of the more
important structural features of the genus. Thanks to the researches begun
by the late Mr Binney of Manchester and considerably extended by
Carruthers, Williamson and later investigators, we are now in a position to
give a fairly complete account of Calamites. The type of stem most
frequently met with in a petrified condition in the English rocks is that to
which Göppert applied the name Arthropitys, and it is this subgenus that
forms the subject of the following description. Our knowledge of
Calamitean anatomy is based on the examination of numerous fragments of
petrified twigs and other portions of different specific types of the genus. It
is seldom possible to differentiate specifically between the isolated
fragments of stems and branches which are met with in calcareous or
siliceous nodules. As so frequently happens in fossil-plant material, large
specimens showing good surface features and broken fragments with well-
preserved internal structure have to be dealt with separately.
YOUNG STEM.
a. Stems.
A transverse section of a young twig, such as is represented in fig. 71,
illustrates the chief characteristics of the primary structure of a young
branch of Calamites. The figure has been drawn from a section originally
described by Hick[605] in 1894. A very young Calamite twig bears an
exceedingly close resemblance to the stem of a recent Equisetum. The axial
region of the stem may be occupied by parenchymatous cells, or the
absence of cells in the centre may indicate the beginning of the gradual
formation of the hollow pith, which is one of the characteristics of
Calamites. The student of petrified Palaeozoic plants must constantly be on
his guard against the possible misinterpretation of Stigmarian ‘rootlets,’
which are frequently found in intimate association with fossil tissues. The
consisted of parenchymatous and sclerenchymatous cells, with scattered
secretory sacs. The increase in girth of the central cylinder was often
accompanied by a considerable development of cortical periderm. The roots
differed from the shoots in having no carinal canals, and in the possession
of a solid pith and centripetally developed primary xylem groups alternating
with strands of phloem.
The above incomplete diagnosis includes only some of the more
important structural features of the genus. Thanks to the researches begun
by the late Mr Binney of Manchester and considerably extended by
Carruthers, Williamson and later investigators, we are now in a position to
give a fairly complete account of Calamites. The type of stem most
frequently met with in a petrified condition in the English rocks is that to
which Göppert applied the name Arthropitys, and it is this subgenus that
forms the subject of the following description. Our knowledge of
Calamitean anatomy is based on the examination of numerous fragments of
petrified twigs and other portions of different specific types of the genus. It
is seldom possible to differentiate specifically between the isolated
fragments of stems and branches which are met with in calcareous or
siliceous nodules. As so frequently happens in fossil-plant material, large
specimens showing good surface features and broken fragments with well-
preserved internal structure have to be dealt with separately.
YOUNG STEM.
a. Stems.
A transverse section of a young twig, such as is represented in fig. 71,
illustrates the chief characteristics of the primary structure of a young
branch of Calamites. The figure has been drawn from a section originally
described by Hick[605] in 1894. A very young Calamite twig bears an
exceedingly close resemblance to the stem of a recent Equisetum. The axial
region of the stem may be occupied by parenchymatous cells, or the
absence of cells in the centre may indicate the beginning of the gradual
formation of the hollow pith, which is one of the characteristics of
Calamites. The student of petrified Palaeozoic plants must constantly be on
his guard against the possible misinterpretation of Stigmarian ‘rootlets,’
which are frequently found in intimate association with fossil tissues. The
Page 320
intrusion of these rootlets is admirably illustrated by a section of a Calamite
stem in the Williamson Collection (No. 1558) in which the hollow pith, 2
cm. broad, contains more than a dozen Stigmarian appendages.
Fig. 71. Transverse section of a young Calamite stem. c, carinal canals; mr, primary
medullary rays; a, b, and d, cortex; e, epidermis. From a section in the Manchester
Museum, Owens College, × 60.
In the figured specimen of a Calamite twig (fig. 71) there is a clearly
marked differentiation into a cortical region and a large stele or central
cylinder. The pith-cells are already partially disorganised, but there still
remain a few fairly large parenchymatous cells internal to the ring of
vascular bundles. The few irregular projections into the cavity of the large
pith consist of small fragments of cells, which may be the result of fungal
action. Mycelia of fungi are occasionally met with in the tissues of older
Calamite stems.
The position of the primary xylem groups is shown by the conspicuous
and regularly placed canals, c; these have been formed in precisely the same
manner as the corresponding spaces in an Equisetum stem, and they are
spoken of in both genera as the carinal canals. Each canal owes its origin to
the disorganization and tearing apart of the protoxylem elements and the
stem in the Williamson Collection (No. 1558) in which the hollow pith, 2
cm. broad, contains more than a dozen Stigmarian appendages.
Fig. 71. Transverse section of a young Calamite stem. c, carinal canals; mr, primary
medullary rays; a, b, and d, cortex; e, epidermis. From a section in the Manchester
Museum, Owens College, × 60.
In the figured specimen of a Calamite twig (fig. 71) there is a clearly
marked differentiation into a cortical region and a large stele or central
cylinder. The pith-cells are already partially disorganised, but there still
remain a few fairly large parenchymatous cells internal to the ring of
vascular bundles. The few irregular projections into the cavity of the large
pith consist of small fragments of cells, which may be the result of fungal
action. Mycelia of fungi are occasionally met with in the tissues of older
Calamite stems.
The position of the primary xylem groups is shown by the conspicuous
and regularly placed canals, c; these have been formed in precisely the same
manner as the corresponding spaces in an Equisetum stem, and they are
spoken of in both genera as the carinal canals. Each canal owes its origin to
the disorganization and tearing apart of the protoxylem elements and the
Page 321
surrounding cells. This may be occasionally seen in examples of very young
Calamites; the canals of a young twig often contain apparently isolated
rings which are coils of elongated spiral threads. Fig. 72, B represents the
canal of a twig, cut in an oblique direction, in which the remains of spiral
tracheids are distinctly seen. In the stem of fig. 71 the development has not
advanced far enough to enable us to clearly define the exact limits of each
xylem strand. The smaller elements bordering the canals constitute the
primary xylem, they are fairly distinct on the outer margin of some of the
canals seen in the section. Between the small patches of primary xylem the
outward extensions of the parenchyma of the pith constitute the primary
medullary rays, mr. The distinct line encircling the canals and primary
xylem has been described by Hick as marking the position of the
endodermis, but it may possibly owe its existence to the tearing of the
tissues along the line where cambial activity is just beginning. This layer of
delicate dividing cells would constitute a natural line of weakness. External
to this line we have a zone of tissue a, d, containing here and there larger
cells with black contents, which are no doubt secretory sacs. It is impossible
to distinguish with certainty any definite phloem groups, but in other
specimens these have been recognised immediately external to each
primary xylem group; the bundles were typically collateral in structure.
Towards the periphery of the twig the preservation is much less perfect; the
outer portion of the inner cortex, d, consists of rather smaller and thicker-
walled cells, but this is succeeded by an ill-defined zone containing a few
scattered cells, b, which have been more perfectly preserved. The twig is
too young to show any secondary tissue in the cortex; but the tangential
walls in some of the cortical cells afford evidence of meristematic activity,
which probably represents the beginning of cork-formation. The limiting
line, e, possibly represents the cuticularised outer walls of an epidermal
layer. The irregularly wavy character of the surface of the specimen is
probably the result of shrinking, and does not indicate original surface
features.
VASCULAR SYSTEM.
In examining sections of calcareous nodules from the coal seams one
meets with numerous fragments of small Calamitean twigs with little or no
secondary wood; in some of these there is a small number of carinal canals,
in others the canals are much more abundant. The former probably
Calamites; the canals of a young twig often contain apparently isolated
rings which are coils of elongated spiral threads. Fig. 72, B represents the
canal of a twig, cut in an oblique direction, in which the remains of spiral
tracheids are distinctly seen. In the stem of fig. 71 the development has not
advanced far enough to enable us to clearly define the exact limits of each
xylem strand. The smaller elements bordering the canals constitute the
primary xylem, they are fairly distinct on the outer margin of some of the
canals seen in the section. Between the small patches of primary xylem the
outward extensions of the parenchyma of the pith constitute the primary
medullary rays, mr. The distinct line encircling the canals and primary
xylem has been described by Hick as marking the position of the
endodermis, but it may possibly owe its existence to the tearing of the
tissues along the line where cambial activity is just beginning. This layer of
delicate dividing cells would constitute a natural line of weakness. External
to this line we have a zone of tissue a, d, containing here and there larger
cells with black contents, which are no doubt secretory sacs. It is impossible
to distinguish with certainty any definite phloem groups, but in other
specimens these have been recognised immediately external to each
primary xylem group; the bundles were typically collateral in structure.
Towards the periphery of the twig the preservation is much less perfect; the
outer portion of the inner cortex, d, consists of rather smaller and thicker-
walled cells, but this is succeeded by an ill-defined zone containing a few
scattered cells, b, which have been more perfectly preserved. The twig is
too young to show any secondary tissue in the cortex; but the tangential
walls in some of the cortical cells afford evidence of meristematic activity,
which probably represents the beginning of cork-formation. The limiting
line, e, possibly represents the cuticularised outer walls of an epidermal
layer. The irregularly wavy character of the surface of the specimen is
probably the result of shrinking, and does not indicate original surface
features.
VASCULAR SYSTEM.
In examining sections of calcareous nodules from the coal seams one
meets with numerous fragments of small Calamitean twigs with little or no
secondary wood; in some of these there is a small number of carinal canals,
in others the canals are much more abundant. The former probably
Page 322
represent the smaller ramifications of a plant, and the latter may be regarded
as the young stages of branches capable of developing into stout woody
shoots[606]. Longitudinal sections of small branches teach us that the xylem
elements next the carinal canals are either spiral or reticulate in character,
the older tracheids being for the most part of the scalariform type, with
bordered pits on the radial walls. This and other histological characters are
admirably shown in the illustrations accompanying Williamson and Scott’s
memoir on Calamites. The student should treat the account of the anatomy
of Calamites given in these pages as introductory to the much more
complete description by these authors. They thus describe the course of the
vascular bundles in a Calamitean branch:—
“The bundle-system of Calamites bears a general resemblance to that of
Equisetum. A single leaf-trace enters the stem from each leaf, and passes
vertically downwards to the next node. In the simplest cases the bundle here
forks, its two branches attaching themselves to the alternating bundles
which enter the stem at this node. In other cases both the forks attach
themselves to the same bundle, so that, in this case, there is no regular
alternation. In other cases, again, the bundle runs past one node without
forking, and ultimately forms a junction with the traces of the second node
below its starting-point. These variations may all occur in the same
specimen. The xylem at the node usually forms a continuous ring, for where
the regular dichotomous forks of the bundles are absent their place is
usually taken by anastomoses[607].”
As in Equisetum, the xylem at the nodes possesses certain characteristic
features which distinguish it from the internodal strands. It has already been
pointed out that the xylem of Equisetum increases in breadth at the nodes
(p. 251, fig. 55, 4); the same is true of Calamites. In fig. 72, C, we have part
of a radial section of a Calamite twig in which the broad mass of short
nodal tracheids is clearly shown; this nodal wood forms a prominent
projection towards the pith. In the lower part of the section the remains of
some spiral protoxylem tracheids are seen in a carinal canal.
as the young stages of branches capable of developing into stout woody
shoots[606]. Longitudinal sections of small branches teach us that the xylem
elements next the carinal canals are either spiral or reticulate in character,
the older tracheids being for the most part of the scalariform type, with
bordered pits on the radial walls. This and other histological characters are
admirably shown in the illustrations accompanying Williamson and Scott’s
memoir on Calamites. The student should treat the account of the anatomy
of Calamites given in these pages as introductory to the much more
complete description by these authors. They thus describe the course of the
vascular bundles in a Calamitean branch:—
“The bundle-system of Calamites bears a general resemblance to that of
Equisetum. A single leaf-trace enters the stem from each leaf, and passes
vertically downwards to the next node. In the simplest cases the bundle here
forks, its two branches attaching themselves to the alternating bundles
which enter the stem at this node. In other cases both the forks attach
themselves to the same bundle, so that, in this case, there is no regular
alternation. In other cases, again, the bundle runs past one node without
forking, and ultimately forms a junction with the traces of the second node
below its starting-point. These variations may all occur in the same
specimen. The xylem at the node usually forms a continuous ring, for where
the regular dichotomous forks of the bundles are absent their place is
usually taken by anastomoses[607].”
As in Equisetum, the xylem at the nodes possesses certain characteristic
features which distinguish it from the internodal strands. It has already been
pointed out that the xylem of Equisetum increases in breadth at the nodes
(p. 251, fig. 55, 4); the same is true of Calamites. In fig. 72, C, we have part
of a radial section of a Calamite twig in which the broad mass of short
nodal tracheids is clearly shown; this nodal wood forms a prominent
projection towards the pith. In the lower part of the section the remains of
some spiral protoxylem tracheids are seen in a carinal canal.
Page 323
Fig. 72.
A. External xylem elements and cambium, c, with imperfect phloem, × 100.
B. Carinal canal containing protoxylem, px. × 65.
C. Radial longitudinal section through nodal xylem, px. × 35.
D. Phloem elements; s, sieve-tubes; p, p, parenchymatous cells.
(A–C. After Williamson and Scott. D. After Renault.)
The tracheids of the nodal wood are often reticularly pitted, and so differ
in appearance from the ordinary scalariform elements.
It is rare to find the phloem clearly preserved, but in specimens where it
has been possible to examine this portion of the vascular bundles, it is
found to consist of elongated cambiform cells and sieve-tubes. An
unusually perfect specimen has been described by Renault[608] in which the
phloem elements are preserved in silica. Fig. 72, D, is copied from one of
Renault’s drawings, the sieve-tubes, s, s, show several distinct sieve-plates
on the lateral walls of the tubes, reminding one to some extent of the sieve-
tubes in a Bracken Fern. The cells, p, p, associated with the sieve-tubes are
square-ended elongated parenchymatous elements. Another characteristic
A. External xylem elements and cambium, c, with imperfect phloem, × 100.
B. Carinal canal containing protoxylem, px. × 65.
C. Radial longitudinal section through nodal xylem, px. × 35.
D. Phloem elements; s, sieve-tubes; p, p, parenchymatous cells.
(A–C. After Williamson and Scott. D. After Renault.)
The tracheids of the nodal wood are often reticularly pitted, and so differ
in appearance from the ordinary scalariform elements.
It is rare to find the phloem clearly preserved, but in specimens where it
has been possible to examine this portion of the vascular bundles, it is
found to consist of elongated cambiform cells and sieve-tubes. An
unusually perfect specimen has been described by Renault[608] in which the
phloem elements are preserved in silica. Fig. 72, D, is copied from one of
Renault’s drawings, the sieve-tubes, s, s, show several distinct sieve-plates
on the lateral walls of the tubes, reminding one to some extent of the sieve-
tubes in a Bracken Fern. The cells, p, p, associated with the sieve-tubes are
square-ended elongated parenchymatous elements. Another characteristic
Page 324
feature illustrated by longitudinal sections is the nodal diaphragm; except in
the smallest branches the interior of each internode is hollow, and the ring
of vascular bundles is separated from the pith-cavity by a band of
parenchymatous tissue. At each node this parenchyma extends across the
central cavity in the form of a nodal diaphragm, as in the stem of
Equisetum.
By far the greater number of the petrified fragments of Calamites afford
proof of cambial activity, and possess obvious secondary tissues. In
exceptionally perfect specimens the xylem tracheids are found to be
succeeded externally by a few flattened thin-walled cells which are in a
meristematic condition (fig. 72, A, c); these constitute the cambium zone,
and it is the secondary structure that results from the activity of the
meristematic cells that we have now to consider.
SECONDARY THICKENING.
In petrified examples of branches in which the secondary thickening has
reached a fairly advanced stage, the wood is usually the outermost tissue
preserved, the more external tissues having been detached along the line of
cambium cells. It is only in a few cases that we are able to examine all the
tissues of older examples.
The specimen represented in fig. 73 illustrates very clearly the extension
of the hollow pith up to the inner surface of the vascular ring; the
disorganisation of the pith-cells which had already begun in the twig of fig.
71 has here advanced much further. The bluntly rounded projections
represent the prominent primary xylem strands, each of which is traversed
by the characteristic carinal canal. Alternating with the wedge-shaped
groups of secondary xylem, x, we have the broad principal medullary rays,
mr, which become slightly narrower towards the outside. The inner face of
each of these wide rays has a concave form, due to the less resistent nature
of the medullary-ray cells as compared with the stronger xylem. The
regularly sinuous form of the inner face of the vascular cylinder enables one
to realise how the Calamite-casts (figs. 82, 99, and 101) have come to have
the regular ridges and grooves on their surface. The broad ridges on the cast
mark the position of the wide medullary rays, while the grooves correspond
to the more prominent ends of the vascular strands. The tissues external to
the wood have not been preserved in the example shown in fig. 73. Some
silicified specimens described by Stur[609] from Bohemia and now in the
the smallest branches the interior of each internode is hollow, and the ring
of vascular bundles is separated from the pith-cavity by a band of
parenchymatous tissue. At each node this parenchyma extends across the
central cavity in the form of a nodal diaphragm, as in the stem of
Equisetum.
By far the greater number of the petrified fragments of Calamites afford
proof of cambial activity, and possess obvious secondary tissues. In
exceptionally perfect specimens the xylem tracheids are found to be
succeeded externally by a few flattened thin-walled cells which are in a
meristematic condition (fig. 72, A, c); these constitute the cambium zone,
and it is the secondary structure that results from the activity of the
meristematic cells that we have now to consider.
SECONDARY THICKENING.
In petrified examples of branches in which the secondary thickening has
reached a fairly advanced stage, the wood is usually the outermost tissue
preserved, the more external tissues having been detached along the line of
cambium cells. It is only in a few cases that we are able to examine all the
tissues of older examples.
The specimen represented in fig. 73 illustrates very clearly the extension
of the hollow pith up to the inner surface of the vascular ring; the
disorganisation of the pith-cells which had already begun in the twig of fig.
71 has here advanced much further. The bluntly rounded projections
represent the prominent primary xylem strands, each of which is traversed
by the characteristic carinal canal. Alternating with the wedge-shaped
groups of secondary xylem, x, we have the broad principal medullary rays,
mr, which become slightly narrower towards the outside. The inner face of
each of these wide rays has a concave form, due to the less resistent nature
of the medullary-ray cells as compared with the stronger xylem. The
regularly sinuous form of the inner face of the vascular cylinder enables one
to realise how the Calamite-casts (figs. 82, 99, and 101) have come to have
the regular ridges and grooves on their surface. The broad ridges on the cast
mark the position of the wide medullary rays, while the grooves correspond
to the more prominent ends of the vascular strands. The tissues external to
the wood have not been preserved in the example shown in fig. 73. Some
silicified specimens described by Stur[609] from Bohemia and now in the
Page 325
Museum of the Austrian Geological Survey, Vienna, admirably illustrate the
connection between the surface features of a Calamite cast and the anatomy
of the stem.
Fig. 73. Transverse section of a Calamite stem.
mr, medullary ray. After Williamson.
x, x, xylem. (No. 1933 A.A. in the Williamson
Collection.)
ARTHROPITYS.
In the large section of a calcareous nodule diagrammatically shown in
fig. 17 ii. (p. 85) the secondary wood of a slightly flattened Calamite is the
most prominent plant fragment. The pith-cavity has been almost obliterated
by the lateral compression of the woody cylinder, but the presence of the
carinal canals along the inner edge of the wood may still be readily
recognised. The appearance presented by a transverse section of the
secondary wood of a Calamite is that of regular radial series of rather small
rectangular tracheids, with occasional secondary medullary rays consisting
of narrow and radially elongated parenchymatous cells. The principal
rays[610] in the Arthropitys type of a Calamite stem are often found to
gradually decrease in breadth as they pass into the secondary wood, until in
the outer portion of the wood the primary medullary rays are practically
obliterated by the formation of interfascicular xylem.
connection between the surface features of a Calamite cast and the anatomy
of the stem.
Fig. 73. Transverse section of a Calamite stem.
mr, medullary ray. After Williamson.
x, x, xylem. (No. 1933 A.A. in the Williamson
Collection.)
ARTHROPITYS.
In the large section of a calcareous nodule diagrammatically shown in
fig. 17 ii. (p. 85) the secondary wood of a slightly flattened Calamite is the
most prominent plant fragment. The pith-cavity has been almost obliterated
by the lateral compression of the woody cylinder, but the presence of the
carinal canals along the inner edge of the wood may still be readily
recognised. The appearance presented by a transverse section of the
secondary wood of a Calamite is that of regular radial series of rather small
rectangular tracheids, with occasional secondary medullary rays consisting
of narrow and radially elongated parenchymatous cells. The principal
rays[610] in the Arthropitys type of a Calamite stem are often found to
gradually decrease in breadth as they pass into the secondary wood, until in
the outer portion of the wood the primary medullary rays are practically
obliterated by the formation of interfascicular xylem.
Page 326
In fig. 74, A, we have a portion of a single xylem group of a thick woody
stem. The stem from which the figure has been drawn was originally
described by Binney[611] as Calamodendron commune; we now recognise it
as a typical example of the subgenus Arthropitys. The specific term
communis was used by Ettingshausen[612] in 1855 in a comprehensive sense
to include more than twenty species of the genus Calamites, but since
Binney’s use of the term it has come to be associated with a definite type of
Arthropitys stem, in which the primary medullary rays decrease rapidly in
breadth towards the periphery of the wood. The wood of Binney’s stem[613]
measures 2·5 cm. across, but the pith-cavity has been crushed to the limits
of a narrow band represented in the figure by the shaded portion. The strand
of cells, s, in the pith is a portion of a Stigmarian appendage (“rootlet”),
which penetrated into the hollow stem of the Calamite and became petrified
by the same agency to which the preservation of the stem is due. These
intruded Stigmarian appendages are of constant occurrence in the
calcareous nodules; their intimate association with the tissues of other
plants is often a serious source of error in the identification of petrified
tissues. The inner portion of one of the xylem groups is shown in fig. 74, A.
External to the carinal canal, the xylem tracheids are disposed in regular
series and associated with numerous narrow secondary medullary rays. The
width of the xylem wedge increases gradually as we pass outwards, this is
due to the formation of interfascicular xylem, which in the more peripheral
portion of the stem extends across the primary medullary rays. The few
primary medullary-ray cells shown in the drawing illustrate the
characteristic tangentially elongated form and large size of the
parenchymatous elements. Williamson and Scott have pointed out that the
tangentially elongated form of the medullary-ray cells is the result of active
growth, and not merely the expression of the tangential stretching of the
stem consequent on secondary thickening.
stem. The stem from which the figure has been drawn was originally
described by Binney[611] as Calamodendron commune; we now recognise it
as a typical example of the subgenus Arthropitys. The specific term
communis was used by Ettingshausen[612] in 1855 in a comprehensive sense
to include more than twenty species of the genus Calamites, but since
Binney’s use of the term it has come to be associated with a definite type of
Arthropitys stem, in which the primary medullary rays decrease rapidly in
breadth towards the periphery of the wood. The wood of Binney’s stem[613]
measures 2·5 cm. across, but the pith-cavity has been crushed to the limits
of a narrow band represented in the figure by the shaded portion. The strand
of cells, s, in the pith is a portion of a Stigmarian appendage (“rootlet”),
which penetrated into the hollow stem of the Calamite and became petrified
by the same agency to which the preservation of the stem is due. These
intruded Stigmarian appendages are of constant occurrence in the
calcareous nodules; their intimate association with the tissues of other
plants is often a serious source of error in the identification of petrified
tissues. The inner portion of one of the xylem groups is shown in fig. 74, A.
External to the carinal canal, the xylem tracheids are disposed in regular
series and associated with numerous narrow secondary medullary rays. The
width of the xylem wedge increases gradually as we pass outwards, this is
due to the formation of interfascicular xylem, which in the more peripheral
portion of the stem extends across the primary medullary rays. The few
primary medullary-ray cells shown in the drawing illustrate the
characteristic tangentially elongated form and large size of the
parenchymatous elements. Williamson and Scott have pointed out that the
tangentially elongated form of the medullary-ray cells is the result of active
growth, and not merely the expression of the tangential stretching of the
stem consequent on secondary thickening.
Page 327
Fig. 74.
A. Transverse section of part of a Calamite stem. [Calamites (Arthropitys) communis
(Binney).]
s, Stigmarian appendage. x, xylem. From a specimen in the Binney Collection,
Cambridge, × 50.
B. Transverse section of a stem.
h, hypodermal tissue; c, inner cortex. From a specimen in the Williamson
Collection (no. 62). × 35.
A glance at the complete transverse section of the stem,—of which a
small portion is shown in fig. 74 A,—suggests the existence of annual rings
in the wood, but this appearance of rings is merely the result of
compression. The secondary wood of a Calamite does not exhibit any
regular zones of growth comparable with the annual rings of our forest
trees.
A. Transverse section of part of a Calamite stem. [Calamites (Arthropitys) communis
(Binney).]
s, Stigmarian appendage. x, xylem. From a specimen in the Binney Collection,
Cambridge, × 50.
B. Transverse section of a stem.
h, hypodermal tissue; c, inner cortex. From a specimen in the Williamson
Collection (no. 62). × 35.
A glance at the complete transverse section of the stem,—of which a
small portion is shown in fig. 74 A,—suggests the existence of annual rings
in the wood, but this appearance of rings is merely the result of
compression. The secondary wood of a Calamite does not exhibit any
regular zones of growth comparable with the annual rings of our forest
trees.
Page 328
Fig. 75. Longitudinal tangential section near the inner edge of the wood of the Calamite of
fig. 74.
x, x, secondary xylem and medullary rays; m, principal medullary ray. From a section in
the Binney Collection, × 50.
Before passing to other examples of Calamitean stems, reference may be
made to the sections shown in figs. 75 and 76, which illustrate some further
points in the structure of Binney’s stems. In fig. 75 the xylem tracheids are
shown at x, and between them the secondary medullary rays present the
appearance of long and narrow parenchymatous cells; as the section is
tangential the characteristic scalariform character of the tracheids is not
shown, the ladder-like bordered pits being confined to the radial walls of
the tracheal elements. The much greater length than breadth of the cells
which form the rays associated with the xylem tracheids, is a characteristic
feature in Calamitean stems. The breadth of the principal ray, m, shows that
the section has passed through the wood a short distance from the pith; in a
tangential section cut further into the wood the breadth of the principal rays
would be considerably reduced. The large medullary-ray tissue consists of
fig. 74.
x, x, secondary xylem and medullary rays; m, principal medullary ray. From a section in
the Binney Collection, × 50.
Before passing to other examples of Calamitean stems, reference may be
made to the sections shown in figs. 75 and 76, which illustrate some further
points in the structure of Binney’s stems. In fig. 75 the xylem tracheids are
shown at x, and between them the secondary medullary rays present the
appearance of long and narrow parenchymatous cells; as the section is
tangential the characteristic scalariform character of the tracheids is not
shown, the ladder-like bordered pits being confined to the radial walls of
the tracheal elements. The much greater length than breadth of the cells
which form the rays associated with the xylem tracheids, is a characteristic
feature in Calamitean stems. The breadth of the principal ray, m, shows that
the section has passed through the wood a short distance from the pith; in a
tangential section cut further into the wood the breadth of the principal rays
would be considerably reduced. The large medullary-ray tissue consists of
Page 329
square-walled parenchymatous cells. The more highly magnified section, in
fig. 76, shows a central group of parenchyma containing a few transversely
cut tracheids, but the two kinds of elements are not clearly differentiated in
the figure; this group of cells is an outgoing leaf-trace which is enclosed by
the strongly curved tracheids of the stem. The section is taken from the
node of a stem where several leaf-trace bundles are passing out to a whorl
of leaves; the few cells intercalated between the tracheids belong to the
parenchyma of the secondary medullary rays.
Fig. 76. Longitudinal tangential section of the same Calamite as that of figs. 74 and 75,
showing a leaf-trace and curved tracheids at a node. From a section in the Binney
Collection, × 100.
ARTHROPITYS. SURFACE FEATURES.
fig. 76, shows a central group of parenchyma containing a few transversely
cut tracheids, but the two kinds of elements are not clearly differentiated in
the figure; this group of cells is an outgoing leaf-trace which is enclosed by
the strongly curved tracheids of the stem. The section is taken from the
node of a stem where several leaf-trace bundles are passing out to a whorl
of leaves; the few cells intercalated between the tracheids belong to the
parenchyma of the secondary medullary rays.
Fig. 76. Longitudinal tangential section of the same Calamite as that of figs. 74 and 75,
showing a leaf-trace and curved tracheids at a node. From a section in the Binney
Collection, × 100.
ARTHROPITYS. SURFACE FEATURES.
Page 330
In the small portion of a stem represented in fig. 74 B, the cortical tissues
have been partially preserved; at the inner edge, next the hollow pith, there
are two xylem groups, each with a carinal canal, and between them is part
of a broad “principal” medullary ray[614]. The cambium has not been
preserved, but beyond this region we have some of the large cells, c, of the
inner cortex; these are followed by a few remnants of a smaller-celled
tissue, and external to this part of the cortex there is a series of triangular
groups, h, consisting of small thick-walled cells alternating with spaces
which were originally occupied by more delicate parenchyma. The darker
groups constitute hypodermal strands of mechanical tissue or stereome
which lent support to the stem. The surface of a stem possessing such
supporting strands would probably assume a longitudinally wrinkled or
grooved appearance on drying; the intervening parenchyma, contracting and
yielding more readily, would tend to produce shallow grooves alternating
with the ridges above the stereome strands.
The complete section of the stem of which a small portion is shown in
fig. 74 B, is figured by Williamson[615] in his 12th memoir on Coal-Measure
plants. The section was obtained from Ashton-under-Lyne in Lancashire; it
illustrates very clearly a method of preservation which is occasionally met
with among petrified plants. The walls of the various tissue elements are
black in colour and somewhat ragged, and the general appearance of the
section is similar to that of a section of a charred piece of stem. It is
possible that the Calamite twig was reduced to charcoal before petrifaction
by a lightning flash or some other cause.
It is often said that the surface of a Calamite stem was probably marked
by regular ridges and grooves similar to those of the pith-cast, and that such
external features are connected with the arrangement of the tissues in the
vascular cylinder. The indication of grooves and ridges on the bark of fossil
Calamites is no doubt the result of the existence in the hypoderm of firm
strands alternating with strands of less resistant cells. It is very common to
find Calamite pith-casts covered with a layer of coal presenting a ribbed
surface, but this is simply due to the moulding of the coaly film on an
internal pith-cast. The broad grooves on such a specimen as that of fig. 77
are, on the other hand, probably an indication of the existence of hypoderm
bands similar to those in fig. 74 B, h. The specimen from which fig. 77 is
drawn shows many interesting features. The figure given by Grand’Eury, of
have been partially preserved; at the inner edge, next the hollow pith, there
are two xylem groups, each with a carinal canal, and between them is part
of a broad “principal” medullary ray[614]. The cambium has not been
preserved, but beyond this region we have some of the large cells, c, of the
inner cortex; these are followed by a few remnants of a smaller-celled
tissue, and external to this part of the cortex there is a series of triangular
groups, h, consisting of small thick-walled cells alternating with spaces
which were originally occupied by more delicate parenchyma. The darker
groups constitute hypodermal strands of mechanical tissue or stereome
which lent support to the stem. The surface of a stem possessing such
supporting strands would probably assume a longitudinally wrinkled or
grooved appearance on drying; the intervening parenchyma, contracting and
yielding more readily, would tend to produce shallow grooves alternating
with the ridges above the stereome strands.
The complete section of the stem of which a small portion is shown in
fig. 74 B, is figured by Williamson[615] in his 12th memoir on Coal-Measure
plants. The section was obtained from Ashton-under-Lyne in Lancashire; it
illustrates very clearly a method of preservation which is occasionally met
with among petrified plants. The walls of the various tissue elements are
black in colour and somewhat ragged, and the general appearance of the
section is similar to that of a section of a charred piece of stem. It is
possible that the Calamite twig was reduced to charcoal before petrifaction
by a lightning flash or some other cause.
It is often said that the surface of a Calamite stem was probably marked
by regular ridges and grooves similar to those of the pith-cast, and that such
external features are connected with the arrangement of the tissues in the
vascular cylinder. The indication of grooves and ridges on the bark of fossil
Calamites is no doubt the result of the existence in the hypoderm of firm
strands alternating with strands of less resistant cells. It is very common to
find Calamite pith-casts covered with a layer of coal presenting a ribbed
surface, but this is simply due to the moulding of the coaly film on an
internal pith-cast. The broad grooves on such a specimen as that of fig. 77
are, on the other hand, probably an indication of the existence of hypoderm
bands similar to those in fig. 74 B, h. The specimen from which fig. 77 is
drawn shows many interesting features. The figure given by Grand’Eury, of
Page 331
which fig. 77 is a copy, is somewhat idealised, but the various surfaces can
be made out in the fossil. The surface of the coaly envelope surrounding the
pith-cast, a, is distinctly grooved, but the depressions have nothing to do
with the surface features of the wood or the pith-cast; they are no doubt due
to the occurrence of alternating bands of thick- and thin-walled tissue in the
hypodermal region of the cortex; the peripheral strands of bast cells would
stand out as prominent ribs as the stem tissue contracted during
fossilisation. At b (fig. 77) we have a view of the wood in which the
position of the principal rays is indicated by fine longitudinal lines at
regular intervals; the oval projections just below the nodal line are probably
the casts of infranodal canals (cf. p. 324). At a the characteristic pith-cast is
seen with a small branch-scar on the node. The scar on the middle node, N
2, is probably that of a root, and a root R is still attached to the node, N 3.
be made out in the fossil. The surface of the coaly envelope surrounding the
pith-cast, a, is distinctly grooved, but the depressions have nothing to do
with the surface features of the wood or the pith-cast; they are no doubt due
to the occurrence of alternating bands of thick- and thin-walled tissue in the
hypodermal region of the cortex; the peripheral strands of bast cells would
stand out as prominent ribs as the stem tissue contracted during
fossilisation. At b (fig. 77) we have a view of the wood in which the
position of the principal rays is indicated by fine longitudinal lines at
regular intervals; the oval projections just below the nodal line are probably
the casts of infranodal canals (cf. p. 324). At a the characteristic pith-cast is
seen with a small branch-scar on the node. The scar on the middle node, N
2, is probably that of a root, and a root R is still attached to the node, N 3.
Page 332
Fig. 77. Portion of a Calamite stem, showing the surface of the bark, c; the wood, b; the
surface of the pith-cast, a. N.1-N.3. Nodes. R. Root. (After Grand’Eury. Partially restored
from a specimen in the École des Mines, Paris.) ¾ nat. size.
PERIDERM IN STEMS.
An interesting feature observed in some specimens of older Calamite
branches is the development of periderm or cork. This is illustrated on a
large scale by a unique specimen originally described by Williamson in
1878[616]. Figs. 78 and 79 represent transverse and longitudinal sections of
this stem. This unusually large petrified stem was found in the Coal-
Measures of Oldham, in Lancashire. In the slightly reduced drawing, fig.
surface of the pith-cast, a. N.1-N.3. Nodes. R. Root. (After Grand’Eury. Partially restored
from a specimen in the École des Mines, Paris.) ¾ nat. size.
PERIDERM IN STEMS.
An interesting feature observed in some specimens of older Calamite
branches is the development of periderm or cork. This is illustrated on a
large scale by a unique specimen originally described by Williamson in
1878[616]. Figs. 78 and 79 represent transverse and longitudinal sections of
this stem. This unusually large petrified stem was found in the Coal-
Measures of Oldham, in Lancashire. In the slightly reduced drawing, fig.
Page 333
78, the large and somewhat flattened pith, p, 4·2 cm. in diameter, is shown
towards the bottom of the figure. Surrounding this we have 58 or 59 wedge-
shaped projecting xylem groups and broad medullary rays; the latter soon
become indistinguishable as they are traced radially through the thick mass
of secondary wood, 5 cm. wide, composed of scalariform tracheids and
secondary medullary rays (fig. 78, 3). The secondary wood presents the
features characteristic of Calamites (Arthropitys) communis (Binney).
External to the wood there is a broken-up mass, about 5·5 cm. wide
composed of regularly arranged (fig. 78, 2) and rather thick-walled cells;
this consists of periderm, a secondary tissue, which has been developed by
a cork-cambium during the increase in girth of the plant. The more delicate
cortical tissues have not been preserved, and the more resistant portion of
the bark has been broken up into small pieces of corky tissue, among which
are seen numerous Stigmarian appendages, pieces of sporangia and other
plant fragments. These associated structures cannot of course be shown in
the small-scale drawing of the figure.
towards the bottom of the figure. Surrounding this we have 58 or 59 wedge-
shaped projecting xylem groups and broad medullary rays; the latter soon
become indistinguishable as they are traced radially through the thick mass
of secondary wood, 5 cm. wide, composed of scalariform tracheids and
secondary medullary rays (fig. 78, 3). The secondary wood presents the
features characteristic of Calamites (Arthropitys) communis (Binney).
External to the wood there is a broken-up mass, about 5·5 cm. wide
composed of regularly arranged (fig. 78, 2) and rather thick-walled cells;
this consists of periderm, a secondary tissue, which has been developed by
a cork-cambium during the increase in girth of the plant. The more delicate
cortical tissues have not been preserved, and the more resistant portion of
the bark has been broken up into small pieces of corky tissue, among which
are seen numerous Stigmarian appendages, pieces of sporangia and other
plant fragments. These associated structures cannot of course be shown in
the small-scale drawing of the figure.
Page 334
Fig. 78.
1. Transverse section of a thick Calamite stem.
p, pith; x, secondary wood; c, bark. (⅔
nat. size.)
2. Periderm cells of bark.
3. Xylem and medullary rays. (2 and 3, × 80.)
From a specimen in the Williamson Collection (no. 79).
In the radial longitudinal section (fig. 79) we see the pith with the
projecting wood and the remains of a diaphragm at the node. The mottled or
watered appearance of the wood is due to numerous medullary rays which
sweep across the tracheids. The periderm elements, as seen in longitudinal
section, are fibrous in form.
1. Transverse section of a thick Calamite stem.
p, pith; x, secondary wood; c, bark. (⅔
nat. size.)
2. Periderm cells of bark.
3. Xylem and medullary rays. (2 and 3, × 80.)
From a specimen in the Williamson Collection (no. 79).
In the radial longitudinal section (fig. 79) we see the pith with the
projecting wood and the remains of a diaphragm at the node. The mottled or
watered appearance of the wood is due to numerous medullary rays which
sweep across the tracheids. The periderm elements, as seen in longitudinal
section, are fibrous in form.
Page 335
Fig. 79. Longitudinal section of the specimen stem in fig. 78.
From a specimen in the Williamson Collection, British Museum (no. 80). ⅔ nat. size.
CALLUS WOOD.
The development of cork in a younger Calamite stem is clearly shown in
a specimen described by Williamson and Scott in their Memoir of 1894. In
a transverse section of the stem several large cells of the inner cortex are
seen to be in process of division by tangential walls, and giving rise to
radially arranged periderm tissue[617].
The section diagrammatically sketched in fig. 80 is that of a Calamite
twig in which the wood appears to have been injured, and the wound has
been almost covered over by the formation of callus wood. The young trees
in a Palaeozoic forest might easily be injured by some of the large
amphibians, which were the highest representatives of animal life during
the Carboniferous period, just as our forest trees are often barked by deer,
rabbits, and other animals. Fissures might also be formed by the expansion
of the bark under the heating influence of the sun’s rays[618]. Such a
specimen as that of fig. 80 gives an air of living reality to the petrified
fragments of the Coal period trees. It is well known how a wound on the
branch of a forest tree becomes gradually overgrown by the activity of the
cambium giving rise to a thick callus, which gradually closes over the
wounded surface in the form of two lips of wood which finally meet over
the middle of the scar. The two lips of callus are clearly shown in the fossil
branch arching over the tear in the wood just beyond the ring of carinal
canals. The tissue external to the wood represents the imperfectly preserved
cortex. A section which was cut parallel to that of fig. 80 shows a
From a specimen in the Williamson Collection, British Museum (no. 80). ⅔ nat. size.
CALLUS WOOD.
The development of cork in a younger Calamite stem is clearly shown in
a specimen described by Williamson and Scott in their Memoir of 1894. In
a transverse section of the stem several large cells of the inner cortex are
seen to be in process of division by tangential walls, and giving rise to
radially arranged periderm tissue[617].
The section diagrammatically sketched in fig. 80 is that of a Calamite
twig in which the wood appears to have been injured, and the wound has
been almost covered over by the formation of callus wood. The young trees
in a Palaeozoic forest might easily be injured by some of the large
amphibians, which were the highest representatives of animal life during
the Carboniferous period, just as our forest trees are often barked by deer,
rabbits, and other animals. Fissures might also be formed by the expansion
of the bark under the heating influence of the sun’s rays[618]. Such a
specimen as that of fig. 80 gives an air of living reality to the petrified
fragments of the Coal period trees. It is well known how a wound on the
branch of a forest tree becomes gradually overgrown by the activity of the
cambium giving rise to a thick callus, which gradually closes over the
wounded surface in the form of two lips of wood which finally meet over
the middle of the scar. The two lips of callus are clearly shown in the fossil
branch arching over the tear in the wood just beyond the ring of carinal
canals. The tissue external to the wood represents the imperfectly preserved
cortex. A section which was cut parallel to that of fig. 80 shows a
Page 336
continuous band of wood beyond the wound, and the latter has the form of a
small triangular gap; this section appears to have passed across the wound
where it was narrower and has already been closed over by the callus. The
formation of a rather different kind of callus wood has been described by
Renault[619] and by Williamson and Scott[620], in stems where aborted or
deciduous branches have been overgrown and sealed up by cambial activity.
Fig. 80. Diagrammatic sketch of a transverse section of a Calamite twig, showing callus
wood. From a specimen in the Cambridge Botanical Laboratory Collection. × ca. 10.
Some of the features to be noticed in longitudinal sections of Calamite
stems have already been described, at least as regards younger branches.
The specimen shown in fig. 81 illustrates the general appearance of a stem
as seen in tangential and radial section. In the lower portion, T, the course
of the vascular bundles is shown by the black lines which represent the
xylem tracheids, bifurcating and usually alternating at each node. Between
the xylem strands are the broad principal medullary rays. At b a branch has
been cut through on its passage out from the parent stem, just above the
nodal line. In tangential sections of Calamite stems one frequently sees both
branches and leaf-trace bundles (fig. 83, A), passing horizontally through
the wood and enclosed by strongly curved and twisted tracheids. In the
upper part of the figure (81, R), the section has passed through the centre of
small triangular gap; this section appears to have passed across the wound
where it was narrower and has already been closed over by the callus. The
formation of a rather different kind of callus wood has been described by
Renault[619] and by Williamson and Scott[620], in stems where aborted or
deciduous branches have been overgrown and sealed up by cambial activity.
Fig. 80. Diagrammatic sketch of a transverse section of a Calamite twig, showing callus
wood. From a specimen in the Cambridge Botanical Laboratory Collection. × ca. 10.
Some of the features to be noticed in longitudinal sections of Calamite
stems have already been described, at least as regards younger branches.
The specimen shown in fig. 81 illustrates the general appearance of a stem
as seen in tangential and radial section. In the lower portion, T, the course
of the vascular bundles is shown by the black lines which represent the
xylem tracheids, bifurcating and usually alternating at each node. Between
the xylem strands are the broad principal medullary rays. At b a branch has
been cut through on its passage out from the parent stem, just above the
nodal line. In tangential sections of Calamite stems one frequently sees both
branches and leaf-trace bundles (fig. 83, A), passing horizontally through
the wood and enclosed by strongly curved and twisted tracheids. In the
upper part of the figure (81, R), the section has passed through the centre of
Page 337
the stem, and the wood is seen in radial view; each
node is bridged across by a diaphragm of
parenchymatous cells capable of giving rise to a
surface layer of periderm[621].
An outgoing branch, as seen in a tangential section
of a stem, consists of a parenchymatous pith
surrounded by a ring of vascular bundles, in which
the characteristic carinal canals have not yet been
formed, but if the section has cut the branch further
from its base, there may be seen a circle of irregular
gaps marking the position of the carinal canals. Such
gaps are often occupied by thin parenchyma, and
contain protoxylem elements. The outgoing branches,
as seen in a tangential section of a Calamite stem, are
seen to be connected with the wood of the parent
stem by curved and sinuous tracheids, which give to
the stem-wood a curiously characteristic
[622]
appearance , as if the xylem elements had been
pushed aside and contorted by the pressure of the
outgoing member. A tangential section through a Pine
stem[623] in the region of a lateral branch presents
precisely the same features as in Calamites. The
branches are given off from the stem immediately
above a node and usually between two outgoing leaf- Fig. 81. Calamites.
trace bundles. Longitudinal section
(R, radial; T,
RHIZOME OF CALAMITES.
tangential) of a small
branch. b, position of a
Specimens of pith-casts occasionally present the lateral branch. From a
appearance of a curved and rapidly tapered ram’s specimen (no. 1937) in
horn, and the narrow end of such a cast is sometimes the Williamson
Collection. Slightly
found in contact with the node of another cast. This enlarged.
juxtaposition of casts is shown unusually well in fig.
82. In some of the published restorations of Calamites the plant is
represented as having thick branches attached to the main stem by little
more than a point. Williamson[624] clearly explained this apparently unusual
and indeed physically impossible method of branching, by means of
sections of petrified stems. The branches seen in fig. 82 are of course pith-
node is bridged across by a diaphragm of
parenchymatous cells capable of giving rise to a
surface layer of periderm[621].
An outgoing branch, as seen in a tangential section
of a stem, consists of a parenchymatous pith
surrounded by a ring of vascular bundles, in which
the characteristic carinal canals have not yet been
formed, but if the section has cut the branch further
from its base, there may be seen a circle of irregular
gaps marking the position of the carinal canals. Such
gaps are often occupied by thin parenchyma, and
contain protoxylem elements. The outgoing branches,
as seen in a tangential section of a Calamite stem, are
seen to be connected with the wood of the parent
stem by curved and sinuous tracheids, which give to
the stem-wood a curiously characteristic
[622]
appearance , as if the xylem elements had been
pushed aside and contorted by the pressure of the
outgoing member. A tangential section through a Pine
stem[623] in the region of a lateral branch presents
precisely the same features as in Calamites. The
branches are given off from the stem immediately
above a node and usually between two outgoing leaf- Fig. 81. Calamites.
trace bundles. Longitudinal section
(R, radial; T,
RHIZOME OF CALAMITES.
tangential) of a small
branch. b, position of a
Specimens of pith-casts occasionally present the lateral branch. From a
appearance of a curved and rapidly tapered ram’s specimen (no. 1937) in
horn, and the narrow end of such a cast is sometimes the Williamson
Collection. Slightly
found in contact with the node of another cast. This enlarged.
juxtaposition of casts is shown unusually well in fig.
82. In some of the published restorations of Calamites the plant is
represented as having thick branches attached to the main stem by little
more than a point. Williamson[624] clearly explained this apparently unusual
and indeed physically impossible method of branching, by means of
sections of petrified stems. The branches seen in fig. 82 are of course pith-
Page 338
casts, and in the living plant the pith of each branch was surrounded by a
mass of secondary wood developed from as many primary groups of xylem
as there are grooves on the surface of the cast, each of the grooves on an
internode corresponding to the projecting edge of a xylem group. At the
junction of one branch with another the pith was much narrower and the
enclosing wood thicker, so that the tapered ends of the cast merely show the
continuity by a narrow union between the pith-cavities of different
branches. Most probably the casts of fig. 82 are those of a branched
rhizome which grew underground, giving off aerial shoots and adventitious
roots. There is a fairly close resemblance between the Calamite casts of fig.
82 and a stout branching rhizome of a Bamboo, e.g. Bambusa arundinacea
Willd.; it is not surprising that the earlier writers looked upon the Calamite
as a reed-like plant.
Before leaving the consideration of stem structures there is another
feature to which attention must be drawn. On the casts shown in fig. 82
there is a circle of small oval scars situated just below the nodes, these are
clearly shown at c, c, c. Each of the scars is in reality a slight projection
from the upper end of an internodal ridge. As the ridges correspond to the
broad inner faces of medullary rays, the small projection at the upper end of
each ridge is a cast of a depression or canal which existed in the medullary
tissue of the living plant. There have been various suggestions as to the
meaning of these oval projections; several writers have referred to them as
the points of attachments of roots or other appendages, but Williamson
proved them to be the casts of canal-like gaps which traversed the upper
ends of principal medullary rays in a horizontal direction. In a tangential
section of a Calamite stem the summit of each primary medullary ray often
contains a group of smaller elements which are in process of
disorganisation, and in some cases these cells give place to an oval and
somewhat irregular canal. In the diagrammatic tangential section
represented in fig. 83, A the upper end of each ray is perforated by a large
oval space, which has been formed as the result of the breaking down of a
horizontal band of cells. Williamson designated these spaces infranodal
canals. While proving that they had nothing to do with the attachment of
lateral members, he suggested that they might be concerned with secretion;
but their physiological significance is still a matter of speculation. The casts
of infranodal canals are especially large and conspicuous in the subgenus
Arthrodendron, a form of Calamite characterised by certain histological
mass of secondary wood developed from as many primary groups of xylem
as there are grooves on the surface of the cast, each of the grooves on an
internode corresponding to the projecting edge of a xylem group. At the
junction of one branch with another the pith was much narrower and the
enclosing wood thicker, so that the tapered ends of the cast merely show the
continuity by a narrow union between the pith-cavities of different
branches. Most probably the casts of fig. 82 are those of a branched
rhizome which grew underground, giving off aerial shoots and adventitious
roots. There is a fairly close resemblance between the Calamite casts of fig.
82 and a stout branching rhizome of a Bamboo, e.g. Bambusa arundinacea
Willd.; it is not surprising that the earlier writers looked upon the Calamite
as a reed-like plant.
Before leaving the consideration of stem structures there is another
feature to which attention must be drawn. On the casts shown in fig. 82
there is a circle of small oval scars situated just below the nodes, these are
clearly shown at c, c, c. Each of the scars is in reality a slight projection
from the upper end of an internodal ridge. As the ridges correspond to the
broad inner faces of medullary rays, the small projection at the upper end of
each ridge is a cast of a depression or canal which existed in the medullary
tissue of the living plant. There have been various suggestions as to the
meaning of these oval projections; several writers have referred to them as
the points of attachments of roots or other appendages, but Williamson
proved them to be the casts of canal-like gaps which traversed the upper
ends of principal medullary rays in a horizontal direction. In a tangential
section of a Calamite stem the summit of each primary medullary ray often
contains a group of smaller elements which are in process of
disorganisation, and in some cases these cells give place to an oval and
somewhat irregular canal. In the diagrammatic tangential section
represented in fig. 83, A the upper end of each ray is perforated by a large
oval space, which has been formed as the result of the breaking down of a
horizontal band of cells. Williamson designated these spaces infranodal
canals. While proving that they had nothing to do with the attachment of
lateral members, he suggested that they might be concerned with secretion;
but their physiological significance is still a matter of speculation. The casts
of infranodal canals are especially large and conspicuous in the subgenus
Arthrodendron, a form of Calamite characterised by certain histological
Page 339
features to be referred to later. Williamson[625] originally regarded the
presence of infranodal canals as one of the distinguishing features of
Arthrodendron, but they occur also in the casts of the commoner type
Arthropitys. As a rule we have only the cast of the inner ends of the
infranodal canals preserved as slight projections like those in fig. 83, A; but
in one exceptionally interesting pith-cast described by Williamson, these
casts of the infranodal canals have been preserved as slender spoke-like
columns radiating from the upper ends of the ridges of the infranodal region
of a pith-cast.
presence of infranodal canals as one of the distinguishing features of
Arthrodendron, but they occur also in the casts of the commoner type
Arthropitys. As a rule we have only the cast of the inner ends of the
infranodal canals preserved as slight projections like those in fig. 83, A; but
in one exceptionally interesting pith-cast described by Williamson, these
casts of the infranodal canals have been preserved as slender spoke-like
columns radiating from the upper ends of the ridges of the infranodal region
of a pith-cast.
Page 340
Fig. 82. Branched rhizome of Calamites. ½ nat. size. C, C, nodes showing casts of infranodal
canals. From a specimen in the Manchester Museum, Owens College.
This specimen, which was figured by Williamson[626] in two of his papers,
and by Lyell[627] in the fifth edition of his Elementary Geology, is
historically interesting as being one of the first important plants obtained by
Williamson early in the fifties, when he began his researches into the
structure of Carboniferous plants. A joiner, who was employed by
Williamson to make a piece of machinery for grinding fossils, brought a
number of sandstone fragments as an offering to his employer, whom he
found to be interested in stones. The specimens “were in the main the
canals. From a specimen in the Manchester Museum, Owens College.
This specimen, which was figured by Williamson[626] in two of his papers,
and by Lyell[627] in the fifth edition of his Elementary Geology, is
historically interesting as being one of the first important plants obtained by
Williamson early in the fifties, when he began his researches into the
structure of Carboniferous plants. A joiner, who was employed by
Williamson to make a piece of machinery for grinding fossils, brought a
number of sandstone fragments as an offering to his employer, whom he
found to be interested in stones. The specimens “were in the main the
Page 341
merest rubbish, but amongst them,” writes Williamson, “I detected a
fragment which was equally elegant and remarkable.... In later days, when
the specimen so oddly and accidentally obtained, came to be intelligently
studied, its history became clear enough, and the priceless fragment is now
one of the most precious gems in my cabinet[628].”
Comparison of three types of structure met with in Calamitean stems,—
Arthropitys, Arthrodendron, and Calamodendron.
ARTHROPITYS.
The anatomical features which have so far been described as
characteristic of Calamites represent the common type met with in the
English Coal-Measures. The same type occurs also in France, Germany and
elsewhere. It is that form of stem known as Arthropitys, a sub-genus of
Calamites.
Arthropitys may be briefly diagnosed as follows,—confining our
attention to the structure of the stem: A ring of collateral bundles surrounds
a large hollow pith, each primary xylem strand terminates internally in a
more or less bluntly rounded apex traversed by a longitudinally carinal
canal. The principal medullary rays consist of large-celled parenchyma, of
which the individual elements are usually tangentially elongated as seen in
transverse section, and four or five times longer than broad as seen in a
tangential longitudinal section. The secondary xylem consists of scalariform
and reticulately pitted tracheids; the interfascicular xylem may be formed
completely across each primary ray at an early stage in the growth of the
stem[629], or it may be developed more gradually so as to leave a tapering
principal ray of parenchyma between each primary xylem bundle. In the
latter case the principal rays present the characteristic appearance shown in
figs. 71, 74, A, 75 and 78, a type of stem which we may refer to as
Calamites (Arthropitys) communis. In the former case the stem presents the
appearance shown in fig. 83, D[630]. A third variety of Arthropitys stem is
one which was originally named by Göppert Arthropitys bistriata; in this
form the principal rays retain their individuality as bands of parenchyma
throughout the whole thickness of the wood[631]. Such stems as those of figs.
73 and 74, B, may be young examples of Arthropitys communis or possibly
of A. bistriata. The narrow secondary medullary rays of Arthropitys usually
consist of a single row of cells which are three to five times higher than
fragment which was equally elegant and remarkable.... In later days, when
the specimen so oddly and accidentally obtained, came to be intelligently
studied, its history became clear enough, and the priceless fragment is now
one of the most precious gems in my cabinet[628].”
Comparison of three types of structure met with in Calamitean stems,—
Arthropitys, Arthrodendron, and Calamodendron.
ARTHROPITYS.
The anatomical features which have so far been described as
characteristic of Calamites represent the common type met with in the
English Coal-Measures. The same type occurs also in France, Germany and
elsewhere. It is that form of stem known as Arthropitys, a sub-genus of
Calamites.
Arthropitys may be briefly diagnosed as follows,—confining our
attention to the structure of the stem: A ring of collateral bundles surrounds
a large hollow pith, each primary xylem strand terminates internally in a
more or less bluntly rounded apex traversed by a longitudinally carinal
canal. The principal medullary rays consist of large-celled parenchyma, of
which the individual elements are usually tangentially elongated as seen in
transverse section, and four or five times longer than broad as seen in a
tangential longitudinal section. The secondary xylem consists of scalariform
and reticulately pitted tracheids; the interfascicular xylem may be formed
completely across each primary ray at an early stage in the growth of the
stem[629], or it may be developed more gradually so as to leave a tapering
principal ray of parenchyma between each primary xylem bundle. In the
latter case the principal rays present the characteristic appearance shown in
figs. 71, 74, A, 75 and 78, a type of stem which we may refer to as
Calamites (Arthropitys) communis. In the former case the stem presents the
appearance shown in fig. 83, D[630]. A third variety of Arthropitys stem is
one which was originally named by Göppert Arthropitys bistriata; in this
form the principal rays retain their individuality as bands of parenchyma
throughout the whole thickness of the wood[631]. Such stems as those of figs.
73 and 74, B, may be young examples of Arthropitys communis or possibly
of A. bistriata. The narrow secondary medullary rays of Arthropitys usually
consist of a single row of cells which are three to five times higher than
Page 342
broad, as seen in tangential longitudinal section. Infranodal canals occur in
some examples of Arthropitys.
ARTHRODENDRON.
In the subgenus Arthrodendron, a type of stem first recognised by
Williamson and named by him Calamopitys[632], the principal medullary
rays consist of prosenchymatous cells (i.e. elongated pointed elements) and
not parenchyma. These elongated elements are not pitted like tracheids, and
they are shorter and broader than the xylem elements. In some examples of
this subgenus the primary rays are bridged across at an early stage by the
formation of secondary interfascicular xylem, and in others they persist as
bands of ray tissue, as in Arthropitys. Other characteristics of
Arthrodendron are the abundance of reticulated instead of scalariform
tracheids in the secondary wood, and the large size of the infranodal canals.
Fig. 83, D represents part of a transverse section of Arthrodendron; in
this stem the rays have been occupied by interfascicular xylem at a very
early stage of the secondary growth. The section from which fig. 83, D is
drawn was described by Williamson in 1871; the complete section shows
about 80 carinal canals and primary xylem groups. The prosenchymatous
form of the principal medullary rays is seen in fig 83, C, and the reticulate
pitting on the radial wall of a tracheid is shown in fig. 83, B. Fig. 83, A
illustrates the large infranodal canals as seen in a tangential section of a
stem. The same section shows also the course of the vascular bundles
characteristic of Calamites as of Equisetum, and the position of outgoing
leaf-traces is represented by unshaded areas in the black vascular strands.
some examples of Arthropitys.
ARTHRODENDRON.
In the subgenus Arthrodendron, a type of stem first recognised by
Williamson and named by him Calamopitys[632], the principal medullary
rays consist of prosenchymatous cells (i.e. elongated pointed elements) and
not parenchyma. These elongated elements are not pitted like tracheids, and
they are shorter and broader than the xylem elements. In some examples of
this subgenus the primary rays are bridged across at an early stage by the
formation of secondary interfascicular xylem, and in others they persist as
bands of ray tissue, as in Arthropitys. Other characteristics of
Arthrodendron are the abundance of reticulated instead of scalariform
tracheids in the secondary wood, and the large size of the infranodal canals.
Fig. 83, D represents part of a transverse section of Arthrodendron; in
this stem the rays have been occupied by interfascicular xylem at a very
early stage of the secondary growth. The section from which fig. 83, D is
drawn was described by Williamson in 1871; the complete section shows
about 80 carinal canals and primary xylem groups. The prosenchymatous
form of the principal medullary rays is seen in fig 83, C, and the reticulate
pitting on the radial wall of a tracheid is shown in fig. 83, B. Fig. 83, A
illustrates the large infranodal canals as seen in a tangential section of a
stem. The same section shows also the course of the vascular bundles
characteristic of Calamites as of Equisetum, and the position of outgoing
leaf-traces is represented by unshaded areas in the black vascular strands.
Page 343
Fig. 83. Calamites (Arthrodendron).
A. Tangential section (diagrammatic) showing the course of the vascular strands, also leaf-
traces and infranodal canals.
B. Radial face of a tracheid.
C. Prosenchymatous elements of a principal medullary ray.
D. Transverse section of the wood. (After Williamson.) No. 36 in the Williamson Collection.
The subgenus Arthrodendron is very rarely met with, and our information
as to this type is far from complete[633].
The third subgenus Calamodendron has not been discovered in English
rocks, and our knowledge of this type is derived from French and German
silicified specimens[634]. There is the same large hollow pith surrounded by a
ring of collateral bundles with carinal canals, as in the two preceding
subgenera. The tracheids are scalariform and reticulate, and the secondary
medullary rays consist of rows of parenchymatous cells which are longer
than broad, as in Arthropitys and Arthrodendron.
A. Tangential section (diagrammatic) showing the course of the vascular strands, also leaf-
traces and infranodal canals.
B. Radial face of a tracheid.
C. Prosenchymatous elements of a principal medullary ray.
D. Transverse section of the wood. (After Williamson.) No. 36 in the Williamson Collection.
The subgenus Arthrodendron is very rarely met with, and our information
as to this type is far from complete[633].
The third subgenus Calamodendron has not been discovered in English
rocks, and our knowledge of this type is derived from French and German
silicified specimens[634]. There is the same large hollow pith surrounded by a
ring of collateral bundles with carinal canals, as in the two preceding
subgenera. The tracheids are scalariform and reticulate, and the secondary
medullary rays consist of rows of parenchymatous cells which are longer
than broad, as in Arthropitys and Arthrodendron.
Page 344
Fig. 84. Calamites (Calamodendron) intermedium, Ren.
Transverse section through two vascular bundles.
a, a, xylem tracheids, b, b, bands of prosenchyma, c, medullary ray. (After Renault.)
The most characteristic feature of Calamodendron is the occurrence of
several rows of radially disposed thick-walled prosenchymatous elements
(fig. 84, b) on either flank of each wedge-shaped group of xylem. Each
principal ray is thus nearly filled up by bands of fibrous cells on the sides of
adjacent xylem groups, but the centre of each principal ray is occupied by a
narrow band of parenchyma (fig. 84, c). The relative breadth of the xylem
and prosenchymatous bands has been made use of by Renault as a specific
character in Calamodendron stems. Fig. 84 is copied from a drawing
recently published by this French author of a new species of
Calamodendron, C. intermedium[635]. In this case the bands of fibrous cells,
b, are slightly broader, as seen in a transverse section of the stem, than the
bands of xylem tracheids, a. The narrow band, c, consists of four rows of
the parenchymatous tissue of a medullary ray. At the inner end of each
group of tracheids there is a large carinal canal.
The question of the recognition of the pith-casts of stems possessing the
structure of any of the three subgenera of Calamites is referred to in a later
section of this chapter.
b. Leaves
Leaves of Calamites and Calamitean foliage-shoots, including an account of (α) Calamocladus
(Asterophyllites) and (β) Annularia.
Transverse section through two vascular bundles.
a, a, xylem tracheids, b, b, bands of prosenchyma, c, medullary ray. (After Renault.)
The most characteristic feature of Calamodendron is the occurrence of
several rows of radially disposed thick-walled prosenchymatous elements
(fig. 84, b) on either flank of each wedge-shaped group of xylem. Each
principal ray is thus nearly filled up by bands of fibrous cells on the sides of
adjacent xylem groups, but the centre of each principal ray is occupied by a
narrow band of parenchyma (fig. 84, c). The relative breadth of the xylem
and prosenchymatous bands has been made use of by Renault as a specific
character in Calamodendron stems. Fig. 84 is copied from a drawing
recently published by this French author of a new species of
Calamodendron, C. intermedium[635]. In this case the bands of fibrous cells,
b, are slightly broader, as seen in a transverse section of the stem, than the
bands of xylem tracheids, a. The narrow band, c, consists of four rows of
the parenchymatous tissue of a medullary ray. At the inner end of each
group of tracheids there is a large carinal canal.
The question of the recognition of the pith-casts of stems possessing the
structure of any of the three subgenera of Calamites is referred to in a later
section of this chapter.
b. Leaves
Leaves of Calamites and Calamitean foliage-shoots, including an account of (α) Calamocladus
(Asterophyllites) and (β) Annularia.
Page 345
Our knowledge of the structure and manner of occurrence of Calamite
leaves is very incomplete. There are numerous foliage-shoots among the
fossils of the Coal-Measures which are no doubt Calamitean, but as they are
nearly always found apart from the main branches and stems, it is generally
impossible to do more than speak of them as probably the leaf-bearing
branches of a Calamite. The familiar fossils known as Asterophyllites, and
in recent years often referred to the genus Calamocladus, are no doubt
Calamitean shoots; but they are usually found as isolated fragments, and it
is seldom that we are able to refer them to definite forms of Calamites.
Another common Coal-Measure genus, Annularia, is also Calamitean, and
at least some of the species are no doubt leafy shoots of Calamites.
Although it is generally accepted that the fossils referred to as
Asterophyllites or Calamocladus are portions of Calamites, and not distinct
plants, it is convenient, and indeed necessary, to retain such a term as
Calamocladus as a means of recording foliage-shoots, which may possess
both a botanical and a geological value.
Some of the Calamite casts, especially those referred to the subgenus
Calamitina, are occasionally found with leaves attached to the nodes. In
some stems the leaves are arranged in a close verticil, and each leaf has a
narrow linear form and is traversed by a single median vein. Figures of
Calamite stems with verticils of long and narrow leaves may be found in
Lindley and Hutton[636], and in the writings of many other authors[637]. In the
specimen shown in fig. 85 the leaves are preserved apart from the stem, but
from their close association with a Calamite cast, and from the proofs
afforded by other specimens, it is quite certain they formed part of a whorl
of leaves attached to the node of a true Calamite, and a stem having that
particular type known as Calamitina[638] (figs. 99, 100). It is probable that in
some Calamites, and especially in younger shoots, the leaves had the form
of narrow sheaths split up into linear segments. This question has already
been referred to in dealing with certain Palaeozoic fossils referred to
Equisetites[639].
leaves is very incomplete. There are numerous foliage-shoots among the
fossils of the Coal-Measures which are no doubt Calamitean, but as they are
nearly always found apart from the main branches and stems, it is generally
impossible to do more than speak of them as probably the leaf-bearing
branches of a Calamite. The familiar fossils known as Asterophyllites, and
in recent years often referred to the genus Calamocladus, are no doubt
Calamitean shoots; but they are usually found as isolated fragments, and it
is seldom that we are able to refer them to definite forms of Calamites.
Another common Coal-Measure genus, Annularia, is also Calamitean, and
at least some of the species are no doubt leafy shoots of Calamites.
Although it is generally accepted that the fossils referred to as
Asterophyllites or Calamocladus are portions of Calamites, and not distinct
plants, it is convenient, and indeed necessary, to retain such a term as
Calamocladus as a means of recording foliage-shoots, which may possess
both a botanical and a geological value.
Some of the Calamite casts, especially those referred to the subgenus
Calamitina, are occasionally found with leaves attached to the nodes. In
some stems the leaves are arranged in a close verticil, and each leaf has a
narrow linear form and is traversed by a single median vein. Figures of
Calamite stems with verticils of long and narrow leaves may be found in
Lindley and Hutton[636], and in the writings of many other authors[637]. In the
specimen shown in fig. 85 the leaves are preserved apart from the stem, but
from their close association with a Calamite cast, and from the proofs
afforded by other specimens, it is quite certain they formed part of a whorl
of leaves attached to the node of a true Calamite, and a stem having that
particular type known as Calamitina[638] (figs. 99, 100). It is probable that in
some Calamites, and especially in younger shoots, the leaves had the form
of narrow sheaths split up into linear segments. This question has already
been referred to in dealing with certain Palaeozoic fossils referred to
Equisetites[639].
Page 346
Fig. 85. Linear leaves of a Calamite (Calamitina). After Weiss, slightly reduced.
A few years ago the late Thomas Hick[640], of Manchester, described the
structure of some leaves which he believed to be those of a Calamite. He
found them attached to a slender axis which possessed the characteristics of
a young Calamite branch. There can be little doubt that his specimens are
true Calamite leaves. The sketches of fig. 86 have been made from the
sections originally described by Hick. Fig. 86, 1 shows a leaf in transverse
section; on the outside there is a well-defined epidermal layer with a
limiting cuticle. Internal to this we have radially elongated parenchymatous
cells forming a loose or spongy tissue, the cells being often separated by
fairly large spaces (fig. 86, 5), especially in the region of the blunt lateral
wings of the leaf. Some of these cells contain a single dark dot, which in all
probability is the mineralised nucleus. These pallisade-like cells probably
contained chlorophyll and constituted the assimilating tissue of the leaf. In
the centre there is a circular strand of cells limited by a layer of larger cells
with black contents, enclosing an inner group of small-celled parenchyma
and traversed by a few spiral or scalariform tracheids constituting the single
median vein. It is hardly possible to recognise any phloem elements in the
small vascular bundle; there appear to be a few narrow tracheids surrounded
by larger parenchymatous elements (fig. 86, 2). At one point in the
epidermis of fig. 86, 1, there appears to be a stoma, but the details are not
very clearly shown (fig. 86, 4); the two cells, s, s, bordering the small
aperture are probably guard-cells.
A few years ago the late Thomas Hick[640], of Manchester, described the
structure of some leaves which he believed to be those of a Calamite. He
found them attached to a slender axis which possessed the characteristics of
a young Calamite branch. There can be little doubt that his specimens are
true Calamite leaves. The sketches of fig. 86 have been made from the
sections originally described by Hick. Fig. 86, 1 shows a leaf in transverse
section; on the outside there is a well-defined epidermal layer with a
limiting cuticle. Internal to this we have radially elongated parenchymatous
cells forming a loose or spongy tissue, the cells being often separated by
fairly large spaces (fig. 86, 5), especially in the region of the blunt lateral
wings of the leaf. Some of these cells contain a single dark dot, which in all
probability is the mineralised nucleus. These pallisade-like cells probably
contained chlorophyll and constituted the assimilating tissue of the leaf. In
the centre there is a circular strand of cells limited by a layer of larger cells
with black contents, enclosing an inner group of small-celled parenchyma
and traversed by a few spiral or scalariform tracheids constituting the single
median vein. It is hardly possible to recognise any phloem elements in the
small vascular bundle; there appear to be a few narrow tracheids surrounded
by larger parenchymatous elements (fig. 86, 2). At one point in the
epidermis of fig. 86, 1, there appears to be a stoma, but the details are not
very clearly shown (fig. 86, 4); the two cells, s, s, bordering the small
aperture are probably guard-cells.
Page 347
Fig. 86. A leaf of Calamites.
1. Transverse section; t, vascular bundle; x, sheath of cells. × 35.
2. Vascular bundle consisting of a few small tracheids, t.
3. A tracheid and a few parenchymatous cells, the latter with nuclei.
4. A stoma; s, s, guard-cells.
5. Pallisade cells and intercellular spaces.
From a section in the Manchester Museum, Owens College.
The nature of the assimilating tissue, the comparatively thick band of
thin-walled cells with intercellular spaces, and the exposed position of the
stomata suggest that the plant lived in a fairly damp climate; at least there is
nothing to indicate any adaptation to a dry climate.
In the Binney collection of plants in the Woodwardian Museum,
Cambridge, there is a species of a very small shoot bearing three or four
verticils of leaves which possess the same structure as those of fig. 86. We
may probably regard such twigs as the slender terminal branches of
Calamitean shoots.
α. Calamocladus (Asterophyllites).
1. Transverse section; t, vascular bundle; x, sheath of cells. × 35.
2. Vascular bundle consisting of a few small tracheids, t.
3. A tracheid and a few parenchymatous cells, the latter with nuclei.
4. A stoma; s, s, guard-cells.
5. Pallisade cells and intercellular spaces.
From a section in the Manchester Museum, Owens College.
The nature of the assimilating tissue, the comparatively thick band of
thin-walled cells with intercellular spaces, and the exposed position of the
stomata suggest that the plant lived in a fairly damp climate; at least there is
nothing to indicate any adaptation to a dry climate.
In the Binney collection of plants in the Woodwardian Museum,
Cambridge, there is a species of a very small shoot bearing three or four
verticils of leaves which possess the same structure as those of fig. 86. We
may probably regard such twigs as the slender terminal branches of
Calamitean shoots.
α. Calamocladus (Asterophyllites).
Page 348
The generic name Asterophyllites was proposed by Brongniart[641] in 1822
for a fossil previously named by Schlotheim[642] Casuarinites, and
afterwards transferred to Sternberg’s genus Annularia. In 1828
Brongniart[643] gave the following diagnosis of the fossils which he included
under the genus Asterophyllites:—“Stems rarely simple, usually branched,
with opposite branches, which are always disposed in the same plane;
leaves flat, more or less linear, pointed, traversed by a simple median vein,
free to the base.” Lindley and Hutton described examples of Brongniart’s
genus as species of Hippurites[644], and other authors adopted different
names for specimens afterwards referred to Asterophyllites.
At a later date Ettingshausen[645] and other writers expressed the view that
the fossils which Brongniart regarded as a distinct genus were the foliage-
shoots of Calamites, and Ettingshausen went so far as to include them in
that genus. In view of the generally expressed opinion as to the Calamitean
nature of Asterophyllites, Schimper[646] proposed the convenient generic
name Calamocladus for “rami et ramuli foliosi” of Calamites. Some recent
authors have adopted this genus, but others prefer to retain Asterophyllites.
In a recent important monograph by Grand’Eury[647] Calamitean foliage-
shoots are included under the two names, Asterophyllites and
Calamocladus; the latter type of foliage-shoots he associates with the stems
of the subgenus Calamodendron, and the former he connects with those
Calamitean stems which belong to the subgenus Arthropitys.
It is an almost hopeless task to attempt to connect the various forms of
foliage-shoots with their respective stems, and to determine what particular
anatomical features characterised the plants bearing these various forms of
shoots. We may adopt Schimper’s generic name Calamocladus in the same
sense as Asterophyllites, but as including such other foliage-shoots as we
have reason to believe belonged to Calamites. Those leaf-bearing branches
which conform to the type known as Annularia are however not included in
Calamocladus, as we cannot definitely assert that these foliage-shoots
belong in all cases to Calamitean stems. Grand’Eury’s use of Calamocladus
in a more restricted sense is inadvisable as leading to confusion, seeing that
this name was originally defined in a more comprehensive manner as
including Calamitean leaf-bearing branches generally. We may define
Calamocladus as follows:—
for a fossil previously named by Schlotheim[642] Casuarinites, and
afterwards transferred to Sternberg’s genus Annularia. In 1828
Brongniart[643] gave the following diagnosis of the fossils which he included
under the genus Asterophyllites:—“Stems rarely simple, usually branched,
with opposite branches, which are always disposed in the same plane;
leaves flat, more or less linear, pointed, traversed by a simple median vein,
free to the base.” Lindley and Hutton described examples of Brongniart’s
genus as species of Hippurites[644], and other authors adopted different
names for specimens afterwards referred to Asterophyllites.
At a later date Ettingshausen[645] and other writers expressed the view that
the fossils which Brongniart regarded as a distinct genus were the foliage-
shoots of Calamites, and Ettingshausen went so far as to include them in
that genus. In view of the generally expressed opinion as to the Calamitean
nature of Asterophyllites, Schimper[646] proposed the convenient generic
name Calamocladus for “rami et ramuli foliosi” of Calamites. Some recent
authors have adopted this genus, but others prefer to retain Asterophyllites.
In a recent important monograph by Grand’Eury[647] Calamitean foliage-
shoots are included under the two names, Asterophyllites and
Calamocladus; the latter type of foliage-shoots he associates with the stems
of the subgenus Calamodendron, and the former he connects with those
Calamitean stems which belong to the subgenus Arthropitys.
It is an almost hopeless task to attempt to connect the various forms of
foliage-shoots with their respective stems, and to determine what particular
anatomical features characterised the plants bearing these various forms of
shoots. We may adopt Schimper’s generic name Calamocladus in the same
sense as Asterophyllites, but as including such other foliage-shoots as we
have reason to believe belonged to Calamites. Those leaf-bearing branches
which conform to the type known as Annularia are however not included in
Calamocladus, as we cannot definitely assert that these foliage-shoots
belong in all cases to Calamitean stems. Grand’Eury’s use of Calamocladus
in a more restricted sense is inadvisable as leading to confusion, seeing that
this name was originally defined in a more comprehensive manner as
including Calamitean leaf-bearing branches generally. We may define
Calamocladus as follows:—
Page 349
Branched or simple articulated branches bearing whorls of uni-nerved
linear leaves at the nodes; the leaves may be either free to the base or fused
basally into a cup-like sheath (e.g. Grand’Eury’s Calamocladus). The
several acicular linear leaves or segments which are given off from the
nodes spread out radially in an open manner in all directions; they may be
either almost at right angles to the axis or inclined at different angles. Each
segment is traversed by a single vein and terminates in an acuminate apex.
As a typical example of a Calamitean foliage-shoot the species
Calamocladus equisetiformis (Schloth.) may be briefly described. The
synonymy of the commoner species of fossil plants is a constant source of
confusion and difficulty; in order to illustrate the necessity of careful
comparison of specimens and published illustrations, it may be helpful to
quote a few synonyms of the species more particularly dealt with. The
exhaustive lists drawn up by Kidston in his Catalogue of Palaeozoic plants
in the British Museum will be found extremely useful by those concerned
with a systematic study of the older plants.
linear leaves at the nodes; the leaves may be either free to the base or fused
basally into a cup-like sheath (e.g. Grand’Eury’s Calamocladus). The
several acicular linear leaves or segments which are given off from the
nodes spread out radially in an open manner in all directions; they may be
either almost at right angles to the axis or inclined at different angles. Each
segment is traversed by a single vein and terminates in an acuminate apex.
As a typical example of a Calamitean foliage-shoot the species
Calamocladus equisetiformis (Schloth.) may be briefly described. The
synonymy of the commoner species of fossil plants is a constant source of
confusion and difficulty; in order to illustrate the necessity of careful
comparison of specimens and published illustrations, it may be helpful to
quote a few synonyms of the species more particularly dealt with. The
exhaustive lists drawn up by Kidston in his Catalogue of Palaeozoic plants
in the British Museum will be found extremely useful by those concerned
with a systematic study of the older plants.
Page 350
Fig. 87. Calamocladus equisetiformis (Schloth.).
From a specimen in the British Museum (McMurtrie Collection, no. v. 2963). ca. ⅓ nat.
size.
Calamocladus equisetiformis (Schloth.). Fig. 87.
1809. Phytolithus, Martin[648].
1820. Casuarinites equisetiformis, Schlotheim[649].
1825. Bornia equisetiformis, Sternberg[650].
1828. Asterophyllites equisetiformis, Brongniart[651].
1836. Hippurites longifolia, Lindley and Hutton[652].
1855. Calamites equisetiformis, Ettingshausen[653].
1869. Calamocladus equisetiformis, Schimper[654].
From a specimen in the British Museum (McMurtrie Collection, no. v. 2963). ca. ⅓ nat.
size.
Calamocladus equisetiformis (Schloth.). Fig. 87.
1809. Phytolithus, Martin[648].
1820. Casuarinites equisetiformis, Schlotheim[649].
1825. Bornia equisetiformis, Sternberg[650].
1828. Asterophyllites equisetiformis, Brongniart[651].
1836. Hippurites longifolia, Lindley and Hutton[652].
1855. Calamites equisetiformis, Ettingshausen[653].
1869. Calamocladus equisetiformis, Schimper[654].
Page 351
1869. Annularia calamitoides, Schimper[654].
The above synonyms do not exhaust the list[655], but they suffice to illustrate
the necessity of a careful comparison in drawing up tables of species, in
connection with geographical distribution or for other purposes.
Calamocladus equisetiformis may be briefly defined as follows:—A
central axis possessing a hollow pith of Calamitean character, divided
externally into well-marked slightly constricted nodes and internodes; from
the nodes long narrow and free leaves are borne in whorls; from the axils of
some of the leaves lateral branches are given off inclined at a fairly wide
angle to the main axis, and bearing crowded verticils of spreading acicular
leaves.
The unusually good specimen, 38·5 cm. long, shown on a much reduced
scale in fig. 87, illustrates the characteristic habit of this form of
Calamocladus. It is from the Radstock coal-field of Somersetshire, one of
the best English localities for Coal-Measure plants. An exceedingly good
collection of Radstock plants has recently been presented to the British
Museum by Mr J. McMurtrie; it includes many fine specimens of
Calamites. A small example—probably of this species—from Coalbrook
Dale, near Dudley, in Shropshire, and now in the British Museum,
illustrates very well the appearance of a young and partially expanded
Calamitean foliage-shoot. The central axis, 6·5 cm. in length, includes
about 15 internodes, and terminates in a bud covered by several small
leaves. Lateral branches are given off at a wide angle, and small
unexpanded buds occur in the axils of several of the leaves.
As an example of the leaf-bearing branches which Grand’Eury has
recently described as Calamocladus, using the genus in a more restricted
sense than is adopted in the present chapter, reference may be made to the
fragment shown in fig. 68, A. The foliage-shoots of this type bore verticils
of linear leaves, coherent basally in the form of a cup, at the ends of
branches and not in a succession of whorls on each branch. The association
of reproductive organs, in the form of long and narrow strobili, with
Calamocladus is referred to in the sequel.
The above synonyms do not exhaust the list[655], but they suffice to illustrate
the necessity of a careful comparison in drawing up tables of species, in
connection with geographical distribution or for other purposes.
Calamocladus equisetiformis may be briefly defined as follows:—A
central axis possessing a hollow pith of Calamitean character, divided
externally into well-marked slightly constricted nodes and internodes; from
the nodes long narrow and free leaves are borne in whorls; from the axils of
some of the leaves lateral branches are given off inclined at a fairly wide
angle to the main axis, and bearing crowded verticils of spreading acicular
leaves.
The unusually good specimen, 38·5 cm. long, shown on a much reduced
scale in fig. 87, illustrates the characteristic habit of this form of
Calamocladus. It is from the Radstock coal-field of Somersetshire, one of
the best English localities for Coal-Measure plants. An exceedingly good
collection of Radstock plants has recently been presented to the British
Museum by Mr J. McMurtrie; it includes many fine specimens of
Calamites. A small example—probably of this species—from Coalbrook
Dale, near Dudley, in Shropshire, and now in the British Museum,
illustrates very well the appearance of a young and partially expanded
Calamitean foliage-shoot. The central axis, 6·5 cm. in length, includes
about 15 internodes, and terminates in a bud covered by several small
leaves. Lateral branches are given off at a wide angle, and small
unexpanded buds occur in the axils of several of the leaves.
As an example of the leaf-bearing branches which Grand’Eury has
recently described as Calamocladus, using the genus in a more restricted
sense than is adopted in the present chapter, reference may be made to the
fragment shown in fig. 68, A. The foliage-shoots of this type bore verticils
of linear leaves, coherent basally in the form of a cup, at the ends of
branches and not in a succession of whorls on each branch. The association
of reproductive organs, in the form of long and narrow strobili, with
Calamocladus is referred to in the sequel.
Page 352
The specimens described by Grand’Eury are in the École des Mines
Museum, Paris; some of the shoots which are well preserved bear a
resemblance in habit of growth to the genus Archaeocalamites.
β. Annularia.
In 1820 this generic name was applied by Sternberg[656] to some
specimens of branches bearing verticils of linear leaves. In 1828
Brongniart[657] thus defined the genus Annularia:—“Slender stem,
articulated, with opposite branches arising above the leaves. Leaves
verticillate, flat, frequently obtuse, traversed by a single vein, fused basally
and of unequal length.”
In the works of earlier writers we find frequent illustrations of specimens
of Annularia, which are compared with Asters and other recent flowering
plants. Lehmann[658] contributed a paper to the Royal Academy of Berlin in
1756, in which he referred to certain fossil plants as probable examples of
flowers, among them being a specimen of Annularia. He refers to the
occurrence of fossil ferns and other plants, and asks why we do not find
flowers of the rose or tulip; his object being “not to acquire vain glory, but
to give occasion for others to look into the matter more clearly.”
The general habit of the fossils which are now included under Annularia
agrees closely with that of Calamocladus. There is the same spreading form
and a similar foliage in the two genera, but in Annularia the members of a
whorl are always fused into a basal sheath, and the segments are not of
equal length. We may thus summarise the characteristic features of the
genus:—
Opposite branches are given off in one plane from the nodes of a main
axis; the leaves are in the form of narrow sheaths divided into numerous
and unequal linear or narrow lanceolate segments, each with a median vein.
The segments in each whorl appear to be spread out in one plane very
oblique to the axis of a branch, instead of spreading radially in all
directions; the lateral segments are usually longer than the upper and lower
members of a whorl. The vegetative branches possess the same type of
structure as Calamites.
A comparison of Annularia and Phyllotheca has already been made in
Chapter IX. (p. 282). Potonié[659] has recently given a detailed account of
Museum, Paris; some of the shoots which are well preserved bear a
resemblance in habit of growth to the genus Archaeocalamites.
β. Annularia.
In 1820 this generic name was applied by Sternberg[656] to some
specimens of branches bearing verticils of linear leaves. In 1828
Brongniart[657] thus defined the genus Annularia:—“Slender stem,
articulated, with opposite branches arising above the leaves. Leaves
verticillate, flat, frequently obtuse, traversed by a single vein, fused basally
and of unequal length.”
In the works of earlier writers we find frequent illustrations of specimens
of Annularia, which are compared with Asters and other recent flowering
plants. Lehmann[658] contributed a paper to the Royal Academy of Berlin in
1756, in which he referred to certain fossil plants as probable examples of
flowers, among them being a specimen of Annularia. He refers to the
occurrence of fossil ferns and other plants, and asks why we do not find
flowers of the rose or tulip; his object being “not to acquire vain glory, but
to give occasion for others to look into the matter more clearly.”
The general habit of the fossils which are now included under Annularia
agrees closely with that of Calamocladus. There is the same spreading form
and a similar foliage in the two genera, but in Annularia the members of a
whorl are always fused into a basal sheath, and the segments are not of
equal length. We may thus summarise the characteristic features of the
genus:—
Opposite branches are given off in one plane from the nodes of a main
axis; the leaves are in the form of narrow sheaths divided into numerous
and unequal linear or narrow lanceolate segments, each with a median vein.
The segments in each whorl appear to be spread out in one plane very
oblique to the axis of a branch, instead of spreading radially in all
directions; the lateral segments are usually longer than the upper and lower
members of a whorl. The vegetative branches possess the same type of
structure as Calamites.
A comparison of Annularia and Phyllotheca has already been made in
Chapter IX. (p. 282). Potonié[659] has recently given a detailed account of
Page 353
Annularian leaves; he compares them with those of Equisetum, and
describes the occurrence on the lamina of each leaf-segment of a broad
central band or midrib, with a groove, probably containing stomata, on
either side. He shows that in well-preserved specimens of Annularia, it is
possible to recognise certain minute surface-features, such as the presence
of hairs and stomata, which enable one to detect a close resemblance
between the leaves of Calamite stems and those of Annularian shoots.
It is not always easy to distinguish between Annularia and
Calamocladus; the collar-like basal sheath in the leaves of the former is a
characteristic feature, but that cannot always be recognised. On the other
hand, the leaves of Calamocladus may sometimes be flattened out on the
surface of the rock and simulate the deeply cut sheaths of Annularia. It is
difficult to decide how far the manner of occurrence of Annularian leaves in
one plane, which is commonly insisted on as a generic character, is an
original feature, or how far it is the result of compression in fossilisation.
Probably the leaves of a living Annularia were spread out at right angles to
the axis, as in the ‘verticils’ of such a plant as Galium.
Dawson[660] has described some fossils from the Devonian rocks of
Canada as species of Asterophyllites; the figures bear a closer resemblance
to the genus Annularia. The same author figures some irregularly whorled
impressions as Protannularia, which appear to be identical with a fossil
described by Nicholson[661] from the Skiddaw slates (Ordovician) of
Cumberland as Buthotrephis radiata, but the specimens are too imperfect to
admit of accurate determination.
Annularia stellata (Schloth.). Fig. 88.
1820. Casuarinites stellatus, Schlotheim[662].
1826. Bornia stellata, Sternberg[663].
1828. Annularia longifolia, Brongniart[664].
1834. Asterophyllites equisetiformis, Lindley and Hutton[665].
1868. Asterophyllites longifolius, Binney[666].
1887. Annularia Geinitzi, Stur[667].
1887. Annularia westphalica, Stur.
This species was figured by Scheuchzer[668] in his Herbarium
Diluvianum, and compared by him with a species of Galium (Bedstraw).
describes the occurrence on the lamina of each leaf-segment of a broad
central band or midrib, with a groove, probably containing stomata, on
either side. He shows that in well-preserved specimens of Annularia, it is
possible to recognise certain minute surface-features, such as the presence
of hairs and stomata, which enable one to detect a close resemblance
between the leaves of Calamite stems and those of Annularian shoots.
It is not always easy to distinguish between Annularia and
Calamocladus; the collar-like basal sheath in the leaves of the former is a
characteristic feature, but that cannot always be recognised. On the other
hand, the leaves of Calamocladus may sometimes be flattened out on the
surface of the rock and simulate the deeply cut sheaths of Annularia. It is
difficult to decide how far the manner of occurrence of Annularian leaves in
one plane, which is commonly insisted on as a generic character, is an
original feature, or how far it is the result of compression in fossilisation.
Probably the leaves of a living Annularia were spread out at right angles to
the axis, as in the ‘verticils’ of such a plant as Galium.
Dawson[660] has described some fossils from the Devonian rocks of
Canada as species of Asterophyllites; the figures bear a closer resemblance
to the genus Annularia. The same author figures some irregularly whorled
impressions as Protannularia, which appear to be identical with a fossil
described by Nicholson[661] from the Skiddaw slates (Ordovician) of
Cumberland as Buthotrephis radiata, but the specimens are too imperfect to
admit of accurate determination.
Annularia stellata (Schloth.). Fig. 88.
1820. Casuarinites stellatus, Schlotheim[662].
1826. Bornia stellata, Sternberg[663].
1828. Annularia longifolia, Brongniart[664].
1834. Asterophyllites equisetiformis, Lindley and Hutton[665].
1868. Asterophyllites longifolius, Binney[666].
1887. Annularia Geinitzi, Stur[667].
1887. Annularia westphalica, Stur.
This species was figured by Scheuchzer[668] in his Herbarium
Diluvianum, and compared by him with a species of Galium (Bedstraw).
Page 354
Brongniart first made use of the generic name Annularia for this common
Coal-Measure species, which may be defined as follows:—
Stem reaching a diameter of about 6–8 cm., with internodes 6–12 cm. in
length, the surface either smooth or faintly ribbed. Primary branches given
off in opposite pairs from the nodes, the lateral branches giving off smaller
branches disposed in the same manner. The smaller branches bear verticils
of leaves at each node; both leaves and ultimate branches being in one
plane. The leaves are narrow, lanceolate-spathulate in form, broadest about
the middle, 1–5 cm. in length and 1–3 mm. broad, hairy on the upper
surface[669]; each leaf is traversed by a single vein.
Fig. 88. Branch of Annularia stellata (Schloth.). ⅘ nat. size.
From a specimen in the Collection of Mr R. Kidston. Upper Coal-Measures, Radstock.
Each whorl contains 16–32 segments, which are connected basally into a
collar or narrow sheath; the lateral segments are usually longer than the
upper and lower. The branches are about 6–20 mm. broad, with finely
ribbed internodes 3–7 cm. long, bearing verticils of leaves; the ultimate
branches arise in pairs in the axils of the lateral segments of the verticils.
Coal-Measure species, which may be defined as follows:—
Stem reaching a diameter of about 6–8 cm., with internodes 6–12 cm. in
length, the surface either smooth or faintly ribbed. Primary branches given
off in opposite pairs from the nodes, the lateral branches giving off smaller
branches disposed in the same manner. The smaller branches bear verticils
of leaves at each node; both leaves and ultimate branches being in one
plane. The leaves are narrow, lanceolate-spathulate in form, broadest about
the middle, 1–5 cm. in length and 1–3 mm. broad, hairy on the upper
surface[669]; each leaf is traversed by a single vein.
Fig. 88. Branch of Annularia stellata (Schloth.). ⅘ nat. size.
From a specimen in the Collection of Mr R. Kidston. Upper Coal-Measures, Radstock.
Each whorl contains 16–32 segments, which are connected basally into a
collar or narrow sheath; the lateral segments are usually longer than the
upper and lower. The branches are about 6–20 mm. broad, with finely
ribbed internodes 3–7 cm. long, bearing verticils of leaves; the ultimate
branches arise in pairs in the axils of the lateral segments of the verticils.
Page 355
The strobili are of the Calamostachys[670] type and are borne on the main
branches or possibly on the stem; they have a long and narrow form and are
attached in verticils at the nodes. Each strobilus consists of a central axis
bearing alternate whorls of linear lanceolate sterile bracts and
sporangiophores, about half as numerous as the sterile bracts; each
sporangiophore bears four ovoid sporangia.
The anatomical structure of a specimen referred to Annularia stellata has
been described by Renault[671]. The cortex consists of parenchyma traversed
by lacunae and limited peripherally by a denser hypodermal tissue. In the
stele Renault describes 14 xylem strands, each with a large carinal canal.
The pith was apparently large and hollow. The same author describes an
Annularia strobilus in which the lower sporangiophores bear
macrosporangia, and the upper microsporangia.
branches or possibly on the stem; they have a long and narrow form and are
attached in verticils at the nodes. Each strobilus consists of a central axis
bearing alternate whorls of linear lanceolate sterile bracts and
sporangiophores, about half as numerous as the sterile bracts; each
sporangiophore bears four ovoid sporangia.
The anatomical structure of a specimen referred to Annularia stellata has
been described by Renault[671]. The cortex consists of parenchyma traversed
by lacunae and limited peripherally by a denser hypodermal tissue. In the
stele Renault describes 14 xylem strands, each with a large carinal canal.
The pith was apparently large and hollow. The same author describes an
Annularia strobilus in which the lower sporangiophores bear
macrosporangia, and the upper microsporangia.
Page 356
Fig. 89. Annularia sphenophylloides (Zenk.).
A. Strobilus (Stachannularia calathifera, Weiss). ⅔ nat. size. B. Vegetative shoot. ⅘ nat.
size.
From specimens in the Collection of Mr R. Kidston. Upper Coal-Measures, Radstock.
The references in the footnote should be consulted for figures of this
species of Annularia; it is from the examination of such specimens as are
referred to in the note that the above diagnosis has been compiled[672].
Annularia sphenophylloides (Zenk.). Fig. 89.
1833. Galium sphenophylloides, Zenker[673].
1865. Annularia brevifolia, Heer[674], Strobilus.
1876. Calamostachys (Stachannularia) calathifera, Weiss[675].
Principal branches 8–12 mm. wide, with internodes 8–10 cm. in length,
giving off two opposite branches at the nodes; from the secondary branches
arise smaller branches in opposite pairs. The leaf-verticils and branches are
all in one plane. Each verticil consists of 12–18 spathulate segments, 3–10
mm. long, cuneiform at the base and broader above, with an acuminate tip;
A. Strobilus (Stachannularia calathifera, Weiss). ⅔ nat. size. B. Vegetative shoot. ⅘ nat.
size.
From specimens in the Collection of Mr R. Kidston. Upper Coal-Measures, Radstock.
The references in the footnote should be consulted for figures of this
species of Annularia; it is from the examination of such specimens as are
referred to in the note that the above diagnosis has been compiled[672].
Annularia sphenophylloides (Zenk.). Fig. 89.
1833. Galium sphenophylloides, Zenker[673].
1865. Annularia brevifolia, Heer[674], Strobilus.
1876. Calamostachys (Stachannularia) calathifera, Weiss[675].
Principal branches 8–12 mm. wide, with internodes 8–10 cm. in length,
giving off two opposite branches at the nodes; from the secondary branches
arise smaller branches in opposite pairs. The leaf-verticils and branches are
all in one plane. Each verticil consists of 12–18 spathulate segments, 3–10
mm. long, cuneiform at the base and broader above, with an acuminate tip;
Page 357
the lateral segments are slightly longer than the upper and lower members
of a whorl.
The small and crowded leaf-whorls give to this species a characteristic
appearance, which readily distinguishes it from the larger-leaved forms
such as Annularia stellata. A fossil figured by Lhwyd[676] in 1699 as
Rubeola mineralis is no doubt an example of Annularia sphenophylloides.
Annularian branches are occasionally found with cones given off from
the axils of some of the leaf-whorls. An interesting specimen, which is now
in the Leipzig Museum, was described by Sterzel in 1882[677], showing
cones attached to a vegetative shoot of Annularia sphenophylloides. The
long and narrow strobili—2·5 cm. long and about 6 mm. broad—appear
very large in proportion to the size of the vegetative branches. A fertile
shoot consists of a central axis bearing whorls of bracts alternating with
sporangiophores, to each of which are attached four sporangia. The
specimen in fig. 89, A, does not show the details clearly; each transverse
constriction represents the attachment of a whorl of linear bracts; the whole
cone appears to consist of a series of short broad segments. The divisions in
the lower half of each segment mark the position of the sterile bracts, while
those of the upper half represent the outlines of the upper sporangia of each
whorl of sporangiophores, the lower sporangia being hidden by the ring of
linear bracts[678]. On some portions of the specimen of fig. 89, A, it is
possible to recognise the outlines of cells on the coaly surface-film; these
probably belong to the sporangium wall. This type of cone is included
under the genus Calamostachys, a name applied to Calamitean strobili with
certain morphological characters, as described on p. 351.
c. Roots.
In 1871 Williamson[679] described some sections of what he considered to
be a distinct variety of a Calamite stem. The chief peculiarity which he
noticed lay in the absence of carinal canals, and in the solid pith. Some
years later the same observer[680] came to the conclusion that the specimens
were probably those of a plant generically distinct from Calamites; he
accordingly proposed a new name Astromyelon. Subsequently Cash and
Hick[681] gave an account of some examples of apparently another form of
plant, to which they gave the name Myriophylloides Williamsonis; and
Williamson[682] suggested the term Helophyton as a more suitable generic
of a whorl.
The small and crowded leaf-whorls give to this species a characteristic
appearance, which readily distinguishes it from the larger-leaved forms
such as Annularia stellata. A fossil figured by Lhwyd[676] in 1699 as
Rubeola mineralis is no doubt an example of Annularia sphenophylloides.
Annularian branches are occasionally found with cones given off from
the axils of some of the leaf-whorls. An interesting specimen, which is now
in the Leipzig Museum, was described by Sterzel in 1882[677], showing
cones attached to a vegetative shoot of Annularia sphenophylloides. The
long and narrow strobili—2·5 cm. long and about 6 mm. broad—appear
very large in proportion to the size of the vegetative branches. A fertile
shoot consists of a central axis bearing whorls of bracts alternating with
sporangiophores, to each of which are attached four sporangia. The
specimen in fig. 89, A, does not show the details clearly; each transverse
constriction represents the attachment of a whorl of linear bracts; the whole
cone appears to consist of a series of short broad segments. The divisions in
the lower half of each segment mark the position of the sterile bracts, while
those of the upper half represent the outlines of the upper sporangia of each
whorl of sporangiophores, the lower sporangia being hidden by the ring of
linear bracts[678]. On some portions of the specimen of fig. 89, A, it is
possible to recognise the outlines of cells on the coaly surface-film; these
probably belong to the sporangium wall. This type of cone is included
under the genus Calamostachys, a name applied to Calamitean strobili with
certain morphological characters, as described on p. 351.
c. Roots.
In 1871 Williamson[679] described some sections of what he considered to
be a distinct variety of a Calamite stem. The chief peculiarity which he
noticed lay in the absence of carinal canals, and in the solid pith. Some
years later the same observer[680] came to the conclusion that the specimens
were probably those of a plant generically distinct from Calamites; he
accordingly proposed a new name Astromyelon. Subsequently Cash and
Hick[681] gave an account of some examples of apparently another form of
plant, to which they gave the name Myriophylloides Williamsonis; and
Williamson[682] suggested the term Helophyton as a more suitable generic
Page 358
designation. It was, however, demonstrated by Spencer[683] that the plant
described by Cash and Hick was identical with Williamson’s Astromyelon.
Williamson[684] then gave an account of several specimens of this type
illustrating various stages in the growth and development of the
Astromyelon ‘stems,’ which he compared with the rhizome of the recent
genus Marsilia.
In 1885 Renault[685] published an account of Astromyelon in which he
brought forward good evidence in favour of regarding it as a Calamitean
root. The same author has recently given some excellent figures and a
detailed description of certain specific types of these Calamite roots, and
Williamson and Scott’s memoir on the roots of Calamites has rendered our
knowledge of Astromyelon almost complete. Some of the finest specimens,
in which the organic connection between typical Calamite stems and
Astromyelon roots is clearly demonstrated, are in the Natural History
Museum, Paris. There are several sections also from English material which
show the connection between root and stem very clearly.
Fig. 90. Pith-cast of a Calamite stem, with roots; embedded in sandstone and shale. (After
Grand’Eury.) Much reduced.
described by Cash and Hick was identical with Williamson’s Astromyelon.
Williamson[684] then gave an account of several specimens of this type
illustrating various stages in the growth and development of the
Astromyelon ‘stems,’ which he compared with the rhizome of the recent
genus Marsilia.
In 1885 Renault[685] published an account of Astromyelon in which he
brought forward good evidence in favour of regarding it as a Calamitean
root. The same author has recently given some excellent figures and a
detailed description of certain specific types of these Calamite roots, and
Williamson and Scott’s memoir on the roots of Calamites has rendered our
knowledge of Astromyelon almost complete. Some of the finest specimens,
in which the organic connection between typical Calamite stems and
Astromyelon roots is clearly demonstrated, are in the Natural History
Museum, Paris. There are several sections also from English material which
show the connection between root and stem very clearly.
Fig. 90. Pith-cast of a Calamite stem, with roots; embedded in sandstone and shale. (After
Grand’Eury.) Much reduced.
Page 359
Casts of the hollow pith of Calamite rhizomes or aerial branches are
occasionally found in which slender appendages are given off either singly
or in tufts from the nodal regions. Many examples of such casts have been
figured by Lindley and Hutton[686], Binney[687], Grand’Eury[688], Weiss[689],
Stur, and other writers[690]. The large stem-cast of fig. 90 illustrates the
manner of occurrence of long branched roots on the nodes of a Calamite
growing in sandy or clay soil. The lower and more darkly shaded portion of
the specimen is covered by a layer of coal representing the carbonised wood
and cortex, which has been moulded on to the sandstone pith-cast. In fig. 77
(p. 316) a fairly thick root is seen, in organic connection with one of the
nodes, N 3, and on N 2 there is a scar of another root.
There are certain external characters by which one may often recognise a
Calamitean root. There is no division into nodes and internodes as in stems,
and as the pith of the root was usually solid the parallel ribs and grooves of
stem-casts are not present. In smaller flattened roots there may sometimes
be seen a central or excentric black line representing the stele, and the
surface of the root presents a curious wrinkled or shagreen texture, probably
due to the shrinkage of the loose lacunar cortex. The occasional excentric
position of the stele is no doubt due to the displacement of the vascular
cylinder as a result of the rapid decay of the cortical tissues. In the
Bergakademie of Berlin there are some unusually good examples of
Calamite casts bearing well-preserved root-impressions; these include the
original specimens figured by Weiss[691].
No doubt some of the roots figured by various writers under the names
Pinnularia[692] and Hydatica[693] belong to Calamites, but it is often
impossible to identify detached specimens with any certainty.
The section figured diagrammatically in fig. 91 A shows the
characteristic single series of large lacunae, l, in the middle cortical region.
In the centre there is a wide solid pith surrounded by a ring of vascular
tissue, x. The appearance of the middle cortex is very like that of the stem
of a water-plant such as Myriophyllum, the Water Milfoil; it shows that the
Calamite roots grew either in water or swampy ground. In fig. 91 B, the root
characters are clearly seen; the centre of the stele is occupied by large
parenchymatous cells which are rather longer than broad in longitudinal
view; at the periphery there are four protoxylem groups px, alternating with
four groups of phloem, ph, the latter being situated a little further from the
occasionally found in which slender appendages are given off either singly
or in tufts from the nodal regions. Many examples of such casts have been
figured by Lindley and Hutton[686], Binney[687], Grand’Eury[688], Weiss[689],
Stur, and other writers[690]. The large stem-cast of fig. 90 illustrates the
manner of occurrence of long branched roots on the nodes of a Calamite
growing in sandy or clay soil. The lower and more darkly shaded portion of
the specimen is covered by a layer of coal representing the carbonised wood
and cortex, which has been moulded on to the sandstone pith-cast. In fig. 77
(p. 316) a fairly thick root is seen, in organic connection with one of the
nodes, N 3, and on N 2 there is a scar of another root.
There are certain external characters by which one may often recognise a
Calamitean root. There is no division into nodes and internodes as in stems,
and as the pith of the root was usually solid the parallel ribs and grooves of
stem-casts are not present. In smaller flattened roots there may sometimes
be seen a central or excentric black line representing the stele, and the
surface of the root presents a curious wrinkled or shagreen texture, probably
due to the shrinkage of the loose lacunar cortex. The occasional excentric
position of the stele is no doubt due to the displacement of the vascular
cylinder as a result of the rapid decay of the cortical tissues. In the
Bergakademie of Berlin there are some unusually good examples of
Calamite casts bearing well-preserved root-impressions; these include the
original specimens figured by Weiss[691].
No doubt some of the roots figured by various writers under the names
Pinnularia[692] and Hydatica[693] belong to Calamites, but it is often
impossible to identify detached specimens with any certainty.
The section figured diagrammatically in fig. 91 A shows the
characteristic single series of large lacunae, l, in the middle cortical region.
In the centre there is a wide solid pith surrounded by a ring of vascular
tissue, x. The appearance of the middle cortex is very like that of the stem
of a water-plant such as Myriophyllum, the Water Milfoil; it shows that the
Calamite roots grew either in water or swampy ground. In fig. 91 B, the root
characters are clearly seen; the centre of the stele is occupied by large
parenchymatous cells which are rather longer than broad in longitudinal
view; at the periphery there are four protoxylem groups px, alternating with
four groups of phloem, ph, the latter being situated a little further from the
Page 360
centre of the stele. The structure is therefore that of a typical tetrarch root.
In the example represented in the figure secondary thickening has begun,
and the cambial cells internal to each phloem group have given rise to a few
radially disposed tracheids, x2. Beyond the phloem there are two layers of
parenchyma representing, as regards position, a pericycle and an
endodermis. In the ordinary pericycle and endodermis of the roots of most
plants the cells of the two layers are on alternate radii, but in the Calamite
root, as in Equisetum roots, the cells of these layers are placed on the same
radii, as seen in the neighbourhood of x2 in the figure. This correspondence
of the radial walls of the endodermal and pericyclic cells points to the
development of both layers from one mother-layer, and suggests the ‘double
endodermis’ or phloeoterma of Equisetum (p. 254). The cells in the outer of
these two layers have slight thickenings on the radial walls recalling the
usual character of endodermal cells. The phloeoterma is succeeded by a few
layers of parenchyma, constituting the inner cortex, and beyond this we
have the large lacunae separated from one another by slender trabeculae of
cells. The outer cortex is limited by a well-defined layer of thick-walled
cells, which may be spoken of as the epidermoidal[694] layer. Roots
possessing this superficial layer of thicker cells have no doubt lost the
original surface-layer which produced the absorptive root-hairs.
In the example represented in the figure secondary thickening has begun,
and the cambial cells internal to each phloem group have given rise to a few
radially disposed tracheids, x2. Beyond the phloem there are two layers of
parenchyma representing, as regards position, a pericycle and an
endodermis. In the ordinary pericycle and endodermis of the roots of most
plants the cells of the two layers are on alternate radii, but in the Calamite
root, as in Equisetum roots, the cells of these layers are placed on the same
radii, as seen in the neighbourhood of x2 in the figure. This correspondence
of the radial walls of the endodermal and pericyclic cells points to the
development of both layers from one mother-layer, and suggests the ‘double
endodermis’ or phloeoterma of Equisetum (p. 254). The cells in the outer of
these two layers have slight thickenings on the radial walls recalling the
usual character of endodermal cells. The phloeoterma is succeeded by a few
layers of parenchyma, constituting the inner cortex, and beyond this we
have the large lacunae separated from one another by slender trabeculae of
cells. The outer cortex is limited by a well-defined layer of thick-walled
cells, which may be spoken of as the epidermoidal[694] layer. Roots
possessing this superficial layer of thicker cells have no doubt lost the
original surface-layer which produced the absorptive root-hairs.
Page 361
Fig. 91.
A. Diagrammatic sketch of a transverse section of a young root of Calamites. x, xylem; l,
lacuna. After Hick.
B. Central cylinder (stele) of root, px, protoxylem; ph, phloem; x2, secondary xylem; l,
phloeoterma. × 75. After Williamson and Scott.
The xylem elements have the form of spiral, reticulate and scalariform
tracheids.
In roots or rootlets smaller than that shown in fig. 91 B, the primary
xylem may extend to the centre of the stele, and form a continuous axial
strand; in such examples the structure may be diarch, triarch or tetrarch. The
A. Diagrammatic sketch of a transverse section of a young root of Calamites. x, xylem; l,
lacuna. After Hick.
B. Central cylinder (stele) of root, px, protoxylem; ph, phloem; x2, secondary xylem; l,
phloeoterma. × 75. After Williamson and Scott.
The xylem elements have the form of spiral, reticulate and scalariform
tracheids.
In roots or rootlets smaller than that shown in fig. 91 B, the primary
xylem may extend to the centre of the stele, and form a continuous axial
strand; in such examples the structure may be diarch, triarch or tetrarch. The
Page 362
origin of the cambium agrees with that in recent roots, the cells immediately
external to the protoxylem tracheids become meristematic, as also those
internal to the phloem. Another root-character is seen in the endogenous
origin of lateral members. Good examples of branching roots are figured by
Williamson[695] and by Williamson and Scott[696].
Older roots[697] are usually found in a decorticated condition. A transverse
section of root in which secondary thickening has been active for some time
presents on a superficial view a close resemblance to a stem of Calamites,
but a careful comparison at once reveals important points of difference. The
specimen diagrammatically sketched in fig. 92 illustrates very clearly the
origin of a root from the node of a Calamite stem. The section has passed
through a stem in a tangential direction, showing the characteristic
arrangement of the vascular bundles x, and principal medullary rays m. The
small leaf-traces, t, t, afford another feature characteristic of a Calamite
stem. The portion of stem to the right of the figure has been slightly
displaced, and between this piece and the root R, one of the ubiquitous
Stigmarian appendages, s, has inserted itself. At R a fairly thick and
decorticated root is seen in oblique transverse section; at the upper end the
root tracheids are seen in direct continuity with the xylem of the stem. In
the centre of the root is the large solid pith surrounded by twelve bluntly
pointed xylem groups, composed in the main of radially disposed
scalariform elements with narrow secondary medullary rays like those in a
stem. Between each xylem group there is a broad medullary ray, which
tapers rapidly towards the outside, and is soon obliterated by the formation
of interfascicular secondary xylem. At R′ a portion of another root is seen in
transverse section, and R″ the inner part of a single xylem group is shown
more clearly. The solid pith and the absence of carinal canals are the two
most obvious distinguishing features of the roots.
external to the protoxylem tracheids become meristematic, as also those
internal to the phloem. Another root-character is seen in the endogenous
origin of lateral members. Good examples of branching roots are figured by
Williamson[695] and by Williamson and Scott[696].
Older roots[697] are usually found in a decorticated condition. A transverse
section of root in which secondary thickening has been active for some time
presents on a superficial view a close resemblance to a stem of Calamites,
but a careful comparison at once reveals important points of difference. The
specimen diagrammatically sketched in fig. 92 illustrates very clearly the
origin of a root from the node of a Calamite stem. The section has passed
through a stem in a tangential direction, showing the characteristic
arrangement of the vascular bundles x, and principal medullary rays m. The
small leaf-traces, t, t, afford another feature characteristic of a Calamite
stem. The portion of stem to the right of the figure has been slightly
displaced, and between this piece and the root R, one of the ubiquitous
Stigmarian appendages, s, has inserted itself. At R a fairly thick and
decorticated root is seen in oblique transverse section; at the upper end the
root tracheids are seen in direct continuity with the xylem of the stem. In
the centre of the root is the large solid pith surrounded by twelve bluntly
pointed xylem groups, composed in the main of radially disposed
scalariform elements with narrow secondary medullary rays like those in a
stem. Between each xylem group there is a broad medullary ray, which
tapers rapidly towards the outside, and is soon obliterated by the formation
of interfascicular secondary xylem. At R′ a portion of another root is seen in
transverse section, and R″ the inner part of a single xylem group is shown
more clearly. The solid pith and the absence of carinal canals are the two
most obvious distinguishing features of the roots.
Page 363
Fig. 92. Tangential section through a node of Calamites, showing a root in organic
connection with the stem.
R, R′. Root (Astromyelon) in transverse and oblique section, x, xylem; m, primary
medullary ray; t, leaf-trace; s, Stigmarian appendage.
R″, the inner portion of one of the xylem wedges of R′ more highly magnified. Sketched
from a section in the Cambridge Botanical Laboratory Collection.
As Renault points out, roots of Calamites have been figured by some
writers[698] as examples of stems, but it is usually comparatively easy to
distinguish between roots and stems. On examining the xylem groups more
closely, one notices that the apex of each is occupied by a triangular group
of centripetally-developed primary tracheids, the narrow spiral protoxylem
connection with the stem.
R, R′. Root (Astromyelon) in transverse and oblique section, x, xylem; m, primary
medullary ray; t, leaf-trace; s, Stigmarian appendage.
R″, the inner portion of one of the xylem wedges of R′ more highly magnified. Sketched
from a section in the Cambridge Botanical Laboratory Collection.
As Renault points out, roots of Calamites have been figured by some
writers[698] as examples of stems, but it is usually comparatively easy to
distinguish between roots and stems. On examining the xylem groups more
closely, one notices that the apex of each is occupied by a triangular group
of centripetally-developed primary tracheids, the narrow spiral protoxylem
Page 364
elements occupying the outwardly directed apex. The protoxylem apex is
usually followed externally by a ray of one or two radially disposed series
of parenchymatous cells. This ray is not distinguished in fig. 92 R″ from the
rows of xylem tracheids. Each xylem group is thus formed partly of
centripetal xylem and in part of secondary centrifugal xylem; the latter is
associated with secondary medullary rays, as in stems, and contains a
broader ray (fascicular ray of Williamson and Scott[699]) immediately
opposite each protoxylem strand. In the roots of recent plants (e.g.
Cucurbita, Phaseolus, &c.) a broad medullary ray is often found opposite
the protoxylem, and such an arrangement is a perfectly normal structure in
roots[700].
Renault has recently described several species of Calamite roots which
he designates by specific names, some of them belonging to stems with the
Arthropitys structure, and others to Calamodendron. Some of the roots
figured by the French author have an axial strand of xylem with 7–15
projecting angles of protoxylem[701]. These he considers true roots, but the
larger specimens with a wide pith he prefers to regard as stolons. In the
latter he mentions the union of the primary centripetal with the secondary
centrifugal wood as a distinguishing feature. It has been shown, however,
that each group of secondary xylem includes a median ray of parenchyma,
and that the whole structure is essentially that of a root, and not that of a
modified stem or stolon. The organs described by Renault as true roots are
probably rootlets, and as Williamson and Scott have demonstrated, there is
every gradation between the smaller specimens with a solid xylem axis and
those with a large central pith.
It is interesting to note that Renault’s figures of Calamodendron roots
show the closest resemblance to those of the subgenus Arthropitys.
d. Cones.
The occurrence of fossil plants in the form of isolated fragments is a
constant source of difficulty, and is well illustrated by the numerous
examples of strobili which cannot be connected with their parent stems. We
are, however, usually able to recognise Calamitean cones if the impressions
or petrified specimens are fairly well preserved, but it is seldom possible to
correlate particular types of cones with the corresponding species of
foliage-shoots or stems. Palaeobotanical literature contains numerous
usually followed externally by a ray of one or two radially disposed series
of parenchymatous cells. This ray is not distinguished in fig. 92 R″ from the
rows of xylem tracheids. Each xylem group is thus formed partly of
centripetal xylem and in part of secondary centrifugal xylem; the latter is
associated with secondary medullary rays, as in stems, and contains a
broader ray (fascicular ray of Williamson and Scott[699]) immediately
opposite each protoxylem strand. In the roots of recent plants (e.g.
Cucurbita, Phaseolus, &c.) a broad medullary ray is often found opposite
the protoxylem, and such an arrangement is a perfectly normal structure in
roots[700].
Renault has recently described several species of Calamite roots which
he designates by specific names, some of them belonging to stems with the
Arthropitys structure, and others to Calamodendron. Some of the roots
figured by the French author have an axial strand of xylem with 7–15
projecting angles of protoxylem[701]. These he considers true roots, but the
larger specimens with a wide pith he prefers to regard as stolons. In the
latter he mentions the union of the primary centripetal with the secondary
centrifugal wood as a distinguishing feature. It has been shown, however,
that each group of secondary xylem includes a median ray of parenchyma,
and that the whole structure is essentially that of a root, and not that of a
modified stem or stolon. The organs described by Renault as true roots are
probably rootlets, and as Williamson and Scott have demonstrated, there is
every gradation between the smaller specimens with a solid xylem axis and
those with a large central pith.
It is interesting to note that Renault’s figures of Calamodendron roots
show the closest resemblance to those of the subgenus Arthropitys.
d. Cones.
The occurrence of fossil plants in the form of isolated fragments is a
constant source of difficulty, and is well illustrated by the numerous
examples of strobili which cannot be connected with their parent stems. We
are, however, usually able to recognise Calamitean cones if the impressions
or petrified specimens are fairly well preserved, but it is seldom possible to
correlate particular types of cones with the corresponding species of
foliage-shoots or stems. Palaeobotanical literature contains numerous
Page 365
illustrations and descriptions of long and narrow strobili designated by
different generic terms such as Volkmannia, Brukmannia, Calamostachys,
Macrostachya and others; many of these have since been recognised as the
cones of Calamites, while some species of Volkmannia have been identified
with Sphenophyllum stems. Before further considering the general question
of Calamite cones, a few examples may be described in detail as types of
fructification which are known to have been borne by Calamites. The
examples selected are species of the two provisional genera Calamostachys
and Palaeostachya.
The usual form of a Calamite cone is illustrated in fig. 93, which
represents a fertile shoot bearing a few narrow linear leaves of the
Calamocladus type; in the axils of some of these are borne the long strobili.
Fig. 93. Calamostachys sp. A fertile Calamitean shoot. From a specimen in the Geological
Survey Museum, Jermyn Street, London. From the Upper Coal-Measures of
Monmouthshire (No. 5539).
Calamostachys Binneyana (Carr.). Figs. 94 and 95.
different generic terms such as Volkmannia, Brukmannia, Calamostachys,
Macrostachya and others; many of these have since been recognised as the
cones of Calamites, while some species of Volkmannia have been identified
with Sphenophyllum stems. Before further considering the general question
of Calamite cones, a few examples may be described in detail as types of
fructification which are known to have been borne by Calamites. The
examples selected are species of the two provisional genera Calamostachys
and Palaeostachya.
The usual form of a Calamite cone is illustrated in fig. 93, which
represents a fertile shoot bearing a few narrow linear leaves of the
Calamocladus type; in the axils of some of these are borne the long strobili.
Fig. 93. Calamostachys sp. A fertile Calamitean shoot. From a specimen in the Geological
Survey Museum, Jermyn Street, London. From the Upper Coal-Measures of
Monmouthshire (No. 5539).
Calamostachys Binneyana (Carr.). Figs. 94 and 95.
Page 366
In 1867 Carruthers[702] gave an account of the structural features of the
species of cones named by him Volkmannia Ludwigi and V. Binneyi, the
generic term having been originally used by Sternberg[703] for some
impressions of Carboniferous strobili. Brongniart[704] in 1849 referred to the
various forms of Volkmannia as cones of Asterophyllitean branches, and the
latter he regarded as the foliage-shoots of a Calamite stem. In 1868
Binney[705] published a description, with several illustrations, of the cones
named by Carruthers Volkmannia Binneyi, and referred to them as the
fructification of that type of Calamite stem spoken of in a previous section
of this chapter (p. 311) as Calamites (Arthropitys) communis (Binney). This
cone is now usually spoken of as Calamostachys Binneyana; the specific
name Binneyana being suggested by Schimper[706] in 1869 as more
euphonious than that proposed by Carruthers. In recent years our
knowledge of both C. Binneyana and C. Ludwigi has been considerably
extended. We shall confine our attention in the following account to the
former species[707]. Some excellent figures of the latter species may be found
in Weiss’ Memoir[708] on Calamarieae.
One of the largest examples of Calamostachys Binneyana so far recorded
has a length of 3–4 cm. and a maximum diameter of about 7·5 mm. The
axis of the cone bears whorls of sterile leaves or bracts at equal distances;
the linear bracts of each whorl are coherent basally as a disc or plate of
tissue attached at right angles to the central axis of the cone. The periphery
of each of these discs divides up into twelve linear segments, which curve
upwards in a direction more or less parallel to the strobilus axis, and at right
angles to the coherent portion of each whorl. The manner of occurrence of
the whorls is shown in fig. 94, which has been sketched from a large section
in the Williamson collection. The segments of the successive sterile verticils
alternate with one another, so that in the surface-view of a cone the long and
narrow free bracts appear spirally disposed. Midway between these
alternating sterile verticils there is a series of fertile appendages, also given
off in regular whorls. Each fertile whorl consists of about half as many
members as the segments of a sterile whorl, and the members of the several
fertile whorls are superposed and not alternate. Each member has the form
of a stalk or sporangiophore given off at right angles from the cone axis;
this is expanded distally into a peltate disc bearing four sporangia attached
to its inner face. In fig. 94 we can only see the basal portions of the
sporangiophores, which are shown in the upper part of the sketch as pointed
species of cones named by him Volkmannia Ludwigi and V. Binneyi, the
generic term having been originally used by Sternberg[703] for some
impressions of Carboniferous strobili. Brongniart[704] in 1849 referred to the
various forms of Volkmannia as cones of Asterophyllitean branches, and the
latter he regarded as the foliage-shoots of a Calamite stem. In 1868
Binney[705] published a description, with several illustrations, of the cones
named by Carruthers Volkmannia Binneyi, and referred to them as the
fructification of that type of Calamite stem spoken of in a previous section
of this chapter (p. 311) as Calamites (Arthropitys) communis (Binney). This
cone is now usually spoken of as Calamostachys Binneyana; the specific
name Binneyana being suggested by Schimper[706] in 1869 as more
euphonious than that proposed by Carruthers. In recent years our
knowledge of both C. Binneyana and C. Ludwigi has been considerably
extended. We shall confine our attention in the following account to the
former species[707]. Some excellent figures of the latter species may be found
in Weiss’ Memoir[708] on Calamarieae.
One of the largest examples of Calamostachys Binneyana so far recorded
has a length of 3–4 cm. and a maximum diameter of about 7·5 mm. The
axis of the cone bears whorls of sterile leaves or bracts at equal distances;
the linear bracts of each whorl are coherent basally as a disc or plate of
tissue attached at right angles to the central axis of the cone. The periphery
of each of these discs divides up into twelve linear segments, which curve
upwards in a direction more or less parallel to the strobilus axis, and at right
angles to the coherent portion of each whorl. The manner of occurrence of
the whorls is shown in fig. 94, which has been sketched from a large section
in the Williamson collection. The segments of the successive sterile verticils
alternate with one another, so that in the surface-view of a cone the long and
narrow free bracts appear spirally disposed. Midway between these
alternating sterile verticils there is a series of fertile appendages, also given
off in regular whorls. Each fertile whorl consists of about half as many
members as the segments of a sterile whorl, and the members of the several
fertile whorls are superposed and not alternate. Each member has the form
of a stalk or sporangiophore given off at right angles from the cone axis;
this is expanded distally into a peltate disc bearing four sporangia attached
to its inner face. In fig. 94 we can only see the basal portions of the
sporangiophores, which are shown in the upper part of the sketch as pointed
Page 367
projections, Sp, from the cone axis. Each sporangiophore is traversed by a
vascular strand which sends off a branch to the base of a sporangium (fig.
95, A, t).
Fig. 94. Calamostachys Binneyana (Carr.) in longitudinal (radial and tangential) section.
Sp, sporangiophores; S, sporangia.
(From specimen no. 1022 in the Williamson Collection, British Museum.)
The axis of the cone is occupied by a single stele, usually triangular in
section; the stele consists of a solid pith of elongated cells surrounded by
six vascular bundles, two at each corner. A somewhat irregular gap marks
the position of the protoxylem of each strand, and portions of spiral or
vascular strand which sends off a branch to the base of a sporangium (fig.
95, A, t).
Fig. 94. Calamostachys Binneyana (Carr.) in longitudinal (radial and tangential) section.
Sp, sporangiophores; S, sporangia.
(From specimen no. 1022 in the Williamson Collection, British Museum.)
The axis of the cone is occupied by a single stele, usually triangular in
section; the stele consists of a solid pith of elongated cells surrounded by
six vascular bundles, two at each corner. A somewhat irregular gap marks
the position of the protoxylem of each strand, and portions of spiral or
Page 368
annular tracheids may occasionally be seen in the cavity. These cavities,
which may be spoken of as the carinal canals, disappear at the nodes, where
there is a mass of short reticulately pitted tracheids, as in a Calamite stem.
Vascular bundles pass upwards in an oblique direction from the central stele
to supply the bracts, each of which is traversed by a single strand of
tracheids. The coherent portion, or disc, of each sterile whorl consists of
sclerenchymatous elements towards the upper surface, and of parenchyma
below. The pedicel of the sporangiophores consists of fairly thick-walled
cells traversed by a single vascular strand, and the peltate distal portions are
made up of parenchymatous cells arranged in a palisade-like form at right
angles to the free surface of the sporangiophores. The vascular strand of the
pedicel forks into two halves just below the peltate head, and these branches
again bifurcate to send a branch to each sporangium. The four sporangia of
each sporangiophore are attached by a narrow band of tissue to the shield-
shaped distal expansion (fig. 95, A).
In a tangential section of a cone, such as the lower portion of fig. 94 and
in fig. 95, B, the sporangiophores present the appearance of narrow stalks
(fig. 95, B, a) in the middle of a cluster of sporangia, and the latter appear
more or less square in outline. The wall of a sporangium is made of a single
layer of cells (fig. 95, B) which present a characteristic appearance in
surface-view (fig. 95, C), the thin walls being crossed at right angles by
small vertical plates. In the tangential section of the coherent sterile whorls
(fig. 95, B, b and b) the vascular strands are occasionally seen in transverse
section (fig. 95, B, t), as they pass outwards to the several free bracts.
which may be spoken of as the carinal canals, disappear at the nodes, where
there is a mass of short reticulately pitted tracheids, as in a Calamite stem.
Vascular bundles pass upwards in an oblique direction from the central stele
to supply the bracts, each of which is traversed by a single strand of
tracheids. The coherent portion, or disc, of each sterile whorl consists of
sclerenchymatous elements towards the upper surface, and of parenchyma
below. The pedicel of the sporangiophores consists of fairly thick-walled
cells traversed by a single vascular strand, and the peltate distal portions are
made up of parenchymatous cells arranged in a palisade-like form at right
angles to the free surface of the sporangiophores. The vascular strand of the
pedicel forks into two halves just below the peltate head, and these branches
again bifurcate to send a branch to each sporangium. The four sporangia of
each sporangiophore are attached by a narrow band of tissue to the shield-
shaped distal expansion (fig. 95, A).
In a tangential section of a cone, such as the lower portion of fig. 94 and
in fig. 95, B, the sporangiophores present the appearance of narrow stalks
(fig. 95, B, a) in the middle of a cluster of sporangia, and the latter appear
more or less square in outline. The wall of a sporangium is made of a single
layer of cells (fig. 95, B) which present a characteristic appearance in
surface-view (fig. 95, C), the thin walls being crossed at right angles by
small vertical plates. In the tangential section of the coherent sterile whorls
(fig. 95, B, b and b) the vascular strands are occasionally seen in transverse
section (fig. 95, B, t), as they pass outwards to the several free bracts.
Page 369
Fig. 95. Calamostachys Binneyana (Carr.).
A. A sporangiophore and one sporangium. t, vascular bundle. × 45.
B. Tangential section showing portions of two sterile discs, b, b; a sporangiophore, a, with
its four sporangia, in two of which are seen the spores; t, vascular bundle. × 35.
C. Surface-view of cells of a sporangium wall. × 130.
D. Spores and remains of mother-cells. × 130.
(After Williamson and Scott.)
The spores in Calamostachys Binneyana are all of the same size, and no
macrospores have ever been seen. In well preserved specimens tetrads of
spores may be seen, still enclosed by the wall of the spore-mother-cell (fig.
95, A and D); and the torn remnants of the mother-cell sometimes simulate
in appearance the elaters of an Equisetum spore. In surface-view a spore
often shows clearly the three-rayed marking, which is a characteristic
feature of daughter-cells formed in a tetrad from a mother-cell. The spores
of a tetrad are in some cases of unequal size, some having developed more
vigorously than others. This unequal growth and nourishment of spores is
clearly shown in fig. 96, which represents a sporangium of a heterosporous
Calamitean strobilus, C. Casheana. Williamson and Scott[709] have described
striking examples of spores in different stages of abortion, and these authors
draw attention to the importance of the phenomenon from the point of view
of the origin of a heterosporous form of cone. The abortion of some of the
members of a spore-tetrad and the consequent increased nutrition of the
more favoured daughter-cells, might well be the starting-point of a process,
A. A sporangiophore and one sporangium. t, vascular bundle. × 45.
B. Tangential section showing portions of two sterile discs, b, b; a sporangiophore, a, with
its four sporangia, in two of which are seen the spores; t, vascular bundle. × 35.
C. Surface-view of cells of a sporangium wall. × 130.
D. Spores and remains of mother-cells. × 130.
(After Williamson and Scott.)
The spores in Calamostachys Binneyana are all of the same size, and no
macrospores have ever been seen. In well preserved specimens tetrads of
spores may be seen, still enclosed by the wall of the spore-mother-cell (fig.
95, A and D); and the torn remnants of the mother-cell sometimes simulate
in appearance the elaters of an Equisetum spore. In surface-view a spore
often shows clearly the three-rayed marking, which is a characteristic
feature of daughter-cells formed in a tetrad from a mother-cell. The spores
of a tetrad are in some cases of unequal size, some having developed more
vigorously than others. This unequal growth and nourishment of spores is
clearly shown in fig. 96, which represents a sporangium of a heterosporous
Calamitean strobilus, C. Casheana. Williamson and Scott[709] have described
striking examples of spores in different stages of abortion, and these authors
draw attention to the importance of the phenomenon from the point of view
of the origin of a heterosporous form of cone. The abortion of some of the
members of a spore-tetrad and the consequent increased nutrition of the
more favoured daughter-cells, might well be the starting-point of a process,
Page 370
which would ultimately lead to the production of well defined macrospores
and microspores. The young microsporangia and macrosporangia of recent
Vascular Cryptogams such as Selaginella, Salvinia and other heterosporous
genera are identical in appearance[710]; it is not until the spore-producing
tissue begins to differentiate into groups of spores, that the sporangia
assume the form of macrosporangia and microsporangia. During the
evolution of the various known types of pteridophytic plants heterospory
gradually succeeded isospory, and this no doubt occurred several times and
in different phyla of the plant kingdom. In the mature sporangia of some of
the Calamitean strobili we have in the inequality of the spores in one
sporangium an indication of the steps by which heterospory arose; and in
the immature sporangia of some recent genera we are carried back to a
stage still nearer the starting-point of the substitution of the heterosporous
for the isosporous condition.
Calamostachys Casheana Will. Fig. 96.
To Williamson[711] again is largely due the information we possess as to
the structure of this type of Calamitean strobilus. Its special interest lies in
the occurrence of macrospores and microspores in the same cone.
The strobilus axis agrees in structure with that of C. Binneyana, but in C.
Casheana a band of secondary xylem forms the peripheral portion of the
triangular stele. Were any further proof needed of the now well-established
fact that secondary growth in thickness is by no means unknown as an
attribute of Vascular Cryptogams, the co-existence in the same cone of a
cambium layer producing secondary wood and bark, and cryptogamic
macrospores and microspores, affords conclusive evidence[712]. The dogma
accepted by many writers for a considerable number of years that the power
of secondary thickening is evidence against a cryptogamic affinity, has been
responsible for no little confusion in palaeobotanical nomenclature.
On the axis of Calamostachys Casheana there are borne alternate whorls
of fertile and sterile appendages similar to those in the homosporous C.
Binneyana, but they are inclined more obliquely to the axis of the cone.
Macrospores and microspores have been found in sporangia borne on the
same sporangiophore.
and microspores. The young microsporangia and macrosporangia of recent
Vascular Cryptogams such as Selaginella, Salvinia and other heterosporous
genera are identical in appearance[710]; it is not until the spore-producing
tissue begins to differentiate into groups of spores, that the sporangia
assume the form of macrosporangia and microsporangia. During the
evolution of the various known types of pteridophytic plants heterospory
gradually succeeded isospory, and this no doubt occurred several times and
in different phyla of the plant kingdom. In the mature sporangia of some of
the Calamitean strobili we have in the inequality of the spores in one
sporangium an indication of the steps by which heterospory arose; and in
the immature sporangia of some recent genera we are carried back to a
stage still nearer the starting-point of the substitution of the heterosporous
for the isosporous condition.
Calamostachys Casheana Will. Fig. 96.
To Williamson[711] again is largely due the information we possess as to
the structure of this type of Calamitean strobilus. Its special interest lies in
the occurrence of macrospores and microspores in the same cone.
The strobilus axis agrees in structure with that of C. Binneyana, but in C.
Casheana a band of secondary xylem forms the peripheral portion of the
triangular stele. Were any further proof needed of the now well-established
fact that secondary growth in thickness is by no means unknown as an
attribute of Vascular Cryptogams, the co-existence in the same cone of a
cambium layer producing secondary wood and bark, and cryptogamic
macrospores and microspores, affords conclusive evidence[712]. The dogma
accepted by many writers for a considerable number of years that the power
of secondary thickening is evidence against a cryptogamic affinity, has been
responsible for no little confusion in palaeobotanical nomenclature.
On the axis of Calamostachys Casheana there are borne alternate whorls
of fertile and sterile appendages similar to those in the homosporous C.
Binneyana, but they are inclined more obliquely to the axis of the cone.
Macrospores and microspores have been found in sporangia borne on the
same sporangiophore.
Page 371
Fig. 96. Calamostachys Casheana Will.
A sporangium with macrospores and abortive spores. × 65.
(After Williamson and Scott.)
The spore-tetrads in the macrosporangia occasionally include aborted
sister-cells like those noticed in C. Binneyana; this phenomenon is well
illustrated by the unequally nourished spores in the sporangium of fig. 96,
but no such starved spores have been found in the microsporangia. In this
cone, then, heterospory has become firmly established, but the occurrence
of undersized spores in a macrospore-tetrad leads us back to the probable
lines of development of heterospory, which are seen in C. Binneyana at
their starting-point.
In the two species of strobili which have been described, Calamostachys
Binneyana and C. Casheana, the sporangiophores or sporophylls are given
off at right angles to the axis, and midway between the sterile whorls. These
are two of the most important distinguishing features of the Calamitean
cones included under the generic term Calamostachys. In another form of
cone, which also belongs to Calamitean stems, the sporangiophores arise in
the axil of the sterile leaves, and are inclined obliquely to the axis of the
cone. To this type the generic name Palaeostachya has been applied by the
late Prof. Weiss[713] of Berlin. The portion of a cone shown in fig. 97 shows
the arrangement of the sterile and fertile appendages characteristic of
Palaeostachya.
A sporangium with macrospores and abortive spores. × 65.
(After Williamson and Scott.)
The spore-tetrads in the macrosporangia occasionally include aborted
sister-cells like those noticed in C. Binneyana; this phenomenon is well
illustrated by the unequally nourished spores in the sporangium of fig. 96,
but no such starved spores have been found in the microsporangia. In this
cone, then, heterospory has become firmly established, but the occurrence
of undersized spores in a macrospore-tetrad leads us back to the probable
lines of development of heterospory, which are seen in C. Binneyana at
their starting-point.
In the two species of strobili which have been described, Calamostachys
Binneyana and C. Casheana, the sporangiophores or sporophylls are given
off at right angles to the axis, and midway between the sterile whorls. These
are two of the most important distinguishing features of the Calamitean
cones included under the generic term Calamostachys. In another form of
cone, which also belongs to Calamitean stems, the sporangiophores arise in
the axil of the sterile leaves, and are inclined obliquely to the axis of the
cone. To this type the generic name Palaeostachya has been applied by the
late Prof. Weiss[713] of Berlin. The portion of a cone shown in fig. 97 shows
the arrangement of the sterile and fertile appendages characteristic of
Palaeostachya.
Page 372
Fig. 97. Palaeostachya pedunculata Will. Part of a cone, × 3. (After Weiss.)
It is practically impossible to distinguish between cones of the
Calamostachys and Palaeostachya type in the case of imperfectly preserved
impressions; indeed we cannot assume that all long and narrow cones with
spirally disposed verticillate bracts are Calamitean. We must have the
additional evidence of internal structure or of the direct association of the
cones with Calamitean foliage.
Palaeostachya vera sp. nov. Fig. 98.
In 1869 Williamson[714] described a fragment of a strobilus which showed
certain anatomical features indicative of a close relationship or even
identity with Calamites. Some years later[715] a much more perfect example
was obtained from the Coal-Measures of Lancashire, and the additional
evidence which it afforded definitely confirmed the earlier views of
Williamson. The cone was more fully described by Williamson in 1888, as
“the true fruit of Calamites.” It is clearly a form of Weiss’ genus
Palaeostachya; Williamson and Scott[716] refer to it in their Memoir as
Calamites pedunculatus. It is preferable, however, to retain the generic
designation Palaeostachya for cones of this type. As the name P.
pedunculata has previously been adopted by Weiss[717] for a cone figured by
Williamson[718] in 1874, and afterwards referred to by that author in writing
as P. pedunculata, it is proposed to substitute the specific name vera; this
specific name being chosen with a view to put on record the fact that it was
this type of cone that Williamson first proved to be the true fructification of
the Calamite.
The axis of P. vera is practically identical in structure with a Calamitean
twig. There is a hollow pith in the centre of the stele surrounded by a ring of
It is practically impossible to distinguish between cones of the
Calamostachys and Palaeostachya type in the case of imperfectly preserved
impressions; indeed we cannot assume that all long and narrow cones with
spirally disposed verticillate bracts are Calamitean. We must have the
additional evidence of internal structure or of the direct association of the
cones with Calamitean foliage.
Palaeostachya vera sp. nov. Fig. 98.
In 1869 Williamson[714] described a fragment of a strobilus which showed
certain anatomical features indicative of a close relationship or even
identity with Calamites. Some years later[715] a much more perfect example
was obtained from the Coal-Measures of Lancashire, and the additional
evidence which it afforded definitely confirmed the earlier views of
Williamson. The cone was more fully described by Williamson in 1888, as
“the true fruit of Calamites.” It is clearly a form of Weiss’ genus
Palaeostachya; Williamson and Scott[716] refer to it in their Memoir as
Calamites pedunculatus. It is preferable, however, to retain the generic
designation Palaeostachya for cones of this type. As the name P.
pedunculata has previously been adopted by Weiss[717] for a cone figured by
Williamson[718] in 1874, and afterwards referred to by that author in writing
as P. pedunculata, it is proposed to substitute the specific name vera; this
specific name being chosen with a view to put on record the fact that it was
this type of cone that Williamson first proved to be the true fructification of
the Calamite.
The axis of P. vera is practically identical in structure with a Calamitean
twig. There is a hollow pith in the centre of the stele surrounded by a ring of
Page 373
16–20 collateral bundles, each of which is accompanied by a carinal canal
as in a vegetative shoot. As the pedicel of the strobilus passes into the cone
proper it undergoes some modification in structure, but retains the
characteristic features of a Calamite. The diagrammatic longitudinal section
of fig. 98, which is copied from a drawing by Williamson[719], shows the
broadening of the vascular strands at the nodes, and here and there a carinal
canal is seen internal to the wood.
The axis of the cone bears whorls of bracts at right angles to the central
column. Each whorl consists of about 30–40 segments coherent basally into
a disc of prosenchymatous and parenchymatous tissue. The free linear
bracts curve sharply upwards from the periphery of the disc, approximately
parallel to the axis of the cone. From each of these sterile whorls there are
given off 16–20 long and slender obliquely-inclined sporangiophores, sp,
which arise from the upper surface of the disc close to the axis. Each
sporangiophore no doubt bore four sporangia, S, containing spores of one
size,—about ·075 mm. in diameter. The specimens of Palaeostachya vera
so far obtained do not show the actual manner of attachment of the
sporangia, but more complete examples of other species of
Palaeostachya[720] enable us to assume with certainty that the
sporangiophores terminated in a distal peltate expansion bearing four
sporangia on its inner face.
as in a vegetative shoot. As the pedicel of the strobilus passes into the cone
proper it undergoes some modification in structure, but retains the
characteristic features of a Calamite. The diagrammatic longitudinal section
of fig. 98, which is copied from a drawing by Williamson[719], shows the
broadening of the vascular strands at the nodes, and here and there a carinal
canal is seen internal to the wood.
The axis of the cone bears whorls of bracts at right angles to the central
column. Each whorl consists of about 30–40 segments coherent basally into
a disc of prosenchymatous and parenchymatous tissue. The free linear
bracts curve sharply upwards from the periphery of the disc, approximately
parallel to the axis of the cone. From each of these sterile whorls there are
given off 16–20 long and slender obliquely-inclined sporangiophores, sp,
which arise from the upper surface of the disc close to the axis. Each
sporangiophore no doubt bore four sporangia, S, containing spores of one
size,—about ·075 mm. in diameter. The specimens of Palaeostachya vera
so far obtained do not show the actual manner of attachment of the
sporangia, but more complete examples of other species of
Palaeostachya[720] enable us to assume with certainty that the
sporangiophores terminated in a distal peltate expansion bearing four
sporangia on its inner face.
Page 374
Fig. 98. Diagrammatic longitudinal section of Palaeostachya vera, sp. nov. S, S, S,
sporangia; x, xylem; sp, sporangiophore. (After Williamson.)
A transverse section of the axis of the cone in the region of the sterile and
fertile appendages shows the vascular bundles arranged in pairs. In a
section through the peduncle of the cone, below the lowest whorl of bracts,
the bundles of the stele are situated at equal distances apart. The cortical
tissue of the peduncle is traversed by a ring of large canals[721] similar to the
vallecular canals of an Equisetum stem.
Isospory is not a constant characteristic of Palaeostachya; some forms
have been found with macrospores and microspores[722].
Other Calamitean cones, and examples illustrating the connection between
Cones and Vegetative Shoots.
sporangia; x, xylem; sp, sporangiophore. (After Williamson.)
A transverse section of the axis of the cone in the region of the sterile and
fertile appendages shows the vascular bundles arranged in pairs. In a
section through the peduncle of the cone, below the lowest whorl of bracts,
the bundles of the stele are situated at equal distances apart. The cortical
tissue of the peduncle is traversed by a ring of large canals[721] similar to the
vallecular canals of an Equisetum stem.
Isospory is not a constant characteristic of Palaeostachya; some forms
have been found with macrospores and microspores[722].
Other Calamitean cones, and examples illustrating the connection between
Cones and Vegetative Shoots.
Page 375
It would be out of place in an introduction to Palaeobotany to attempt an
exhaustive account of the various cones which were probably borne by
Calamitean plants, but there are a few general points to which the attention
of the student should be directed. The examples dealt with in the foregoing
description illustrate the fact, that plants included under the comprehensive
genus Calamites bore cones possessing distinct morphological features.
There are, however, other types of strobili which have been found in
organic connection with Calamites; and some of these must be taken into
account in dealing with Calamarian plants. The genera Volkmannia,
Brukmannia, Huttonia, Macrostachya, in addition to Calamostachys and
Palaeostachya and others, have been applied by different writers to
Calamitean cones. As Solms-Laubach[723] has suggested, it is wiser to
discard Volkmannia and Brukmannia, as they have been made to do duty for
cones of widely different forms. It is better to adhere to the provisional
generic names used by Weiss, as they enable us to conveniently systematise
the various Calamarian strobili.
The following classification may be given of the better known cones,
some of which we are able to describe in considerable detail, while others
are still very imperfectly known. We have good evidence that all these
strobili were borne by vegetative shoots of the type of Calamites,
Calamocladus or Annularia.
1. Calamostachys[724] (including Paracalamostachys and Stachannularia).
Cones long and narrow, consisting of a central axis bearing alternate
whorls of sterile and fertile appendages, the latter having the form of
sporangiophores attached at right angles to the axis midway between the
sterile verticils, and bearing four sporangia on the inner face of a peltate
distal expansion.
Calamostachys Binneyana Schimp., C. Ludwigi Carr., C. Casheana Will.,
may be referred to as examples of this type of cone; also some of the
strobili described by different authors as species of Volkmannia[725],
Brukmannia[726], &c.
Although one cannot make out the detailed structure of a Calamite cone
in the absence of internal structure, it is often possible to recognise the
essential features in specimens preserved in ironstone nodules, such as
exhaustive account of the various cones which were probably borne by
Calamitean plants, but there are a few general points to which the attention
of the student should be directed. The examples dealt with in the foregoing
description illustrate the fact, that plants included under the comprehensive
genus Calamites bore cones possessing distinct morphological features.
There are, however, other types of strobili which have been found in
organic connection with Calamites; and some of these must be taken into
account in dealing with Calamarian plants. The genera Volkmannia,
Brukmannia, Huttonia, Macrostachya, in addition to Calamostachys and
Palaeostachya and others, have been applied by different writers to
Calamitean cones. As Solms-Laubach[723] has suggested, it is wiser to
discard Volkmannia and Brukmannia, as they have been made to do duty for
cones of widely different forms. It is better to adhere to the provisional
generic names used by Weiss, as they enable us to conveniently systematise
the various Calamarian strobili.
The following classification may be given of the better known cones,
some of which we are able to describe in considerable detail, while others
are still very imperfectly known. We have good evidence that all these
strobili were borne by vegetative shoots of the type of Calamites,
Calamocladus or Annularia.
1. Calamostachys[724] (including Paracalamostachys and Stachannularia).
Cones long and narrow, consisting of a central axis bearing alternate
whorls of sterile and fertile appendages, the latter having the form of
sporangiophores attached at right angles to the axis midway between the
sterile verticils, and bearing four sporangia on the inner face of a peltate
distal expansion.
Calamostachys Binneyana Schimp., C. Ludwigi Carr., C. Casheana Will.,
may be referred to as examples of this type of cone; also some of the
strobili described by different authors as species of Volkmannia[725],
Brukmannia[726], &c.
Although one cannot make out the detailed structure of a Calamite cone
in the absence of internal structure, it is often possible to recognise the
essential features in specimens preserved in ironstone nodules, such as
Page 376
those from Coalbrook Dale in Shropshire, or by carefully examining the
carbonised impressions on shale under a simple microscope.
Weiss applies the term Paracalamostachys[727] to cones of the
Calamostachys form, but in which the manner of attachment cannot be
made out. Such a cone as that of fig. 93 should probably be referred to this
sub-type of Calamostachys in the absence of definite evidence as to the
position of the sporangia.
Another term Stachannularia, originally used by Weiss as a genus[728],
was afterwards[729] applied to cones of the same general type as
Calamostachys, in which the sporangiophores have the form of thorn-like
structures bearing on their upper side a lamellar expansion. There is
however some doubt as to the correct interpretation of the features
associated with cones included in Stachannularia; for an account of such
forms reference must be made to the writings of Weiss, Renault[730], Solms-
Laubach[731] and others[732].
Calamostachys cones have been found in organic union with branches
bearing leaves of the Annularia type, also with Calamocladus foliage, and
the branches bearing such cones have been found in actual connection with
Calamitean stems. The association of cones and vegetative stems and
branches is shown in tabular form on p. 363.
2. Palaeostachya[733].
In this genus the general habit agrees with that of Calamostachys, and in
imperfectly preserved specimens it may be impossible to discriminate
between Calamostachys and Palaeostachya. The latter form is characterised
by the attachment of the sporangiophores in the axil of the sterile bracts, or
immediately above them, as shown in figs. 97 and 98.
Examples. Palaeostachya vera sp. nov., P. pedunculata Will. afford
examples of this form of strobilus. The genus Palaeostachya includes
several species previously described under the genus Volkmannia[734].
Strobili of this generic type are known in organic association with
Annularian branches, as well as with Calamocladus and Calamites.
3. Macrostachya.
carbonised impressions on shale under a simple microscope.
Weiss applies the term Paracalamostachys[727] to cones of the
Calamostachys form, but in which the manner of attachment cannot be
made out. Such a cone as that of fig. 93 should probably be referred to this
sub-type of Calamostachys in the absence of definite evidence as to the
position of the sporangia.
Another term Stachannularia, originally used by Weiss as a genus[728],
was afterwards[729] applied to cones of the same general type as
Calamostachys, in which the sporangiophores have the form of thorn-like
structures bearing on their upper side a lamellar expansion. There is
however some doubt as to the correct interpretation of the features
associated with cones included in Stachannularia; for an account of such
forms reference must be made to the writings of Weiss, Renault[730], Solms-
Laubach[731] and others[732].
Calamostachys cones have been found in organic union with branches
bearing leaves of the Annularia type, also with Calamocladus foliage, and
the branches bearing such cones have been found in actual connection with
Calamitean stems. The association of cones and vegetative stems and
branches is shown in tabular form on p. 363.
2. Palaeostachya[733].
In this genus the general habit agrees with that of Calamostachys, and in
imperfectly preserved specimens it may be impossible to discriminate
between Calamostachys and Palaeostachya. The latter form is characterised
by the attachment of the sporangiophores in the axil of the sterile bracts, or
immediately above them, as shown in figs. 97 and 98.
Examples. Palaeostachya vera sp. nov., P. pedunculata Will. afford
examples of this form of strobilus. The genus Palaeostachya includes
several species previously described under the genus Volkmannia[734].
Strobili of this generic type are known in organic association with
Annularian branches, as well as with Calamocladus and Calamites.
3. Macrostachya.
Page 377
This generic name was originally applied by Schimper[735] to certain
forms of Calamitean stems, of the type afterwards referred to the sub-genus
Calamitina by Weiss, bearing long and thick cones. The name is, however,
more appropriately restricted to strobili, which differ from the two
preceding genera in their greater length (14–16 cm.) and in the more
crowded and imbricating whorls of bracts. The internodes of the cones are
very short, and each whorl of bracts consists of about 20 coherent members
separated at the periphery of the disc into short pointed teeth. The internal
structure of Macrostachya has not been satisfactorily determined. An
account by Renault[736] of a petrified specimen does not present a very clear
idea as to the structural features of this form of Calamitean strobilus.
The association of Calamitean vegetative shoots and cones.
Strobilus Foliage-shoot Stem
Calamostachys Annularia ramosa Weiss Calamites ramosus Artis
(Stachannularia) ramosa
Weiss[737]
C. (Stachannularia) A. sphenophylloides Zenk. Stem bearing verticils of long and
calathifera Weiss[738] narrow leaves[739]. Probably a young
Calamites
C. (Stachannularia) A. stellata(Schloth.)[740] (A. Calamites sp.[741]
tuberculata (Stern.) longifolia Brongn.)
C. Solmsi[742] Weiss Calamocladus sp. Calamites (Calamitina) sp.
C. longifolia (Stern.)[743] Calamocladus sp.
Palaeostachya pedunculata Calamocladus
Will.[744]
P. arborescens (Stern.)[745] Calamites (Stylocalamites)
arborescens (Stern.)
Macrostachya[746] Calamocladus Calamites (Calamitina) sp.
equisetiformis (Schloth.)
HUTTONIA.
The generic name Huttonia, suggested by Sternberg[747] in 1837, is
applied to cones which closely resemble Macrostachya in habit, but differ
—so far as our scanty knowledge enables us to judge—in the arrangement
of the members. The student must refer to Weiss[748], Solms-Laubach[749] and
other writers[750] for a further account of these types, and of another rare and
little-known form of cone, called by Weiss Cingularia[751].
Macrostachyan cones have been found attached to stems of Calamites
which are included in the sub-genus Calamitina (p. 367). The larger size of
forms of Calamitean stems, of the type afterwards referred to the sub-genus
Calamitina by Weiss, bearing long and thick cones. The name is, however,
more appropriately restricted to strobili, which differ from the two
preceding genera in their greater length (14–16 cm.) and in the more
crowded and imbricating whorls of bracts. The internodes of the cones are
very short, and each whorl of bracts consists of about 20 coherent members
separated at the periphery of the disc into short pointed teeth. The internal
structure of Macrostachya has not been satisfactorily determined. An
account by Renault[736] of a petrified specimen does not present a very clear
idea as to the structural features of this form of Calamitean strobilus.
The association of Calamitean vegetative shoots and cones.
Strobilus Foliage-shoot Stem
Calamostachys Annularia ramosa Weiss Calamites ramosus Artis
(Stachannularia) ramosa
Weiss[737]
C. (Stachannularia) A. sphenophylloides Zenk. Stem bearing verticils of long and
calathifera Weiss[738] narrow leaves[739]. Probably a young
Calamites
C. (Stachannularia) A. stellata(Schloth.)[740] (A. Calamites sp.[741]
tuberculata (Stern.) longifolia Brongn.)
C. Solmsi[742] Weiss Calamocladus sp. Calamites (Calamitina) sp.
C. longifolia (Stern.)[743] Calamocladus sp.
Palaeostachya pedunculata Calamocladus
Will.[744]
P. arborescens (Stern.)[745] Calamites (Stylocalamites)
arborescens (Stern.)
Macrostachya[746] Calamocladus Calamites (Calamitina) sp.
equisetiformis (Schloth.)
HUTTONIA.
The generic name Huttonia, suggested by Sternberg[747] in 1837, is
applied to cones which closely resemble Macrostachya in habit, but differ
—so far as our scanty knowledge enables us to judge—in the arrangement
of the members. The student must refer to Weiss[748], Solms-Laubach[749] and
other writers[750] for a further account of these types, and of another rare and
little-known form of cone, called by Weiss Cingularia[751].
Macrostachyan cones have been found attached to stems of Calamites
which are included in the sub-genus Calamitina (p. 367). The larger size of
Page 378
Macrostachya as a distinguishing feature is not always a safe test; some
cones which belong to Palaeostachya [e.g. P. arborescens Sternb.] and
Calamostachys (e.g. C. Solmsi) are much thicker and larger than the
majority of species of these two genera.
It would appear from the examples selected to illustrate the connection
between strobili and vegetative shoots, that the Annularia type of branch
usually bears cones which conform to the genus Calamostachys
(Stachannularia); while the Asterophyllitean branches—Calamocladus—
are associated with Palaeostachya and Macrostachya. But this rule is not
constant, and we are not in a position to speak of cones of a particular type
as necessarily characteristic of definite types of Calamitean shoots.
• • • • •
Although it is admitted by the great majority of Palaeobotanists that the
Calamites were all true Vascular Cryptogams, the older view that some
members of the Calamarieae are gymnospermous has not been given up by
Renault[752]. This observer has recently described some seeds which he
believes were borne by Calamitean stems; he admits, however, that no
undoubted female cones of Calamodendron have so far been found. In view
of the unsatisfactory evidence on which Renault’s opinion is based, we need
not further discuss the questions which he raises.
[The following specimens in the Williamson Cabinet in the British Museum, may be found
useful in illustration of the structure of Calamites.
Stems. (i. Arthropitys.) Young twigs and small branches 1, 2, 6, 10, 14, 19, 116*, 1002, 1007,
1020.
Older stems (transverse sections) 15–17, 62, 77–87, 115 a, 117*, 118*, 120, 122*–124*, 1933
a, 1934, 1941.
(Tangential sections) 20, 24, 26, 37, 38, 49, 90, 91, 130, 138, 1937, 1943.
(Radial sections) 20, 20 a, 21, 22, 48, 65–68, 83–91, 137*, 138*, 1937.
(ii. Arthrodendron) 36, 37, 38, 52, 54.
Roots. 1335, 1347, 1350, 1356.
Strobili. i. Calamostachys Binneyana. 991, 996, 997, 1000, 1003, 1005, 1007, 1008, 1011,
1013, 1016, 1017, 1022, 1023, 1037 a, 1043.
ii. C. Casheana. 1024, 1025, 1587, 1588.
iii. Palaeostachya vera. 110, 1564, 1567, 1569, 1579, 1583.]
III. Pith-casts of Calamites.
cones which belong to Palaeostachya [e.g. P. arborescens Sternb.] and
Calamostachys (e.g. C. Solmsi) are much thicker and larger than the
majority of species of these two genera.
It would appear from the examples selected to illustrate the connection
between strobili and vegetative shoots, that the Annularia type of branch
usually bears cones which conform to the genus Calamostachys
(Stachannularia); while the Asterophyllitean branches—Calamocladus—
are associated with Palaeostachya and Macrostachya. But this rule is not
constant, and we are not in a position to speak of cones of a particular type
as necessarily characteristic of definite types of Calamitean shoots.
• • • • •
Although it is admitted by the great majority of Palaeobotanists that the
Calamites were all true Vascular Cryptogams, the older view that some
members of the Calamarieae are gymnospermous has not been given up by
Renault[752]. This observer has recently described some seeds which he
believes were borne by Calamitean stems; he admits, however, that no
undoubted female cones of Calamodendron have so far been found. In view
of the unsatisfactory evidence on which Renault’s opinion is based, we need
not further discuss the questions which he raises.
[The following specimens in the Williamson Cabinet in the British Museum, may be found
useful in illustration of the structure of Calamites.
Stems. (i. Arthropitys.) Young twigs and small branches 1, 2, 6, 10, 14, 19, 116*, 1002, 1007,
1020.
Older stems (transverse sections) 15–17, 62, 77–87, 115 a, 117*, 118*, 120, 122*–124*, 1933
a, 1934, 1941.
(Tangential sections) 20, 24, 26, 37, 38, 49, 90, 91, 130, 138, 1937, 1943.
(Radial sections) 20, 20 a, 21, 22, 48, 65–68, 83–91, 137*, 138*, 1937.
(ii. Arthrodendron) 36, 37, 38, 52, 54.
Roots. 1335, 1347, 1350, 1356.
Strobili. i. Calamostachys Binneyana. 991, 996, 997, 1000, 1003, 1005, 1007, 1008, 1011,
1013, 1016, 1017, 1022, 1023, 1037 a, 1043.
ii. C. Casheana. 1024, 1025, 1587, 1588.
iii. Palaeostachya vera. 110, 1564, 1567, 1569, 1579, 1583.]
III. Pith-casts of Calamites.
Page 379
A. Calamitina. B. Stylocalamites. C. Eucalamites.
Palaeobotanical literature contains a large number of species of
Calamites founded on pith-casts alone. Many of these so-called species are
of little or no value botanically, but while we may admit the futility of
attempting to recognise specific types in the same sense as in the
determination of recent plants, it is necessary to pay attention to such
characters as are likely to prove of value for descriptive and comparative
purposes. From the nature of the specimens it is clear that many of the
differences may be such as are likely to be met with in different branches of
the same species, while in others the pith-casts of distinct species or genera
may be almost identical.
The most striking differences observable in Calamite casts are in the
character of the internodes, the infranodal canals, the number and
disposition of branch-scars, and other surface features. Occasionally it is
possible to recognise certain anatomical characters in the coaly layer which
often surrounds a shale- or sandstone-cast, and the surface of a well
preserved cast may give a clue to the nature of the wood in the faint outlines
of cells which can sometimes be detected on the cast itself[753]. The breadth
of the carbonaceous envelope on a cast has been frequently relied on by
some writers as an important character. It has been suggested[754] that we
may arrive at the original thickness of the wood of a stem by measuring the
coaly layer and multiplying the breadth by 27; the explanation being that a
zone of wood 27 mm. in thickness is reduced in the process of
carbonisation to a layer 1 mm. thick.
The breadth of the coal on the same form of cast may vary considerably;
on this account, and for various other reasons, such a character can have but
little value. Our knowledge of anatomy may often help us to interpret
certain features of internal casts and to appreciate apparently unimportant
details. One occasionally notices that a Calamite pith-cast has large
infranodal canals, and in some specimens each internodal ridge may be
traversed by a narrow median line or small groove; large infranodal canal
casts suggest the type of stem referred to the subgenus Arthrodendron, and
the median line on the ridges may be due to bands of hard tissue in each
principal medullary ray.
Palaeobotanical literature contains a large number of species of
Calamites founded on pith-casts alone. Many of these so-called species are
of little or no value botanically, but while we may admit the futility of
attempting to recognise specific types in the same sense as in the
determination of recent plants, it is necessary to pay attention to such
characters as are likely to prove of value for descriptive and comparative
purposes. From the nature of the specimens it is clear that many of the
differences may be such as are likely to be met with in different branches of
the same species, while in others the pith-casts of distinct species or genera
may be almost identical.
The most striking differences observable in Calamite casts are in the
character of the internodes, the infranodal canals, the number and
disposition of branch-scars, and other surface features. Occasionally it is
possible to recognise certain anatomical characters in the coaly layer which
often surrounds a shale- or sandstone-cast, and the surface of a well
preserved cast may give a clue to the nature of the wood in the faint outlines
of cells which can sometimes be detected on the cast itself[753]. The breadth
of the carbonaceous envelope on a cast has been frequently relied on by
some writers as an important character. It has been suggested[754] that we
may arrive at the original thickness of the wood of a stem by measuring the
coaly layer and multiplying the breadth by 27; the explanation being that a
zone of wood 27 mm. in thickness is reduced in the process of
carbonisation to a layer 1 mm. thick.
The breadth of the coal on the same form of cast may vary considerably;
on this account, and for various other reasons, such a character can have but
little value. Our knowledge of anatomy may often help us to interpret
certain features of internal casts and to appreciate apparently unimportant
details. One occasionally notices that a Calamite pith-cast has large
infranodal canals, and in some specimens each internodal ridge may be
traversed by a narrow median line or small groove; large infranodal canal
casts suggest the type of stem referred to the subgenus Arthrodendron, and
the median line on the ridges may be due to bands of hard tissue in each
principal medullary ray.
Page 380
In attempting to identify pith-casts the student must keep in view the
probable differences presented by the branching rhizome, the main aerial
branches and the finer shoots of the same individual. The long internodal
ridges of some casts may be mistaken for the parallel veins of such a leaf as
Cordaites, a Palaeozoic Gymnosperm, if there are no nodes visible on the
specimen. The fossil figured by Lindley and Hutton[755] as Poacites, and
regarded by them as a Monocotyledon, is no doubt a portion of a Calamite
with very long internodes. An interesting example of incorrect
determination has recently been pointed out by Nathorst[756] in the case of
certain casts from Bear Island, originally described by Heer as examples of
Calamites; the vertical rows of leaf-trace casts on a Knorria were mistaken
for the ribs of a Calamite stem. The specimens in the Stockholm Museum
fully bear out Nathorst’s interpretation. The undulating course of internodal
ridges and grooves is not in itself a character of specific value. If a Calamite
stem were bent slightly, the wood and medullary-ray tissues on the concave
side might adapt themselves to the shortening of the stem by becoming
more or less folded, and a cast of such a stem would show undulating ridges
and grooves on one side and straight ones on the other[757].
A convenient classification of Calamite casts was proposed by Weiss in
1884, founded chiefly on the number and manner of occurrence of branch-
scars—or rather branch-depressions—on the surface of pith-casts. Weiss[758]
recognised the imperfection of his proposed grouping, and Zeiller[759] has
also expressed reasonable doubts as to the scientific value of such group-
characters. Weiss instituted three subgenera—Calamitina, Eucalamites and
Stylocalamites, which are made use of as convenient terms in descriptive
treatment of Calamite casts. The following account of a few of the more
typical casts may serve to illustrate the methods employed in the description
of such specimens; the synonomy given for the different species is not
intended to be complete, but it is added with a view to drawing attention to
the necessity for careful comparison in systematic work.
A. Calamitina.
This sub-genus of Calamites, as instituted by Weiss[760], includes
Calamitean stems or branches, which are characterised by the periodic
occurrence of branch-whorls usually represented by fairly large oval or
circular scars just above a nodal line (figs. 99, 100 and 101). The branch-
probable differences presented by the branching rhizome, the main aerial
branches and the finer shoots of the same individual. The long internodal
ridges of some casts may be mistaken for the parallel veins of such a leaf as
Cordaites, a Palaeozoic Gymnosperm, if there are no nodes visible on the
specimen. The fossil figured by Lindley and Hutton[755] as Poacites, and
regarded by them as a Monocotyledon, is no doubt a portion of a Calamite
with very long internodes. An interesting example of incorrect
determination has recently been pointed out by Nathorst[756] in the case of
certain casts from Bear Island, originally described by Heer as examples of
Calamites; the vertical rows of leaf-trace casts on a Knorria were mistaken
for the ribs of a Calamite stem. The specimens in the Stockholm Museum
fully bear out Nathorst’s interpretation. The undulating course of internodal
ridges and grooves is not in itself a character of specific value. If a Calamite
stem were bent slightly, the wood and medullary-ray tissues on the concave
side might adapt themselves to the shortening of the stem by becoming
more or less folded, and a cast of such a stem would show undulating ridges
and grooves on one side and straight ones on the other[757].
A convenient classification of Calamite casts was proposed by Weiss in
1884, founded chiefly on the number and manner of occurrence of branch-
scars—or rather branch-depressions—on the surface of pith-casts. Weiss[758]
recognised the imperfection of his proposed grouping, and Zeiller[759] has
also expressed reasonable doubts as to the scientific value of such group-
characters. Weiss instituted three subgenera—Calamitina, Eucalamites and
Stylocalamites, which are made use of as convenient terms in descriptive
treatment of Calamite casts. The following account of a few of the more
typical casts may serve to illustrate the methods employed in the description
of such specimens; the synonomy given for the different species is not
intended to be complete, but it is added with a view to drawing attention to
the necessity for careful comparison in systematic work.
A. Calamitina.
This sub-genus of Calamites, as instituted by Weiss[760], includes
Calamitean stems or branches, which are characterised by the periodic
occurrence of branch-whorls usually represented by fairly large oval or
circular scars just above a nodal line (figs. 99, 100 and 101). The branch-
Page 381
scars may form a row of contiguous discs, or a
whorl may consist of a smaller number of
branches which are not in contact basally. A
form described by Weiss as C. pauciramis,
Weiss[761], has only one branch in each whorl, as
represented by a single large oval scar on some
of the nodes of the cast. A stem of this form is
by no means a typical Calamitina, but it serves
to show the existence of forms connecting
Weiss’ sub-genera Calamitina and Eucalamites.
The number of internodes and nodes between
the branch whorls varies in different specimens,
and is indeed not constant in the same plant.
Each nodal line bears numerous elliptical scars
which mark the points of attachment of leaves;
each branch-whorl is situated immediately
above a node, and in some forms this nodal line
pursues a somewhat irregular course across the
stem, following the outlines of the several
branch-scars[762]. The surface of the internodes is
either perfectly smooth or it is more frequently
traversed by short longitudinal ridges or grooves
probably representing fissures in the bark of the Fig. 99. Calamites (Calamitina)
living stem; these are indicated by lines in fig. Göpperti
scars.
(Ett.). b, branch
99 and by elongated elliptical ridges in fig. 101. From a specimen in the
On young stems the leaves are occasionally Manchester Museum, Owens
found in place, as for example in an example College. ¼ nat. size.
figured by Weiss[763] (C. Göpperti), or we may have leaf-verticils still in
place in much older and thicker branches[764] (cf. fig. 85, p. 330).
It occasionally happens that the bark of Calamitina stems has been
preserved as a detached shell[765] reminding one of the sheets of Birch bark
often met with in forests, the separation being no doubt due in the fossil as
in the recent trees to the manner of occurrence of the cork-cambium.
In a few cases branches have been preserved still attached to a stem or
branch of higher order; examples of such specimens are figured by Lindley
and Hutton[766], Stur[767], and others. Grand’Eury[768] has given an idealised
whorl may consist of a smaller number of
branches which are not in contact basally. A
form described by Weiss as C. pauciramis,
Weiss[761], has only one branch in each whorl, as
represented by a single large oval scar on some
of the nodes of the cast. A stem of this form is
by no means a typical Calamitina, but it serves
to show the existence of forms connecting
Weiss’ sub-genera Calamitina and Eucalamites.
The number of internodes and nodes between
the branch whorls varies in different specimens,
and is indeed not constant in the same plant.
Each nodal line bears numerous elliptical scars
which mark the points of attachment of leaves;
each branch-whorl is situated immediately
above a node, and in some forms this nodal line
pursues a somewhat irregular course across the
stem, following the outlines of the several
branch-scars[762]. The surface of the internodes is
either perfectly smooth or it is more frequently
traversed by short longitudinal ridges or grooves
probably representing fissures in the bark of the Fig. 99. Calamites (Calamitina)
living stem; these are indicated by lines in fig. Göpperti
scars.
(Ett.). b, branch
99 and by elongated elliptical ridges in fig. 101. From a specimen in the
On young stems the leaves are occasionally Manchester Museum, Owens
found in place, as for example in an example College. ¼ nat. size.
figured by Weiss[763] (C. Göpperti), or we may have leaf-verticils still in
place in much older and thicker branches[764] (cf. fig. 85, p. 330).
It occasionally happens that the bark of Calamitina stems has been
preserved as a detached shell[765] reminding one of the sheets of Birch bark
often met with in forests, the separation being no doubt due in the fossil as
in the recent trees to the manner of occurrence of the cork-cambium.
In a few cases branches have been preserved still attached to a stem or
branch of higher order; examples of such specimens are figured by Lindley
and Hutton[766], Stur[767], and others. Grand’Eury[768] has given an idealised
Page 382
drawing of a typical Calamitina bearing a whorl of branches with the
foliage and habit of Asterophyllites equisetiformis. The specimen on which
this drawing is based is in the Natural History Museum, Paris; it shows
Asterophyllitean branches in organic connection with a Calamitean stem,
but it is not quite clear if the stem is a true Calamitina. A large drawing of
this interesting specimen is given by Stur[769] in his monograph on
Calamites, also a smaller sketch by Renault[770] in his Cours de botanique
fossile. Similar branches of the Asterophyllites type attached to an
undoubted Calamitina are figured also by Lindley and Hutton. There is, in
short, good evidence that stems of this sub-genus bore branches with
Asterophyllitean shoots.
The wood of stems of the Calamitina group of Calamites, in some
instances at least, was of the Arthropitys type; this has been shown to be the
case in some French specimens from the Commentry coal-field[771] and in
others described by Stur[772]. The pith-casts of Calamitina are characterised
by comparatively short internodes separated by deep nodal constrictions, as
shown in fig. 100. From Permian specimens from Neu Paka in Bohemia,
described by Stur[773], we learn that there were the usual Calamite
diaphragms bridging across the wide pith-cavity at each node. Such a cast
as that shown in fig. 100 is often referred to as Calamites approximatus
Brongn.; the length of the internodes and the periodic occurrence of branch-
scars in the form of circular or oval depressions along a nodal line enable us
to recognise the Calamitina casts. Weiss[774] points out that in pith-casts of
this form the branch-scars occur on the nodal constriction, and not
immediately above the node as is the case on the surface of a typical
Calamitina. This distinction is however of little or no value; the point of
attachment of a branch may be above the nodal line, while on the pith-cast
of the same stem the point of origin of the vascular bundles of the branch is
on the nodal constriction[775].
The specimen shown in fig. 100 illustrates the appearance of a
Calamitina cast. There is a verticil of branch-scars on the lowest nodal
constriction; on the right of the pith-cast the broad band of wood is faintly
indicated by the smooth surface of the rock (x). Other examples
demonstrating the existence of a broad woody cylinder in Calamitina stems
have been figured by Weiss[776] and other writers, and some good examples
may be seen in the British Museum.
foliage and habit of Asterophyllites equisetiformis. The specimen on which
this drawing is based is in the Natural History Museum, Paris; it shows
Asterophyllitean branches in organic connection with a Calamitean stem,
but it is not quite clear if the stem is a true Calamitina. A large drawing of
this interesting specimen is given by Stur[769] in his monograph on
Calamites, also a smaller sketch by Renault[770] in his Cours de botanique
fossile. Similar branches of the Asterophyllites type attached to an
undoubted Calamitina are figured also by Lindley and Hutton. There is, in
short, good evidence that stems of this sub-genus bore branches with
Asterophyllitean shoots.
The wood of stems of the Calamitina group of Calamites, in some
instances at least, was of the Arthropitys type; this has been shown to be the
case in some French specimens from the Commentry coal-field[771] and in
others described by Stur[772]. The pith-casts of Calamitina are characterised
by comparatively short internodes separated by deep nodal constrictions, as
shown in fig. 100. From Permian specimens from Neu Paka in Bohemia,
described by Stur[773], we learn that there were the usual Calamite
diaphragms bridging across the wide pith-cavity at each node. Such a cast
as that shown in fig. 100 is often referred to as Calamites approximatus
Brongn.; the length of the internodes and the periodic occurrence of branch-
scars in the form of circular or oval depressions along a nodal line enable us
to recognise the Calamitina casts. Weiss[774] points out that in pith-casts of
this form the branch-scars occur on the nodal constriction, and not
immediately above the node as is the case on the surface of a typical
Calamitina. This distinction is however of little or no value; the point of
attachment of a branch may be above the nodal line, while on the pith-cast
of the same stem the point of origin of the vascular bundles of the branch is
on the nodal constriction[775].
The specimen shown in fig. 100 illustrates the appearance of a
Calamitina cast. There is a verticil of branch-scars on the lowest nodal
constriction; on the right of the pith-cast the broad band of wood is faintly
indicated by the smooth surface of the rock (x). Other examples
demonstrating the existence of a broad woody cylinder in Calamitina stems
have been figured by Weiss[776] and other writers, and some good examples
may be seen in the British Museum.
Page 383
Fig. 100. Calamites (Calamitina) approximatus Brongn. Lower Coal-Measures of Ayrshire.
x, impression of the wood.
(From a specimen in the collection of Mr R. Kidston.)
We have so far noticed the connection of certain forms of pith-casts (e.g.
Calamites approximatus), and Asterophyllitean shoots with stems of the
sub-genus Calamitina.
As regards the strobili our knowledge is far from satisfactory. Stur[777]
figures some fertile branches bearing long and narrow strobili, either
Palaeostachya or Calamostachys, in close association with Calamitina
stems, and Renault and Zeiller[778] give illustrations of the association of
Calamitina stems with large strobili of the Macrostachya form.
x, impression of the wood.
(From a specimen in the collection of Mr R. Kidston.)
We have so far noticed the connection of certain forms of pith-casts (e.g.
Calamites approximatus), and Asterophyllitean shoots with stems of the
sub-genus Calamitina.
As regards the strobili our knowledge is far from satisfactory. Stur[777]
figures some fertile branches bearing long and narrow strobili, either
Palaeostachya or Calamostachys, in close association with Calamitina
stems, and Renault and Zeiller[778] give illustrations of the association of
Calamitina stems with large strobili of the Macrostachya form.
Page 384
Before Weiss proposed the term Calamitina, various authors had figured
this form of Calamite under a distinct generic name (e.g. Hippurites of
Lindley and Hutton[779], Cyclocladia[780], Macrostachya[781], &c.). Stems of
this type have also been described by more recent writers under different
names, and considerable confusion has been caused by the use of numerous
generic designations for forms of Calamitina. Some small fragments of
Calamitina stems were described by Salter[782] in 1863 as portions of a new
species of the Crustacean Eurypterus (E. mammatus). In 1869 Grand’Eury
proposed the generic name Calamophyllites[783] for stems bearing verticils
of Asterophyllites shoots; his description of such stems agrees with Weiss’
Calamitina, but as Grand’Eury’s name is used in a narrower sense as
implying a connection with Asterophyllites, it is more convenient to adopt
Weiss’ term in spite of the priority of Calamophyllites. In the Fossil flora of
Commentry we find some flattened stems of the Calamitina type described
under different generic names, as Arthropitys approximatus[784] and as
Macrostachya[785].
The determination of distinct species of the sub-genus Calamitina is
rendered almost hopeless by the variation in the different branches of the
same individual, and by the difficulty of connecting surface-impressions
with casts of the pith-cavity.
A typical example of the Calamitina type of Calamites was figured by
Sternberg[786] in 1821 as Calamites varians. This has been adopted by
Weiss[787] as a comprehensive species including several different ‘forms’ of
stems, which differ from Sternberg’s fossil in such points as the number of
nodes between the branch-whorls and the number of branches in each
whorl. The result of this system of nomenclature is the separation of
portions of one specific type under different form-names. It must be clearly
recognised that accurate specific diagnoses are practically impossible when
we have to deal with fragments of plants, some of which are mere pith-
casts, while others show the surface features. The specimen represented in
fig. 99 agrees with a stem described by Ettingshausen[788] in 1855 as
Calamites Göpperti, and as a matter of convenience a member of the
Calamitina group showing such characters may be referred to as Calamites
(Calamitina) Göpperti (Ett.). The following list, which includes a few
synonyms of this form, may suffice to illustrate the difficulties connected
with accurate systematic determinations.
this form of Calamite under a distinct generic name (e.g. Hippurites of
Lindley and Hutton[779], Cyclocladia[780], Macrostachya[781], &c.). Stems of
this type have also been described by more recent writers under different
names, and considerable confusion has been caused by the use of numerous
generic designations for forms of Calamitina. Some small fragments of
Calamitina stems were described by Salter[782] in 1863 as portions of a new
species of the Crustacean Eurypterus (E. mammatus). In 1869 Grand’Eury
proposed the generic name Calamophyllites[783] for stems bearing verticils
of Asterophyllites shoots; his description of such stems agrees with Weiss’
Calamitina, but as Grand’Eury’s name is used in a narrower sense as
implying a connection with Asterophyllites, it is more convenient to adopt
Weiss’ term in spite of the priority of Calamophyllites. In the Fossil flora of
Commentry we find some flattened stems of the Calamitina type described
under different generic names, as Arthropitys approximatus[784] and as
Macrostachya[785].
The determination of distinct species of the sub-genus Calamitina is
rendered almost hopeless by the variation in the different branches of the
same individual, and by the difficulty of connecting surface-impressions
with casts of the pith-cavity.
A typical example of the Calamitina type of Calamites was figured by
Sternberg[786] in 1821 as Calamites varians. This has been adopted by
Weiss[787] as a comprehensive species including several different ‘forms’ of
stems, which differ from Sternberg’s fossil in such points as the number of
nodes between the branch-whorls and the number of branches in each
whorl. The result of this system of nomenclature is the separation of
portions of one specific type under different form-names. It must be clearly
recognised that accurate specific diagnoses are practically impossible when
we have to deal with fragments of plants, some of which are mere pith-
casts, while others show the surface features. The specimen represented in
fig. 99 agrees with a stem described by Ettingshausen[788] in 1855 as
Calamites Göpperti, and as a matter of convenience a member of the
Calamitina group showing such characters may be referred to as Calamites
(Calamitina) Göpperti (Ett.). The following list, which includes a few
synonyms of this form, may suffice to illustrate the difficulties connected
with accurate systematic determinations.
Page 385
Calamites (Calamitina) Göpperti (Ett.). Fig. 99.
1855. Calamites Göpperti, Ettingshausen[789].
1869. Calamites (Calamophyllites) Göpperti, Grand’Eury[790].
1874. Cyclocladia major, Feistmantel[791].
1874. Calamites verticillatus, Williamson[792].
1876. Calamitina Göpperti, Weiss[793].
1884. Calamites (Calamitina) varians abbreviatus, Weiss[794].
1884. Calamites (Calamitina) varians inconstans, Weiss[795].
1887. Calamites Sachsei, Stur[796].
1888. Calamophyllites Göpperti, Zeiller[797].
This species is characterised by the smooth bark, which may be traversed
by a few irregular longitudinal fissures; most of the nodes bear a series of
small leaf-scars, and at fairly regular intervals a node is immediately
succeeded by a circle of contiguous branch-scars, 8–12 in a whorl. The pith-
cast of this type of stem has short ribbed internodes separated by rather
deep nodal constrictions; the branch-whorls being represented by a series of
pits on the nodal constrictions recurring at corresponding intervals to the
whorls of branch-scars on the surface of the stem. Leaves narrow and linear
in form, like those on Asterophyllitean branches, are occasionally
associated with this type of stem.
1855. Calamites Göpperti, Ettingshausen[789].
1869. Calamites (Calamophyllites) Göpperti, Grand’Eury[790].
1874. Cyclocladia major, Feistmantel[791].
1874. Calamites verticillatus, Williamson[792].
1876. Calamitina Göpperti, Weiss[793].
1884. Calamites (Calamitina) varians abbreviatus, Weiss[794].
1884. Calamites (Calamitina) varians inconstans, Weiss[795].
1887. Calamites Sachsei, Stur[796].
1888. Calamophyllites Göpperti, Zeiller[797].
This species is characterised by the smooth bark, which may be traversed
by a few irregular longitudinal fissures; most of the nodes bear a series of
small leaf-scars, and at fairly regular intervals a node is immediately
succeeded by a circle of contiguous branch-scars, 8–12 in a whorl. The pith-
cast of this type of stem has short ribbed internodes separated by rather
deep nodal constrictions; the branch-whorls being represented by a series of
pits on the nodal constrictions recurring at corresponding intervals to the
whorls of branch-scars on the surface of the stem. Leaves narrow and linear
in form, like those on Asterophyllitean branches, are occasionally
associated with this type of stem.
Page 386
Fig. 101. Calamites (Calamitina) sp. From a specimen in the British Museum. (After
Carruthers.) Slightly reduced.
The fragment of a Calamitina stem shown in fig. 101 is the counterpart
of a specimen originally figured by Steinhauer[798] in 1818 as a species of
Phytolithus. This may be specifically identical with C. Göpperti; but it is
better to speak of so small a specimen as merely one of the Calamitina
stems, to be compared with Calamites (Calamitina) Göpperti. The
specimen measures 14·5 cm. in length and 7 cm. in breadth.
The form of pith-cast represented in fig. 100 is no doubt that of one of
the Calamitina species, but as it is seldom possible to determine the
connection between such casts and the particular species of stems to which
they belong, they are often referred to as Calamites (Calamitina)
approximatus (Brongn.). The specimen of which fig. 100 is a photograph
was originally described and figured by Mr Kidston[799] from the lower
Coal-Measures of Ayrshire. Both Calamites (Calamitina) Göpperti (Ett.)
Carruthers.) Slightly reduced.
The fragment of a Calamitina stem shown in fig. 101 is the counterpart
of a specimen originally figured by Steinhauer[798] in 1818 as a species of
Phytolithus. This may be specifically identical with C. Göpperti; but it is
better to speak of so small a specimen as merely one of the Calamitina
stems, to be compared with Calamites (Calamitina) Göpperti. The
specimen measures 14·5 cm. in length and 7 cm. in breadth.
The form of pith-cast represented in fig. 100 is no doubt that of one of
the Calamitina species, but as it is seldom possible to determine the
connection between such casts and the particular species of stems to which
they belong, they are often referred to as Calamites (Calamitina)
approximatus (Brongn.). The specimen of which fig. 100 is a photograph
was originally described and figured by Mr Kidston[799] from the lower
Coal-Measures of Ayrshire. Both Calamites (Calamitina) Göpperti (Ett.)
Page 387
and C. (Calamitina) approximatus (Brongn.) are recorded from the
Transition, Middle and Lower Coal-Measures[800].
B. Stylocalamites.
In the members of this sub-genus the branch-scars are either irregular in
their occurrence or absent. In some Calamites the branch-scars are very few
and far between, and other species appear to have been almost without
branches; pith-casts of such stems may be referred to the sub-genus
Stylocalamites[801].
An exceedingly common Calamitean cast, C. Suckowi Brongn. (fig. 82)
affords a good illustration of this type of stem. In the specimen shown in
fig. 82 we have a cast of a rhizome, which is rather exceptional in showing
three branches in connection with one another. The appearance of the fossil
suggests a rhizome, rather than an aerial shoot, bearing lateral branches; the
narrowing of the branches and the rapid decrease in the length of the
internodes towards the point of attachment being features associated with
rhizomes rather than with aerial branches.
Calamites (Stylocalamites) Suckowi, Brongn. Fig. 82.
1818. Phytolithus sulcatus, Steinhauer[802].
1825. Calamites decoratus, Artis[803].
1828. Calamites Suckowi, Brongniart[804].
1833. Calamites cannaeformis, Lindley and Hutton[805].
For more complete lists of synonyms of this species reference should be
made to Kidston[806], Zeiller[807], and other authors.
Casts of Calamites Suckowi are characterised by flat or slightly convex
internodal ridges separated by shallow depressions, the ridges are rounded
at the upper end of each internode, and usually bear circular casts of
infranodal canals. There are some unusually large examples of casts of this
species in the British Museum from the Radstock Coal-Measures; one of
these has a length of 81 cm., and a diameter of 27 cm. Specimens are not
infrequently found with verticils of slender roots in close proximity to the
nodes of the cast; figures of such root-bearing casts have been given by
Lindley and Hutton[808], Weiss[809], and other authors.
Transition, Middle and Lower Coal-Measures[800].
B. Stylocalamites.
In the members of this sub-genus the branch-scars are either irregular in
their occurrence or absent. In some Calamites the branch-scars are very few
and far between, and other species appear to have been almost without
branches; pith-casts of such stems may be referred to the sub-genus
Stylocalamites[801].
An exceedingly common Calamitean cast, C. Suckowi Brongn. (fig. 82)
affords a good illustration of this type of stem. In the specimen shown in
fig. 82 we have a cast of a rhizome, which is rather exceptional in showing
three branches in connection with one another. The appearance of the fossil
suggests a rhizome, rather than an aerial shoot, bearing lateral branches; the
narrowing of the branches and the rapid decrease in the length of the
internodes towards the point of attachment being features associated with
rhizomes rather than with aerial branches.
Calamites (Stylocalamites) Suckowi, Brongn. Fig. 82.
1818. Phytolithus sulcatus, Steinhauer[802].
1825. Calamites decoratus, Artis[803].
1828. Calamites Suckowi, Brongniart[804].
1833. Calamites cannaeformis, Lindley and Hutton[805].
For more complete lists of synonyms of this species reference should be
made to Kidston[806], Zeiller[807], and other authors.
Casts of Calamites Suckowi are characterised by flat or slightly convex
internodal ridges separated by shallow depressions, the ridges are rounded
at the upper end of each internode, and usually bear circular casts of
infranodal canals. There are some unusually large examples of casts of this
species in the British Museum from the Radstock Coal-Measures; one of
these has a length of 81 cm., and a diameter of 27 cm. Specimens are not
infrequently found with verticils of slender roots in close proximity to the
nodes of the cast; figures of such root-bearing casts have been given by
Lindley and Hutton[808], Weiss[809], and other authors.
Page 388
Renault[810] has drawn attention to the thinness of the layer of wood which
is often associated with large casts of C. Suckowi; he concludes that the
stems must have possessed little or no secondary wood. In a more recent
work by Grand’Eury[811] Calamites Suckowi is spoken of as having had
wood of the Calamodendron type, but as wood of this kind has not been
found in England, it is suggested that the plant may not have assumed an
arborescent habit until late in the Coal-Measure period. During the Lower
and Middle Coal-Measures, at which horizon it commonly occurs in
England, it may have been herbaceous. This suggestion has little to
commend it; the close agreement between C. Suckowi from English and
French localities points to a plant of the same form, and we have no
satisfactory evidence as to any difference in stem-structure in the two cases.
Stur has figured a specimen of a Calamite cast, which he compares with
C. Suckowi, surrounded by a band of silicified wood apparently of the
Arthropitys type. From this and other facts it would appear probable that
some of the English stems with the Arthropitys structure possessed casts
referable to Calamites (Stylocalamites) Suckowi.
We are not in a position to speak with confidence as to the strobili of C.
Suckowi, but Stur adduces evidence in support of a connection between this
species of Calamite and certain Asterophyllitean branches (Calamocladus
equisetiformis) bearing Calamostachyan cones. He does not appear to have
found the foliage-shoots and stems in organic contact, but draws this
conclusion from the association of the fertile branches and stems in the
same rocks[812]. This species is abundant in the Lower, Middle and Upper
Coal-Measures; it has also been recorded from the Millstone Grit[813].
C. Eucalamites.
In this sub-genus branch-scars occur on every node; the scars never form
a contiguous whorl as in Calamitina, but there may be from 3 to 10 on each
node. The scars of successive nodes often alternate in position, and thus
form more or less regular vertical series as shown in fig. 102. The most
obvious feature as regards the arrangement of the branch-scars is their spiral
disposition on the surface of the pith-cast. The internodes are fairly uniform
in length, and there is no periodic recurrence of narrower internodes as in
Calamitina. From an examination of specimens of Eucalamites in which the
pith-cast is covered with a coaly layer representing the carbonised remains
is often associated with large casts of C. Suckowi; he concludes that the
stems must have possessed little or no secondary wood. In a more recent
work by Grand’Eury[811] Calamites Suckowi is spoken of as having had
wood of the Calamodendron type, but as wood of this kind has not been
found in England, it is suggested that the plant may not have assumed an
arborescent habit until late in the Coal-Measure period. During the Lower
and Middle Coal-Measures, at which horizon it commonly occurs in
England, it may have been herbaceous. This suggestion has little to
commend it; the close agreement between C. Suckowi from English and
French localities points to a plant of the same form, and we have no
satisfactory evidence as to any difference in stem-structure in the two cases.
Stur has figured a specimen of a Calamite cast, which he compares with
C. Suckowi, surrounded by a band of silicified wood apparently of the
Arthropitys type. From this and other facts it would appear probable that
some of the English stems with the Arthropitys structure possessed casts
referable to Calamites (Stylocalamites) Suckowi.
We are not in a position to speak with confidence as to the strobili of C.
Suckowi, but Stur adduces evidence in support of a connection between this
species of Calamite and certain Asterophyllitean branches (Calamocladus
equisetiformis) bearing Calamostachyan cones. He does not appear to have
found the foliage-shoots and stems in organic contact, but draws this
conclusion from the association of the fertile branches and stems in the
same rocks[812]. This species is abundant in the Lower, Middle and Upper
Coal-Measures; it has also been recorded from the Millstone Grit[813].
C. Eucalamites.
In this sub-genus branch-scars occur on every node; the scars never form
a contiguous whorl as in Calamitina, but there may be from 3 to 10 on each
node. The scars of successive nodes often alternate in position, and thus
form more or less regular vertical series as shown in fig. 102. The most
obvious feature as regards the arrangement of the branch-scars is their spiral
disposition on the surface of the pith-cast. The internodes are fairly uniform
in length, and there is no periodic recurrence of narrower internodes as in
Calamitina. From an examination of specimens of Eucalamites in which the
pith-cast is covered with a coaly layer representing the carbonised remains
Page 389
of the wood and cortex, it would appear that the surface of the stems was
practically smooth. The coaly investment on Eucalamites casts varies
considerably in thickness[814]; it is very unsafe to make use of the thickness
of this layer as a test of the breadth of the wood in Calamitean stems. The
branch-scars as seen in a surface-view of a stem are situated a little above
the nodal lines, while depressions on the pith-casts occur in the slight nodal
constriction or immediately above it. Small leaf-scars have been described
as occurring on the nodes between the branch-scars in specimens showing
the surface features[815].
The species long known as Calamites cruciatus Sternb. is usually taken
as the type of the sub-genus Eucalamites. Weiss[816] has subdivided this
species into several ‘forms,’ which he bases on the number of branch-scars
on each node and on other characters; a more extended subdivision of C.
cruciatus has recently been made by Sterzel[817], who admits the
impossibility of separating the specific forms by means of the data at our
disposal, but for purposes of geological correlation he prefers to express
slight differences by means of definite ‘forms’ or varieties. The more
comprehensive use of the specific name cruciatus as adopted by Zeiller in
his Flore de Valenciennes[818] is, I believe, the better method to adopt. The
specimen shown in fig. 102 affords a good example of a typical Calamites
cruciatus, it was found in the Middle Coal-Measures near Barnsley,
Yorkshire.
practically smooth. The coaly investment on Eucalamites casts varies
considerably in thickness[814]; it is very unsafe to make use of the thickness
of this layer as a test of the breadth of the wood in Calamitean stems. The
branch-scars as seen in a surface-view of a stem are situated a little above
the nodal lines, while depressions on the pith-casts occur in the slight nodal
constriction or immediately above it. Small leaf-scars have been described
as occurring on the nodes between the branch-scars in specimens showing
the surface features[815].
The species long known as Calamites cruciatus Sternb. is usually taken
as the type of the sub-genus Eucalamites. Weiss[816] has subdivided this
species into several ‘forms,’ which he bases on the number of branch-scars
on each node and on other characters; a more extended subdivision of C.
cruciatus has recently been made by Sterzel[817], who admits the
impossibility of separating the specific forms by means of the data at our
disposal, but for purposes of geological correlation he prefers to express
slight differences by means of definite ‘forms’ or varieties. The more
comprehensive use of the specific name cruciatus as adopted by Zeiller in
his Flore de Valenciennes[818] is, I believe, the better method to adopt. The
specimen shown in fig. 102 affords a good example of a typical Calamites
cruciatus, it was found in the Middle Coal-Measures near Barnsley,
Yorkshire.
Page 390
Fig. 102. Calamites (Eucalamites) cruciatus, Sternb.
From a specimen in the Barnsley Museum, Yorkshire. ½ nat. size.
Calamites (Eucalamites) cruciatus (Sternb.). Fig. 102.
1826. Calamites cruciatus, Sternberg[819].
1828. Calamites cruciatus, Brongniart[820].
1831. Calamites alternans, Germar and Kaulfuss[821].
1837. Calamites approximatus, Lindley and Hutton[822].
1877. Calamodendrofloyos cruciatus, Grand’Eury[823].
1878. Calamodendron cruciatum, Zeiller[824].
1884. Calamites (Eucalamites) cruciatus ternarius, Weiss[825].
From a specimen in the Barnsley Museum, Yorkshire. ½ nat. size.
Calamites (Eucalamites) cruciatus (Sternb.). Fig. 102.
1826. Calamites cruciatus, Sternberg[819].
1828. Calamites cruciatus, Brongniart[820].
1831. Calamites alternans, Germar and Kaulfuss[821].
1837. Calamites approximatus, Lindley and Hutton[822].
1877. Calamodendrofloyos cruciatus, Grand’Eury[823].
1878. Calamodendron cruciatum, Zeiller[824].
1884. Calamites (Eucalamites) cruciatus ternarius, Weiss[825].
Page 391
1884. „ „ „ quaternarius, Weiss[825].
1884. „ „ „ genarius, Weiss[825].
1884. „ „ multiramis, Weiss[825].
1888. Calamites (Calamodendron) cruciatus, Zeiller[826].
This species occurs in the Upper, Middle and Lower Coal-Measures[827].
The casts of the cruciatus type have been found associated with wood
possessing the structural features of the sub-genus Calamodendron[828], but
our knowledge of the structure of the stem, and of the fertile branches of C.
cruciatus is very imperfect. A restoration of Calamites (Eucalamites)
cruciatus is given by Stur[829] in his classic work on the Calamites, but he
does not make quite clear the supposed connection with the stems and the
fertile shoots of the Asterophyllites type[830] which he describes. Another
member of the Eucalamites group, which is better known as regards its
foliage-shoots, is Calamites ramosus, a species first described by Artis[831]
in 1825. Stems of this species have been found in connection with the
branches and leaves of the Annularia[6] type, bearing Calamostachys[832]
cones. In all probability pith-casts included in the sub-genus Eucalamites
belonged to stems with foliage-shoots and probably also with cones of more
than one form.
NOMENCLATURE.
In the above account of a few common pith-casts it has been pointed out
that there is occasionally satisfactory evidence for connecting certain casts
with wood of a particular structure, and with sterile and fertile foliage-
shoots of a definite type. It is, however, impossible in many cases to
recognise with any certainty the leaf-bearing branches and strobili of the
different casts of Calamites; it is equally impossible to determine what type
of pith-cast or what type of foliage-shoots belongs to petrified stem-
fragments in which it is possible to investigate the microscopical features.
The scattered and piece-meal nature of the material on which our general
knowledge of Calamitean plants is based, necessitates a system of
nomenclature which is artificial and clumsy; but the apparent absurdity of
attaching different names to fragments, which we believe to be portions of
the same genus, is of convenience from the point of view of the geologist
and the systematist. As our material increases it will be possible to further
simplify the nomenclature for Calamarian plants, but it is unwise to allow
our desire for a simpler terminology to lead us into proposals which are
1884. „ „ „ genarius, Weiss[825].
1884. „ „ multiramis, Weiss[825].
1888. Calamites (Calamodendron) cruciatus, Zeiller[826].
This species occurs in the Upper, Middle and Lower Coal-Measures[827].
The casts of the cruciatus type have been found associated with wood
possessing the structural features of the sub-genus Calamodendron[828], but
our knowledge of the structure of the stem, and of the fertile branches of C.
cruciatus is very imperfect. A restoration of Calamites (Eucalamites)
cruciatus is given by Stur[829] in his classic work on the Calamites, but he
does not make quite clear the supposed connection with the stems and the
fertile shoots of the Asterophyllites type[830] which he describes. Another
member of the Eucalamites group, which is better known as regards its
foliage-shoots, is Calamites ramosus, a species first described by Artis[831]
in 1825. Stems of this species have been found in connection with the
branches and leaves of the Annularia[6] type, bearing Calamostachys[832]
cones. In all probability pith-casts included in the sub-genus Eucalamites
belonged to stems with foliage-shoots and probably also with cones of more
than one form.
NOMENCLATURE.
In the above account of a few common pith-casts it has been pointed out
that there is occasionally satisfactory evidence for connecting certain casts
with wood of a particular structure, and with sterile and fertile foliage-
shoots of a definite type. It is, however, impossible in many cases to
recognise with any certainty the leaf-bearing branches and strobili of the
different casts of Calamites; it is equally impossible to determine what type
of pith-cast or what type of foliage-shoots belongs to petrified stem-
fragments in which it is possible to investigate the microscopical features.
The scattered and piece-meal nature of the material on which our general
knowledge of Calamitean plants is based, necessitates a system of
nomenclature which is artificial and clumsy; but the apparent absurdity of
attaching different names to fragments, which we believe to be portions of
the same genus, is of convenience from the point of view of the geologist
and the systematist. As our material increases it will be possible to further
simplify the nomenclature for Calamarian plants, but it is unwise to allow
our desire for a simpler terminology to lead us into proposals which are
Page 392
based rather on suppositions than on established fact. If it were possible to
discriminate between pith-casts of stems having the different anatomical
characters designated by the three sub-genera, Arthropitys, Arthrodendron
and Calamodendron, the genus Calamites might be used in a much
narrower and probably more natural sense than that which we have adopted.
The tests made use of by some authors for separating pith-casts of
Calamodendron and Arthropitys stems do not appear to be satisfactory; we
want some term to apply to all Calamitean casts irrespective of the
anatomical features of the stems, or of the precise nature of the foliage-
branches. As used in the present chapter, Calamites stands for plants
differing in certain features but possessing common structural characters,
which must be defined in a broad sense so as to include types which may be
worthy of generic rank, but which for convenience sake are included in a
comprehensive generic name. The attempts to associate certain forms of
foliage with Arthropitys on the one hand and with Calamodendron on the
other, cannot be said to be entirely satisfactory; we still lack data for a
trustworthy diagnosis of distinct Calamarian genera which shall include
external characters as well as histological features. If we restricted the
genus Calamites to stems with an Arthropitys structure and an
Asterophyllitean foliage, we should be driven into unavoidable error.
Within certain limits it is possible to distinguish generically or even
specifically between petrified branches, and we already possess material
enough for fairly complete diagnoses founded on internal structure; but it is
not possible to make a parallel classification for pith-casts and foliage-
shoots. For this reason, and especially bearing in mind the importance of
naming isolated foliage-shoots and stem-casts for geological purposes, I
believe it is better to admit the artificially wide application of the name
Calamites, and to express more accurate knowledge, where possible, by the
addition of a subgeneric term. In dealing with distinctions exhibited by
Calamitean stems it may be advisable to make use of specific names, but
we must keep before us the probability of the pith-cast and petrified stem-
fragment of the same plant receiving different specific names. If the
structural type is designated by a special sub-genus, this will tend to
minimise the anomaly of using more than one binominal designation for
what may be the same individual.
CALAMITES AND EQUISETUM.
discriminate between pith-casts of stems having the different anatomical
characters designated by the three sub-genera, Arthropitys, Arthrodendron
and Calamodendron, the genus Calamites might be used in a much
narrower and probably more natural sense than that which we have adopted.
The tests made use of by some authors for separating pith-casts of
Calamodendron and Arthropitys stems do not appear to be satisfactory; we
want some term to apply to all Calamitean casts irrespective of the
anatomical features of the stems, or of the precise nature of the foliage-
branches. As used in the present chapter, Calamites stands for plants
differing in certain features but possessing common structural characters,
which must be defined in a broad sense so as to include types which may be
worthy of generic rank, but which for convenience sake are included in a
comprehensive generic name. The attempts to associate certain forms of
foliage with Arthropitys on the one hand and with Calamodendron on the
other, cannot be said to be entirely satisfactory; we still lack data for a
trustworthy diagnosis of distinct Calamarian genera which shall include
external characters as well as histological features. If we restricted the
genus Calamites to stems with an Arthropitys structure and an
Asterophyllitean foliage, we should be driven into unavoidable error.
Within certain limits it is possible to distinguish generically or even
specifically between petrified branches, and we already possess material
enough for fairly complete diagnoses founded on internal structure; but it is
not possible to make a parallel classification for pith-casts and foliage-
shoots. For this reason, and especially bearing in mind the importance of
naming isolated foliage-shoots and stem-casts for geological purposes, I
believe it is better to admit the artificially wide application of the name
Calamites, and to express more accurate knowledge, where possible, by the
addition of a subgeneric term. In dealing with distinctions exhibited by
Calamitean stems it may be advisable to make use of specific names, but
we must keep before us the probability of the pith-cast and petrified stem-
fragment of the same plant receiving different specific names. If the
structural type is designated by a special sub-genus, this will tend to
minimise the anomaly of using more than one binominal designation for
what may be the same individual.
CALAMITES AND EQUISETUM.
Page 393
The following summary may serve to bring together the different generic
and subgeneric terms which have been used in the foregoing account of
Calamites.
CALAMITES.
Subgenera having reference to Subgenera founded on Genus proposed for roots of
the method of branching as seen anatomical characters in Calamites before their real
in casts or impressions of the stems and branches. nature was recognised. The
stem-surface or in pith-casts. Arthropitys, name refers to anatomical
Calamitina, Calamodendron, characters.
Eucalamites, Arthrodendron (new Astromyelon.
Stylocalamites. sub-genus substituted
for Calamopitys).
Genera of which some species, Generic names applied Genus including
if not all, are the leaf-bearing to strobili belonging to impressions of Calamite roots.
branches of Calamites. Calamites. Pinnularia.
Calamocladus (including Calamostachys,
Asterophyllites), Palaeostachya,
Annularia. Macrostachya,
etc.
IV. Conclusion.
A brief sketch of the main features of Calamites suffices to bring out the
many points of agreement between the arborescent Calamite plants and the
recent Equisetums. The slight variation in morphological character among
the present-day Horse-tails, contrasts with the greater range as regards
structural features among the types included in Calamites. The Horse-tails
probably represent one of several lines of development which tend to
converge in the Palaeozoic period; the Calamite itself would appear to mark
the culminating point of a certain phylum of which we have one degenerate
but closely allied descendant in the genus Equisetum. We shall, however, be
in a better position to consider the general question of plant-evolution after
we have made ourselves familiar with other types of Palaeozoic plants.
Grand’Eury’s[833] striking descriptions of forests of Calamites in the Coal-
Measures of central France, enable us to form some idea of the habit of
growth of these plants with their stout branching rhizomes and erect aerial
shoots.
By piecing together the evidence derived from different sources we may
form some idea of the appearance of a living Calamite. A stout branching
and subgeneric terms which have been used in the foregoing account of
Calamites.
CALAMITES.
Subgenera having reference to Subgenera founded on Genus proposed for roots of
the method of branching as seen anatomical characters in Calamites before their real
in casts or impressions of the stems and branches. nature was recognised. The
stem-surface or in pith-casts. Arthropitys, name refers to anatomical
Calamitina, Calamodendron, characters.
Eucalamites, Arthrodendron (new Astromyelon.
Stylocalamites. sub-genus substituted
for Calamopitys).
Genera of which some species, Generic names applied Genus including
if not all, are the leaf-bearing to strobili belonging to impressions of Calamite roots.
branches of Calamites. Calamites. Pinnularia.
Calamocladus (including Calamostachys,
Asterophyllites), Palaeostachya,
Annularia. Macrostachya,
etc.
IV. Conclusion.
A brief sketch of the main features of Calamites suffices to bring out the
many points of agreement between the arborescent Calamite plants and the
recent Equisetums. The slight variation in morphological character among
the present-day Horse-tails, contrasts with the greater range as regards
structural features among the types included in Calamites. The Horse-tails
probably represent one of several lines of development which tend to
converge in the Palaeozoic period; the Calamite itself would appear to mark
the culminating point of a certain phylum of which we have one degenerate
but closely allied descendant in the genus Equisetum. We shall, however, be
in a better position to consider the general question of plant-evolution after
we have made ourselves familiar with other types of Palaeozoic plants.
Grand’Eury’s[833] striking descriptions of forests of Calamites in the Coal-
Measures of central France, enable us to form some idea of the habit of
growth of these plants with their stout branching rhizomes and erect aerial
shoots.
By piecing together the evidence derived from different sources we may
form some idea of the appearance of a living Calamite. A stout branching
Page 394
rhizome ascended obliquely or spread horizontally through sand or clay,
with numerous whorls or tufts of roots penetrating into swampy soil. From
the underground rhizome strong erect branches grew up as columnar stems
to a height of fifty feet or more; in the lower and thicker portions the bark
was fissured and somewhat rugged, but smoother nearer the summit.
Looking up the stem we should see old and partially obliterated scars
marking the position of a ring of lateral branches, and at a higher level tiers
of branches given off at regular or gradually decreasing intervals, bearing
on their upper portions graceful green branchlets with whorls of narrow
linear leaves. On the younger parts of the main shoot rings of long and
narrow leaves were borne at short intervals, several leaf-circles succeeding
one another in the intervals between each radiating series of branches. On
some of the leaf-bearing branchlets long and slender cones would be found
here and there taking the place of the ordinary leafy twigs. Passing to the
apical region of the stem the lateral branches given off at a less and less
angle would appear more crowded, and at the actual tips there would be a
crowded succession of leaf-segments forming a series of overlapping circles
of narrow sheaths with thin slender teeth bending over the apex of the tree.
Thus we may feebly attempt to picture to ourselves one of the many
types of Calamite trees in a Palaeozoic forest, growing in a swampy marsh
or on gently sloping ground on the shores of an inland sea, into which
running water carried its burden of sand and mud, and broken twigs of
Calamites and other trees which contributed to the Coal Period sediments.
The large proportions of a Calamite tree are strikingly illustrated by some of
the broad and long pith-casts occasionally seen in Museums; in the Breslau
Collection there is a cast of a stem belonging to the sub-genus Calamitina,
which measures about 2 m. in length and 23 cm. in breadth, with 36 nodes.
In the Natural History Museum, Paris, there is a cast nearly 2 metres long
and more than 20 cm. wide, which is referred to the sub-genus
Calamodendron.
E. Archaeocalamites.
In the Upper Devonian and Culm rocks casts of a well-defined
Calamitean plant are characteristic fossils; stems, leaf-bearing branches,
roots and cones have been described by several authors, and the genus
Archaeocalamites has been instituted for their reception. Although this
with numerous whorls or tufts of roots penetrating into swampy soil. From
the underground rhizome strong erect branches grew up as columnar stems
to a height of fifty feet or more; in the lower and thicker portions the bark
was fissured and somewhat rugged, but smoother nearer the summit.
Looking up the stem we should see old and partially obliterated scars
marking the position of a ring of lateral branches, and at a higher level tiers
of branches given off at regular or gradually decreasing intervals, bearing
on their upper portions graceful green branchlets with whorls of narrow
linear leaves. On the younger parts of the main shoot rings of long and
narrow leaves were borne at short intervals, several leaf-circles succeeding
one another in the intervals between each radiating series of branches. On
some of the leaf-bearing branchlets long and slender cones would be found
here and there taking the place of the ordinary leafy twigs. Passing to the
apical region of the stem the lateral branches given off at a less and less
angle would appear more crowded, and at the actual tips there would be a
crowded succession of leaf-segments forming a series of overlapping circles
of narrow sheaths with thin slender teeth bending over the apex of the tree.
Thus we may feebly attempt to picture to ourselves one of the many
types of Calamite trees in a Palaeozoic forest, growing in a swampy marsh
or on gently sloping ground on the shores of an inland sea, into which
running water carried its burden of sand and mud, and broken twigs of
Calamites and other trees which contributed to the Coal Period sediments.
The large proportions of a Calamite tree are strikingly illustrated by some of
the broad and long pith-casts occasionally seen in Museums; in the Breslau
Collection there is a cast of a stem belonging to the sub-genus Calamitina,
which measures about 2 m. in length and 23 cm. in breadth, with 36 nodes.
In the Natural History Museum, Paris, there is a cast nearly 2 metres long
and more than 20 cm. wide, which is referred to the sub-genus
Calamodendron.
E. Archaeocalamites.
In the Upper Devonian and Culm rocks casts of a well-defined
Calamitean plant are characteristic fossils; stems, leaf-bearing branches,
roots and cones have been described by several authors, and the genus
Archaeocalamites has been instituted for their reception. Although this
Page 395
genus agrees in certain respects with Calamites, and as recent work has
shown this agreement extends to internal structure, it has been the custom to
regard the Lower Carboniferous and Devonian plants as genetically distinct.
The surface features of the stem-casts, the form of the leaves, and
apparently the cones, possess certain distinctive characters which would
seem to justify the retention of a separate generic designation.
We may briefly summarise the characteristics of the genus as follows:—
Pith-casts articulated, with very slightly constricted nodes; the internodes
traversed by longitudinal ribs slightly elevated or almost flat, separated by
shallow grooves. The ribs and grooves are continuous from one internode to
another, and do not usually show the characteristic alternation of
Calamites[834]. Along the nodal line there are occasionally found short
longitudinal depressions, probably marking the points of origin of outgoing
bundles. Branches were given off from the nodes without any regular order;
a pith-cast may have branch-scars on many of the nodes, or there may be no
trace of branches on casts consisting of several nodes. The leaves[835] are in
whorls; in some cases they occur as free, linear, lanceolate leaves, or on
younger branches they are long, filiform and repeatedly forked. The
structure of the wood agrees with that of some forms of Arthropitys. The
strobili consist of an articulated axis bearing whorls of sporangiophores,
and each sporangiophore has four sporangia. Our knowledge of the fertile
shoots is, however, very imperfect.
Renault[836] has recently described the structure of the wood in some
small silicified stems of Archaeocalamites from Autun. A large hollow pith
is surrounded by a cylinder of wood consisting of wedge-shaped groups of
xylem tracheids associated with secondary medullary rays; at the apex of
each primary xylem group there is a carinal canal. The primary medullary
rays appear to have been bridged across by bands of xylem at an early stage
of secondary thickening, as in the Calamite of fig. 83, D.
Our knowledge of the cones of Archaeocalamites is far from satisfactory.
Renault[837] has recently described a small fertile branch bearing a
succession of verticils of sporangiophores; each sporangiophore stands at
right angles to the axis of the cone and bears four sporangia, as in
Calamostachys. It is not clear how far there is better evidence than that
afforded by the association of the specimen with pith-casts of stems, for
shown this agreement extends to internal structure, it has been the custom to
regard the Lower Carboniferous and Devonian plants as genetically distinct.
The surface features of the stem-casts, the form of the leaves, and
apparently the cones, possess certain distinctive characters which would
seem to justify the retention of a separate generic designation.
We may briefly summarise the characteristics of the genus as follows:—
Pith-casts articulated, with very slightly constricted nodes; the internodes
traversed by longitudinal ribs slightly elevated or almost flat, separated by
shallow grooves. The ribs and grooves are continuous from one internode to
another, and do not usually show the characteristic alternation of
Calamites[834]. Along the nodal line there are occasionally found short
longitudinal depressions, probably marking the points of origin of outgoing
bundles. Branches were given off from the nodes without any regular order;
a pith-cast may have branch-scars on many of the nodes, or there may be no
trace of branches on casts consisting of several nodes. The leaves[835] are in
whorls; in some cases they occur as free, linear, lanceolate leaves, or on
younger branches they are long, filiform and repeatedly forked. The
structure of the wood agrees with that of some forms of Arthropitys. The
strobili consist of an articulated axis bearing whorls of sporangiophores,
and each sporangiophore has four sporangia. Our knowledge of the fertile
shoots is, however, very imperfect.
Renault[836] has recently described the structure of the wood in some
small silicified stems of Archaeocalamites from Autun. A large hollow pith
is surrounded by a cylinder of wood consisting of wedge-shaped groups of
xylem tracheids associated with secondary medullary rays; at the apex of
each primary xylem group there is a carinal canal. The primary medullary
rays appear to have been bridged across by bands of xylem at an early stage
of secondary thickening, as in the Calamite of fig. 83, D.
Our knowledge of the cones of Archaeocalamites is far from satisfactory.
Renault[837] has recently described a small fertile branch bearing a
succession of verticils of sporangiophores; each sporangiophore stands at
right angles to the axis of the cone and bears four sporangia, as in
Calamostachys. It is not clear how far there is better evidence than that
afforded by the association of the specimen with pith-casts of stems, for
Page 396
referring this cone to Archaeocalamites, but the
association of vegetative and fertile shoots
certainly suggests an organic connection. The
cone described by the French author agrees with
Equisetum in the absence of sterile bracts
between the whorls of sporangiophores. It is an
interesting fact that such a distinctly
Equisetaceous strobilus is known to have
existed in Lower Carboniferous rocks.
Stur[838] has also described Archaeocalamites
at considerable length; he gives several good
figures of stem-casts and foliage-shoots bearing
long and often forked narrow leaves. The same
writer describes specimens of imperfectly
preserved cones in which portions of whorls of
forked filiform leaves are given off from the
base of the strobilus[839]. Kidston[840] published
an important memoir on the cones of
Archaeocalamites in 1883, in which he
advanced good evidence in support of the view
that certain strobili, which were originally
described as Monocotyledonous inflorescences,
under the generic name Pothocites[841], are the
fertile shoots of this Calamarian genus.
Kidston’s conclusions are based on the
occurrence on the Pothocites cones, of leaves
like those of Archaeocalamites, on the non-
alternation of the sporangiophores of successive
whorls, and on the close resemblance between Figscrobiculatus
. 103. Archaeocalamites
(Schloth.).
his specimens and those described by Stur. From a specimen in the
Good specimens of the cones, formerly known Woodwardian Museum,
as Pothocites, may be seen in the Botanical Carboniferous limestone the
Cambridge. From
of
Museum in the Royal Gardens, Edinburgh; as Northumberland. ½ nat. size.
they are in the form of casts without internal
structure it is difficult to form a clear conception as to their morphological
features.
association of vegetative and fertile shoots
certainly suggests an organic connection. The
cone described by the French author agrees with
Equisetum in the absence of sterile bracts
between the whorls of sporangiophores. It is an
interesting fact that such a distinctly
Equisetaceous strobilus is known to have
existed in Lower Carboniferous rocks.
Stur[838] has also described Archaeocalamites
at considerable length; he gives several good
figures of stem-casts and foliage-shoots bearing
long and often forked narrow leaves. The same
writer describes specimens of imperfectly
preserved cones in which portions of whorls of
forked filiform leaves are given off from the
base of the strobilus[839]. Kidston[840] published
an important memoir on the cones of
Archaeocalamites in 1883, in which he
advanced good evidence in support of the view
that certain strobili, which were originally
described as Monocotyledonous inflorescences,
under the generic name Pothocites[841], are the
fertile shoots of this Calamarian genus.
Kidston’s conclusions are based on the
occurrence on the Pothocites cones, of leaves
like those of Archaeocalamites, on the non-
alternation of the sporangiophores of successive
whorls, and on the close resemblance between Figscrobiculatus
. 103. Archaeocalamites
(Schloth.).
his specimens and those described by Stur. From a specimen in the
Good specimens of the cones, formerly known Woodwardian Museum,
as Pothocites, may be seen in the Botanical Carboniferous limestone the
Cambridge. From
of
Museum in the Royal Gardens, Edinburgh; as Northumberland. ½ nat. size.
they are in the form of casts without internal
structure it is difficult to form a clear conception as to their morphological
features.
Page 397
The fossils included under Archaeocalamites have been referred by
different authors to various genera, and considerable confusion has arisen in
both generic and specific nomenclature. The following synonomy of the
best known species, A. scrobiculatus (Schloth.) illustrates the unfortunate
use of several terms for the same plant.
Archaeocalamites scrobiculatus (Schloth.). Fig. 103.
1720. Lithoxylon, Volkmann[842].
1820. Calamites scrobiculatus, Schlotheim[843].
1825. Bornia scrobiculata, Sternberg[844].
1828. Calamites radiatus, Brongniart[845].
1841. Pothocites Grantoni, Paterson[846].
1852. Calamites transitionis, Göppert[847].
—— Stigmatocanna Volkmanniana, ibid.
—— Anarthrocanna tuberculata, ibid.
—— Calamites variolatus, ibid.
—— C. obliquus, ibid.
—— C. tenuissimus, ibid.
—— Asterophyllites elegans, ibid.
1866. Calamites laticulatus, Ettingshausen[848].
—— Equisetites Göpperti, ibid.
—— Sphenophyllum furcatum, ibid.
1873. Asterophyllites spaniophyllus, Feistmantel[849].
1880. Asterocalamites scrobiculatus, Zeiller[850].
For other lists of synonyms reference may be made to Binney[851],
Stur[852], Kidston[853] and other authors.
Some of the best specimens of this species are to be seen in the Museums
of Breslau and Vienna, which contain the original examples described by
Göppert and Stur. An examination of the original specimens, figured by
Göppert under various names, enables one to refer them with confidence to
the single species, Archaeocalamites scrobiculatus. The generic name
Archaeocalamites, which has been employed by some authors, was
suggested by Schimper[854] in 1862, as a subgenus of Calamites, on account
different authors to various genera, and considerable confusion has arisen in
both generic and specific nomenclature. The following synonomy of the
best known species, A. scrobiculatus (Schloth.) illustrates the unfortunate
use of several terms for the same plant.
Archaeocalamites scrobiculatus (Schloth.). Fig. 103.
1720. Lithoxylon, Volkmann[842].
1820. Calamites scrobiculatus, Schlotheim[843].
1825. Bornia scrobiculata, Sternberg[844].
1828. Calamites radiatus, Brongniart[845].
1841. Pothocites Grantoni, Paterson[846].
1852. Calamites transitionis, Göppert[847].
—— Stigmatocanna Volkmanniana, ibid.
—— Anarthrocanna tuberculata, ibid.
—— Calamites variolatus, ibid.
—— C. obliquus, ibid.
—— C. tenuissimus, ibid.
—— Asterophyllites elegans, ibid.
1866. Calamites laticulatus, Ettingshausen[848].
—— Equisetites Göpperti, ibid.
—— Sphenophyllum furcatum, ibid.
1873. Asterophyllites spaniophyllus, Feistmantel[849].
1880. Asterocalamites scrobiculatus, Zeiller[850].
For other lists of synonyms reference may be made to Binney[851],
Stur[852], Kidston[853] and other authors.
Some of the best specimens of this species are to be seen in the Museums
of Breslau and Vienna, which contain the original examples described by
Göppert and Stur. An examination of the original specimens, figured by
Göppert under various names, enables one to refer them with confidence to
the single species, Archaeocalamites scrobiculatus. The generic name
Archaeocalamites, which has been employed by some authors, was
suggested by Schimper[854] in 1862, as a subgenus of Calamites, on account
Page 398
of the occurrence of a deeply divided leaf-sheath, attached to the node of a
pith-cast, which seemed to differ from the usual type of Calamitean leaf.
The specimens described by Schimper are in the Strassburg Museum; the
leaf-sheath which he figures is not very accurately represented.
The example given in fig. 103 shews very clearly the continuous course
of the ribs and grooves of the pith-cast. Each rib is traversed by a narrow
median groove which would seem to represent the projecting edge of some
hard tissue in the middle of each principal medullary ray of the stem. The
specimen was found in a Carboniferous limestone quarry, Northumberland;
there is a similar cast from the same locality in the Museum of the
Geological Survey.
Affinities of Archaeocalamites.
This genus agrees very closely with Calamites both in the anatomical
structure of the stem and in the verticillate disposition of the leaves. The
strobili appear to be Equisetaceous in character, and there is no satisfactory
evidence of the existence of whorls of sterile bracts in the cone, such as
occur in Calamostachys and in other Calamitean strobili. The continuous
course of the vascular bundles of the stem from one internode to the next is
the most striking feature in the ordinary specimens of the genus; but it
sometimes happens that the grooves on a pith-cast shew the same
alternation at the node as in Calamites. This is the case in a specimen in the
Göppert collection in the Breslau Museum, and Feistmantel[855] has called
attention to such an alternation in specimens from Rothwaltersdorf. In the
true Calamites, on the other hand, the usual nodal alternation of the
vascular strands is by no means a constant character[856]. Stur[857],
Rothpletz[858], and other authors have pointed out the resemblance of
Archaeocalamites to Sphenophyllum. The deeply divided leaves of some
Sphenophyllums and those of Archaeocalamites are very similar in form;
and the course of the vascular strands in Sphenophyllum may be compared
with that in Archaeocalamites. But the striking difference in the structure of
the stele forms a wide gap between the two genera. We have evidence that
the Calamites and Sphenophyllums were probably descended from a
common ancestral stock, and it may be that in Archaeocalamites, some of
the Sphenophyllum characters have been retained; but there is no close
affinity between the two plants.
pith-cast, which seemed to differ from the usual type of Calamitean leaf.
The specimens described by Schimper are in the Strassburg Museum; the
leaf-sheath which he figures is not very accurately represented.
The example given in fig. 103 shews very clearly the continuous course
of the ribs and grooves of the pith-cast. Each rib is traversed by a narrow
median groove which would seem to represent the projecting edge of some
hard tissue in the middle of each principal medullary ray of the stem. The
specimen was found in a Carboniferous limestone quarry, Northumberland;
there is a similar cast from the same locality in the Museum of the
Geological Survey.
Affinities of Archaeocalamites.
This genus agrees very closely with Calamites both in the anatomical
structure of the stem and in the verticillate disposition of the leaves. The
strobili appear to be Equisetaceous in character, and there is no satisfactory
evidence of the existence of whorls of sterile bracts in the cone, such as
occur in Calamostachys and in other Calamitean strobili. The continuous
course of the vascular bundles of the stem from one internode to the next is
the most striking feature in the ordinary specimens of the genus; but it
sometimes happens that the grooves on a pith-cast shew the same
alternation at the node as in Calamites. This is the case in a specimen in the
Göppert collection in the Breslau Museum, and Feistmantel[855] has called
attention to such an alternation in specimens from Rothwaltersdorf. In the
true Calamites, on the other hand, the usual nodal alternation of the
vascular strands is by no means a constant character[856]. Stur[857],
Rothpletz[858], and other authors have pointed out the resemblance of
Archaeocalamites to Sphenophyllum. The deeply divided leaves of some
Sphenophyllums and those of Archaeocalamites are very similar in form;
and the course of the vascular strands in Sphenophyllum may be compared
with that in Archaeocalamites. But the striking difference in the structure of
the stele forms a wide gap between the two genera. We have evidence that
the Calamites and Sphenophyllums were probably descended from a
common ancestral stock, and it may be that in Archaeocalamites, some of
the Sphenophyllum characters have been retained; but there is no close
affinity between the two plants.
Page 399
On the whole, considering the age of Archaeocalamites and the few
characters with which we are acquainted, it is probable that this genus is
very closely related to the typical Calamites, and may be regarded as a type
which is in the direct line of development of the more modern Calamite and
the living Equisetum. Weiss[859] includes Archaeocalamites as one of his
subgenera with Calamitina and others, and it is quite possible that the genus
has not more claim to stand alone than other forms at present included in
the comprehensive genus Calamites.
The student will find detailed descriptions of this genus in the works
which have been referred to in the preceding pages.
characters with which we are acquainted, it is probable that this genus is
very closely related to the typical Calamites, and may be regarded as a type
which is in the direct line of development of the more modern Calamite and
the living Equisetum. Weiss[859] includes Archaeocalamites as one of his
subgenera with Calamitina and others, and it is quite possible that the genus
has not more claim to stand alone than other forms at present included in
the comprehensive genus Calamites.
The student will find detailed descriptions of this genus in the works
which have been referred to in the preceding pages.
Page 400
Page 401
CHAPTER XI.
II. SPHENOPHYLLALES.
I. SPHENOPHYLLUM.
The genus Sphenophyllum is placed in a special class, as representing a
type which cannot be legitimately included in any of the existing groups of
Vascular Cryptogams. Although this Palaeozoic genus possesses points of
contact with various living plants, it is generally admitted by
palaeobotanists that it constitutes a somewhat isolated type among the
Pteridophytes of the Coal-Measures. Our knowledge of the anatomy of both
vegetative shoots and strobili is now fairly complete, and the facts that we
possess are in favour of excluding the genus from any of the three main
divisions of the Pteridophyta.
In Scheuchzer’s Herbarium Diluvianum there is a careful drawing of
some fragments of slender twigs, from an English locality, bearing verticils
of cuneiform leaves, which the author compares with the common
Galium[860]. As regards superficial external resemblance, the Galium of our
hedgerows agrees very closely with what must have been the appearance of
fresh green shoots of Sphenophyllum.
A twig of the same species of Sphenophyllum is figured by
Schlotheim[861] in the first part of his work on fossil plants; he regards it as
probably a fragment of some species of Palm. Sternberg[862] was the first to
institute a generic name for this genus of plants, and specimens were
described by him in 1825 as a species of the genus Rotularia. The name
Sphenophyllites was proposed by Brongniart[863] in 1822 as a substitute for
Schlotheim’s genus, and in a later work[864] the French author instituted the
genus Sphenophyllum. Dawson[865] was the first to make any reference to the
anatomy of this genus; but it is from the examination of the much more
perfect material from St. Étienne, Autun, and other continental localities,
II. SPHENOPHYLLALES.
I. SPHENOPHYLLUM.
The genus Sphenophyllum is placed in a special class, as representing a
type which cannot be legitimately included in any of the existing groups of
Vascular Cryptogams. Although this Palaeozoic genus possesses points of
contact with various living plants, it is generally admitted by
palaeobotanists that it constitutes a somewhat isolated type among the
Pteridophytes of the Coal-Measures. Our knowledge of the anatomy of both
vegetative shoots and strobili is now fairly complete, and the facts that we
possess are in favour of excluding the genus from any of the three main
divisions of the Pteridophyta.
In Scheuchzer’s Herbarium Diluvianum there is a careful drawing of
some fragments of slender twigs, from an English locality, bearing verticils
of cuneiform leaves, which the author compares with the common
Galium[860]. As regards superficial external resemblance, the Galium of our
hedgerows agrees very closely with what must have been the appearance of
fresh green shoots of Sphenophyllum.
A twig of the same species of Sphenophyllum is figured by
Schlotheim[861] in the first part of his work on fossil plants; he regards it as
probably a fragment of some species of Palm. Sternberg[862] was the first to
institute a generic name for this genus of plants, and specimens were
described by him in 1825 as a species of the genus Rotularia. The name
Sphenophyllites was proposed by Brongniart[863] in 1822 as a substitute for
Schlotheim’s genus, and in a later work[864] the French author instituted the
genus Sphenophyllum. Dawson[865] was the first to make any reference to the
anatomy of this genus; but it is from the examination of the much more
perfect material from St. Étienne, Autun, and other continental localities,
Page 402
the North of England and Pettycur in Scotland, by Renault, Williamson,
Zeiller and Scott, that our more complete knowledge has been acquired.
The affinity of Sphenophyllum has always been a matter of speculation; it
has been compared with Dicotyledons, Palms, Conifers (Ginkgo and
Phyllocladus), and various Pteridophytes, such as Ophioglossum,
Tmesipteris, Marsilia, Salvinia, Equisetum and the Lycopodiaceae[866].
DEFINITION.
We may define the genus Sphenophyllum as follows:—
Stem comparatively slender (1·5–15 mm.?), articulated, usually
somewhat tumid at the nodes; the surface of the internodes is marked by
more or less distinct ribs and grooves which do not alternate at the nodes,
but follow a straight course from one internode to the next. A single branch
is occasionally given off from a node. Adventitious roots are very rarely
seen, their surface does not show the ridges and grooves of the foliage-
shoots.
The leaves are borne in verticils at the nodes, those in the same whorl
being usually of the same size, but in some forms two of the leaves are
distinctly smaller than the others. Each verticil contains normally 6, 9, 12,
18 or more leaves, which are separate to the base and not fused into a
sheath; the number of leaves in a verticil is not always a multiple of six.
They vary in form from cuneiform with a narrow tapered base, and a lamina
traversed by several forked veins, to narrow uninerved leaves and leaves
with a lamina dissected into dichotomously branched linear segments. The
leaves of successive whorls are superposed.
The strobili are long and narrow in form, having a length in some cases
of 12 cm., and a diameter of 12 mm.; they occur as shortly stalked lateral
branches, or terminate long leaf-bearing shoots. The axis of the cone bears
whorls of numerous linear lanceolate bracts fused basally into a coherent
funnel-shaped disc, bearing on its upper surface sporangiophores and
sporangia.
The strobili are usually isosporous, but possibly heterosporous in some
forms.
The stem is monostelic, with a triarch or hexarch triangular strand of
centripetally developed primary xylem, consisting of reticulate, scalariform
Zeiller and Scott, that our more complete knowledge has been acquired.
The affinity of Sphenophyllum has always been a matter of speculation; it
has been compared with Dicotyledons, Palms, Conifers (Ginkgo and
Phyllocladus), and various Pteridophytes, such as Ophioglossum,
Tmesipteris, Marsilia, Salvinia, Equisetum and the Lycopodiaceae[866].
DEFINITION.
We may define the genus Sphenophyllum as follows:—
Stem comparatively slender (1·5–15 mm.?), articulated, usually
somewhat tumid at the nodes; the surface of the internodes is marked by
more or less distinct ribs and grooves which do not alternate at the nodes,
but follow a straight course from one internode to the next. A single branch
is occasionally given off from a node. Adventitious roots are very rarely
seen, their surface does not show the ridges and grooves of the foliage-
shoots.
The leaves are borne in verticils at the nodes, those in the same whorl
being usually of the same size, but in some forms two of the leaves are
distinctly smaller than the others. Each verticil contains normally 6, 9, 12,
18 or more leaves, which are separate to the base and not fused into a
sheath; the number of leaves in a verticil is not always a multiple of six.
They vary in form from cuneiform with a narrow tapered base, and a lamina
traversed by several forked veins, to narrow uninerved leaves and leaves
with a lamina dissected into dichotomously branched linear segments. The
leaves of successive whorls are superposed.
The strobili are long and narrow in form, having a length in some cases
of 12 cm., and a diameter of 12 mm.; they occur as shortly stalked lateral
branches, or terminate long leaf-bearing shoots. The axis of the cone bears
whorls of numerous linear lanceolate bracts fused basally into a coherent
funnel-shaped disc, bearing on its upper surface sporangiophores and
sporangia.
The strobili are usually isosporous, but possibly heterosporous in some
forms.
The stem is monostelic, with a triarch or hexarch triangular strand of
centripetally developed primary xylem, consisting of reticulate, scalariform
Page 403
and spiral tracheae; the protoxylem elements being situated at the blunt
corners of the xylem-strand. Foliar bundles are given off, either singly or in
pairs, from each angle of the central primary strand. The secondary xylem
consists of radially disposed reticulate or scalariform tracheae, developed
from a cambium-layer. The phloem is made up of thin-walled elements,
including sieve-tubes and parenchyma. Both xylem and phloem include
secondary medullary rays of parenchymatous cells. The cortex consists in
part of fairly thick-walled elements; in older stems the greater part of the
cortical region is cut off by the development of deep-seated layers of
periderm.
The roots are apparently diarch in structure, with a lacunar and smooth
cortex.
• • • • •
The branch of Sphenophyllum emarginatum Brongn. given in fig. 109
shows the characteristic appearance of the genus as represented by this
well-known species which Brongniart figured in 1822. The Indian species
shown in fig. 111 illustrates the occurrence of unequal leaves in the same
whorl, and in fig. 110, B, we have a form of verticil in which the leaves are
deeply divided into filiform segments. A larger-leaved form is represented
by S. Thoni, Mahr. (fig. 110, A), a species occasionally met with in Permian
rocks.
No specimens of Sphenophyllum have so far been found attached to a
thick stem; they always occur as slender shoots, which sometimes reach a
considerable length. One of the longest examples known is in the collection
of the Austrian Geological Survey; the axis is 4 mm. in breadth and 85 cm.
long, bearing a slender branch 61 cm. in length. The manner of occurrence
of the specimen as a curved slender stem on the surface of the rock suggests
a weak plant, which must have depended for support on some external aid,
either water or another plant. The anatomical structure and other features do
not favour the suggestion of some writers that Sphenophyllum was a water-
plant[867], but there would seem to be no serious obstacle in the way of
regarding it as possibly a slender plant which flung itself on the branches
and stems of stronger forest trees for support.
A. The anatomy of Sphenophyllum.
corners of the xylem-strand. Foliar bundles are given off, either singly or in
pairs, from each angle of the central primary strand. The secondary xylem
consists of radially disposed reticulate or scalariform tracheae, developed
from a cambium-layer. The phloem is made up of thin-walled elements,
including sieve-tubes and parenchyma. Both xylem and phloem include
secondary medullary rays of parenchymatous cells. The cortex consists in
part of fairly thick-walled elements; in older stems the greater part of the
cortical region is cut off by the development of deep-seated layers of
periderm.
The roots are apparently diarch in structure, with a lacunar and smooth
cortex.
• • • • •
The branch of Sphenophyllum emarginatum Brongn. given in fig. 109
shows the characteristic appearance of the genus as represented by this
well-known species which Brongniart figured in 1822. The Indian species
shown in fig. 111 illustrates the occurrence of unequal leaves in the same
whorl, and in fig. 110, B, we have a form of verticil in which the leaves are
deeply divided into filiform segments. A larger-leaved form is represented
by S. Thoni, Mahr. (fig. 110, A), a species occasionally met with in Permian
rocks.
No specimens of Sphenophyllum have so far been found attached to a
thick stem; they always occur as slender shoots, which sometimes reach a
considerable length. One of the longest examples known is in the collection
of the Austrian Geological Survey; the axis is 4 mm. in breadth and 85 cm.
long, bearing a slender branch 61 cm. in length. The manner of occurrence
of the specimen as a curved slender stem on the surface of the rock suggests
a weak plant, which must have depended for support on some external aid,
either water or another plant. The anatomical structure and other features do
not favour the suggestion of some writers that Sphenophyllum was a water-
plant[867], but there would seem to be no serious obstacle in the way of
regarding it as possibly a slender plant which flung itself on the branches
and stems of stronger forest trees for support.
A. The anatomy of Sphenophyllum.
Page 404
The following account of the structural features of the stem and root is
based on the work of Renault[868], Williamson[869] and Williamson and
Scott[870]. We may first consider such characters as have been recognised in
different examples of the genus, and then notice briefly the distinguishing
peculiarities of two well-marked specific types.
a. Stems.
i. Primary structure.
In a transverse section of a young Sphenophyllum stem such as that
diagrammatically sketched in fig. 105, A, we find in the centre the xylem
portion of a single stele with a characteristic triangular form. The primary
xylem consists mainly of fairly large tracheae with numerous pits on their
walls; towards the end of each arm the tracheids become scalariform, and at
the apex there is a group of narrower spiral protoxylem elements. In the
British species there is a single protoxylem group at the apex of each arm,
but Renault has described some French stems in which the stele appears to
be hexarch, having two protoxylem groups at the end of each of the three
rays of the stele. The primary xylem strand of Sphenophyllum has therefore
a root-like structure, the tracheids having been developed centripetally from
the three initial protoxylem groups. This type of structure is typical of roots,
but it also occurs in the stems of some recent Vascular Cryptogams.
based on the work of Renault[868], Williamson[869] and Williamson and
Scott[870]. We may first consider such characters as have been recognised in
different examples of the genus, and then notice briefly the distinguishing
peculiarities of two well-marked specific types.
a. Stems.
i. Primary structure.
In a transverse section of a young Sphenophyllum stem such as that
diagrammatically sketched in fig. 105, A, we find in the centre the xylem
portion of a single stele with a characteristic triangular form. The primary
xylem consists mainly of fairly large tracheae with numerous pits on their
walls; towards the end of each arm the tracheids become scalariform, and at
the apex there is a group of narrower spiral protoxylem elements. In the
British species there is a single protoxylem group at the apex of each arm,
but Renault has described some French stems in which the stele appears to
be hexarch, having two protoxylem groups at the end of each of the three
rays of the stele. The primary xylem strand of Sphenophyllum has therefore
a root-like structure, the tracheids having been developed centripetally from
the three initial protoxylem groups. This type of structure is typical of roots,
but it also occurs in the stems of some recent Vascular Cryptogams.
Page 405
Fig. 104. Diagrammatic longitudinal section of Sphenophyllum.
c, outer cortex; b, space next the stele, originally occupied by phloem etc.; a, xylem
strand. (After Renault[871].) × 7.
As a rule the tissue next the xylem has not been petrified, but in
exceptionally well-preserved examples it is seen to consist of a band of
thin-walled elements, of which those in contact with the xylem may be
spoken of as phloem, and those beyond as the pericycle. Succeeding this
band of delicate tissue there is a broader band of thicker-walled and
somewhat elongated elements, constituting the cortex. The specimen drawn
in fig. 105, A, shows very prominent grooves in the cortex opposite the
middle of each bay of the primary wood. It is these grooves that give to the
ordinary casts of Sphenophyllum branches the appearance of longitudinal
lines traversing each internode. In a longitudinal section of a stem, the
cortical tissue (fig. 104, c) is found to be broader in the nodal regions, thus
giving rise to the tumid nodes referred to in the diagnosis. The increased
breadth at the nodes does not mean that the xylem is broader in these
regions, as it is in Calamite stems. Small strands of vascular tissue are given
off from the three edges of the triangular stele (fig. 105 A) at each node;
these branch in passing through the cortex on their way to the verticils of
leaves. The space b in the diagrammatic section of fig. 104 was originally
c, outer cortex; b, space next the stele, originally occupied by phloem etc.; a, xylem
strand. (After Renault[871].) × 7.
As a rule the tissue next the xylem has not been petrified, but in
exceptionally well-preserved examples it is seen to consist of a band of
thin-walled elements, of which those in contact with the xylem may be
spoken of as phloem, and those beyond as the pericycle. Succeeding this
band of delicate tissue there is a broader band of thicker-walled and
somewhat elongated elements, constituting the cortex. The specimen drawn
in fig. 105, A, shows very prominent grooves in the cortex opposite the
middle of each bay of the primary wood. It is these grooves that give to the
ordinary casts of Sphenophyllum branches the appearance of longitudinal
lines traversing each internode. In a longitudinal section of a stem, the
cortical tissue (fig. 104, c) is found to be broader in the nodal regions, thus
giving rise to the tumid nodes referred to in the diagnosis. The increased
breadth at the nodes does not mean that the xylem is broader in these
regions, as it is in Calamite stems. Small strands of vascular tissue are given
off from the three edges of the triangular stele (fig. 105 A) at each node;
these branch in passing through the cortex on their way to the verticils of
leaves. The space b in the diagrammatic section of fig. 104 was originally
Page 406
occupied by the phloem and inner cortex. In some species of
Sphenophyllum the apex of each arm of the xylem strand, as seen in
transverse section, is occupied by a longitudinal canal surrounded by spiral
tracheids, as in the primary xylem of the old stem shown in fig. 105, C.
Sphenophyllum the apex of each arm of the xylem strand, as seen in
transverse section, is occupied by a longitudinal canal surrounded by spiral
tracheids, as in the primary xylem of the old stem shown in fig. 105, C.
Page 407
Fig. 105. Sphenophyllum.
A. Transverse section of young stem.
B. Transverse section of the wood of a young stem; px, protoxylem; x, secondary xylem. (A
and B. Sphenophyllum plurifoliatum.) × 20.
C. Transverse section of an old stem; (S. insigne); a, phloem; b, periderm; c, fascicular
secondary xylem; d, interfascicular secondary xylem. × 9. (No. 914 in the
Williamson Collection.)
D. Longitudinal section of the reticulate tracheae and medullary rays; r, r, r, of S.
plurifoliatum. × 36.
E. Similar section of S. insigne. × 75. (D and E after Williamson and Scott.)
ii. Secondary structure.
With the exception of very young twigs the petrified Sphenophyllum
stems usually show a greater or less development of secondary wood. In the
A. Transverse section of young stem.
B. Transverse section of the wood of a young stem; px, protoxylem; x, secondary xylem. (A
and B. Sphenophyllum plurifoliatum.) × 20.
C. Transverse section of an old stem; (S. insigne); a, phloem; b, periderm; c, fascicular
secondary xylem; d, interfascicular secondary xylem. × 9. (No. 914 in the
Williamson Collection.)
D. Longitudinal section of the reticulate tracheae and medullary rays; r, r, r, of S.
plurifoliatum. × 36.
E. Similar section of S. insigne. × 75. (D and E after Williamson and Scott.)
ii. Secondary structure.
With the exception of very young twigs the petrified Sphenophyllum
stems usually show a greater or less development of secondary wood. In the
Page 408
xylem-strand of fig. 105, B, the broad concave bays of the primary wood
have been filled in by the development of two rows of large secondary
tracheids, x, but opposite the protoxylem groups, px, there are no signs of
cambial activity. In the unusually large stem represented by a rough sketch
in fig. 105, C, the triangular primary xylem lies in the centre of a thick mass
of secondary vascular tissue. The secondary and primary wood together
have a diameter of about 5 mm.
After the bays between each protoxylem corner have been filled in, the
formation of secondary wood proceeds uniformly along the stem radii, but
the rows of tracheids and medullary rays which are developed opposite the
corners of the primary strand, c, differ in certain characters from the broader
masses of wood opposite the bays. For convenience, the secondary wood, c,
opposite the protoxylem groups has been spoken of as fascicular wood, and
the rest, d, as interfascicular wood.
The secondary xylem consists either of tracheae with numerous bordered
pits on their radial walls (fig. 105, D), or of tracheae with broad and
bordered scalariform pits (fig. 105, E). The suggestion of concentric rings
of growth in the wood in fig. 105, C, is rather deceptive; there are no well-
marked regular rings in Sphenophyllum stems, but irregular bands of
smaller elements occasionally interrupt the uniformity of the secondary
xylem. In some stems the medullary rays have the form of rows of
parenchymatous cells, which in tangential longitudinal section are found to
consist frequently of a single row of radially disposed elements; this type of
medullary rays occurs in the species Sphenophyllum insigne, in which the
tracheae are scalariform. Three medullary rays, r, are seen on the radial face
of the scalariform tracheids in fig. 105, E, which represents a radial section
of this species. In other species, e.g. S. plurifoliatum, the medullary rays
have a peculiar and characteristic structure; in a transverse section of the
stem they appear as groups of a few parenchymatous cells in the spaces
between the truncated angles of the large tracheae (fig. 106). In longitudinal
section these medullary-ray elements resemble thick bars stretching radially
across the face of the tracheae (fig. 105, D, r); the apparent septa or bars are
however thin-walled cells connecting the different groups of medullary-ray
cells, as seen in a transverse section. These radial connecting cells are
occasionally seen as short rays in transverse sections of stems.
have been filled in by the development of two rows of large secondary
tracheids, x, but opposite the protoxylem groups, px, there are no signs of
cambial activity. In the unusually large stem represented by a rough sketch
in fig. 105, C, the triangular primary xylem lies in the centre of a thick mass
of secondary vascular tissue. The secondary and primary wood together
have a diameter of about 5 mm.
After the bays between each protoxylem corner have been filled in, the
formation of secondary wood proceeds uniformly along the stem radii, but
the rows of tracheids and medullary rays which are developed opposite the
corners of the primary strand, c, differ in certain characters from the broader
masses of wood opposite the bays. For convenience, the secondary wood, c,
opposite the protoxylem groups has been spoken of as fascicular wood, and
the rest, d, as interfascicular wood.
The secondary xylem consists either of tracheae with numerous bordered
pits on their radial walls (fig. 105, D), or of tracheae with broad and
bordered scalariform pits (fig. 105, E). The suggestion of concentric rings
of growth in the wood in fig. 105, C, is rather deceptive; there are no well-
marked regular rings in Sphenophyllum stems, but irregular bands of
smaller elements occasionally interrupt the uniformity of the secondary
xylem. In some stems the medullary rays have the form of rows of
parenchymatous cells, which in tangential longitudinal section are found to
consist frequently of a single row of radially disposed elements; this type of
medullary rays occurs in the species Sphenophyllum insigne, in which the
tracheae are scalariform. Three medullary rays, r, are seen on the radial face
of the scalariform tracheids in fig. 105, E, which represents a radial section
of this species. In other species, e.g. S. plurifoliatum, the medullary rays
have a peculiar and characteristic structure; in a transverse section of the
stem they appear as groups of a few parenchymatous cells in the spaces
between the truncated angles of the large tracheae (fig. 106). In longitudinal
section these medullary-ray elements resemble thick bars stretching radially
across the face of the tracheae (fig. 105, D, r); the apparent septa or bars are
however thin-walled cells connecting the different groups of medullary-ray
cells, as seen in a transverse section. These radial connecting cells are
occasionally seen as short rays in transverse sections of stems.
Page 409
The cambium and phloem elements are occasionally preserved in good
specimens of older stems; the former consist of tabular flatted thin-walled
cells, and the latter in some cases include large sieve-tubes and narrower
parenchymatous elements.
The sections shown in fig. 107, E and F, illustrate the preservation of
cambial and phloem tissue. In the transverse section of fig. 107, F, the
secondary xylem with the medullary rays, r, is succeeded by a few tabular
cambium cells, and external to these there are thin-walled elements of
unequal size representing the phloem. In fig. 107, E, the scalariform
tracheids are succeeded by narrow thin-walled cells, and the larger elements
with transverse and oblique septa are no doubt sieve-tubes.
In the large stem of fig. 105, C, the xylem is succeeded by a band of
tissue, a, which is no doubt phloem, and external to this there is a
considerable development of periderm (b). The periderm in Sphenophyllum
stems had a deep-seated origin, the phellogen or cork-cambium
occasionally being formed in the secondary phloem-parenchyma, and in
other cases in the pericycle, as in the stems of some living dicotyledons.
Williamson and Scott[872] describe stems in which a succession of
phellogens were formed at different levels, thus producing a scaly type of
bark, such as we find in the Pine or the Plane tree.
SPHENOPHYLLUM PLURIFOLIATUM.
Before describing the structure of the strobili of Sphenophyllum, we may
briefly point out the distinguishing features of two specific types of the
genus recently described by Williamson and Scott. One of these species, S.
insigne, was originally described by Williamson as an Asterophyllites; the
numerous narrow linear leaves in each verticil led to the inclusion of the
specimens in the latter genus. The material on which this species is founded
is from the volcanic beds of Pettycur, Burntisland, on the coast of the Firth
of Forth.
1. Sphenophyllum insigne (Will.). Figs. 105, C and E, and 107, E and F.
1891. Asterophyllites insignis. Williamson[873].
An intercellular space occurs at each angle of the three-rayed primary
xylem strand, and spiral tracheae are abundant. The tracheae of the
secondary wood have scalariform markings on the radial walls. Regular
specimens of older stems; the former consist of tabular flatted thin-walled
cells, and the latter in some cases include large sieve-tubes and narrower
parenchymatous elements.
The sections shown in fig. 107, E and F, illustrate the preservation of
cambial and phloem tissue. In the transverse section of fig. 107, F, the
secondary xylem with the medullary rays, r, is succeeded by a few tabular
cambium cells, and external to these there are thin-walled elements of
unequal size representing the phloem. In fig. 107, E, the scalariform
tracheids are succeeded by narrow thin-walled cells, and the larger elements
with transverse and oblique septa are no doubt sieve-tubes.
In the large stem of fig. 105, C, the xylem is succeeded by a band of
tissue, a, which is no doubt phloem, and external to this there is a
considerable development of periderm (b). The periderm in Sphenophyllum
stems had a deep-seated origin, the phellogen or cork-cambium
occasionally being formed in the secondary phloem-parenchyma, and in
other cases in the pericycle, as in the stems of some living dicotyledons.
Williamson and Scott[872] describe stems in which a succession of
phellogens were formed at different levels, thus producing a scaly type of
bark, such as we find in the Pine or the Plane tree.
SPHENOPHYLLUM PLURIFOLIATUM.
Before describing the structure of the strobili of Sphenophyllum, we may
briefly point out the distinguishing features of two specific types of the
genus recently described by Williamson and Scott. One of these species, S.
insigne, was originally described by Williamson as an Asterophyllites; the
numerous narrow linear leaves in each verticil led to the inclusion of the
specimens in the latter genus. The material on which this species is founded
is from the volcanic beds of Pettycur, Burntisland, on the coast of the Firth
of Forth.
1. Sphenophyllum insigne (Will.). Figs. 105, C and E, and 107, E and F.
1891. Asterophyllites insignis. Williamson[873].
An intercellular space occurs at each angle of the three-rayed primary
xylem strand, and spiral tracheae are abundant. The tracheae of the
secondary wood have scalariform markings on the radial walls. Regular
Page 410
medullary rays extend through the secondary wood. The phloem contains
large sieve-tubes.
This species occurs in the Calciferous sandstone rocks of Burntisland,
and has lately been recorded from Germany. It characterises a lower horizon
than S. plurifoliatum (Will. and Scott).
2. Sphenophyllum plurifoliatum (Williamson and Scott)[874]. Figs. 105, A, B,
and D, and 106.
1891. Asterophyllites sphenophylloides. Will.[875]
The specific name plurifoliatum was proposed by Williamson and Scott
for a type of stem originally described by Williamson[876] as an
Asterophyllites, from the Coal-Measures of Oldham, Lancashire. This form
of stem has not so far been connected with any of the older species founded
on external characters, but it evidently bore foliage in which the leaves were
deeply divided, as in Sphenophyllum trichomatosum (fig. 110, B).
Fig. 106. Sphenophyllum plurifoliatum, Will. and Scott.
From a photograph by Mr Highly from a section in the Williamson Collection (no. 899).
× 27.
large sieve-tubes.
This species occurs in the Calciferous sandstone rocks of Burntisland,
and has lately been recorded from Germany. It characterises a lower horizon
than S. plurifoliatum (Will. and Scott).
2. Sphenophyllum plurifoliatum (Williamson and Scott)[874]. Figs. 105, A, B,
and D, and 106.
1891. Asterophyllites sphenophylloides. Will.[875]
The specific name plurifoliatum was proposed by Williamson and Scott
for a type of stem originally described by Williamson[876] as an
Asterophyllites, from the Coal-Measures of Oldham, Lancashire. This form
of stem has not so far been connected with any of the older species founded
on external characters, but it evidently bore foliage in which the leaves were
deeply divided, as in Sphenophyllum trichomatosum (fig. 110, B).
Fig. 106. Sphenophyllum plurifoliatum, Will. and Scott.
From a photograph by Mr Highly from a section in the Williamson Collection (no. 899).
× 27.
Page 411
In this species there are no canals at the angles of the primary xylem, and
there are fewer spiral tracheae than in S. insigne. The tracheae of the
secondary wood have numerous small pits on the radial walls, and the
medullary rays are chiefly composed of parenchymatous cells, which
appear in transverse section as groups of cells between the truncated angles
of the tracheae. The characters are fairly well seen in the xylem portion of a
stele shown in fig. 106. The fascicular wood includes some rows of
parenchymatous medullary-ray cells in addition to the characteristic groups,
as seen in the figure. A slightly oblique transverse section of a stem is often
convenient in the interpretation of histological features; one of the sections
of S. plurifoliatum in the Williamson collection (no. 893), which has been
cut somewhat obliquely, shows very clearly the differences in pitting
exhibited by the different xylem elements.
b. Roots.
Our knowledge of the anatomy of Sphenophyllum roots is very limited.
Renault has described a somewhat imperfect example of a silicified root
from St. Étienne and Autun. The drawing in fig. 107, B, which is copied
from one of Renault’s figures, shows a cylindrical mass of xylem with a
small band of narrower elements occupying the centre, and surrounded by
rows of larger secondary tracheae. The central bipolar band is described as
the diarch primary xylem, around which the secondary pitted elements have
been developed.
It is probable that the specimen described by Renault is a root of
Sphenophyllum, but my impression gained from an examination of the
section was that the diarch primary strand is not quite so clear as in the
published figures. Until we possess better material we cannot attempt any
very satisfactory description of the anatomical features of the roots of this
genus.
A section of a Sphenophyllum stem has been figured by Felix[877], in
which a lateral member is being given off; this may possibly represent the
origin of an adventitious root, but the preservation is not sufficiently distinct
to render this certain.
c. Leaves.
there are fewer spiral tracheae than in S. insigne. The tracheae of the
secondary wood have numerous small pits on the radial walls, and the
medullary rays are chiefly composed of parenchymatous cells, which
appear in transverse section as groups of cells between the truncated angles
of the tracheae. The characters are fairly well seen in the xylem portion of a
stele shown in fig. 106. The fascicular wood includes some rows of
parenchymatous medullary-ray cells in addition to the characteristic groups,
as seen in the figure. A slightly oblique transverse section of a stem is often
convenient in the interpretation of histological features; one of the sections
of S. plurifoliatum in the Williamson collection (no. 893), which has been
cut somewhat obliquely, shows very clearly the differences in pitting
exhibited by the different xylem elements.
b. Roots.
Our knowledge of the anatomy of Sphenophyllum roots is very limited.
Renault has described a somewhat imperfect example of a silicified root
from St. Étienne and Autun. The drawing in fig. 107, B, which is copied
from one of Renault’s figures, shows a cylindrical mass of xylem with a
small band of narrower elements occupying the centre, and surrounded by
rows of larger secondary tracheae. The central bipolar band is described as
the diarch primary xylem, around which the secondary pitted elements have
been developed.
It is probable that the specimen described by Renault is a root of
Sphenophyllum, but my impression gained from an examination of the
section was that the diarch primary strand is not quite so clear as in the
published figures. Until we possess better material we cannot attempt any
very satisfactory description of the anatomical features of the roots of this
genus.
A section of a Sphenophyllum stem has been figured by Felix[877], in
which a lateral member is being given off; this may possibly represent the
origin of an adventitious root, but the preservation is not sufficiently distinct
to render this certain.
c. Leaves.
Page 412
Renault[878] has described some silicified leaves of Sphenophyllum from
Autun in which the laminae consist of thin-walled loose parenchyma,
traversed by small groups of tracheids constituting the simple or forked
veins. The epidermis is made up of a single layer of cells, with here and
there indistinct indications of stomata. A more perfect stoma has, however,
been described by Solms-Laubach from the epidermis of a bract in a
strobilus (fig. 107, A).
Fig. 107. A. Stoma in a bract of Sphenophyllostachys. B. Root of Sphenophyllum. C.
Sphenophyllostachys Römeri, Solms. s, sporangiophore, b, bract. D. Sporangium. E and F.
Sections through the cambium, phloem and secondary xylem of Sphenophyllum insigne
(Will.). s, sieve-tube. G. Sporangium and pedicel. A, C, D. After Solms-Laubach. B. After
Renault. E–G. After Williamson and Scott. E. F. × 100. G. × 115.
d. Cones.
The history of the recognition of the cones of Sphenophyllum has already
been briefly alluded to in chapter V., p. 100. The main points in the
structure of the cones of this genus were known for several years, before the
fact was established that they belonged to Sphenophyllum stems. In 1871
Williamson[879] published an account of an imperfect fossil strobilus from
Autun in which the laminae consist of thin-walled loose parenchyma,
traversed by small groups of tracheids constituting the simple or forked
veins. The epidermis is made up of a single layer of cells, with here and
there indistinct indications of stomata. A more perfect stoma has, however,
been described by Solms-Laubach from the epidermis of a bract in a
strobilus (fig. 107, A).
Fig. 107. A. Stoma in a bract of Sphenophyllostachys. B. Root of Sphenophyllum. C.
Sphenophyllostachys Römeri, Solms. s, sporangiophore, b, bract. D. Sporangium. E and F.
Sections through the cambium, phloem and secondary xylem of Sphenophyllum insigne
(Will.). s, sieve-tube. G. Sporangium and pedicel. A, C, D. After Solms-Laubach. B. After
Renault. E–G. After Williamson and Scott. E. F. × 100. G. × 115.
d. Cones.
The history of the recognition of the cones of Sphenophyllum has already
been briefly alluded to in chapter V., p. 100. The main points in the
structure of the cones of this genus were known for several years, before the
fact was established that they belonged to Sphenophyllum stems. In 1871
Williamson[879] published an account of an imperfect fossil strobilus from
Page 413
the Lower Coal-Measures of Oldham, Lancashire, under the name of
Volkmannia Dawsoni. The generic term Volkmannia has been used by
different writers for cones varying considerably in structural features; in the
case of Williamson’s fossil, Weiss[880] substituted the name Bowmanites, a
genus instituted by Binney[881] for a strobilus apparently of the same type as
Volkmannia Dawsoni. In 1891 Williamson[882] described some additional
specimens of Bowmanites Dawsoni, and, as in his earlier paper, he
compared the strobilus with Asterophyllites and Sphenophyllum, but it was
still a matter of speculation as to what was the form of the vegetative
branches. Soon after the more complete account of the English cones was
published, Zeiller[883] recognised a close agreement between some French
and Belgian specimens of Sphenophyllum strobili and the strobilus
described by Williamson. A closer comparison thoroughly established the
connection between Bowmanites Dawsoni and Sphenophyllum; and there is
little doubt that this strobilus belongs to the stem known as Sphenophyllum
cuneifolium (Sternb.)—a well-known species of the genus.
STROBILUS.
The most important morphological features of the strobilus of
Sphenophyllum may best be illustrated by a detailed account of one specific
type, and by a brief reference to other forms which are characterised by
certain differences in the number and attachment of the sporangia. When we
know that a given strobilus must have grown on a Sphenophyllum stem, the
obvious name to assign to it would seem to be that of the plant which bore
it; but there are advantages in making use of special generic terms for
detached cones, which cannot be referred with certainty to a particular
species of stem. The genus Calamostachys affords an example of a name
which is intended to denote that a cone so called belongs to a Calamarian
plant; similarly such a name as Sphenophyllostachys may be used for
Sphenophylloid cones which cannot be connected with certainty to
particular species of Sphenophyllum. It has been suggested that the genus
Bowmanites, first used for a cone which was afterwards recognised as
belonging to a Sphenophyllum, should be employed instead of the
sesquipedalian term Sphenophyllostachys. The latter is used here as being in
accordance with a generally accepted and convenient system of
Volkmannia Dawsoni. The generic term Volkmannia has been used by
different writers for cones varying considerably in structural features; in the
case of Williamson’s fossil, Weiss[880] substituted the name Bowmanites, a
genus instituted by Binney[881] for a strobilus apparently of the same type as
Volkmannia Dawsoni. In 1891 Williamson[882] described some additional
specimens of Bowmanites Dawsoni, and, as in his earlier paper, he
compared the strobilus with Asterophyllites and Sphenophyllum, but it was
still a matter of speculation as to what was the form of the vegetative
branches. Soon after the more complete account of the English cones was
published, Zeiller[883] recognised a close agreement between some French
and Belgian specimens of Sphenophyllum strobili and the strobilus
described by Williamson. A closer comparison thoroughly established the
connection between Bowmanites Dawsoni and Sphenophyllum; and there is
little doubt that this strobilus belongs to the stem known as Sphenophyllum
cuneifolium (Sternb.)—a well-known species of the genus.
STROBILUS.
The most important morphological features of the strobilus of
Sphenophyllum may best be illustrated by a detailed account of one specific
type, and by a brief reference to other forms which are characterised by
certain differences in the number and attachment of the sporangia. When we
know that a given strobilus must have grown on a Sphenophyllum stem, the
obvious name to assign to it would seem to be that of the plant which bore
it; but there are advantages in making use of special generic terms for
detached cones, which cannot be referred with certainty to a particular
species of stem. The genus Calamostachys affords an example of a name
which is intended to denote that a cone so called belongs to a Calamarian
plant; similarly such a name as Sphenophyllostachys may be used for
Sphenophylloid cones which cannot be connected with certainty to
particular species of Sphenophyllum. It has been suggested that the genus
Bowmanites, first used for a cone which was afterwards recognised as
belonging to a Sphenophyllum, should be employed instead of the
sesquipedalian term Sphenophyllostachys. The latter is used here as being in
accordance with a generally accepted and convenient system of
Page 414
nomenclature, and as a name which at once denotes the fact that the fossil is
not only a cone but that it belongs to a Sphenophyllum.
Sphenophyllostachys Dawsoni (Will.). Figs. 107, A and G, 108.
Probably the strobilus of Sphenophyllum cuneifolium (Sternb.).
Fig. 108. Diagrammatic longitudinal section of a Sphenophyllum strobilus.
The upper figure represents a portion of a whorl of bracts. (The smaller figure, after
Zeiller.)
The cone consists of a central axis bearing a number of verticils of bracts
coherent in their lower portions in the form of a widely open funnel-shaped
disc, which splits up peripherally into 14–20 linear-lanceolate segments.
The free segments of each verticil have an obliquely ascending or almost
vertical position, and extend upwards for a distance of about six internodes.
The smaller drawing in fig. 108 shows the appearance in side view of the
narrow bracts of a single whorl. A transverse section of a strobilus would
include, therefore, sections of several concentric series of ascending bracts.
The verticils of Sphenophyllostachys Dawsoni are probably superposed, but
this point has not been definitely settled. From the upper surface of the
coherent basal portion of each verticil, there are given off twice as many
not only a cone but that it belongs to a Sphenophyllum.
Sphenophyllostachys Dawsoni (Will.). Figs. 107, A and G, 108.
Probably the strobilus of Sphenophyllum cuneifolium (Sternb.).
Fig. 108. Diagrammatic longitudinal section of a Sphenophyllum strobilus.
The upper figure represents a portion of a whorl of bracts. (The smaller figure, after
Zeiller.)
The cone consists of a central axis bearing a number of verticils of bracts
coherent in their lower portions in the form of a widely open funnel-shaped
disc, which splits up peripherally into 14–20 linear-lanceolate segments.
The free segments of each verticil have an obliquely ascending or almost
vertical position, and extend upwards for a distance of about six internodes.
The smaller drawing in fig. 108 shows the appearance in side view of the
narrow bracts of a single whorl. A transverse section of a strobilus would
include, therefore, sections of several concentric series of ascending bracts.
The verticils of Sphenophyllostachys Dawsoni are probably superposed, but
this point has not been definitely settled. From the upper surface of the
coherent basal portion of each verticil, there are given off twice as many
Page 415
sporangiophores as there are free segments, and these are attached close to
the line of junction of the axis of the cone and the funnel-shaped disc. Each
sporangiophore has the form of a slender stalk which bends inwards at its
distal end and bears a single sporangium (cf. fig. 107, D). The
sporangiophores given off from the same verticil of bracts vary in length.
All the sporangiophores are attached to the coherent bracts at the same
distance from the axis of the cone; but as the sporangia between each
verticil of bracts are arranged in two or three concentric series, it follows
that the length of the sporangiophores varies considerably. The
diagrammatic longitudinal section of a strobilus in fig. 108 shows three
concentric series of sporangia between successive bract-verticils. A similar
diagram was published by Williamson in 1892[884], and afterwards copied by
Potonié[885], but in Williamson’s restoration the sporangiophores of the three
series of sporangia are erroneously represented as arising from different
points on the surface of the bracts. There is little doubt, as regards the
strobilus of S. cuneifolium, that the sporangiophores were given off in a
single series close to the axils of the bracts, as is partially shown in fig. 108.
The central part of the axis of the cone is occupied by a single triangular
stele like that of the stem, except that each ray of the xylem strand has a
comparatively broad blunt termination, and is not tapered to a narrow arm
as in fig. 105, A and B. The wood consists of pitted tracheae, with two
groups of protoxylem elements at each of the truncated angles of the solid
strand of xylem. From the angles of the stele branches of vascular tissue
pass out through the cortex to supply the sterile and fertile segments of each
verticil. One of the transverse sections of the Sphenophyllum cone in the
British Museum Collection (no. 1898 E) affords a good example of the
misleading appearance occasionally presented by an intruded ‘rootlet’ of
Stigmaria; the vascular tissue of the cone has disappeared, and a Stigmarian
appendage with its vascular bundle occupies the position of the stelar
tissues.
The bracts consist of parenchymatous tissue limited externally by an
epidermis containing stomata. A single stoma with subsidiary cells is
represented in fig. 107, A. The sporangiophores are composed internally of
thin-walled cells with stronger cells towards the surface. The longer
sporangiophores in a series may be more or less coherent for part of their
length to the upper surface of the verticil of bracts. In fig. 108 the slender
the line of junction of the axis of the cone and the funnel-shaped disc. Each
sporangiophore has the form of a slender stalk which bends inwards at its
distal end and bears a single sporangium (cf. fig. 107, D). The
sporangiophores given off from the same verticil of bracts vary in length.
All the sporangiophores are attached to the coherent bracts at the same
distance from the axis of the cone; but as the sporangia between each
verticil of bracts are arranged in two or three concentric series, it follows
that the length of the sporangiophores varies considerably. The
diagrammatic longitudinal section of a strobilus in fig. 108 shows three
concentric series of sporangia between successive bract-verticils. A similar
diagram was published by Williamson in 1892[884], and afterwards copied by
Potonié[885], but in Williamson’s restoration the sporangiophores of the three
series of sporangia are erroneously represented as arising from different
points on the surface of the bracts. There is little doubt, as regards the
strobilus of S. cuneifolium, that the sporangiophores were given off in a
single series close to the axils of the bracts, as is partially shown in fig. 108.
The central part of the axis of the cone is occupied by a single triangular
stele like that of the stem, except that each ray of the xylem strand has a
comparatively broad blunt termination, and is not tapered to a narrow arm
as in fig. 105, A and B. The wood consists of pitted tracheae, with two
groups of protoxylem elements at each of the truncated angles of the solid
strand of xylem. From the angles of the stele branches of vascular tissue
pass out through the cortex to supply the sterile and fertile segments of each
verticil. One of the transverse sections of the Sphenophyllum cone in the
British Museum Collection (no. 1898 E) affords a good example of the
misleading appearance occasionally presented by an intruded ‘rootlet’ of
Stigmaria; the vascular tissue of the cone has disappeared, and a Stigmarian
appendage with its vascular bundle occupies the position of the stelar
tissues.
The bracts consist of parenchymatous tissue limited externally by an
epidermis containing stomata. A single stoma with subsidiary cells is
represented in fig. 107, A. The sporangiophores are composed internally of
thin-walled cells with stronger cells towards the surface. The longer
sporangiophores in a series may be more or less coherent for part of their
length to the upper surface of the verticil of bracts. In fig. 108 the slender
Page 416
sporangiophores do not appear to come off always from the same portion of
the bracts, but this is due to some of them lying on the surface of the latter
during part of their course to support the external circle of sporangia. The
hook-like distal end of a sporangiophore, towards the point of attachment of
the sporangium, is characterised by the larger size and greater prominence
of the surface cells; these larger cells, which pass over the upper surface of
a sporangium base, probably constitute a kind of annulus which determines
the dehiscence of the sporangial wall[886].
Fig. 107, G, represents a sporangiophore and its sporangium cut through
transversely just below the point of attachment of the latter to the end of the
hook-like termination of the former. The spores are characterised by an
irregularly reticulate thickening of the outer coat or exospore, as seen in the
figure.
One of the chief points of interest suggested by a Sphenophyllum cone is
the exact morphological nature of the sporangiophores. Are they branches
borne in the axils of bracts, or may we regard each sporangiophore as a
modified leaf, which has become coherent with the whorls of sterile leaves?
Or is a sporangiophore merely a stalk of a sporangium; or a ventral lobe of
a leaf, of which the sterile bracts represent the dorsal lobes? Although it is
impossible without the evidence of development to decide with certainty
between these alternatives, it would seem most probable that a
sporangiophore may be looked upon as a ventral lobe of a leaf, the sterile
lobes forming the bracts or members of the sterile whorls of the cone. This
question is discussed by Zeiller[887] and Williamson and Scott[888], also more
recently by Scott[889] in his memoir on Cheirostrobus.
Sphenophyllostachys Römeri (Solms-Laubach)[890]. Fig. 107, C and D.
In another type of Sphenophyllum strobilus, recently described by Solms-
Laubach, the incurved end of each sporangiophore bore two sporangia. In
most respects this species, which has not been found in connection with a
vegetative shoot, agrees with Sphenophyllostachys Dawsoni.
In fig. 107, C, which is copied from one of Solms-Laubach’s
drawings[891], we have an oblique transverse section of part of a strobilus,
including portions of two series of sporangia borne on one verticil of bracts,
and at the right-hand edge the section has passed through the sporangia
the bracts, but this is due to some of them lying on the surface of the latter
during part of their course to support the external circle of sporangia. The
hook-like distal end of a sporangiophore, towards the point of attachment of
the sporangium, is characterised by the larger size and greater prominence
of the surface cells; these larger cells, which pass over the upper surface of
a sporangium base, probably constitute a kind of annulus which determines
the dehiscence of the sporangial wall[886].
Fig. 107, G, represents a sporangiophore and its sporangium cut through
transversely just below the point of attachment of the latter to the end of the
hook-like termination of the former. The spores are characterised by an
irregularly reticulate thickening of the outer coat or exospore, as seen in the
figure.
One of the chief points of interest suggested by a Sphenophyllum cone is
the exact morphological nature of the sporangiophores. Are they branches
borne in the axils of bracts, or may we regard each sporangiophore as a
modified leaf, which has become coherent with the whorls of sterile leaves?
Or is a sporangiophore merely a stalk of a sporangium; or a ventral lobe of
a leaf, of which the sterile bracts represent the dorsal lobes? Although it is
impossible without the evidence of development to decide with certainty
between these alternatives, it would seem most probable that a
sporangiophore may be looked upon as a ventral lobe of a leaf, the sterile
lobes forming the bracts or members of the sterile whorls of the cone. This
question is discussed by Zeiller[887] and Williamson and Scott[888], also more
recently by Scott[889] in his memoir on Cheirostrobus.
Sphenophyllostachys Römeri (Solms-Laubach)[890]. Fig. 107, C and D.
In another type of Sphenophyllum strobilus, recently described by Solms-
Laubach, the incurved end of each sporangiophore bore two sporangia. In
most respects this species, which has not been found in connection with a
vegetative shoot, agrees with Sphenophyllostachys Dawsoni.
In fig. 107, C, which is copied from one of Solms-Laubach’s
drawings[891], we have an oblique transverse section of part of a strobilus,
including portions of two series of sporangia borne on one verticil of bracts,
and at the right-hand edge the section has passed through the sporangia
Page 417
belonging to another whorl of bracts. There were probably three concentric
series of sporangia attached to each verticil of bracts, as in the case of fig.
108. The unshaded area, b (fig. 107, C), represents the bracts of two
successive sterile whorls in transverse section. The shaded areas are the
sporangia, with their sporangiophores, s. The relative position of the
sporangia and sporangiophores suggests that each pedicel bore two
sporangia at its tip, instead of one, as in the strobilus of Sphenophyllum
cuneifolium (Sternb.).
A further variation in the structure of the strobili is illustrated by some
specimens of S. trichomatosum Stur, described by Kidston[892], from the
Coal-Measures of Barnsley. Each whorl of bracts bears a single series of
oval sporangia which appear to be sessile on the basal portion of the whorl.
It is possible that delicate sporangiophores may have been present, but in
the imperfect examples in Kidston’s collection[893] the sporangia present the
appearance of being seated directly on the surface of the bracts. As the
specimens do not show any internal structure, it would be unwise to lay too
much stress on the apparent absence of the characteristic sporangiophores.
In any case, Kidston’s cones afford an illustration of the occurrence of a
single series of sporangia in each whorl, instead of the pluriseriate manner
of occurrence in some other species.
The statement is occasionally met with that some Sphenophyllum cones
possessed two kinds of spores, but we are still in want of satisfactory
evidence that this was really the case. Renault has described an imperfect
specimen, which he considers points to the heterosporous nature of a
Sphenophyllum cone, but Zeiller and Williamson and Scott have expressed
doubts as to the correctness of Renault’s conclusions. While admitting the
possibility of undoubted heterosporous strobili being discovered, we are not
in a position to refer to Sphenophyllum as having borne strobili containing
two kinds of spores[894].
SPHENOPHYLLUM EMARGINATUM.
[The following are some of the specimens in the Williamson Cabinet
which illustrate the structure of Sphenophyllum:—
S. plurifoliatum. 874, 882, 884, 893, 894, 897, 899, 901, 903, 908, 1893.
S. insigne. 910, 914, 919, 921, 922, 924, 926, 1420, 1898.
Sphenophyllostachys. 1049a–1049c, 1898.]
series of sporangia attached to each verticil of bracts, as in the case of fig.
108. The unshaded area, b (fig. 107, C), represents the bracts of two
successive sterile whorls in transverse section. The shaded areas are the
sporangia, with their sporangiophores, s. The relative position of the
sporangia and sporangiophores suggests that each pedicel bore two
sporangia at its tip, instead of one, as in the strobilus of Sphenophyllum
cuneifolium (Sternb.).
A further variation in the structure of the strobili is illustrated by some
specimens of S. trichomatosum Stur, described by Kidston[892], from the
Coal-Measures of Barnsley. Each whorl of bracts bears a single series of
oval sporangia which appear to be sessile on the basal portion of the whorl.
It is possible that delicate sporangiophores may have been present, but in
the imperfect examples in Kidston’s collection[893] the sporangia present the
appearance of being seated directly on the surface of the bracts. As the
specimens do not show any internal structure, it would be unwise to lay too
much stress on the apparent absence of the characteristic sporangiophores.
In any case, Kidston’s cones afford an illustration of the occurrence of a
single series of sporangia in each whorl, instead of the pluriseriate manner
of occurrence in some other species.
The statement is occasionally met with that some Sphenophyllum cones
possessed two kinds of spores, but we are still in want of satisfactory
evidence that this was really the case. Renault has described an imperfect
specimen, which he considers points to the heterosporous nature of a
Sphenophyllum cone, but Zeiller and Williamson and Scott have expressed
doubts as to the correctness of Renault’s conclusions. While admitting the
possibility of undoubted heterosporous strobili being discovered, we are not
in a position to refer to Sphenophyllum as having borne strobili containing
two kinds of spores[894].
SPHENOPHYLLUM EMARGINATUM.
[The following are some of the specimens in the Williamson Cabinet
which illustrate the structure of Sphenophyllum:—
S. plurifoliatum. 874, 882, 884, 893, 894, 897, 899, 901, 903, 908, 1893.
S. insigne. 910, 914, 919, 921, 922, 924, 926, 1420, 1898.
Sphenophyllostachys. 1049a–1049c, 1898.]
Page 418
B. Types of vegetative branches of Sphenophyllum.
1. Sphenophyllum emarginatum (Brongniart). Fig.
109.
1822. Sphenophyllites emarginatus, Brongniart[895].
1828. Sphenophyllum emarginatum, Brongniart[896].
1828. Sphenophyllum truncatum, Brongniart[896].
1828. Rotularia marsileaefolia, Bischoff[897].
1862. Sphenophyllum osnabrugense, Römer[898].
Fig. 109. Sphenophyllum emarginatum (Brongniart).
From a specimen in the Collection of Mr R. Kidston, Upper Coal-Measures, Radstock. ⅚
nat. size.
This species of Sphenophyllum bears verticils of six or eight wedge-
shaped leaves varying in breadth and in the extent of dissection of the
laminae; they are truncated distally, and terminate in a margin characterised
by blunt or obtusely-rounded teeth, each of which receives a single vein.
The larger leaves are usually more or less deeply divided by a median slit.
1. Sphenophyllum emarginatum (Brongniart). Fig.
109.
1822. Sphenophyllites emarginatus, Brongniart[895].
1828. Sphenophyllum emarginatum, Brongniart[896].
1828. Sphenophyllum truncatum, Brongniart[896].
1828. Rotularia marsileaefolia, Bischoff[897].
1862. Sphenophyllum osnabrugense, Römer[898].
Fig. 109. Sphenophyllum emarginatum (Brongniart).
From a specimen in the Collection of Mr R. Kidston, Upper Coal-Measures, Radstock. ⅚
nat. size.
This species of Sphenophyllum bears verticils of six or eight wedge-
shaped leaves varying in breadth and in the extent of dissection of the
laminae; they are truncated distally, and terminate in a margin characterised
by blunt or obtusely-rounded teeth, each of which receives a single vein.
The larger leaves are usually more or less deeply divided by a median slit.
Page 419
The narrow base of each leaf receives a single vein which branches
repeatedly in a dichotomous manner in the substance of the lamina. Several
drawings have been given by Sterzel[899] in a memoir on Permian plants,
showing the variation in leaf-form in Sphenophyllum emarginatum, but as
Kidston[900] and Zeiller[901] have pointed out Sterzel’s specimens probably
belong to S. cuneifolium (Sternb.).
Branches are given off singly from the nodes, and the cones are borne at
the tips of branches or branchlets. The cone of S. emarginatum agrees very
closely with that of S. cuneifolium, and is of the same type as that shown in
fig. 108. The small branch of S. emarginatum represented in fig. 109 does
not show clearly the detailed characters of the species, as the leaf-margins
are not well preserved.
In one of the largest specimens of this species which I have seen, in the
Leipzig Museum, the main stem has internodes of about 3·9 cm. in length,
from which a lateral branch with much shorter internodes is given off from
a node.
It is important to notice the close resemblance, as pointed out by Zeiller,
between some of the narrower-leaved forms of S. emarginatum and S.
cuneifolium (Sternb.)[902]; but in the latter species the margins of the leaves
have sharp, and not blunt teeth.
The cone described and figured by Weiss[903] as Bowmanites germanicus,
since investigated by Solms-Laubach[904], must be referred to this species.
Geinitz[905] figured a cone in 1855 as that of S. emarginatum, but his
determination of the species is a little doubtful. Good figures of the true
cone of S. emarginatum have been given by Zeiller[906] in his Flore de
Valenciennes, as well as in his important memoir on the fructification of
Sphenophyllum.
LEAVES.
2. Sphenophyllum trichomatosum Stur. Fig. 110, B.
The finely-divided leaves of the single whorl shown in fig. 110, B (from
the Middle Coal-Measures of Barnsley, Yorkshire), afford an example of a
form of Sphenophyllum which is represented by such species as S.
tenerrimum Ett.[907], S. trichomatosum Stur[908], and S. myriophyllum[909]
Crép. Probably the specimen should be referred to S. trichomatosum, but it
repeatedly in a dichotomous manner in the substance of the lamina. Several
drawings have been given by Sterzel[899] in a memoir on Permian plants,
showing the variation in leaf-form in Sphenophyllum emarginatum, but as
Kidston[900] and Zeiller[901] have pointed out Sterzel’s specimens probably
belong to S. cuneifolium (Sternb.).
Branches are given off singly from the nodes, and the cones are borne at
the tips of branches or branchlets. The cone of S. emarginatum agrees very
closely with that of S. cuneifolium, and is of the same type as that shown in
fig. 108. The small branch of S. emarginatum represented in fig. 109 does
not show clearly the detailed characters of the species, as the leaf-margins
are not well preserved.
In one of the largest specimens of this species which I have seen, in the
Leipzig Museum, the main stem has internodes of about 3·9 cm. in length,
from which a lateral branch with much shorter internodes is given off from
a node.
It is important to notice the close resemblance, as pointed out by Zeiller,
between some of the narrower-leaved forms of S. emarginatum and S.
cuneifolium (Sternb.)[902]; but in the latter species the margins of the leaves
have sharp, and not blunt teeth.
The cone described and figured by Weiss[903] as Bowmanites germanicus,
since investigated by Solms-Laubach[904], must be referred to this species.
Geinitz[905] figured a cone in 1855 as that of S. emarginatum, but his
determination of the species is a little doubtful. Good figures of the true
cone of S. emarginatum have been given by Zeiller[906] in his Flore de
Valenciennes, as well as in his important memoir on the fructification of
Sphenophyllum.
LEAVES.
2. Sphenophyllum trichomatosum Stur. Fig. 110, B.
The finely-divided leaves of the single whorl shown in fig. 110, B (from
the Middle Coal-Measures of Barnsley, Yorkshire), afford an example of a
form of Sphenophyllum which is represented by such species as S.
tenerrimum Ett.[907], S. trichomatosum Stur[908], and S. myriophyllum[909]
Crép. Probably the specimen should be referred to S. trichomatosum, but it
Page 420
is almost impossible to speak with certainty as to the specific value of an
isolated leaf-whorl of this form. It has long been known that the leaves of
Sphenophyllum may vary considerably, as regards the size of the segments,
on the same plant; and the occurrence of such finely-divided leaves has lent
support to an opinion which was formerly held by some writers, that
Asterophyllites and Sphenophyllum could not be regarded as well-defined
separate genera. This heterophylly of Sphenophyllum has thus been
responsible for certain mistaken opinions both as to the relation of the
genus to Calamocladus[910] (Asterophyllites), and as regards the view that
the finely-divided laminae belonged to submerged leaf-whorls, while the
broader segments were those of floating or subaerial whorls.
There is a very close resemblance between some of the deeply-cut and
linear segments of a Sphenophyllum and the leaves of Calamocladus, but in
the former genus the linear segments are found to be connected basally into
a narrow common sheath. The assertion[911] that the deeply-cut leaves occur
on the lower portions of stems is not supported by the facts. Kidston[912] has
pointed out that the cones are often borne on branches with such leaves, and
the same author refers to a figure by Germar, in which entire and much-
divided leaves occur mixed together in the same individual specimen. M.
Zeiller recently pointed out to me a similar irregular association of broader
and narrower leaf-segments on the same shoots in some large specimens in
the École des Mines, Paris. Cones of Sphenophyllum tenerrimum have been
figured by Stur[913] and others; they are characterised by their small size and
by the dissection of the slender free portions of the narrow bracts[914].
3. Sphenophyllum Thoni Mahr. Fig. 110, A.
Another type of Sphenophyllum is illustrated by S. Thoni Mahr as shown
in fig. 110, A. This species was first described by Mahr[915] from the Coal-
Measures of Ilmenau, and has since been figured by Zeiller and other
authors. Each whorl consists of six large obcuneiform leaves with the broad
margin somewhat irregularly fringed. The unusually good specimen of
which fig. 110, A, represents a single verticil was originally described and
figured by Zeiller in 1880[916]; it is now in the École des Mines Museum,
Paris.
isolated leaf-whorl of this form. It has long been known that the leaves of
Sphenophyllum may vary considerably, as regards the size of the segments,
on the same plant; and the occurrence of such finely-divided leaves has lent
support to an opinion which was formerly held by some writers, that
Asterophyllites and Sphenophyllum could not be regarded as well-defined
separate genera. This heterophylly of Sphenophyllum has thus been
responsible for certain mistaken opinions both as to the relation of the
genus to Calamocladus[910] (Asterophyllites), and as regards the view that
the finely-divided laminae belonged to submerged leaf-whorls, while the
broader segments were those of floating or subaerial whorls.
There is a very close resemblance between some of the deeply-cut and
linear segments of a Sphenophyllum and the leaves of Calamocladus, but in
the former genus the linear segments are found to be connected basally into
a narrow common sheath. The assertion[911] that the deeply-cut leaves occur
on the lower portions of stems is not supported by the facts. Kidston[912] has
pointed out that the cones are often borne on branches with such leaves, and
the same author refers to a figure by Germar, in which entire and much-
divided leaves occur mixed together in the same individual specimen. M.
Zeiller recently pointed out to me a similar irregular association of broader
and narrower leaf-segments on the same shoots in some large specimens in
the École des Mines, Paris. Cones of Sphenophyllum tenerrimum have been
figured by Stur[913] and others; they are characterised by their small size and
by the dissection of the slender free portions of the narrow bracts[914].
3. Sphenophyllum Thoni Mahr. Fig. 110, A.
Another type of Sphenophyllum is illustrated by S. Thoni Mahr as shown
in fig. 110, A. This species was first described by Mahr[915] from the Coal-
Measures of Ilmenau, and has since been figured by Zeiller and other
authors. Each whorl consists of six large obcuneiform leaves with the broad
margin somewhat irregularly fringed. The unusually good specimen of
which fig. 110, A, represents a single verticil was originally described and
figured by Zeiller in 1880[916]; it is now in the École des Mines Museum,
Paris.
Page 421
Fig. 110.
A. Sphenophyllum Thoni, Mahr. (After Zeiller.)
B. Sphenophyllum trichomatosum, Stur. From a specimen in the Woodwardian Museum;
from the Coal-Measures of Barnsley, Yorks. A and B ¾ nat. size.
The leaf-forms illustrated by figs. 109 and 110 are some of the more
extreme types of Sphenophyllum leaves; but these are more or less
connected by a series of intermediate forms. For a more complete
systematic account of the different species the student should consult such
works as those by Coemans and Kickx[917], Zeiller, Schimper, and others.
4. Sphenophyllum speciosum (Royle). Fig. 111.
1834. Trizygia speciosa, Royle[918].
The species shown in fig. 111 has been usually described as a separate
genus Trizygia, a name instituted by Royle in 1834 for some Indian fossils
from the Lower Gondwana rocks of India[919]. Zeiller[920] has lately pointed
out the advisability of including this Asiatic type in the genus
Sphenophyllum. The slender stem bears verticils of cuneate leaves in three
pairs at each node, the anterior pair being smaller than the two lateral pairs.
The characteristic Sphenophyllum venation is clearly seen in the enlarged
leaf, fig. 111, B.
A. Sphenophyllum Thoni, Mahr. (After Zeiller.)
B. Sphenophyllum trichomatosum, Stur. From a specimen in the Woodwardian Museum;
from the Coal-Measures of Barnsley, Yorks. A and B ¾ nat. size.
The leaf-forms illustrated by figs. 109 and 110 are some of the more
extreme types of Sphenophyllum leaves; but these are more or less
connected by a series of intermediate forms. For a more complete
systematic account of the different species the student should consult such
works as those by Coemans and Kickx[917], Zeiller, Schimper, and others.
4. Sphenophyllum speciosum (Royle). Fig. 111.
1834. Trizygia speciosa, Royle[918].
The species shown in fig. 111 has been usually described as a separate
genus Trizygia, a name instituted by Royle in 1834 for some Indian fossils
from the Lower Gondwana rocks of India[919]. Zeiller[920] has lately pointed
out the advisability of including this Asiatic type in the genus
Sphenophyllum. The slender stem bears verticils of cuneate leaves in three
pairs at each node, the anterior pair being smaller than the two lateral pairs.
The characteristic Sphenophyllum venation is clearly seen in the enlarged
leaf, fig. 111, B.
Page 422
Fig. 111. Sphenophyllum speciosum (Royle).
A. Nat. size. B. enlarged leaf.
From the Raniganj Coal-field, India. (After Feistmantel.)
The inequality of the members of a single whorl, which characterises this
Indian plant, is sometimes met with in European species. A specimen of
Sphenophyllum oblongifolium, which Prof. Zeiller showed me in illustration
of this point, was practically indistinguishable from Trizygia[921].
In some of the earlier descriptions of the Indian species the generic name
Sphenophyllum[922] was used by McClelland and others, but the supposed
difference in the leaf-whorls was made the ground of reverting to the
distinct generic term Trizygia. Now that a similar type of leaf-whorl is
known to occur in Sphenophyllum, it is better to adopt that genus rather
than to allow the question of locality to unduly influence the choice of a
separate generic name for an Indian plant.
GEOLOGICAL RANGE.
C. Affinities, range and habit of Sphenophyllum.
It has been pointed out in the description of Sphenophyllum, that the most
widely separated families of recent plants have been selected by different
authors as the nearest living allies of this Palaeozoic genus. It is now
generally admitted that Sphenophyllum is a generic type apart; it cannot be
A. Nat. size. B. enlarged leaf.
From the Raniganj Coal-field, India. (After Feistmantel.)
The inequality of the members of a single whorl, which characterises this
Indian plant, is sometimes met with in European species. A specimen of
Sphenophyllum oblongifolium, which Prof. Zeiller showed me in illustration
of this point, was practically indistinguishable from Trizygia[921].
In some of the earlier descriptions of the Indian species the generic name
Sphenophyllum[922] was used by McClelland and others, but the supposed
difference in the leaf-whorls was made the ground of reverting to the
distinct generic term Trizygia. Now that a similar type of leaf-whorl is
known to occur in Sphenophyllum, it is better to adopt that genus rather
than to allow the question of locality to unduly influence the choice of a
separate generic name for an Indian plant.
GEOLOGICAL RANGE.
C. Affinities, range and habit of Sphenophyllum.
It has been pointed out in the description of Sphenophyllum, that the most
widely separated families of recent plants have been selected by different
authors as the nearest living allies of this Palaeozoic genus. It is now
generally admitted that Sphenophyllum is a generic type apart; it cannot be
Page 423
classed in any family or sub-class of recent or fossil plants, without
considerably extending or modifying the recognised characteristics of
existing divisions of the plant-kingdom. The anatomical characters of the
Sphenophyllum stem are such as one finds in some recent genera of the
Lycopodineae, especially Psilotum. If the stele of Psilotum were composed
internally of a solid strand of xylem, we should have a close
correspondence between the centripetally-developed wood of this genus
and that of Sphenophyllum. Similar comparisons might be drawn with other
existing genera, but the more detailed consideration of the affinities of the
Palaeozoic plant will be more easily dealt with after other members of the
Pteridophytes have been described. The recent discovery of an entirely new
type of Carboniferous strobilus in rocks of Calciferous sandstone age on the
shores of the Firth of Forth has thrown new light on the position of
Sphenophyllum. Cheirostrobus Pettycurensis, the new cone which Scott has
described in an able memoir, affords certain points of contact with
Sphenophyllum on the one hand and with Calamites on the other. This
important question will be dealt with after we have given an account of
Cheirostrobus[923]. To put the matter shortly, Sphenophyllum agrees with
some Lycopodinous plants in its anatomical features; with the Equisetales it
is connected by the verticillate disposition of the leaves, and some of the
forms of Sphenophyllum strobili present features which also point to
Equisetinous affinities.
In his Presidential address to the Botanical Section at the British
Association Meeting of 1896 Scott[924] thus refers to the Sphenophyllums:
—“We may hazard the guess that this interesting group may have been
derived from some unknown form lying at the root of both Calamites and
Lycopods. The existence of the Sphenophyllae certainly suggests the
probability of a common origin for these two series.” The result of the
subsequent investigation of the new cone Cheirostrobus amply justifies this
opinion as to the position of Sphenophyllum.
It is probable that Sphenophyllum lived during the Devonian period, but
the unsatisfactory specimens on which Dawson has founded a species of
this age, S. antiquum[925], can hardly be said to afford positive evidence of
the Pre-Carboniferous existence of the genus. From the Culm rocks and
other strata older than the Coal-Measures, we have such species as S.
insigne (Will.), Sphenophyllostachys Römeri (Solms-Laubach), and
considerably extending or modifying the recognised characteristics of
existing divisions of the plant-kingdom. The anatomical characters of the
Sphenophyllum stem are such as one finds in some recent genera of the
Lycopodineae, especially Psilotum. If the stele of Psilotum were composed
internally of a solid strand of xylem, we should have a close
correspondence between the centripetally-developed wood of this genus
and that of Sphenophyllum. Similar comparisons might be drawn with other
existing genera, but the more detailed consideration of the affinities of the
Palaeozoic plant will be more easily dealt with after other members of the
Pteridophytes have been described. The recent discovery of an entirely new
type of Carboniferous strobilus in rocks of Calciferous sandstone age on the
shores of the Firth of Forth has thrown new light on the position of
Sphenophyllum. Cheirostrobus Pettycurensis, the new cone which Scott has
described in an able memoir, affords certain points of contact with
Sphenophyllum on the one hand and with Calamites on the other. This
important question will be dealt with after we have given an account of
Cheirostrobus[923]. To put the matter shortly, Sphenophyllum agrees with
some Lycopodinous plants in its anatomical features; with the Equisetales it
is connected by the verticillate disposition of the leaves, and some of the
forms of Sphenophyllum strobili present features which also point to
Equisetinous affinities.
In his Presidential address to the Botanical Section at the British
Association Meeting of 1896 Scott[924] thus refers to the Sphenophyllums:
—“We may hazard the guess that this interesting group may have been
derived from some unknown form lying at the root of both Calamites and
Lycopods. The existence of the Sphenophyllae certainly suggests the
probability of a common origin for these two series.” The result of the
subsequent investigation of the new cone Cheirostrobus amply justifies this
opinion as to the position of Sphenophyllum.
It is probable that Sphenophyllum lived during the Devonian period, but
the unsatisfactory specimens on which Dawson has founded a species of
this age, S. antiquum[925], can hardly be said to afford positive evidence of
the Pre-Carboniferous existence of the genus. From the Culm rocks and
other strata older than the Coal-Measures, we have such species as S.
insigne (Will.), Sphenophyllostachys Römeri (Solms-Laubach), and
Page 424
Sphenophyllum tenerrimum, Ett.[926] while S. emarginatum[5], Brongn.
occurs in the Upper Coal-Measures and in the Transition rocks. S.
cuneifolium[927] (Sternb.) has been recorded from the Transition, Middle and
Lower Coal-Measures. Sphenophyllum oblongifolium, Germ.[928], is
recorded from Lower Permian rocks, as is also S. Thoni[929], Mahr.
The comparison which has naturally been drawn between Sphenophyllum
with its slender stems bearing occasionally dimorphic leaves, and water-
plants is not, I believe, supported by the facts of anatomy or external
characters. The entire and finely-dissected leaves do not exhibit that
regularity of relative disposition which is characteristic of aquatic plants;
the two forms of leaves may occur indiscriminately on the same branch.
The well-developed and thick xylem is not in accordance with the
anatomical features usually associated with water-plants. It is true that in
some living dicotyledons of the family Leguminosae, which inhabit
swampy places, the secondary xylem is represented by a thick mass of
unlignified and thin-walled parenchyma, as in the genus Aeschynomene[930],
from which the material of ‘pith’-helmets is obtained; but the wood of
Sphenophyllum was obviously thick-walled and thoroughly lignified.
It is not improbable that the long and slender stems of this plant may
have grown like small lianas in the Coal-Measure forests, supporting
themselves to a large extent on the stouter branches of Calamites and other
trees. The anatomical structure of a Sphenophyllum stem would seem to be
in accord with the requirements of a climbing plant. It has been shewn[931]
that in recent climbing plants the tracheae and sieve-tubes are characterised
by their large diameter, a fact which may be correlated with the small
diameter of climbing stems and the need for rapid transport of food
material. In Sphenophyllum the tracheae of the xylem have a wide bore, and
in S. insigne the phloem contains unusually wide sieve-tubes. The central
position of the stele is another feature which is not inconsistent with a
climbing habit. Schwendener and others[932] have demonstrated that in
climbing organs, as in underground stems and roots, there is a tendency
towards a centripetal concentration of mechanical or strengthening tissue.
The axial xylem strand of Sphenophyllum would afford an efficient
resistance to the tension or pulling force which climbing stems encounter.
occurs in the Upper Coal-Measures and in the Transition rocks. S.
cuneifolium[927] (Sternb.) has been recorded from the Transition, Middle and
Lower Coal-Measures. Sphenophyllum oblongifolium, Germ.[928], is
recorded from Lower Permian rocks, as is also S. Thoni[929], Mahr.
The comparison which has naturally been drawn between Sphenophyllum
with its slender stems bearing occasionally dimorphic leaves, and water-
plants is not, I believe, supported by the facts of anatomy or external
characters. The entire and finely-dissected leaves do not exhibit that
regularity of relative disposition which is characteristic of aquatic plants;
the two forms of leaves may occur indiscriminately on the same branch.
The well-developed and thick xylem is not in accordance with the
anatomical features usually associated with water-plants. It is true that in
some living dicotyledons of the family Leguminosae, which inhabit
swampy places, the secondary xylem is represented by a thick mass of
unlignified and thin-walled parenchyma, as in the genus Aeschynomene[930],
from which the material of ‘pith’-helmets is obtained; but the wood of
Sphenophyllum was obviously thick-walled and thoroughly lignified.
It is not improbable that the long and slender stems of this plant may
have grown like small lianas in the Coal-Measure forests, supporting
themselves to a large extent on the stouter branches of Calamites and other
trees. The anatomical structure of a Sphenophyllum stem would seem to be
in accord with the requirements of a climbing plant. It has been shewn[931]
that in recent climbing plants the tracheae and sieve-tubes are characterised
by their large diameter, a fact which may be correlated with the small
diameter of climbing stems and the need for rapid transport of food
material. In Sphenophyllum the tracheae of the xylem have a wide bore, and
in S. insigne the phloem contains unusually wide sieve-tubes. The central
position of the stele is another feature which is not inconsistent with a
climbing habit. Schwendener and others[932] have demonstrated that in
climbing organs, as in underground stems and roots, there is a tendency
towards a centripetal concentration of mechanical or strengthening tissue.
The axial xylem strand of Sphenophyllum would afford an efficient
resistance to the tension or pulling force which climbing stems encounter.
Page 425
Page 426
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298, 1888.
Batters, E. A. (90) Vide Holmes, E. M.
—— (92) On Conchocelis, a new genus of perforating Algae. Phycological
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Bertrand, C. E. (93) Les Bogheads à Algues. Bull. Soc. Belg. Géol.
Paléont. Hydrol. vol. vii. p. 45, 1893.
—— (96) Nouvelles remarques sur le Kerosene Shale de la Nouvelle-
Galles du Sud. Soc. d’hist. nat. Autun, 1896.
Bertrand, C. E. and Renault, B. (92) Pila bibractensis et le Boghead
d’Autun. Soc. d’hist. nat. Autun., 1892.
—— (94) Reinschia Australia et premières remarques sur le Kerosene
Shale de la Nouvelle-Galles du Sud. Soc. d’hist. nat. Autun, 1894.
Binney, E. W. (68) Observations on the Structure of Fossil plants found in
the Carboniferous Strata. Pt. i. Calamites and Calamodendron. Palaeont.
Soc. London, 1868.
—— (71) Ibid. Pt. ii. Lepidostrobus and some allied cones.
Bischoff, G. W. (28) Die cryptogamischen Gewächse. Nürnberg, 1828.
Bornemann, J. G. (56) Über organische Reste der Lettenkohlen-Gruppe
Thüringens. Leipzig, 1856.
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—— (86) Geologische Algenstudien. Jahrb. K. Preuss. Geol. Landesanst.
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—— (87) Die Versteinerungen des Cambrischen Schichtensystems der Insel
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—— (91) Ibid. vol. lvi., 1891.
Bornet, E. and Flahault. (89) Note sur deux nouveaux genres d’algues
perforantes. Journ. Bot. vol. ii. p. 161, 1888.
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—— (28) Prodrome d’une histoire des végétaux fossiles. Paris, 1828.
—— (282) Histoire des végétaux fossiles. Paris, 1828.
—— (39) Observations sur la structure intérieure du Sigillaria elegans.
Arch. Mus. d’hist. nat. vol. i. p. 405, 1839.
—— (49) Tableau des genres de végétaux fossiles. Extrait du Dictionnaire
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Brown, R. (11) Some observations on the parts of fructification in Mosses,
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—— (38) Vide Bennett, J. J.
Bryce, J. (72) The Geology of Arran. Glasgow and London, 1872.
Buckland, W. (37) Geology and Mineralogy considered with reference to
Natural Theology. London, 1858.
Bergakad., 1886.
—— (87) Die Versteinerungen des Cambrischen Schichtensystems der Insel
Sardinien. Nova Acta Acad. Caes. Leop. Car. vol. li., 1887.
—— (91) Ibid. vol. lvi., 1891.
Bornet, E. and Flahault. (89) Note sur deux nouveaux genres d’algues
perforantes. Journ. Bot. vol. ii. p. 161, 1888.
—— (892) Sur quelques plantes vivant dans le test calcaire des mollusques.
Bull. Soc. Bot. France, vol. xxxvi. p. clxvii., 1889.
Bower, F. O. (94) Studies in the morphology of Spore-producing members.
Equisetineae and Lycopodineae. Phil. Trans. R. Soc. vol. clxxxv. B. p.
473, 1894.
Brongniart, A. (22) Sur la classification et la distribution des végétaux
fossiles en général. Mém. Mus. Hist. Nat. Paris, vol. viii. p. 233, 1822.
—— (28) Prodrome d’une histoire des végétaux fossiles. Paris, 1828.
—— (282) Histoire des végétaux fossiles. Paris, 1828.
—— (39) Observations sur la structure intérieure du Sigillaria elegans.
Arch. Mus. d’hist. nat. vol. i. p. 405, 1839.
—— (49) Tableau des genres de végétaux fossiles. Extrait du Dictionnaire
d’histoire naturelle, vol. xiii. p. 49. Paris, 1849.
Brown, A. (94) On the structure and affinities of the genus Solenopora.
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Brown, R. (11) Some observations on the parts of fructification in Mosses,
with characters and descriptions of two new genera of that order. Trans.
Linn. Soc. vol. x. p. 312, 1811.
—— (38) Vide Bennett, J. J.
Bryce, J. (72) The Geology of Arran. Glasgow and London, 1872.
Buckland, W. (37) Geology and Mineralogy considered with reference to
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Page 429
Buckman, J. (50) On some fossil plants from the Lower Lias. Quart.
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—— (61) Notes on a collection of fossil plants from Nágpur, Central India.
Ibid. vol. xvii. p. 325, 1861.
—— (83) Botanical Fragments. London, 1883.
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Carpenter, W. B., Parker, W. K. and Jones, T. R. (62) Introduction to the
study of the Foraminifera. (Ray Society) London, 1862.
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Nematophycus Logani, Carr. (Prototaxites Logani, Dawson), an alga of
Devonian age. Micros. Journ. vol. viii. p. 160, 1872.
—— (722) Vide Woodward, H., p. 168.
— (76) Address before the Geologists’ Association, 1876–77. Proc. Geol.
Assoc. vol. v. p. 17, 1876.
Cash, W. and Hick, T. (78) A contribution to the flora of the Lower Coal-
Measures of the Parish of Halifax, Yorkshire. Proc. Yorks. Geol. Polyt.
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Yorks. Geol. Polyt. Soc. vol. vii. p. 115, 1878.
—— (81) A contribution to the flora of the Lower Coal-Measures of the
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—— (61) Notes on a collection of fossil plants from Nágpur, Central India.
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—— (83) Botanical Fragments. London, 1883.
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Campbell, D. (95) The structure and development of the Mosses and Ferns.
London, 1895.
Carpenter, W. B., Parker, W. K. and Jones, T. R. (62) Introduction to the
study of the Foraminifera. (Ray Society) London, 1862.
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—— (72) On the history, histological structure, and affinities of
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—— (722) Vide Woodward, H., p. 168.
— (76) Address before the Geologists’ Association, 1876–77. Proc. Geol.
Assoc. vol. v. p. 17, 1876.
Cash, W. and Hick, T. (78) A contribution to the flora of the Lower Coal-
Measures of the Parish of Halifax, Yorkshire. Proc. Yorks. Geol. Polyt.
Soc. vol. vii. p. 73, 1878–81.
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Yorks. Geol. Polyt. Soc. vol. vii. p. 115, 1878.
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Parish of Halifax, Yorkshire. Pt. iii. Proc. Yorks. Geol. Polyt. Soc. vol. vii.
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Costa, Mendes da. (1758) An account of the impressions of plants on the
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Cymopolia. Denksch. Schweiz. Nat. Ges. vol. xxv. 1887.
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Credner, H. (87) Elemente der Geologie. Leipzig, 1887.
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Page 432
—— (81) Notes on new Erian (Devonian) plants. Quart. Journ. Geol. Soc.
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—— (82) Notes on Prototaxites and Pachytheca discovered by Dr Hicks in
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1882.
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1882.
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Lisbon, 1886.
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Tertiary Corals, with a notice of their presence in Calceolina sandalina
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Etheridge, R. (81) Vide Hicks, H.
Etheridge, R. junr. (92) On the occurrence of microscopic fungi, allied to
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Schenk, A. (65) Vide Schoenlein.
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Saporta, de G. (68) Prodrome d’une flore fossile des travertins anciens de
Sézanne. Mém. Soc. Géol. France, vol. viii. [2] 1865–68.
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—— (75) Ibid. vol. ii. Cycadées, 1875.
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du terrain Silurien. Compt. Rend. vol. lxxxv. p. 500, 1877.
—— (79) Le monde des plantes avant l’apparition de l’homme. Paris,
1879.
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—— (84) Les organismes problématiques des anciennes mers. Paris, 1884.
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traces d’invertébrés associés dans les anciens terrains. Bull. Soc. bot.
France, vol. xiv. [3] p. 407, 1886.
—— (91) Plantes Jurassiques. Vol. iv. Paris, 1891.
Saporta, de G. and Marion, A. F. (81) L’Évolution du règne végétal. Les
Cryptogames. Paris, 1881.
Schenk, A. (65) Vide Schoenlein.
—— (67) Die fossile Flora der Grenzschichten des Keupers und Lias
Frankens. Wiesbaden, 1867.
—— (83) Pflanzliche Versteinerungen. Richthofen’s “China,” vol. iv.
Berlin, 1883.
—— (88) Die fossile Pflanzenreste. (Handbuch der Botanik.) Breslau,
1888.
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Thier- und Pflanzenreichs der Vorwelt erläutert. Gotha, 1820.
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Pflanzenfamilien. Teil i. Abt. 1. b. 1896.
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Schwendener, S. (74) Das mechanische Princip im anatomischen Bau der
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Scott, D. H. (94) (95) (96) Vide Williamson, W. C.
—— (96) An introduction to structural Botany. Pt. ii. Flowerless plants.
London, 1896.
—— (962) Presidential address. (Liverpool Meeting.) British Assoc. Report,
p. 992, 1896.
—— (97) On the structure and affinities of fossil plants from the Palaeozoic
rocks. On Cheirostrobus, a new type of fossil cone from the Lower
Carboniferous strata (Calciferous Sandstone Series). Phil. Trans. R. Soc.
vol. clxxxix. B. p. 1, 1897.
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Seward, A. C. (88) On Calamites undulatus. Geol. Mag. vol. v. p. 289,
1888.
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Page 453
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—— (942) Catalogue of the Mesozoic plants in the Department of Geology,
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—— (95) Ibid. Pt. ii. London, 1895.
—— (952) Coal: its structure and formation. Science Progress, vol. ii. p.
355, 1895.
—— (953) Notes on Pachytheca. Proc. Phil. Soc. Cambridge, vol. viii. pt. 5,
p. 278, 1895.
—— (96) Notes on the geological history of Monocotyledons. Annals Bot.
vol. x. p. 205, 1896.
—— (962) Vide Feilden, H. W.
—— (97) On Cycadeoidea gigantea, a new Cycadean stem from the
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—— (942) Catalogue of the Mesozoic plants in the Department of Geology,
British Museum. The Wealden Flora, Pt. i. London, 1894.
—— (95) Ibid. Pt. ii. London, 1895.
—— (952) Coal: its structure and formation. Science Progress, vol. ii. p.
355, 1895.
—— (953) Notes on Pachytheca. Proc. Phil. Soc. Cambridge, vol. viii. pt. 5,
p. 278, 1895.
—— (96) Notes on the geological history of Monocotyledons. Annals Bot.
vol. x. p. 205, 1896.
—— (962) Vide Feilden, H. W.
—— (97) On Cycadeoidea gigantea, a new Cycadean stem from the
Purbeck beds of Portland. Quart. Journ. Geol. Soc. vol. liii. p. 22, 1897.
—— (972) On the association of Sigillaria and Glossopteris in South
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Mag. vol. v. p. 563, 1868.
Sherborn, C. D. (93) An index to the genera and species of the
Foraminifera. Smithsonian Miscellaneous Collections, 856. Washington,
1893.
Shrubsole, W. H. and Kitton, F. (81) The Diatoms of the London Clay.
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Skertchly, J. B. J. (77) The geology of the Fenland. Mem. Geol. Surv.
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499.
Sollas, W. J. (86) On a specimen of slate from Bray-Head traversed by the
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Page 462
Page 463
INDEX.
Acetabularia, 165, 166
A. mediterranea, 162, 165, 166
Achyla, 127
Acicularia, 162, 166, 167
A. Andrussowi, 162, 168
A. miocenica, 162, 168
A. pavantina, 167
A. Schencki, 162, 166, 168
Aegoceras planicosta, 61
Aeolian rocks, 25
Aeschynomene, 414
Africa, South, 80, 284
Agaricus melleus, 211, 212, 215
Algae, 138–202
Algites, 148, 149, 204, 205
Amazons, 66
Amber, 70, 71, 206, 211, 221, 255
America, 182
Amphiroa, 184
Anarthrocanna, 283
A. tuberculata, 386
Acetabularia, 165, 166
A. mediterranea, 162, 165, 166
Achyla, 127
Acicularia, 162, 166, 167
A. Andrussowi, 162, 168
A. miocenica, 162, 168
A. pavantina, 167
A. Schencki, 162, 166, 168
Aegoceras planicosta, 61
Aeolian rocks, 25
Aeschynomene, 414
Africa, South, 80, 284
Agaricus melleus, 211, 212, 215
Algae, 138–202
Algites, 148, 149, 204, 205
Amazons, 66
Amber, 70, 71, 206, 211, 221, 255
America, 182
Amphiroa, 184
Anarthrocanna, 283
A. tuberculata, 386
Page 464
Andersson, G., 60
Andrae, K. J., 276
Andreaeales, 236
Andrussow, N., 168
Annularia, 255, 260, 282, 283, 289, 329, 332, 333, 336–339, 340, 361,
362, 379, 381
A. calamitoides, 335
A. Geinitzi, 338
A. longifolia, 338, 341
A. radiata, 283
A. ramosa, 363
A. sphenophylloides, 340, 341, 363
A. stellata, 338–341, 363
A. westphalica, 338
Antigua, 79
Aphlebia, 142
Araucaria imbricata, 101, 104
Araucarioxylon Withami, 81, 82
Archaean system, 34–36
Archaeocalamites, 254, 255, 256, 263, 285, 336, 383–388
A. scrobiculatus, 385–387
d’Archiac, A., 166, 167
Arctic plants, 16, 17
Arenig series, 37
Arran, 88, 89
Arthrodendron, 301, 302, 324, 325, 326, 327, 366, 379, 381
Andrae, K. J., 276
Andreaeales, 236
Andrussow, N., 168
Annularia, 255, 260, 282, 283, 289, 329, 332, 333, 336–339, 340, 361,
362, 379, 381
A. calamitoides, 335
A. Geinitzi, 338
A. longifolia, 338, 341
A. radiata, 283
A. ramosa, 363
A. sphenophylloides, 340, 341, 363
A. stellata, 338–341, 363
A. westphalica, 338
Antigua, 79
Aphlebia, 142
Araucaria imbricata, 101, 104
Araucarioxylon Withami, 81, 82
Archaean system, 34–36
Archaeocalamites, 254, 255, 256, 263, 285, 336, 383–388
A. scrobiculatus, 385–387
d’Archiac, A., 166, 167
Arctic plants, 16, 17
Arenig series, 37
Arran, 88, 89
Arthrodendron, 301, 302, 324, 325, 326, 327, 366, 379, 381
Page 465
Arthropitys, 300, 301, 302, 304, 311, 324, 325, 326, 328, 333, 349,
369, 375, 379, 380, 381, 384
A. approximata, 371
A. bistriata, 326
Arthropod eggs, 108
Artis, F. T., 4, 104, 297
Artisia, 104
Ascomycetes, 208, 209, 220
Asia Minor, Coal-Measures of, 282, 283
Asterocalamites scrobiculatus, 386
Asterophyllites, 264, 276, 329, 332, 333, 338, 369, 371, 379, 397, 409
A. elegans, 386
A. equisetiformis, 335, 338
A. insignis, 397
A. longifolius, 338
A. spaniophyllus, 386
A. sphenophylloides, 397
Astromyelon, 342, 343, 381
Australia, 179, 290, 291
Autun, 6, 46, 83, 179, 181, 182, 206, 390, 399
Azoic system, 36
Bacillariaceae, 150–156
Bacillus, 135, 136
B. amylobacter, 136
B. permicus, 135
B. Tieghemi, 135, 136
369, 375, 379, 380, 381, 384
A. approximata, 371
A. bistriata, 326
Arthropod eggs, 108
Artis, F. T., 4, 104, 297
Artisia, 104
Ascomycetes, 208, 209, 220
Asia Minor, Coal-Measures of, 282, 283
Asterocalamites scrobiculatus, 386
Asterophyllites, 264, 276, 329, 332, 333, 338, 369, 371, 379, 397, 409
A. elegans, 386
A. equisetiformis, 335, 338
A. insignis, 397
A. longifolius, 338
A. spaniophyllus, 386
A. sphenophylloides, 397
Astromyelon, 342, 343, 381
Australia, 179, 290, 291
Autun, 6, 46, 83, 179, 181, 182, 206, 390, 399
Azoic system, 36
Bacillariaceae, 150–156
Bacillus, 135, 136
B. amylobacter, 136
B. permicus, 135
B. Tieghemi, 135, 136
Page 466
Bacteria, 75, 132, 138
Bactryllium, 154–156
B. deplanatum, 155
Bala series, 37
Balanoglossus, 145
Balfour, Bayley, 178
Balfour, J. H., 101
Bambusa arundinacea, 322
Barbados, 188
Barber, C. A., 193, 197, 198, 203, 204
Barrois, C., 146
Barton, R., 80
de Bary, A., 132
Basidiomycetes, 208, 211, 212
Bates, H. W., 64, 66
Bauhin, C., 225
Bear Island, 366
Bentham, G., 98, 99
Bergeria, 101
Bernician series, 43
Bertrand, C. E., 87, 154, 178, 181
Beyrich, E., 52
Bilin, 152
Bilobites, 148
Binney, E. W., 9, 10, 304, 311, 343, 351, 386, 401
Bituminous deposits, 178–183
Bactryllium, 154–156
B. deplanatum, 155
Bala series, 37
Balanoglossus, 145
Balfour, Bayley, 178
Balfour, J. H., 101
Bambusa arundinacea, 322
Barbados, 188
Barber, C. A., 193, 197, 198, 203, 204
Barrois, C., 146
Barton, R., 80
de Bary, A., 132
Basidiomycetes, 208, 211, 212
Bates, H. W., 64, 66
Bauhin, C., 225
Bear Island, 366
Bentham, G., 98, 99
Bergeria, 101
Bernician series, 43
Bertrand, C. E., 87, 154, 178, 181
Beyrich, E., 52
Bilin, 152
Bilobites, 148
Binney, E. W., 9, 10, 304, 311, 343, 351, 386, 401
Bituminous deposits, 178–183
Page 467
Blackman, V. H., 119, 120
Blandowia, 231
Boghead, 178–183
Boring algae, 127, 128
Boring fungi, 127, 128
Bornemann, J. G., 129, 130, 148, 177
Bornet, E., 181
Bornet, E. and Flahault, 128, 129
Bornetella, 177
Bornia, 263
B. equisetiformis, 335
B. scrobiculata, 386
B. stellata, 338
Bostrychus, 210, 211
Bothrodendron, 133, 134
Botrydium, 157
Bowmanites, 401, 402
B. Dawsoni, 401
B. Germanicus, 408
Brazil, 79
Brodie, P. B., 240
Brongniart, A., 5, 6, 9, 11, 17, 18, 111, 112, 145, 177, 233, 269, 281,
288, 289, 291, 297, 299, 300, 301, 332, 336, 351, 390, 391
Bronn, H. G., 118
Brora, 269
Brown, A., 189, 190
Blandowia, 231
Boghead, 178–183
Boring algae, 127, 128
Boring fungi, 127, 128
Bornemann, J. G., 129, 130, 148, 177
Bornet, E., 181
Bornet, E. and Flahault, 128, 129
Bornetella, 177
Bornia, 263
B. equisetiformis, 335
B. scrobiculata, 386
B. stellata, 338
Bostrychus, 210, 211
Bothrodendron, 133, 134
Botrydium, 157
Bowmanites, 401, 402
B. Dawsoni, 401
B. Germanicus, 408
Brazil, 79
Brodie, P. B., 240
Brongniart, A., 5, 6, 9, 11, 17, 18, 111, 112, 145, 177, 233, 269, 281,
288, 289, 291, 297, 299, 300, 301, 332, 336, 351, 390, 391
Bronn, H. G., 118
Brora, 269
Brown, A., 189, 190
Page 468
Brukmannia, 350, 360, 361
Bryales, 236
Bryophyta, 229–241, 243
Bryozoa, 187
Buccinum, 159
Buckman, J., 240, 278
Bunbury, Sir C. J. F., 270, 271, 273, 284, 287, 288, 289
Bunter series, 47, 267, 292, 293
Burntisland, 88, 90, 397
Buthotrephis radiata, 338
Büzistock, 28
Calamarieae, 255, 295–388
Calamitea, 298, 300, 301, 303
C. bistriata, 301
Calamites, 18, 19, 77, 86, 94, 104, 114, 252, 254–257, 259, 260, 262,
264, 269, 285, 286, 289, 295–383, 386–388, 413
Calamites, sub-genera of, 381
C. alternans, 378
C. approximatus, 369, 370, 374, 378
C. arborescens, 363
C. Beani, 270, 273
C. cannaeformis, 374
C. communis, 326, 351
C. cruciatus, 376–378
C. decoratus, 374
C. equisetiformis, 335
Bryales, 236
Bryophyta, 229–241, 243
Bryozoa, 187
Buccinum, 159
Buckman, J., 240, 278
Bunbury, Sir C. J. F., 270, 271, 273, 284, 287, 288, 289
Bunter series, 47, 267, 292, 293
Burntisland, 88, 90, 397
Buthotrephis radiata, 338
Büzistock, 28
Calamarieae, 255, 295–388
Calamitea, 298, 300, 301, 303
C. bistriata, 301
Calamites, 18, 19, 77, 86, 94, 104, 114, 252, 254–257, 259, 260, 262,
264, 269, 285, 286, 289, 295–383, 386–388, 413
Calamites, sub-genera of, 381
C. alternans, 378
C. approximatus, 369, 370, 374, 378
C. arborescens, 363
C. Beani, 270, 273
C. cannaeformis, 374
C. communis, 326, 351
C. cruciatus, 376–378
C. decoratus, 374
C. equisetiformis, 335
Page 469
C. giganteus, 271
C. gigas, 271
C. Göpperti, 368, 372–374
C. lateralis, 276
C. laticulatus, 386
C. obliquus, 386
C. pedunculatus, 358
C. ramosus, 363
C. Sachsei, 372
C. scrobiculatus, 386
C. Suckowi, 372, 374, 375
C. transitionis, 386
C. varians, 371
C. variolatus, 386
C. verticillatus, 372
Calamitina, 260, 266, 267, 329, 330, 362, 364, 365, 367–376, 381,
383, 388
C. pauciramis, 367
Calamocladus, 227, 289, 328, 329, 332, 333, 336, 337, 350, 361–364,
381, 409
C. equisetiformis, 333–335, 363
C. frondosus, 289
Calamodendron, 300–302, 328, 349, 364, 375, 378, 379, 380, 382
C. bistriatum, 300
C. commune, 311, 317
C. cruciatum, 378
C. intermedium, 328
C. gigas, 271
C. Göpperti, 368, 372–374
C. lateralis, 276
C. laticulatus, 386
C. obliquus, 386
C. pedunculatus, 358
C. ramosus, 363
C. Sachsei, 372
C. scrobiculatus, 386
C. Suckowi, 372, 374, 375
C. transitionis, 386
C. varians, 371
C. variolatus, 386
C. verticillatus, 372
Calamitina, 260, 266, 267, 329, 330, 362, 364, 365, 367–376, 381,
383, 388
C. pauciramis, 367
Calamocladus, 227, 289, 328, 329, 332, 333, 336, 337, 350, 361–364,
381, 409
C. equisetiformis, 333–335, 363
C. frondosus, 289
Calamodendron, 300–302, 328, 349, 364, 375, 378, 379, 380, 382
C. bistriatum, 300
C. commune, 311, 317
C. cruciatum, 378
C. intermedium, 328
Page 470
C. striatum, 300
Calamophyllites, 371
C. Göpperti, 372
Calamopitys, 301, 302, 381
Calamostachys, 339, 342, 350, 351–357, 362, 371, 379, 381, 384, 387,
402
C. Binneyana, 351–355, 356, 357, 361
C. calathifera, 341, 363
C. Casheana, 355–357, 361
C. longifolia, 363
C. ramosa, 363
C. Solmsi, 363, 364
C. tenuissima, 261
C. tuberculata, 363
Calciferous sandstone, 43, 148, 397, 412
Callus wood, in Calamites, 319, 320
Calothrix, 126
Cambrian, 36, 37, 149, 177
de Candolle, A., 297
Carboniferous limestone, 40, 42, 43, 387
Carboniferous system, 39–45
Carinal canals, 249, 306, 307, 308
Carlsbad, 123, 126
Carpenter, W. B., 167
Carpolithus, 280
Carruthers, W., 9, 10, 87, 193, 197, 202, 212, 217, 240, 304, 351
Calamophyllites, 371
C. Göpperti, 372
Calamopitys, 301, 302, 381
Calamostachys, 339, 342, 350, 351–357, 362, 371, 379, 381, 384, 387,
402
C. Binneyana, 351–355, 356, 357, 361
C. calathifera, 341, 363
C. Casheana, 355–357, 361
C. longifolia, 363
C. ramosa, 363
C. Solmsi, 363, 364
C. tenuissima, 261
C. tuberculata, 363
Calciferous sandstone, 43, 148, 397, 412
Callus wood, in Calamites, 319, 320
Calothrix, 126
Cambrian, 36, 37, 149, 177
de Candolle, A., 297
Carboniferous limestone, 40, 42, 43, 387
Carboniferous system, 39–45
Carinal canals, 249, 306, 307, 308
Carlsbad, 123, 126
Carpenter, W. B., 167
Carpolithus, 280
Carruthers, W., 9, 10, 87, 193, 197, 202, 212, 217, 240, 304, 351
Page 471
Cash, W. and Hick, T., 206, 218, 219, 342
Castracane, F., 154
Casuarina stricta, 95, 96
Casuarinites, 332
C. equisetiformis, 335
C. stellata, 338
Caterpillars, Liassic, 240
Caulerpa, 157–159
C. abies-marina, 142
C. cactoides, 142, 158
C. Carruthersi, 159
C. ericifolia, 142
C. plumaris, 142
C. pusilla, 142
C. scalpelliformis, 142
C. taxifolia, 142
Caulerpaceae, 157–159
Caulerpites, 142, 158
C. cactoides, 158
Celastrum, 181
Celluloxylon primaevum, 198
Ceratium, 117
Chalk, 26, 50, 120
Challenger, H. M. S., 65, 66, 101, 117, 118, 119, 122, 151
Chara, 69, 223, 228
C. Bleicheri, 226
Castracane, F., 154
Casuarina stricta, 95, 96
Casuarinites, 332
C. equisetiformis, 335
C. stellata, 338
Caterpillars, Liassic, 240
Caulerpa, 157–159
C. abies-marina, 142
C. cactoides, 142, 158
C. Carruthersi, 159
C. ericifolia, 142
C. plumaris, 142
C. pusilla, 142
C. scalpelliformis, 142
C. taxifolia, 142
Caulerpaceae, 157–159
Caulerpites, 142, 158
C. cactoides, 158
Celastrum, 181
Celluloxylon primaevum, 198
Ceratium, 117
Chalk, 26, 50, 120
Challenger, H. M. S., 65, 66, 101, 117, 118, 119, 122, 151
Chara, 69, 223, 228
C. Bleicheri, 226
Page 472
C. foetida, 224, 225
C. Jaccardi, 226
C. Knowltoni, 224, 226, 227
C. Wrighti, 226, 227
Characeæ, 222–228
Chareae, 223–228
Charophyta, 222–228
Cheirostrobus, 258, 413
C. Pettycurensis, 412
Chert, 227
Chlorophyceae, 127–130, 156–190
Chondrites, 142, 144
C. plumosa, 148
C. verisimilis, 146, 147
Chondrus, 231
C. crispus, 191
Chroococcaceae, 122, 123, 181
Church, A. H., 171
Chytridineae, 216
Cingularia, 290, 364
Cladochytrium, 216
Cladosporites bipartitus, 217, 220
Clayton, fossil tree, 71
Coal, 44, 45, 68, 76, 92, 133, 134, 178, 179
Coal-balls, 85, 86
Coalbrook Dale, 361
C. Jaccardi, 226
C. Knowltoni, 224, 226, 227
C. Wrighti, 226, 227
Characeæ, 222–228
Chareae, 223–228
Charophyta, 222–228
Cheirostrobus, 258, 413
C. Pettycurensis, 412
Chert, 227
Chlorophyceae, 127–130, 156–190
Chondrites, 142, 144
C. plumosa, 148
C. verisimilis, 146, 147
Chondrus, 231
C. crispus, 191
Chroococcaceae, 122, 123, 181
Church, A. H., 171
Chytridineae, 216
Cingularia, 290, 364
Cladochytrium, 216
Cladosporites bipartitus, 217, 220
Clayton, fossil tree, 71
Coal, 44, 45, 68, 76, 92, 133, 134, 178, 179
Coal-balls, 85, 86
Coalbrook Dale, 361
Page 473
Coal-Measures, 40–45, 55, 84, 85, 217, 238, 256, 259, 261, 268, 282,
283, 296, 301, 302, 325, 329, 358, 375, 376, 378, 382, 397, 401,
406, 413
Coccoliths, 120
Coccospheres, 118–121
Codiaceae, 159–164
Codium, 159, 160
C. Bursa, 160
C. tomentosum, 160
Coelotrochium, 176
Coemans, E. and Kickx, J. J., 411
Coenocyte, 116, 117
Cohn, F., 123, 126
Cole, G., 83
Cone-in-cone structure, 83
Confervites, 177
C. chantransioides, 178
Confervoideae, 177–178
Conglomerate, 24
Coniferae, 232
Convallarites, 291
Conwentz, H., 80, 211, 212, 221
Cook, Capt., 122
Coprolites, 108, 135, 137, 182
Coral reefs, 26, 40, 48
Corallina officinalis, 183, 184
Corallinaceae, 183–190
283, 296, 301, 302, 325, 329, 358, 375, 376, 378, 382, 397, 401,
406, 413
Coccoliths, 120
Coccospheres, 118–121
Codiaceae, 159–164
Codium, 159, 160
C. Bursa, 160
C. tomentosum, 160
Coelotrochium, 176
Coemans, E. and Kickx, J. J., 411
Coenocyte, 116, 117
Cohn, F., 123, 126
Cole, G., 83
Cone-in-cone structure, 83
Confervites, 177
C. chantransioides, 178
Confervoideae, 177–178
Conglomerate, 24
Coniferae, 232
Convallarites, 291
Conwentz, H., 80, 211, 212, 221
Cook, Capt., 122
Coprolites, 108, 135, 137, 182
Coral reefs, 26, 40, 48
Corallina officinalis, 183, 184
Corallinaceae, 183–190
Page 474
Corallineae, 184
Corallines, 159, 169, 184
Coralliodendron, 163
Corals, fossil, 25
Corda, A. J., 5, 8
Cordaites, 75, 80, 99, 104, 366
Cormack, B. G., 251, 252
Coscinodiscus, 153
Costa, Mendes da, 3
Cotta, C. B., 9, 298
‘Crag’, 53, 62
Craigleith Quarry, Edinburgh, 81
Cramer, C., 171, 177
Credner, H., 149
Crépin, F., 109
Cretaceous system, 50, 51, 188
Cromer Forest bed, 53
Crossochorda, 148
Cruziana, 144, 145
Culm rocks, 42, 68, 383, 413
Cuticles, fossil, 68, 133
Cyanophyceae, 121, 122–132
Cyathophyllum bulbosum, 237
Cycadaceæ, 98
Cycadeoidea gigantea, 88, 214
Cycadorachis, 114, 115
Corallines, 159, 169, 184
Coralliodendron, 163
Corals, fossil, 25
Corda, A. J., 5, 8
Cordaites, 75, 80, 99, 104, 366
Cormack, B. G., 251, 252
Coscinodiscus, 153
Costa, Mendes da, 3
Cotta, C. B., 9, 298
‘Crag’, 53, 62
Craigleith Quarry, Edinburgh, 81
Cramer, C., 171, 177
Credner, H., 149
Crépin, F., 109
Cretaceous system, 50, 51, 188
Cromer Forest bed, 53
Crossochorda, 148
Cruziana, 144, 145
Culm rocks, 42, 68, 383, 413
Cuticles, fossil, 68, 133
Cyanophyceae, 121, 122–132
Cyathophyllum bulbosum, 237
Cycadaceæ, 98
Cycadeoidea gigantea, 88, 214
Cycadorachis, 114, 115
Page 475
Cycads, 49, 56, 99, 281
Cyclocladia, 371
C. major, 372
Cymopolia, 165, 169, 170, 172, 177
C. barbata, 162, 169, 171
C. elongata, 172
C. Mexicana, 169
Dactylopora, 175, 176
D. cylindracea, 176
Dactyloporella, 176
Darwin, C., 16, 17, 65, 70, 79, 100
Dasycladaceae, 164–176
Dasyporella, 176
Dawes, J. S., 297, 302
Dawson, Sir W., 147, 192, 193, 195, 338, 390, 413
Dawsonia, 237
D. polytrichoides, 237
D. superba, 237
Decorticated stems, 105
Deecke, W., 173
Defrance, J. L. M., 172
Dendrophycus triassicus, 146
Denudation, 23, 24, 35
Desmideae, 221
Devonian system, 39, 133, 173, 193, 195, 225, 256, 338, 383, 413
Cyclocladia, 371
C. major, 372
Cymopolia, 165, 169, 170, 172, 177
C. barbata, 162, 169, 171
C. elongata, 172
C. Mexicana, 169
Dactylopora, 175, 176
D. cylindracea, 176
Dactyloporella, 176
Darwin, C., 16, 17, 65, 70, 79, 100
Dasycladaceae, 164–176
Dasyporella, 176
Dawes, J. S., 297, 302
Dawson, Sir W., 147, 192, 193, 195, 338, 390, 413
Dawsonia, 237
D. polytrichoides, 237
D. superba, 237
Decorticated stems, 105
Deecke, W., 173
Defrance, J. L. M., 172
Dendrophycus triassicus, 146
Denudation, 23, 24, 35
Desmideae, 221
Devonian system, 39, 133, 173, 193, 195, 225, 256, 338, 383, 413
Page 476
Diatomaceae, 150–156
Diatomite, 151
Diatoms, 117, 118, 123, 141, 185
Dichothrix, 123
Dicotyledons, 98, 99
Dictyogens, 99
Dinoflagellata, 118
Diplopora, 173–176
Dirt-beds, of Portland, 56, 57
Dismal swamp, 74
Dixon, H. N. and Joly, J., 120
Dorset, coast, 56, 226
Dover coal, 45
Drifting of trees &c., 64
Duncan, M., 127, 129
Duval-jouve, J., 247
Dyas system, 46, 209
Echinoid spines, 177
Ehrenberg, C. G., 117, 118, 151, 153
Elaters, 245
Ellis, J., 159, 169
Endophytic algae, 132
Eocene rocks, 29, 52, 164, 171
Eophyton, 144, 148
Eopteris Morierei, 106
Diatomite, 151
Diatoms, 117, 118, 123, 141, 185
Dichothrix, 123
Dicotyledons, 98, 99
Dictyogens, 99
Dinoflagellata, 118
Diplopora, 173–176
Dirt-beds, of Portland, 56, 57
Dismal swamp, 74
Dixon, H. N. and Joly, J., 120
Dorset, coast, 56, 226
Dover coal, 45
Drifting of trees &c., 64
Duncan, M., 127, 129
Duval-jouve, J., 247
Dyas system, 46, 209
Echinoid spines, 177
Ehrenberg, C. G., 117, 118, 151, 153
Elaters, 245
Ellis, J., 159, 169
Endophytic algae, 132
Eocene rocks, 29, 52, 164, 171
Eophyton, 144, 148
Eopteris Morierei, 106
Page 477
Ephedra distachya, 95, 97
Equisetaceae, 19, 244–254, 255, 256
Equisetales, fossil, 254–388
Equisetales, recent, 244–254
Equisetites, 254, 257–273, 282, 291, 330, 413
E. arenaceus, 268, 269, 275, 280
E. Beani, 270–275
E. Brodii, 278
E. Burchardti, 279, 280
E. Burejensis, 280
E. columnaris, 72, 265, 269–271
E. Göpperti, 386
E. Hemingwayi, 259, 262–264
E. lateralis, 265, 275–279
E. Monyi, 266
E. Mougeoti, 267
E. Münsteri, 278, 279
E. Parlatori, 280
E. platyodon, 267
E. rotiferum, 279
E. spatulatus, 264, 265
E. Vaujolyi, 261
E. Yokoyamae, 280
E. zeaeformis, 265–266
Equisetum, 19, 245–254, 258, 262, 263, 267, 268, 281, 282, 285, 286,
287, 290, 292, 297, 298, 304, 307, 308, 309, 327, 337, 346, 360,
381, 384, 388, 390
Equisetaceae, 19, 244–254, 255, 256
Equisetales, fossil, 254–388
Equisetales, recent, 244–254
Equisetites, 254, 257–273, 282, 291, 330, 413
E. arenaceus, 268, 269, 275, 280
E. Beani, 270–275
E. Brodii, 278
E. Burchardti, 279, 280
E. Burejensis, 280
E. columnaris, 72, 265, 269–271
E. Göpperti, 386
E. Hemingwayi, 259, 262–264
E. lateralis, 265, 275–279
E. Monyi, 266
E. Mougeoti, 267
E. Münsteri, 278, 279
E. Parlatori, 280
E. platyodon, 267
E. rotiferum, 279
E. spatulatus, 264, 265
E. Vaujolyi, 261
E. Yokoyamae, 280
E. zeaeformis, 265–266
Equisetum, 19, 245–254, 258, 262, 263, 267, 268, 281, 282, 285, 286,
287, 290, 292, 297, 298, 304, 307, 308, 309, 327, 337, 346, 360,
381, 384, 388, 390
Page 478
E. arvense, 246, 247, 251, 279
E. debile, 95, 96, 97
E. giganteum, 245, 297
E. hiemale, 270
E. limosum, 263
E. litorale, 253
E. maximum, 245, 246, 247, 250–253
E. palustre, 247, 253
E. ramosissimum, 259, 265, 270
E. sylvaticum, 247, 279
E. Telmateia, 245
E. trachyodon, 270
E. variegatum, 95, 252
E. xylochaetum, 250
Eryngium Lassauxi, 99
E. montanum, 99
Etheridge, R., 200, 215, 290
Ettingshausen, C. von, 6, 7, 311, 332, 372
Eucalamites, 367, 376, 379
Eurypterus, 371
E. mammatus, 371
Feilden, Col. H. W., 211
Feistmantel, O., 284, 291, 293, 387
Felix, J., 399
Fischer, A., 217
E. debile, 95, 96, 97
E. giganteum, 245, 297
E. hiemale, 270
E. limosum, 263
E. litorale, 253
E. maximum, 245, 246, 247, 250–253
E. palustre, 247, 253
E. ramosissimum, 259, 265, 270
E. sylvaticum, 247, 279
E. Telmateia, 245
E. trachyodon, 270
E. variegatum, 95, 252
E. xylochaetum, 250
Eryngium Lassauxi, 99
E. montanum, 99
Etheridge, R., 200, 215, 290
Ettingshausen, C. von, 6, 7, 311, 332, 372
Eucalamites, 367, 376, 379
Eurypterus, 371
E. mammatus, 371
Feilden, Col. H. W., 211
Feistmantel, O., 284, 291, 293, 387
Felix, J., 399
Fischer, A., 217
Page 479
Fish-scales, 127, 182
Fleurs d’eau, 132, 182
Fliche, P. and Bleicher, 232
Flint, 62
Florideae, 175, 183–190
Flowers, fossil, 70
Flysch, 147, 148, 192
Fontinalis, 240
Foraminifera, 26, 161, 163, 175, 185
Forbes, E., 16
Forbes, H. O., 63
Forest-bed, 53
Forests, fossil, 56
Fossil, meaning of term, 67
Fossil plants, determination of, 93–109
Fossil trees, 74, 79, 80
Fossils in half-relief, 77
Fracastaro, 2
Freeman, E. J., 23
Frullania, 236
Frustules of Diatoms, 150
Fuchs, T., 159, 164
Fucoides, 142, 191
F. erectus, 233
Fucoids, 87, 147, 148
Fucus, 191, 192, 202, 231
Fleurs d’eau, 132, 182
Fliche, P. and Bleicher, 232
Flint, 62
Florideae, 175, 183–190
Flowers, fossil, 70
Flysch, 147, 148, 192
Fontinalis, 240
Foraminifera, 26, 161, 163, 175, 185
Forbes, E., 16
Forbes, H. O., 63
Forest-bed, 53
Forests, fossil, 56
Fossil, meaning of term, 67
Fossil plants, determination of, 93–109
Fossil trees, 74, 79, 80
Fossils in half-relief, 77
Fracastaro, 2
Freeman, E. J., 23
Frullania, 236
Frustules of Diatoms, 150
Fuchs, T., 159, 164
Fucoides, 142, 191
F. erectus, 233
Fucoids, 87, 147, 148
Fucus, 191, 192, 202, 231
Page 480
F. crispus, 191
Funafuti Island, 184
Fungi, 207–222, 305
Galium, 338, 389
G. sphenophylloides, 341
Gallionella, 153
Gardiner, Stanley, 184
Gardner, Starkie, 58, 240, 273
Geikie, Sir A., 39
Geinitz, H. B., 408
Geological evolution, 53
Geological history, 22–53
Germar, E. F., 297, 409
Geysers, 92, 126
Ginkgo, 58, 210, 390
G. biloba, 15
Girvanella, 124–126, 160
Globigerine ooze, 118
Glœocapsa, 122, 130
Glœotheca, 122
Gloioconis, 130
Glossopteris Browniana, 182
Glossopteris Flora, 291, 294
Gomphonema, 153
Gomphosphaeria, 181
Funafuti Island, 184
Fungi, 207–222, 305
Galium, 338, 389
G. sphenophylloides, 341
Gallionella, 153
Gardiner, Stanley, 184
Gardner, Starkie, 58, 240, 273
Geikie, Sir A., 39
Geinitz, H. B., 408
Geological evolution, 53
Geological history, 22–53
Germar, E. F., 297, 409
Geysers, 92, 126
Ginkgo, 58, 210, 390
G. biloba, 15
Girvanella, 124–126, 160
Globigerine ooze, 118
Glœocapsa, 122, 130
Glœotheca, 122
Gloioconis, 130
Glossopteris Browniana, 182
Glossopteris Flora, 291, 294
Gomphonema, 153
Gomphosphaeria, 181
Page 481
Gondwana system, 46–47, 84, 288, 292, 411
Gondwana Land, 294
Goniada maculata, 143, 144
Goniolina, 176, 177
Göppert, H. R., 1, 9, 146, 283, 284, 300, 301, 304, 386, 387
Göppert and Berendt, 235
Göppert and Menge, 206
Gottsche, 236
Gottschea, 237
Gramineae, 273
Grand’Croix, 80, 137
Grand’Eury, C., 101, 261, 262, 289, 316, 332, 336, 343, 371, 375, 381
Gray, Asa, 16
Greensand rocks, 50, 145
Grevillea, 99
Gryllotalpa vulgaris, 146
Guillemard, F. H. H., 90
Gümbel, C. W., 171, 176, 188
Gymnostomum, 241
Gyroporella, 174, 175, 176
G. bellerophontis, 175
Hakea, 99
Half-relief fossils, 77
Halimeda, 164, 185, 202
H. gracilis, 164
Gondwana Land, 294
Goniada maculata, 143, 144
Goniolina, 176, 177
Göppert, H. R., 1, 9, 146, 283, 284, 300, 301, 304, 386, 387
Göppert and Berendt, 235
Göppert and Menge, 206
Gottsche, 236
Gottschea, 237
Gramineae, 273
Grand’Croix, 80, 137
Grand’Eury, C., 101, 261, 262, 289, 316, 332, 336, 343, 371, 375, 381
Gray, Asa, 16
Greensand rocks, 50, 145
Grevillea, 99
Gryllotalpa vulgaris, 146
Guillemard, F. H. H., 90
Gümbel, C. W., 171, 176, 188
Gymnostomum, 241
Gyroporella, 174, 175, 176
G. bellerophontis, 175
Hakea, 99
Half-relief fossils, 77
Halimeda, 164, 185, 202
H. gracilis, 164
Page 482
H. Saportae, 164
Haplographites cateniger, 217, 220
Haploporella fasciculata, 177
Hartig, R., 212
Harvey, W. H., 164
Hauck, F., 187, 188
Heer, O., 6, 40, 51, 68, 132, 155, 276, 280, 286, 290, 366
Heim, A., 28
Helophyton, 342
Henson, 118
Hepaticae, 230–236
Herzer, H., 211
Heterospory, 355, 356, 357, 406
Hick, T., 304, 306, 330
Hicks, H., 199, 200, 203
Hippurites, 332, 371
H. gigantea, 267
H. longifolia, 335
Holmes, W. H., 79
Homotaxis, 31
Hooker, Sir J., 10, 16, 63, 90, 139, 151, 203, 204
Hookeria pennata, 231
Hostinella, 200
Hughes, T. McKenny, 31
Humboldt, A. von, 14
Hutton, W., 87
Haplographites cateniger, 217, 220
Haploporella fasciculata, 177
Hartig, R., 212
Harvey, W. H., 164
Hauck, F., 187, 188
Heer, O., 6, 40, 51, 68, 132, 155, 276, 280, 286, 290, 366
Heim, A., 28
Helophyton, 342
Henson, 118
Hepaticae, 230–236
Herzer, H., 211
Heterospory, 355, 356, 357, 406
Hick, T., 304, 306, 330
Hicks, H., 199, 200, 203
Hippurites, 332, 371
H. gigantea, 267
H. longifolia, 335
Holmes, W. H., 79
Homotaxis, 31
Hooker, Sir J., 10, 16, 63, 90, 139, 151, 203, 204
Hookeria pennata, 231
Hostinella, 200
Hughes, T. McKenny, 31
Humboldt, A. von, 14
Hutton, W., 87
Page 483
Huttonia, 360, 363
Huxley, T. H., 31
Hydatica, 344
Hydrozoa, 187, 190
Hyella, 127
Hyphochytrium infestans, 217
Ice-Age, 17, 53
Igneous rocks, 26, 27, 35
Incrustation, 79
Incrusting springs, 68
India, 84, 287–289, 292–294, 411
Infranodal canals, 285, 324, 327, 375
Inversion of strata, 29, 30
Italy, 286, 287, 291
James, J. F., 210
Jungermannia, 230, 236
Jurassic system, 48–50, 55, 226, 257, 269, 282, 283, 290, 291
Kaulfussia æsculifolia, 97, 98
Keeling Island, 65
Keeping, W., 147
Kellaways rock, 49
Kent, S., 184
Kerguelen Land, 16
Kerosene shale, 179–182
Huxley, T. H., 31
Hydatica, 344
Hydrozoa, 187, 190
Hyella, 127
Hyphochytrium infestans, 217
Ice-Age, 17, 53
Igneous rocks, 26, 27, 35
Incrustation, 79
Incrusting springs, 68
India, 84, 287–289, 292–294, 411
Infranodal canals, 285, 324, 327, 375
Inversion of strata, 29, 30
Italy, 286, 287, 291
James, J. F., 210
Jungermannia, 230, 236
Jurassic system, 48–50, 55, 226, 257, 269, 282, 283, 290, 291
Kaulfussia æsculifolia, 97, 98
Keeling Island, 65
Keeping, W., 147
Kellaways rock, 49
Kent, S., 184
Kerguelen Land, 16
Kerosene shale, 179–182
Page 484
Keuper series, 47, 48, 130
Kickx, J. J., 411
Kidston, R., 44, 82, 148, 263, 264, 334, 374, 375, 385, 386, 406, 408,
409
Kieselguhr, 150
Kiltorkan beds, 39
Kimeridge clay, 49, 78, 158, 159
Kjellman, F. R., 187
Koechlin-Schlumberger, J., 269
Kolguev Island, 211
Kölliker, A., 127
König, C., 269
Knorria, 101, 102, 366
Knowlton, F. H., 8, 225
Krakatoa, 58, 131
Kuntze, O., 92
Laggan Bay, Arran, 88
Lake, P., 200
Lamarck, de, 161, 175
Laminaria, 140, 141, 194, 202
Lamouroux, J., 161
Lapworth, C., 37, 147
Laurentian rocks, 36
Lavas, Tertiary, 58
Leasowe, 58, 59
Leckenby, J., 233, 234
Kickx, J. J., 411
Kidston, R., 44, 82, 148, 263, 264, 334, 374, 375, 385, 386, 406, 408,
409
Kieselguhr, 150
Kiltorkan beds, 39
Kimeridge clay, 49, 78, 158, 159
Kjellman, F. R., 187
Koechlin-Schlumberger, J., 269
Kolguev Island, 211
Kölliker, A., 127
König, C., 269
Knorria, 101, 102, 366
Knowlton, F. H., 8, 225
Krakatoa, 58, 131
Kuntze, O., 92
Laggan Bay, Arran, 88
Lake, P., 200
Lamarck, de, 161, 175
Laminaria, 140, 141, 194, 202
Lamouroux, J., 161
Lapworth, C., 37, 147
Laurentian rocks, 36
Lavas, Tertiary, 58
Leasowe, 58, 59
Leckenby, J., 233, 234
Page 485
Lehmann, 336
Leithakalk, 169, 187
Leocarpus, 206
Lepidodendron, 10, 57, 72, 75, 81, 82, 89, 101, 107, 216, 217, 218,
237
L. Veltheimianum, 101
Lepidostrobus, 3
Leptothrix, 126
Lesquereux, L., 6, 210, 240
Lessonia, 140, 141, 191, 193, 202
Lettenkohle, 48, 268
Lhwyd, E., 4, 112, 341
Lias, 48, 49, 61, 120, 154, 229, 240, 278
Limestone, 25
Limulus, 145
Lindley, T., 99, 105
Lindley, T. and Hutton, W., 10, 267, 276, 298, 330, 332, 343, 366, 369,
371, 375
Linnaeus, 113, 225
Lithophyllum, 183–187
Lithothamnion, 183–189
L. crassum, 185
L. fasciculatum, 185
L. mamillosum, 155, 188
L. suganum, 186, 188
Lithoxylon, 112, 386
Llandeilo flags, 37
Leithakalk, 169, 187
Leocarpus, 206
Lepidodendron, 10, 57, 72, 75, 81, 82, 89, 101, 107, 216, 217, 218,
237
L. Veltheimianum, 101
Lepidostrobus, 3
Leptothrix, 126
Lesquereux, L., 6, 210, 240
Lessonia, 140, 141, 191, 193, 202
Lettenkohle, 48, 268
Lhwyd, E., 4, 112, 341
Lias, 48, 49, 61, 120, 154, 229, 240, 278
Limestone, 25
Limulus, 145
Lindley, T., 99, 105
Lindley, T. and Hutton, W., 10, 267, 276, 298, 330, 332, 343, 366, 369,
371, 375
Linnaeus, 113, 225
Lithophyllum, 183–187
Lithothamnion, 183–189
L. crassum, 185
L. fasciculatum, 185
L. mamillosum, 155, 188
L. suganum, 186, 188
Lithoxylon, 112, 386
Llandeilo flags, 37
Page 486
London clay, 153
Lough Neagh, 80
Ludlow rocks, 38, 203
Ludwig, R., 212, 241
Lulworth Cove, 56
Lunularia, 231
Lycopodiaceae, 390, 412, 413
Lycopodites, 232, 237
L. Meeki, 240
Lycopodium phlegmaria, 237
Lyell, Sir C., 52, 60, 64, 65, 74, 227, 324
Lyginodendron, 19, 20, 88, 103, 221
Lyme Regis, 61
McClelland, 412
McCoy, F., 284, 288
McMurtrie, J., 335
Macrocystis, 191, 194
Macrostachya, 350, 360, 362, 363, 364, 371, 381
Magnesian limestone, 46
Mahr, 410
Mantell, G., 62, 145
Marattiaceae, 98
Marchantia, 230–235
M. oolithus, 232
Marchantiales, 233–236
Lough Neagh, 80
Ludlow rocks, 38, 203
Ludwig, R., 212, 241
Lulworth Cove, 56
Lunularia, 231
Lycopodiaceae, 390, 412, 413
Lycopodites, 232, 237
L. Meeki, 240
Lycopodium phlegmaria, 237
Lyell, Sir C., 52, 60, 64, 65, 74, 227, 324
Lyginodendron, 19, 20, 88, 103, 221
Lyme Regis, 61
McClelland, 412
McCoy, F., 284, 288
McMurtrie, J., 335
Macrocystis, 191, 194
Macrostachya, 350, 360, 362, 363, 364, 371, 381
Magnesian limestone, 46
Mahr, 410
Mantell, G., 62, 145
Marattiaceae, 98
Marchantia, 230–235
M. oolithus, 232
Marchantiales, 233–236
Page 487
Marchantites, 233–236
M. erectus, 233
M. Sezannensis, 235
M. Zeilleri, 234
Marcou, J., 46
Marsh, O. C., 79
Marsilia, 342, 390
Martin, W., 297
Massalongo, E. G., 6
Medusa, 144
Meek, F. B., 235
Melobesia, 184
Melobesieae, 184
Memecylon, 214
Meschinelli, 210
Mesomycetes, 208, 211
Metamorphism, 30
Michelin, H., 163, 167
Micrococci, 138
Micrococcus, 135, 136
M. Guignardi, 136
M. Zeilleri, 134
Migula, W., 222
Millstone grit, 40, 42, 43, 376
Miocene rocks, 52, 187, 241
Mississippi, rafts, 64, 65
M. erectus, 233
M. Sezannensis, 235
M. Zeilleri, 234
Marcou, J., 46
Marsh, O. C., 79
Marsilia, 342, 390
Martin, W., 297
Massalongo, E. G., 6
Medusa, 144
Meek, F. B., 235
Melobesia, 184
Melobesieae, 184
Memecylon, 214
Meschinelli, 210
Mesomycetes, 208, 211
Metamorphism, 30
Michelin, H., 163, 167
Micrococci, 138
Micrococcus, 135, 136
M. Guignardi, 136
M. Zeilleri, 134
Migula, W., 222
Millstone grit, 40, 42, 43, 376
Miocene rocks, 52, 187, 241
Mississippi, rafts, 64, 65
Page 488
Mniaceae, 239
Möbius, K. A., 166, 167
Monocotyledons, 99, 240, 273, 291, 366
Mougeot, A., 300
Mountain limestone, 40, 43
Mucor, 213, 221
M. combrensis, 213
Mull, leaf-beds in, 58
Munier-Chalmas, E., 161, 163, 167, 168, 171, 172, 176
Murchison, Sir R., 37, 38, 42
Murray, G., 119–121, 125, 158, 159, 170, 204, 240
Murray, J., 118, 120
Murray, Dr, 87
Muschelkalk series, 47
Musci, 236–241
Muscites, 238, 239, 241
M. ferrugineus, 241
M. polytrichaceus, 239
Mycelium, 207
Mycomycetes, 208, 211
Myeloxylon, 19, 86
Myriophylloides Williamsonis, 342
Myriophyllum, 344
Myxomycetes, 205, 206, 220
M. Mangini, 205, 206
Möbius, K. A., 166, 167
Monocotyledons, 99, 240, 273, 291, 366
Mougeot, A., 300
Mountain limestone, 40, 43
Mucor, 213, 221
M. combrensis, 213
Mull, leaf-beds in, 58
Munier-Chalmas, E., 161, 163, 167, 168, 171, 172, 176
Murchison, Sir R., 37, 38, 42
Murray, G., 119–121, 125, 158, 159, 170, 204, 240
Murray, J., 118, 120
Murray, Dr, 87
Muschelkalk series, 47
Musci, 236–241
Muscites, 238, 239, 241
M. ferrugineus, 241
M. polytrichaceus, 239
Mycelium, 207
Mycomycetes, 208, 211
Myeloxylon, 19, 86
Myriophylloides Williamsonis, 342
Myriophyllum, 344
Myxomycetes, 205, 206, 220
M. Mangini, 205, 206
Page 489
Najadita, 240
Nansen, 151
Nathorst, A. G., 60, 77, 78, 144, 145, 148, 232, 366
Navicula, 153
Nematophycus, 192–204
N. crassus, 198, 201, 202
N. Dechianus, 201
N. Hicksi, 199, 201
N. laxus, 201
N. Logani, 194–197, 199, 201, 202
N. Ortoni, 200, 201
N. Storriei, 193, 198–201
N. tenuis, 201
Nesea, 161
Neumayr, M., 49
Neu Paka, 369
Neuropteris Scheuchzeri, 45
New South Wales, 179, 181, 182, 288
Newberry, J. S., 146
Nicholson, H. A., 338
Nicholson, H. A. and Etheridge, J., 123, 124, 190
Nicol, W., 8
Nipa fruticans, 63
Nitelleæ, 222, 223, 225
Nodules, calcareous, 85, 86, 108
Nomenclature, 110–115
Nansen, 151
Nathorst, A. G., 60, 77, 78, 144, 145, 148, 232, 366
Navicula, 153
Nematophycus, 192–204
N. crassus, 198, 201, 202
N. Dechianus, 201
N. Hicksi, 199, 201
N. laxus, 201
N. Logani, 194–197, 199, 201, 202
N. Ortoni, 200, 201
N. Storriei, 193, 198–201
N. tenuis, 201
Nesea, 161
Neumayr, M., 49
Neu Paka, 369
Neuropteris Scheuchzeri, 45
New South Wales, 179, 181, 182, 288
Newberry, J. S., 146
Nicholson, H. A., 338
Nicholson, H. A. and Etheridge, J., 123, 124, 190
Nicol, W., 8
Nipa fruticans, 63
Nitelleæ, 222, 223, 225
Nodules, calcareous, 85, 86, 108
Nomenclature, 110–115
Page 490
Nostoc, 123, 132
Nostocaceae, 122, 123
Nuclei, fossil, 87, 88, 331
Nullipores, 171, 184, 185
Odontocaulis Keepingi, 147
Old Red Sandstone, 39, 204
Oldhamia, 146
O. antiqua, 145
O. radiata, 145, 146
Olenellus, 37
Oligocene, 52, 188, 209, 211, 234
Olpidium, 216
Oncylogonatum carbonarium, 269
Onychiopsis Mantelli, 112
Onychium, 112
Oochytrium Lepidodendri, 216, 217
Oolite, 49, 72, 269, 271, 276, 286
Oolitic structure, 123–126
Ophioglossum, 390
d’Orbigny, A. D., 175
Ordovician, 37, 38, 189, 338
Oscillariaceae, 122
Osmunda, 87
Osmundites Dowkeri, 212
Ostracoblabe, 129
Nostocaceae, 122, 123
Nuclei, fossil, 87, 88, 331
Nullipores, 171, 184, 185
Odontocaulis Keepingi, 147
Old Red Sandstone, 39, 204
Oldhamia, 146
O. antiqua, 145
O. radiata, 145, 146
Olenellus, 37
Oligocene, 52, 188, 209, 211, 234
Olpidium, 216
Oncylogonatum carbonarium, 269
Onychiopsis Mantelli, 112
Onychium, 112
Oochytrium Lepidodendri, 216, 217
Oolite, 49, 72, 269, 271, 276, 286
Oolitic structure, 123–126
Ophioglossum, 390
d’Orbigny, A. D., 175
Ordovician, 37, 38, 189, 338
Oscillariaceae, 122
Osmunda, 87
Osmundites Dowkeri, 212
Ostracoblabe, 129
Page 491
O. implexa, 129
Ovulites, 161–164, 173
O. elongata, 163
O. margaritula, 162, 163, 174
Oxford clay, 49
Pachytheca, 202–204
Palaeachyla, 127, 129
Palaeomyces, 221
P. gracilis, 218
Palaeoperone endophytica, 215
Palaeostachya, 350, 357–360, 362, 364, 371, 381
P. arborescens, 363, 364
P. pedunculata, 357, 358, 362, 363
P. vera, 358, 359, 362
Paleohepatica Rostafinski, 234
Pandanus, 99
Paracalamostachys, 361
Paris basin, 161, 167, 171, 176
Parkinson, J., 1, 78
Parsons, J., 4
Peat, 26, 75, 228, 236
Pellia, 230, 231
Penarth, 48
Penhallow, D. P., 193, 194, 197, 201, 202, 210
Penicillus, 159, 161, 163, 164, 202
Ovulites, 161–164, 173
O. elongata, 163
O. margaritula, 162, 163, 174
Oxford clay, 49
Pachytheca, 202–204
Palaeachyla, 127, 129
Palaeomyces, 221
P. gracilis, 218
Palaeoperone endophytica, 215
Palaeostachya, 350, 357–360, 362, 364, 371, 381
P. arborescens, 363, 364
P. pedunculata, 357, 358, 362, 363
P. vera, 358, 359, 362
Paleohepatica Rostafinski, 234
Pandanus, 99
Paracalamostachys, 361
Paris basin, 161, 167, 171, 176
Parkinson, J., 1, 78
Parsons, J., 4
Peat, 26, 75, 228, 236
Pellia, 230, 231
Penarth, 48
Penhallow, D. P., 193, 194, 197, 201, 202, 210
Penicillus, 159, 161, 163, 164, 202
Page 492
P. pyramidalis, 162
Peridiniaceae, 117
Peridiniales, 117, 118
Peridinium, 117, 118
P. divergens, 118
P. pyrophorum, 118
Permian system, 45, 47, 130, 182, 209, 256, 282, 283, 298, 300, 391,
408, 413
Permo-Carboniferous, 46, 213, 222, 256, 284, 289, 292, 293
Peronosporites, 218
P. antiquarius, 214, 217, 219
Petrifaction, 79–90, 92
Petrified wood, 79–90
Petrifying springs, 68
Pettycur, 88, 390, 397
Petzholdt, A., 298, 299
Phaeophyceae, 150, 191–202
Philippi, R. A., 185
Phillips, J., 275, 276
Phloeoterma, 254
Phycodes, 149
Phycomycetes, 218
Phycopsis, 192
Phyllotheca, 254–256, 276, 277, 281–289, 292, 293, 337
P. australis, 284, 287–289
P. Brongniarti, 286, 287
Peridiniaceae, 117
Peridiniales, 117, 118
Peridinium, 117, 118
P. divergens, 118
P. pyrophorum, 118
Permian system, 45, 47, 130, 182, 209, 256, 282, 283, 298, 300, 391,
408, 413
Permo-Carboniferous, 46, 213, 222, 256, 284, 289, 292, 293
Peronosporites, 218
P. antiquarius, 214, 217, 219
Petrifaction, 79–90, 92
Petrified wood, 79–90
Petrifying springs, 68
Pettycur, 88, 390, 397
Petzholdt, A., 298, 299
Phaeophyceae, 150, 191–202
Philippi, R. A., 185
Phillips, J., 275, 276
Phloeoterma, 254
Phycodes, 149
Phycomycetes, 218
Phycopsis, 192
Phyllotheca, 254–256, 276, 277, 281–289, 292, 293, 337
P. australis, 284, 287–289
P. Brongniarti, 286, 287
Page 493
P. carnosa, 291
P. deliquescens, 283
P. indica, 284, 287–289
P. Rallii, 283
P. sibirica, 290
Phymatoderma, 120, 146, 154
Phytolithus, 297, 335, 373
P. sulcatus, 374
Pila, 180–182
P. bibractensis, 181
P. scotica, 181
Pinnularia, 344, 381
Pith-casts, of Calamites, 365–380
Plagiochila, 232
Plankton, 117, 118, 152
Plauenscher Grund, 298
Pleurococcaceae, 181
Pliocene rocks, 52, 53
Plot, R., 4
Poacites, 366
Podocarpus cupressina, 231, 232
Podostemaceae, 231
Pollen-grains, 182
Polydonia frondosa, 144
Polygonaceæ, 96
Polygonum equisetiforme, 96, 97
P. deliquescens, 283
P. indica, 284, 287–289
P. Rallii, 283
P. sibirica, 290
Phymatoderma, 120, 146, 154
Phytolithus, 297, 335, 373
P. sulcatus, 374
Pila, 180–182
P. bibractensis, 181
P. scotica, 181
Pinnularia, 344, 381
Pith-casts, of Calamites, 365–380
Plagiochila, 232
Plankton, 117, 118, 152
Plauenscher Grund, 298
Pleurococcaceae, 181
Pliocene rocks, 52, 53
Plot, R., 4
Poacites, 366
Podocarpus cupressina, 231, 232
Podostemaceae, 231
Pollen-grains, 182
Polydonia frondosa, 144
Polygonaceæ, 96
Polygonum equisetiforme, 96, 97
Page 494
Polyporus, 208, 211, 212
P. vaporarius, 217, 221
Polytrichum, 236, 239
Polytrypa, 172
Polyzoa, 142, 231
Portland, Dirt-beds, 49, 56, 57
Pothocites, 385
P. Grantoni, 386
Potonié, R., 209, 259, 286, 337, 403
Precambrian rocks, 36
Presl, R., 5
Priority, rule of, 113
Protannularia, 338
Proteaceæ, 98
Protonema, 230
Prototaxites, 192, 193
Psilotum, 412
Pteridophyta, 242–414
Pteropods, 156
Puccinia, 213
Purbeck, 49, 56, 57, 227
Pyrula, 158
Pyxidicula, 154
Quekett, J., 127
Rachiopteris, 86
P. vaporarius, 217, 221
Polytrichum, 236, 239
Polytrypa, 172
Polyzoa, 142, 231
Portland, Dirt-beds, 49, 56, 57
Pothocites, 385
P. Grantoni, 386
Potonié, R., 209, 259, 286, 337, 403
Precambrian rocks, 36
Presl, R., 5
Priority, rule of, 113
Protannularia, 338
Proteaceæ, 98
Protonema, 230
Prototaxites, 192, 193
Psilotum, 412
Pteridophyta, 242–414
Pteropods, 156
Puccinia, 213
Purbeck, 49, 56, 57, 227
Pyrula, 158
Pyxidicula, 154
Quekett, J., 127
Rachiopteris, 86
Page 495
Radiolaria, 42, 118
Radstock, 335, 375
Reboulia, 231
Reefs, 184, 185
Reid, Clement, 60
Reinsch, 106
Reinschia, 180–182
Renault, B., 108, 130, 134, 136, 138, 178, 206, 213, 216, 217, 218,
221, 222, 309, 320, 328, 339, 340, 342, 348, 349, 362–364, 369,
375, 384, 390, 392, 399, 406
Renault, B. and Bertrand, C. E., 135, 137, 178, 180, 181
Renault, B. and Zeiller, R., 240, 266, 371
Restio tetraphylla, 95
Reuss, A. E., 169
Rhabdoliths, 120
Rhabdospheres, 118, 121
Rhacophyllum, 142
Rhaetic series, 48, 155, 278, 279
Rhizodendron oppoliense, 84
Rhizogonium, 239
Rhodophyceae, 127, 183, 190
Richea dracophylla, 99
Richmond, Virginia, 152
Rill-marks, 144
Rivularia, 126
Rivulariaceae, 129
Rock-building, 23
Radstock, 335, 375
Reboulia, 231
Reefs, 184, 185
Reid, Clement, 60
Reinsch, 106
Reinschia, 180–182
Renault, B., 108, 130, 134, 136, 138, 178, 206, 213, 216, 217, 218,
221, 222, 309, 320, 328, 339, 340, 342, 348, 349, 362–364, 369,
375, 384, 390, 392, 399, 406
Renault, B. and Bertrand, C. E., 135, 137, 178, 180, 181
Renault, B. and Zeiller, R., 240, 266, 371
Restio tetraphylla, 95
Reuss, A. E., 169
Rhabdoliths, 120
Rhabdospheres, 118, 121
Rhacophyllum, 142
Rhaetic series, 48, 155, 278, 279
Rhizodendron oppoliense, 84
Rhizogonium, 239
Rhodophyceae, 127, 183, 190
Richea dracophylla, 99
Richmond, Virginia, 152
Rill-marks, 144
Rivularia, 126
Rivulariaceae, 129
Rock-building, 23
Page 496
Rodway, J., 64
Roots, Calamites, 342–349
Rosanoff, 187
Rose, C. B., 127, 128
Rosellinia congregata, 209
Rosellinites, 209
R. Beyschlagii, 209
Rosenvinge, L. K., 187
Ross, Sir J., 139
Rothliegendes strata, 46
Rothpletz, A., 120, 147, 148, 154, 160, 175, 177, 192, 387
Rotularia, 390
R. marsileaefolia, 407
Rotuma Island, 184
Royle, J. F., 411
Rubeola mineralis, 341
Rufford, P., 114, 280
Rules for nomenclature, 111–115
Russia, 282
Saccamina, 151
Saccardo, P. A., 210
St. Étienne, 137, 390, 399
Salt Lake, 122, 123
Salvinia, 355, 390
Sandberger, F., 173
Roots, Calamites, 342–349
Rosanoff, 187
Rose, C. B., 127, 128
Rosellinia congregata, 209
Rosellinites, 209
R. Beyschlagii, 209
Rosenvinge, L. K., 187
Ross, Sir J., 139
Rothliegendes strata, 46
Rothpletz, A., 120, 147, 148, 154, 160, 175, 177, 192, 387
Rotularia, 390
R. marsileaefolia, 407
Rotuma Island, 184
Royle, J. F., 411
Rubeola mineralis, 341
Rufford, P., 114, 280
Rules for nomenclature, 111–115
Russia, 282
Saccamina, 151
Saccardo, P. A., 210
St. Étienne, 137, 390, 399
Salt Lake, 122, 123
Salvinia, 355, 390
Sandberger, F., 173
Page 497
Sanderson, 8
Sandstone, 24
Saporta, Marquis de, 6, 106, 114, 176, 234, 235
Saprolegnia, 215
Sardinia, 177
Sargassum, 191
Saxony, 79
Scale-insects, 210
Schenk, A., 9, 279
Scheuchzer, J. T., 4, 296, 338, 389
Schimper, W. P., 9, 269, 271, 276, 322, 351, 362, 386, 411
Schimper and Mougeot, 291, 293
Schizomycetes, 121, 132–138
Schizoneura, 254–256, 276, 284, 285, 291–294
S. gondwanensis, 292, 293
S. paradoxa, 292, 293
Schizophyceae, 121–132
Schizophyta, 121–138
Schizopteris dichotoma, 232
S. trichomanoides, 232
Schizothrix, 125
Schlotheim, E. F. von, 5, 297, 332, 389
Schlüter, C., 176
Schmalhausen, J., 282, 283, 286, 289, 290
Schoenlein, J. L. and Schenk, A., 269
Schröter, J., 206
Sandstone, 24
Saporta, Marquis de, 6, 106, 114, 176, 234, 235
Saprolegnia, 215
Sardinia, 177
Sargassum, 191
Saxony, 79
Scale-insects, 210
Schenk, A., 9, 279
Scheuchzer, J. T., 4, 296, 338, 389
Schimper, W. P., 9, 269, 271, 276, 322, 351, 362, 386, 411
Schimper and Mougeot, 291, 293
Schizomycetes, 121, 132–138
Schizoneura, 254–256, 276, 284, 285, 291–294
S. gondwanensis, 292, 293
S. paradoxa, 292, 293
Schizophyceae, 121–132
Schizophyta, 121–138
Schizopteris dichotoma, 232
S. trichomanoides, 232
Schizothrix, 125
Schlotheim, E. F. von, 5, 297, 332, 389
Schlüter, C., 176
Schmalhausen, J., 282, 283, 286, 289, 290
Schoenlein, J. L. and Schenk, A., 269
Schröter, J., 206
Page 498
Schulze, C. F., 296
Schulze, F., 87
Schütt, F., 118, 119, 121, 154
Schweinfurth, G., 92
Schwendener, S., 414
Sclerotia, 207
Sclerotites Salisburiae, 210
Scott, D. H., 301, 390, 405, 412, 413
Sea sawdust, 122
Secondary thickening, 300
Sections, geological, 27–29
Sedgwick, A., 36, 37, 42
Seeds, fossil, 91
Selaginella, 231, 232, 237, 355
S. Oregana, 231, 232, 240
S. rupestris, 232
Selaginellites, 232, 236
Sequoia, 16
Sézanne, 70, 235
Shales, 24
Sharpe, S., 69, 227
Shell-boring organisms, 183
Shells, 24
Sheppey fruits, 4
Shrubsole, W. H. and Kitton, F., 153
Siberia, 290
Schulze, F., 87
Schütt, F., 118, 119, 121, 154
Schweinfurth, G., 92
Schwendener, S., 414
Sclerotia, 207
Sclerotites Salisburiae, 210
Scott, D. H., 301, 390, 405, 412, 413
Sea sawdust, 122
Secondary thickening, 300
Sections, geological, 27–29
Sedgwick, A., 36, 37, 42
Seeds, fossil, 91
Selaginella, 231, 232, 237, 355
S. Oregana, 231, 232, 240
S. rupestris, 232
Selaginellites, 232, 236
Sequoia, 16
Sézanne, 70, 235
Shales, 24
Sharpe, S., 69, 227
Shell-boring organisms, 183
Shells, 24
Sheppey fruits, 4
Shrubsole, W. H. and Kitton, F., 153
Siberia, 290
Page 499
Sigillaria, 3, 6, 10, 75, 108
Silurian system, 38, 171, 173, 176, 204
Siphoneae, 125, 156, 157–177, 193
Siphonema, 160
Skiddaw slate, 338
Skye, Island of, 151
Smilax, 99
Smith, William, 43, 48
Smith, Worthington, 217, 218
Solenhofen plants, 78
Solenopora, 189, 190
S. compacta, 189
Sollas, W. J., 146
Solms-Laubach, Graf zu, 77, 92, 149, 166–168, 175, 177, 187, 193,
194, 200, 204, 277, 282, 286, 360, 362, 399, 405
Solomon Islands, 65
Sorby, H. C., 120
Spencer, J., 342
Sphaeriaceae, 209, 220
Sphaerites, 209
Sphaerocodium, 160
S. Bornemanni, 160, 186
Sphaerospermum, 87
Sphagnales, 236
Sphagnum, 236, 241
Sphenophyllales, 389–414
Silurian system, 38, 171, 173, 176, 204
Siphoneae, 125, 156, 157–177, 193
Siphonema, 160
Skiddaw slate, 338
Skye, Island of, 151
Smilax, 99
Smith, William, 43, 48
Smith, Worthington, 217, 218
Solenhofen plants, 78
Solenopora, 189, 190
S. compacta, 189
Sollas, W. J., 146
Solms-Laubach, Graf zu, 77, 92, 149, 166–168, 175, 177, 187, 193,
194, 200, 204, 277, 282, 286, 360, 362, 399, 405
Solomon Islands, 65
Sorby, H. C., 120
Spencer, J., 342
Sphaeriaceae, 209, 220
Sphaerites, 209
Sphaerocodium, 160
S. Bornemanni, 160, 186
Sphaerospermum, 87
Sphagnales, 236
Sphagnum, 236, 241
Sphenophyllales, 389–414
Page 500
Sphenophyllites, 390
S. emarginatus, 407
Sphenophyllostachys, 400, 402
S. Dawsoni, 402, 403, 405
S. Römeri, 405, 413
Sphenophyllum, 100, 350, 387–414
S. antiquum, 413
S. cuneifolium, 401, 402, 405, 408, 413
S. emarginatum, 391, 407, 408
S. furcatum, 386
S. insigne, 394, 396, 397, 400, 413
S. myriophyllum, 409
S. oblongifolium, 413
S. osnabrugense, 407
S. plurifoliatum, 394, 396–398, 400
S. speciosum, 411
S. tenerrimum, 409, 413
S. Thoni, 391, 410, 413
S. trichomatosum, 398, 408, 409
S. truncatum, 407
Sphenopteris, 77, 112
S. Mantelli, 112
Sphenothallus angustifolia, 148
Spiridens, 237
S. longifolius, 237
Spirophyton, 144
S. emarginatus, 407
Sphenophyllostachys, 400, 402
S. Dawsoni, 402, 403, 405
S. Römeri, 405, 413
Sphenophyllum, 100, 350, 387–414
S. antiquum, 413
S. cuneifolium, 401, 402, 405, 408, 413
S. emarginatum, 391, 407, 408
S. furcatum, 386
S. insigne, 394, 396, 397, 400, 413
S. myriophyllum, 409
S. oblongifolium, 413
S. osnabrugense, 407
S. plurifoliatum, 394, 396–398, 400
S. speciosum, 411
S. tenerrimum, 409, 413
S. Thoni, 391, 410, 413
S. trichomatosum, 398, 408, 409
S. truncatum, 407
Sphenopteris, 77, 112
S. Mantelli, 112
Sphenothallus angustifolia, 148
Spiridens, 237
S. longifolius, 237
Spirophyton, 144
Page 501
Sprengel, A., 7
Sprudelstein, 123
Stachannularia, 340, 361
Starch-grains, in fossil cells, 213
Stefani, K. de, 155, 156
Steinhauer, H., 5, 297, 373
Stenopora crinita, 215
Stenzel, G., 9, 298
Stephanopyxis, 154
Sternberg, Graf C. von, 5, 104, 257, 297, 332, 336, 363, 371, 389
Sternbergia, 104
Sterzel, J. T., 341, 378, 408
Stigmaria and Stigmarian appendages, 3, 10, 57, 71, 72, 73, 106, 111,
123, 218, 305, 311, 348, 404
Stigmatocanna Volkmanniana, 386
Stokes, C., 80
Stolley, E., 172
Stoneworts, 222–228
Storrie, J., 198, 203, 204
Strata, table of, 31, 32
Stratigraphical Geology, 26
Strickland, H. E., 111, 203
Stromatopora compacta, 189
Stur, D., 310, 343, 369, 370, 375, 376, 378, 384, 385, 386, 387, 409
Stylocalamites, 367, 374–376
Submerged forests, 59, 60
Sprudelstein, 123
Stachannularia, 340, 361
Starch-grains, in fossil cells, 213
Stefani, K. de, 155, 156
Steinhauer, H., 5, 297, 373
Stenopora crinita, 215
Stenzel, G., 9, 298
Stephanopyxis, 154
Sternberg, Graf C. von, 5, 104, 257, 297, 332, 336, 363, 371, 389
Sternbergia, 104
Sterzel, J. T., 341, 378, 408
Stigmaria and Stigmarian appendages, 3, 10, 57, 71, 72, 73, 106, 111,
123, 218, 305, 311, 348, 404
Stigmatocanna Volkmanniana, 386
Stokes, C., 80
Stolley, E., 172
Stoneworts, 222–228
Storrie, J., 198, 203, 204
Strata, table of, 31, 32
Stratigraphical Geology, 26
Strickland, H. E., 111, 203
Stromatopora compacta, 189
Stur, D., 310, 343, 369, 370, 375, 376, 378, 384, 385, 386, 387, 409
Stylocalamites, 367, 374–376
Submerged forests, 59, 60
Page 502
Suckow, G. A., 296, 297, 302
Surface-soils, 55–60
Swanage, 227
Sycidium, 173
S. melo, 155, 173
Synedra, 153
Tchikatcheff, P. de, 283
Teleutospora Milloti, 213
Tenison-Woods, J. E., 279, 291
Teredo, 61, 62
Tertiary Period, 51–53
Thallophyta, 116–228
Thiselton-Dyer, W. T., 87
Thomas, K., 71
van Tieghem, 136
Tmesipteris, 390
Torbanehill, 179, 182
Torbanite, 178, 179
Toula paper-coal, 68, 133
Trametes radiciperda, 215
Transition series, 40, 44, 413
Travertine, 69, 70, 234, 235
Treub, M., 131
Triassic system, 47, 48, 77, 78, 80, 146, 155, 160, 171, 174, 175, 256,
267, 268, 292–294
Trichomanes Goebelianum, 242
Surface-soils, 55–60
Swanage, 227
Sycidium, 173
S. melo, 155, 173
Synedra, 153
Tchikatcheff, P. de, 283
Teleutospora Milloti, 213
Tenison-Woods, J. E., 279, 291
Teredo, 61, 62
Tertiary Period, 51–53
Thallophyta, 116–228
Thiselton-Dyer, W. T., 87
Thomas, K., 71
van Tieghem, 136
Tmesipteris, 390
Torbanehill, 179, 182
Torbanite, 178, 179
Toula paper-coal, 68, 133
Trametes radiciperda, 215
Transition series, 40, 44, 413
Travertine, 69, 70, 234, 235
Treub, M., 131
Triassic system, 47, 48, 77, 78, 80, 146, 155, 160, 171, 174, 175, 256,
267, 268, 292–294
Trichomanes Goebelianum, 242
Page 503
Trigonocarpon, 91
Triploporella, 177
Tristichia hypnoides, 231, 232
Trizygia, 411, 412
T. speciosa, 411
Tuedian series, 43
Tulip tree, 16
Turner, D., 191
Tylodendron, 104
Udotea, 171, 185, 202
Unconformity, 27
Underclay, 43
Unger, F., 187, 298, 299, 301
Uteria, 177
Vaillant, S., 225
Vascular Cryptogams, 242–414
Vaucheria, 157, 178
Venation, 99
Vermiporella, 172, 176
Vexillum, 149
Vinci, Leonardo da, 2
Vogelsang, H., 137
Volcanic rocks, 34, 51, 88, 89, 90
Volkmann, G. A., 296
Volkmannia, 350, 360, 361, 362
Triploporella, 177
Tristichia hypnoides, 231, 232
Trizygia, 411, 412
T. speciosa, 411
Tuedian series, 43
Tulip tree, 16
Turner, D., 191
Tylodendron, 104
Udotea, 171, 185, 202
Unconformity, 27
Underclay, 43
Unger, F., 187, 298, 299, 301
Uteria, 177
Vaillant, S., 225
Vascular Cryptogams, 242–414
Vaucheria, 157, 178
Venation, 99
Vermiporella, 172, 176
Vexillum, 149
Vinci, Leonardo da, 2
Vogelsang, H., 137
Volcanic rocks, 34, 51, 88, 89, 90
Volkmann, G. A., 296
Volkmannia, 350, 360, 361, 362
Page 504
V. Binneyi, 351
V. Dawsoni, 401
V. Ludwigi, 351
Wallace, A. R., 245
Ward, L., 1
Wealden, 50, 55, 112, 114, 234, 257, 279, 280
Weed, W. H., 126
Weiss, C. E., 290, 343, 344, 351, 357, 358, 360–364, 367, 369, 370,
371, 375, 377, 388, 401, 408
Wenlock series, 38, 124, 200, 203
Wethered, E., 124
Willdenow, K. L., 231
Wille, N., 170
Williamson, W. C., 9, 10, 71, 94, 100, 103, 132, 154, 218, 220, 231,
273, 276, 301, 304, 315, 322, 324–326, 342, 346, 355, 358, 390,
392, 397, 401, 403
Williamson, W. C. and Scott, D. H., 88, 307, 312, 319, 320, 342, 346,
349, 355, 358, 390, 392, 396, 397, 405, 406
Witham, H., 7, 8
Withamia, 115
Wood-boring insects, 107
Woodward, J., 3, 10, 34, 71, 296
Woronina, 216
Wünsch, 89
Yellowstone Park, 79, 92, 126, 150
Yoredale rocks, 40, 43
V. Dawsoni, 401
V. Ludwigi, 351
Wallace, A. R., 245
Ward, L., 1
Wealden, 50, 55, 112, 114, 234, 257, 279, 280
Weed, W. H., 126
Weiss, C. E., 290, 343, 344, 351, 357, 358, 360–364, 367, 369, 370,
371, 375, 377, 388, 401, 408
Wenlock series, 38, 124, 200, 203
Wethered, E., 124
Willdenow, K. L., 231
Wille, N., 170
Williamson, W. C., 9, 10, 71, 94, 100, 103, 132, 154, 218, 220, 231,
273, 276, 301, 304, 315, 322, 324–326, 342, 346, 355, 358, 390,
392, 397, 401, 403
Williamson, W. C. and Scott, D. H., 88, 307, 312, 319, 320, 342, 346,
349, 355, 358, 390, 392, 396, 397, 405, 406
Witham, H., 7, 8
Withamia, 115
Wood-boring insects, 107
Woodward, J., 3, 10, 34, 71, 296
Woronina, 216
Wünsch, 89
Yellowstone Park, 79, 92, 126, 150
Yoredale rocks, 40, 43
Page 505
Yorkshire coast, 55
Young, G. and Bird, J., 269
Zechstein series, 46
Zeiller, R., 76, 100, 133, 146, 232, 261, 264, 265, 282, 283, 289, 367,
375, 378, 390, 401, 403, 405, 406, 408, 409, 410, 411
Zigno, A. de, 6, 271, 276, 287
Zonatrichia calcivora, 130
Zonatrichites, 129, 130
Zygosporites, 214, 220, 221
Young, G. and Bird, J., 269
Zechstein series, 46
Zeiller, R., 76, 100, 133, 146, 232, 261, 264, 265, 282, 283, 289, 367,
375, 378, 390, 401, 403, 405, 406, 408, 409, 410, 411
Zigno, A. de, 6, 271, 276, 287
Zonatrichia calcivora, 130
Zonatrichites, 129, 130
Zygosporites, 214, 220, 221
Page 506
CAMBRIDGE: PRINTED BY J. AND C. F. CLAY, AT THE UNIVERSITY PRESS.
FOOTNOTES:
[1] Ward (84).
[2] Göppert (36).
[3] Parkinson (11), vol. i.
[4] For an account of the early views on fossils, v. Lyell (67), Vol. i. Vide also Leonardo da
Vinci (83).
[5] Woodward, J. (1695), Preface.
[6] Woodward, J. (1728), p. 59.
[7] Mendes da Costa (1758), p. 232.
[8] Scheuchzer (1723), p. 7, Pl. i. fig. 1.
[9] Parsons (1757), p. 402.
[10] Plot (1705), p. 125, Pl. vi. fig. 2.
[11] Ibid. Pl. vi. fig. 2.
[12] Lhwyd (1760).
[13] Artis (25).
[14] Steinhauer (18).
[15] Schlotheim (04).
[16] Sternberg (20).
[17] Brongniart (28) (282) (49).
[18] Brongniart (39).
[19] Heer (55) (68) (76).
[20] Lesquereux (66) (70) (80) etc.
[21] Zigno (56).
[22] Massalongo (51).
[23] Saporta (72) (73).
[24] Ettingshausen (79). Also numerous papers on fossil plants from Austria and other
countries.
[25] Sprengel (28).
[26] Witham (33).
[27] ibid., p. 3.
[28] Witham (33), p. 5.
FOOTNOTES:
[1] Ward (84).
[2] Göppert (36).
[3] Parkinson (11), vol. i.
[4] For an account of the early views on fossils, v. Lyell (67), Vol. i. Vide also Leonardo da
Vinci (83).
[5] Woodward, J. (1695), Preface.
[6] Woodward, J. (1728), p. 59.
[7] Mendes da Costa (1758), p. 232.
[8] Scheuchzer (1723), p. 7, Pl. i. fig. 1.
[9] Parsons (1757), p. 402.
[10] Plot (1705), p. 125, Pl. vi. fig. 2.
[11] Ibid. Pl. vi. fig. 2.
[12] Lhwyd (1760).
[13] Artis (25).
[14] Steinhauer (18).
[15] Schlotheim (04).
[16] Sternberg (20).
[17] Brongniart (28) (282) (49).
[18] Brongniart (39).
[19] Heer (55) (68) (76).
[20] Lesquereux (66) (70) (80) etc.
[21] Zigno (56).
[22] Massalongo (51).
[23] Saporta (72) (73).
[24] Ettingshausen (79). Also numerous papers on fossil plants from Austria and other
countries.
[25] Sprengel (28).
[26] Witham (33).
[27] ibid., p. 3.
[28] Witham (33), p. 5.
Page 507
[29] Nicol (34). See note by Prof. Jameson on p. 157 of the paper quoted, to the effect that
he has long known of this method of preparing sections.
[30] Limpricht (90) in Rabenhorst, vol. iv. p. 73.
[31] Knowlton (89).
[32] Corda (45).
[33] Binney (68), Introductory remarks.
[34] Williamson (71), etc.
[35] Solms-Laubach (95), p. 442.
[36] Lindley and Hutton (31).
[37] Woodward (1729), Pt. ii. p. 106.
[38] Humboldt (48), vol. i. p. 274.
[39] Vide Hooker, J. D. (81), for references to other writers on this subject; also Darwin
(82), ch. xii.
[40] Darwin (87), vol. iii. p. 247.
[41] Brongniart (49), p. 94.
[42] Grand’Eury (77), Potonié (96), Kidston (94), &c.
[43] Ward (92), Knowlton (94), Grand’Eury (90), p. 155.
[44] Old Persian writer, quoted by E. G. Browne in A Year among the Persians, p. 220,
London, 1893.
[45] W. R. W. Stephens, Life of Freeman, p. 132, London, 1895.
[46] Rothpletz (94).
[47] Heim (78).
[48] Geikie (93), p. 706.
[49] Hughes (79), p. 248.
[50] Whitney and Wadsworth (84).
[51] Murchison (72), p. 5.
[52] Kayser and Lake (95), p. 88.
[53] Kidston (94).
[54] Geikie (93), p. 825.
[55] Woodward, H. B. (87), p. 197.
[56] Hinde and Fox (95), p. 662.
[57] Kidston (94).
[58] Vide Zeiller (92) for a list of species of Coal-Measure plants found in the pieces of
shale included in the core brought up by the borer.
[59] Jukes-Browne (86), p. 252.
[60] Kayser and Lake (95), p. 196.
[61] Neumayr (83).
[62] Woodward, H. B. (87), p. 255.
he has long known of this method of preparing sections.
[30] Limpricht (90) in Rabenhorst, vol. iv. p. 73.
[31] Knowlton (89).
[32] Corda (45).
[33] Binney (68), Introductory remarks.
[34] Williamson (71), etc.
[35] Solms-Laubach (95), p. 442.
[36] Lindley and Hutton (31).
[37] Woodward (1729), Pt. ii. p. 106.
[38] Humboldt (48), vol. i. p. 274.
[39] Vide Hooker, J. D. (81), for references to other writers on this subject; also Darwin
(82), ch. xii.
[40] Darwin (87), vol. iii. p. 247.
[41] Brongniart (49), p. 94.
[42] Grand’Eury (77), Potonié (96), Kidston (94), &c.
[43] Ward (92), Knowlton (94), Grand’Eury (90), p. 155.
[44] Old Persian writer, quoted by E. G. Browne in A Year among the Persians, p. 220,
London, 1893.
[45] W. R. W. Stephens, Life of Freeman, p. 132, London, 1895.
[46] Rothpletz (94).
[47] Heim (78).
[48] Geikie (93), p. 706.
[49] Hughes (79), p. 248.
[50] Whitney and Wadsworth (84).
[51] Murchison (72), p. 5.
[52] Kayser and Lake (95), p. 88.
[53] Kidston (94).
[54] Geikie (93), p. 825.
[55] Woodward, H. B. (87), p. 197.
[56] Hinde and Fox (95), p. 662.
[57] Kidston (94).
[58] Vide Zeiller (92) for a list of species of Coal-Measure plants found in the pieces of
shale included in the core brought up by the borer.
[59] Jukes-Browne (86), p. 252.
[60] Kayser and Lake (95), p. 196.
[61] Neumayr (83).
[62] Woodward, H. B. (87), p. 255.
Page 508
[63] Kayser and Lake (95), p. 326.
[64] Huxley (93), p. 27.
[65] Discussed at greater length in vol. II.
[66] Woodward, H. B. (95), Figs. 124 and 133 from photographs by Mr Strahan.
[67] Buckland (37) Pl. LVII.
[68] Young, Glen, and Kidston (88).
[69] Gardner (87), p. 279.
[70] Treub (88).
[71] Morton (91), p. 228.
[72] Lyell (45), vol. I. p. 180.
[73] Mantell (44), vol. I. p. 168.
[74] Forbes, H. O. (85), p. 254.
[75] Hooker, J. D. (91), p. 477.
[76] Hooker, J. D. (91), p. 1. There are several good specimens of the black pyritised
nipadite fruits in the British Museum and other collections.
[77] Rodway (95), p. 106.
[78] Bates (63), p. 139.
[79] Bates (63), p. 239.
[80] Lyell (67) vol. II. p. 361.
[81] Lyell (67) vol. I. p. 445.
[82] Darwin (90) p. 443.
[83] Challenger (85), Narrative, vol. I. Pt. ii. p. 679.
[84] Bates (63) p. 389.
[85] Challenger (85), Narrative, vol. I. p. 459.
[86] Zeiller (82) and Renault (95).
[87] Heer (76).
[88] Schimper and Mougeot (44).
[89] Sharpe, S. (68) p. 563.
[90] There are still more perfect casts from Sézanne in Prof. Munier-Chalmas’ Geological
collection in the Sorbonne. The best examples have not yet been figured.
[91] Saporta (68).
[92] Darwin (90) p. 432.
[93] For figures of fossil plants in amber, vide Göppert and Berendt (45), Conwentz (90),
Conwentz (96) &c.
[94] Thomas (48).
[95] Adamson (88).
[96] Williamson (87) Pl. xv. p. 45. A very fine specimen, similar to that in the Manchester
Museum, has recently been added to the School of Mines Museum in Berlin; Potonié (90).
[64] Huxley (93), p. 27.
[65] Discussed at greater length in vol. II.
[66] Woodward, H. B. (95), Figs. 124 and 133 from photographs by Mr Strahan.
[67] Buckland (37) Pl. LVII.
[68] Young, Glen, and Kidston (88).
[69] Gardner (87), p. 279.
[70] Treub (88).
[71] Morton (91), p. 228.
[72] Lyell (45), vol. I. p. 180.
[73] Mantell (44), vol. I. p. 168.
[74] Forbes, H. O. (85), p. 254.
[75] Hooker, J. D. (91), p. 477.
[76] Hooker, J. D. (91), p. 1. There are several good specimens of the black pyritised
nipadite fruits in the British Museum and other collections.
[77] Rodway (95), p. 106.
[78] Bates (63), p. 139.
[79] Bates (63), p. 239.
[80] Lyell (67) vol. II. p. 361.
[81] Lyell (67) vol. I. p. 445.
[82] Darwin (90) p. 443.
[83] Challenger (85), Narrative, vol. I. Pt. ii. p. 679.
[84] Bates (63) p. 389.
[85] Challenger (85), Narrative, vol. I. p. 459.
[86] Zeiller (82) and Renault (95).
[87] Heer (76).
[88] Schimper and Mougeot (44).
[89] Sharpe, S. (68) p. 563.
[90] There are still more perfect casts from Sézanne in Prof. Munier-Chalmas’ Geological
collection in the Sorbonne. The best examples have not yet been figured.
[91] Saporta (68).
[92] Darwin (90) p. 432.
[93] For figures of fossil plants in amber, vide Göppert and Berendt (45), Conwentz (90),
Conwentz (96) &c.
[94] Thomas (48).
[95] Adamson (88).
[96] Williamson (87) Pl. xv. p. 45. A very fine specimen, similar to that in the Manchester
Museum, has recently been added to the School of Mines Museum in Berlin; Potonié (90).
Page 509
[97] The British Museum collection contains a specimen of Stigmaria preserved in the
same manner as the example shown in fig. 12.
[98] Lyell (45) vol. i. p. 60.
[99] Lyell (45) vol. i. p. 147.
[100] Warming (96) p. 170.
[101] Bornemann (56), Schenk (67), Zeiller (82).
[102] Solms-Laubach (952).
[103] Nathorst (86) p. 9. See also Delgado (86).
[104] Parkinson (11) vol. i. p. 431.
[105] The British Museum collection contains many good examples of the Solenhofen
plants.
[106] There is a splendid silicified tree stem from Tasmania of Tertiary age several feet in
height in the National Museum.
[107] Darwin (90) p. 317.
[108] Holmes (80) p. 126, fig. 1.
[109] Marsh (71).
[110] Conwentz (78).
[111] A large piece from one of these South African trees is in the Fossil-plant Gallery of
the British Museum.
[112] Barton (1751) p. 58.
[113] Gardner (84) p. 314.
[114] Stokes (40) p. 207.
[115] Witham (81), Christison (76).
[116] Cole (94), figs. 1 and 3.
[117] Harker (95) p. 233, fig. 56.
[118] I am indebted to Dr Renault of Paris for showing to me several preparations
illustrating this method of petrifaction.
[119] Cash and Hick (78).
[120] Stur (85).
[121] Thiselton-Dyer (72) Pl. vi.
[122] Carruthers (70).
[123] Schultze (55).
[124] I am indebted to Prof. Lebour of the Durham College of Science for the loan of this
letter.
[125] Seward (97).
[126] Williamson and Scott (96) Pl. xxiv. fig. 16.
[127] Bryce (72) p. 126, fig. 23.
[128] An erroneous interpretation of the Arran stems is given in Lyell’s Elements of
Geology: Lyell (78) p. 547.
same manner as the example shown in fig. 12.
[98] Lyell (45) vol. i. p. 60.
[99] Lyell (45) vol. i. p. 147.
[100] Warming (96) p. 170.
[101] Bornemann (56), Schenk (67), Zeiller (82).
[102] Solms-Laubach (952).
[103] Nathorst (86) p. 9. See also Delgado (86).
[104] Parkinson (11) vol. i. p. 431.
[105] The British Museum collection contains many good examples of the Solenhofen
plants.
[106] There is a splendid silicified tree stem from Tasmania of Tertiary age several feet in
height in the National Museum.
[107] Darwin (90) p. 317.
[108] Holmes (80) p. 126, fig. 1.
[109] Marsh (71).
[110] Conwentz (78).
[111] A large piece from one of these South African trees is in the Fossil-plant Gallery of
the British Museum.
[112] Barton (1751) p. 58.
[113] Gardner (84) p. 314.
[114] Stokes (40) p. 207.
[115] Witham (81), Christison (76).
[116] Cole (94), figs. 1 and 3.
[117] Harker (95) p. 233, fig. 56.
[118] I am indebted to Dr Renault of Paris for showing to me several preparations
illustrating this method of petrifaction.
[119] Cash and Hick (78).
[120] Stur (85).
[121] Thiselton-Dyer (72) Pl. vi.
[122] Carruthers (70).
[123] Schultze (55).
[124] I am indebted to Prof. Lebour of the Durham College of Science for the loan of this
letter.
[125] Seward (97).
[126] Williamson and Scott (96) Pl. xxiv. fig. 16.
[127] Bryce (72) p. 126, fig. 23.
[128] An erroneous interpretation of the Arran stems is given in Lyell’s Elements of
Geology: Lyell (78) p. 547.
Page 510
[129] Guillemard (86) p. 322.
[130] Heer (55).
[131] Göppert (36), etc.
[132] Hirschwald (73).
[133] Kuntze (80) p. 8.
[134] Schweinfurth (82).
[135] Solms-Laubach (91), p. 29.
[136] Göppert (57). Some of the large silicified trees mentioned by Göppert may be seen
in the Breslau Botanic gardens.
[137] An example referred to by Carruthers (71) p. 444.
[138] Williamson (71) p. 507.
[139] Dealt with more fully in vol. ii.
[140] Bentham (70).
[141] See also Bunbury (83) p. 309.
[142] Seward (96) p. 208.
[143] Darwin (90) p. 416.
[144] Solms-Laubach (91) p. 9.
[145] Balfour (72) p. 5.
[146] Grand’Eury (77) Pt. i., p. 3.
[147] 1 Renault and Zeiller (88) Pl. lx. fig. 1.
[148] Williamson (73) p. 393, Pl. xxvii. Described in detail in vol. ii. See also Solms-
Laubach (91) p. 7, fig. 1.
[149] A good example is figured by Newberry (88) Pl. xxv. as a decorticated coniferous
stem of Triassic age.
[150] Potonié (87).
[151] Lindley and Hutton (31) vol. iii. p. 4. See also Schenk (88) p. 202.
[152] Saporta (79) (77). Eopteris is included among the ferns in Schimper and Schenk’s
volume of Zittel’s Handbuch der Palaeontologie (p. 115), and in some other modern
works.
[153] Reinsch (81).
[154] Williamson has drawn attention to the occurrence of such borings and coprolites in
Coal-Measure plant tissues. E.g. Williamson (80) Pl. 20, figs. 65 and 66.
[155] Renault (96) p. 437.
[156] Slide No. 1923 in the Williamson collection.
[157] Crépin (81).
[158] Rules for Zoological Nomenclature, drawn up by the late H. E. Strickland, M.A.,
F.R.S., London, 1878.
[159] Lhwyd (1699).
[160] Knowlton (96) p. 82.
[130] Heer (55).
[131] Göppert (36), etc.
[132] Hirschwald (73).
[133] Kuntze (80) p. 8.
[134] Schweinfurth (82).
[135] Solms-Laubach (91), p. 29.
[136] Göppert (57). Some of the large silicified trees mentioned by Göppert may be seen
in the Breslau Botanic gardens.
[137] An example referred to by Carruthers (71) p. 444.
[138] Williamson (71) p. 507.
[139] Dealt with more fully in vol. ii.
[140] Bentham (70).
[141] See also Bunbury (83) p. 309.
[142] Seward (96) p. 208.
[143] Darwin (90) p. 416.
[144] Solms-Laubach (91) p. 9.
[145] Balfour (72) p. 5.
[146] Grand’Eury (77) Pt. i., p. 3.
[147] 1 Renault and Zeiller (88) Pl. lx. fig. 1.
[148] Williamson (73) p. 393, Pl. xxvii. Described in detail in vol. ii. See also Solms-
Laubach (91) p. 7, fig. 1.
[149] A good example is figured by Newberry (88) Pl. xxv. as a decorticated coniferous
stem of Triassic age.
[150] Potonié (87).
[151] Lindley and Hutton (31) vol. iii. p. 4. See also Schenk (88) p. 202.
[152] Saporta (79) (77). Eopteris is included among the ferns in Schimper and Schenk’s
volume of Zittel’s Handbuch der Palaeontologie (p. 115), and in some other modern
works.
[153] Reinsch (81).
[154] Williamson has drawn attention to the occurrence of such borings and coprolites in
Coal-Measure plant tissues. E.g. Williamson (80) Pl. 20, figs. 65 and 66.
[155] Renault (96) p. 437.
[156] Slide No. 1923 in the Williamson collection.
[157] Crépin (81).
[158] Rules for Zoological Nomenclature, drawn up by the late H. E. Strickland, M.A.,
F.R.S., London, 1878.
[159] Lhwyd (1699).
[160] Knowlton (96) p. 82.
Page 511
[161] Thiselton-Dyer (95) p. 846.
[162] Saporta (75) p. 193.
[163] Seward (95) p. 173.
[164] Ward (96) p. 874.
[165] Challenger (85) p. 934.
[166] Ehrenberg (36) p. 117, Pl. I. figs. 1 and 4, and Ehrenberg (54) Pl. xxxvii. fig. vii.
[167] Schütt (96) p. 22.
[168] Bütschli (83–87) p. 1028.
[169] Challenger Reports (85) p. 939.
[170] Challenger Reports (91) p. 257.
[171] Hensen (92), Schütt (93) p. 44.
[172] Murray, G., and Blackman, V. H. (97).
[173] Dixon and Joly (97).
[174] Sorby (79) p. 78.
[175] Rothpletz (96), p. 909, Pl. xxiii. fig. 4.
[176] Challenger (85) passim. Schütt (93).
[177] Phillips W. (93).
[178] Kippis (78) p. 115.
[179] Darwin (90) p. 13.
[180] Rothpletz (92).
[181] Walther (88).
[182] Cohn (62).
[183] Murray, G. (952).
[184] Thiselton-Dyer (91) p. 226.
[185] Nicholson and Etheridge (80) p. 28, Pl. ix. fig. 24.
[186] Wethered (93) p. 237.
[187] For figures of the sheaths of Cyanophyceous algae, see Murray (952), Pl. xix. fig. 5.
Gomont (88) and (92); etc.
[188] Brown (94) p. 203.
[189] For references to the papers of Wethered and others, see Seward (94), p. 24.
[190] E. G. Bornemann (87), Pl. ii.
[191] Moseley, H. N. (75), p. 321.
[192] Weed (87–88), vide also Tilden (97).
[193] Bornet and Flahault (892) Pl. xi.
[194] Batters (92).
[195] Quekett (54), fig. 78.
[196] Kölliker (59) and (592); good figures in the latter paper.
[162] Saporta (75) p. 193.
[163] Seward (95) p. 173.
[164] Ward (96) p. 874.
[165] Challenger (85) p. 934.
[166] Ehrenberg (36) p. 117, Pl. I. figs. 1 and 4, and Ehrenberg (54) Pl. xxxvii. fig. vii.
[167] Schütt (96) p. 22.
[168] Bütschli (83–87) p. 1028.
[169] Challenger Reports (85) p. 939.
[170] Challenger Reports (91) p. 257.
[171] Hensen (92), Schütt (93) p. 44.
[172] Murray, G., and Blackman, V. H. (97).
[173] Dixon and Joly (97).
[174] Sorby (79) p. 78.
[175] Rothpletz (96), p. 909, Pl. xxiii. fig. 4.
[176] Challenger (85) passim. Schütt (93).
[177] Phillips W. (93).
[178] Kippis (78) p. 115.
[179] Darwin (90) p. 13.
[180] Rothpletz (92).
[181] Walther (88).
[182] Cohn (62).
[183] Murray, G. (952).
[184] Thiselton-Dyer (91) p. 226.
[185] Nicholson and Etheridge (80) p. 28, Pl. ix. fig. 24.
[186] Wethered (93) p. 237.
[187] For figures of the sheaths of Cyanophyceous algae, see Murray (952), Pl. xix. fig. 5.
Gomont (88) and (92); etc.
[188] Brown (94) p. 203.
[189] For references to the papers of Wethered and others, see Seward (94), p. 24.
[190] E. G. Bornemann (87), Pl. ii.
[191] Moseley, H. N. (75), p. 321.
[192] Weed (87–88), vide also Tilden (97).
[193] Bornet and Flahault (892) Pl. xi.
[194] Batters (92).
[195] Quekett (54), fig. 78.
[196] Kölliker (59) and (592); good figures in the latter paper.
Page 512
[197] Rose (55), Pl. i.
[198] For other references vide Bornet and Flahault (892).
[199] Duncan (76) and (762).
[200] Similar borings are figured by Kölliker (592), Pl. xvi. 14, in a scale of Beryx ornatus
from the Chalk.
[201] Bornet and Flahault (892).
[202] E. G. Wedl (59). Good figures are given in this paper.
[203] Bornemann (86), p. 126, Pls. v. and vi.
[204] Renault (961) p. 446.
[205] Treub (88).
[206] Williamson (88).
[207] Heer (55) vol. i. p. 21, Pl. iv. fig. 2.
[208] de Bary (87) p. 9. A good account of the Schizomycetes has lately been written by
Migula in Engler and Prantl’s Pflanzenfamilien, Leipzig, 1896.
[209] 1 µ = 0·001 millimetres.
[210] James (982), translation of a paper by M. Ferry in the Revue Mycologique, 1893.
[211] Zeiller (82).
[212] Renault (951), (961) p. 478, (962) p. 106. (Several figures of the cuticles are given in
these publications.)
[213] Renault (961) p. 492.
[214] Renault (952), (961), (962).
[215] Renault and Bertrand (94). See also Renault (952) p. 3, (961) p. 449, Pl. lxxxix. (962)
p. 94, and (963) p. 280, fig. 3.
[216] Renault (952) p. 17, fig. 9, (961) p. 460, fig. 102, and (963) p. 292, fig. 10.
[217] Renault (963) p. 297, fig. 14.
[218] Van Tieghem (77).
[219] Van Tieghem (79).
[220] Vogelsang (74). Vide also Rutley (92).
[221] I am indebted to Prof. Kanthack for calling my attention to an interesting account of
Bacilli in small stones found in gall-bladders; a manner of occurrence comparable to that
of the fossil forms in petrified tissues. Vide Naunyn (96) p. 51.
[222] Renault (963) p. 277.
[223] Hooker, J. D. (44) p. 457. Pls. clxvii. clxviii. and clxxi. D.
[224] An American writer has recently discussed the literature and history of Fucoides; he
gives a list of 85 species. It is very doubtful if such work as this is worth the labour. (James
[93].)
[225] Wille (97) p. 136, also Murray, G. (95) p. 121.
[226] Linnarsson (69) Pl. xi. fig. 3. There are many good specimens of this fossil in the
Geological Survey Museum, Stockholm.
[227] Nathorst (812), and (96).
[198] For other references vide Bornet and Flahault (892).
[199] Duncan (76) and (762).
[200] Similar borings are figured by Kölliker (592), Pl. xvi. 14, in a scale of Beryx ornatus
from the Chalk.
[201] Bornet and Flahault (892).
[202] E. G. Wedl (59). Good figures are given in this paper.
[203] Bornemann (86), p. 126, Pls. v. and vi.
[204] Renault (961) p. 446.
[205] Treub (88).
[206] Williamson (88).
[207] Heer (55) vol. i. p. 21, Pl. iv. fig. 2.
[208] de Bary (87) p. 9. A good account of the Schizomycetes has lately been written by
Migula in Engler and Prantl’s Pflanzenfamilien, Leipzig, 1896.
[209] 1 µ = 0·001 millimetres.
[210] James (982), translation of a paper by M. Ferry in the Revue Mycologique, 1893.
[211] Zeiller (82).
[212] Renault (951), (961) p. 478, (962) p. 106. (Several figures of the cuticles are given in
these publications.)
[213] Renault (961) p. 492.
[214] Renault (952), (961), (962).
[215] Renault and Bertrand (94). See also Renault (952) p. 3, (961) p. 449, Pl. lxxxix. (962)
p. 94, and (963) p. 280, fig. 3.
[216] Renault (952) p. 17, fig. 9, (961) p. 460, fig. 102, and (963) p. 292, fig. 10.
[217] Renault (963) p. 297, fig. 14.
[218] Van Tieghem (77).
[219] Van Tieghem (79).
[220] Vogelsang (74). Vide also Rutley (92).
[221] I am indebted to Prof. Kanthack for calling my attention to an interesting account of
Bacilli in small stones found in gall-bladders; a manner of occurrence comparable to that
of the fossil forms in petrified tissues. Vide Naunyn (96) p. 51.
[222] Renault (963) p. 277.
[223] Hooker, J. D. (44) p. 457. Pls. clxvii. clxviii. and clxxi. D.
[224] An American writer has recently discussed the literature and history of Fucoides; he
gives a list of 85 species. It is very doubtful if such work as this is worth the labour. (James
[93].)
[225] Wille (97) p. 136, also Murray, G. (95) p. 121.
[226] Linnarsson (69) Pl. xi. fig. 3. There are many good specimens of this fossil in the
Geological Survey Museum, Stockholm.
[227] Nathorst (812), and (96).
Page 513
[228] Nathorst (81) p. 14.
[229] Mantell (33) p. 166. Vide also Morris (54) p. 6.
[230] Bateson (88).
[231] Nathorst (81), (86) &c. Dawson (88) p. 26 et seq. Dawson (90) Delgado (86)
Williamson (85) Hughes (84) Zeiller (84) Saporta (81) (82) (84) (86) Fuchs (95) Rothpletz
(96).
[232] Kinahan (58).
[233] Sollas (86).
[234] Barrois (88). References to other records of this genus may be found in Barrois’
paper.
[235] Zeiller (84). Phymatoderma is probably a horny sponge (vide p. 154).
[236] Newberry (88) p. 82, Pl. xxi. There are some large specimens of this supposed alga
in the National Museum, Washington; they are undoubtedly of the nature of rill-marks.
[237] Vide Williamson (85).
[238] Dawson (90) p. 615.
[239] Salter (78) p. 99.
[240] Lapworth (81) p. 176, Pl. vii. fig. 7.
[241] Rothpletz (96).
[242] A term applied to a certain facies of Eocene and Oligocene rocks in Central Europe.
[243] Hall (47) Pl. lxviii. 1 and 2, p. 261.
[244] Nathorst (83) p. 453.
[245] Seward (942) p. 4.
[246] Kidston (83) Pl. xxxii. fig. 2. Specimens of this form may be seen in the British
Museum collection.
[247] Cf. Matthew, G. F. (89). Hall called attention in 1852 to the prevalent habit of
describing ‘algae’ from the older strata, without any evidence for a vegetable origin. (Hall
[52] p. 18.)
[248] Credner (87) p. 431.
[249] Saporta (84) p. 45, Pl. vii.
[250] Solms-Laubach (91) p. 51.
[251] A monograph on the Diatomaceae has recently been written by Schütt for Engler and
Prantl’s systematic work. See also Murray, G. (97) and Pfitzer (71).
[252] Darwin (90) p. 5.
[253] Weed (87).
[254] Wilson (87).
[255] Ehrenberg (54).
[256] Noll (95) p. 248.
[257] Hooker, J. D. (44) vol. i. p. 503.
[258] Murray, J. and Renard (91) p. 208.
[229] Mantell (33) p. 166. Vide also Morris (54) p. 6.
[230] Bateson (88).
[231] Nathorst (81), (86) &c. Dawson (88) p. 26 et seq. Dawson (90) Delgado (86)
Williamson (85) Hughes (84) Zeiller (84) Saporta (81) (82) (84) (86) Fuchs (95) Rothpletz
(96).
[232] Kinahan (58).
[233] Sollas (86).
[234] Barrois (88). References to other records of this genus may be found in Barrois’
paper.
[235] Zeiller (84). Phymatoderma is probably a horny sponge (vide p. 154).
[236] Newberry (88) p. 82, Pl. xxi. There are some large specimens of this supposed alga
in the National Museum, Washington; they are undoubtedly of the nature of rill-marks.
[237] Vide Williamson (85).
[238] Dawson (90) p. 615.
[239] Salter (78) p. 99.
[240] Lapworth (81) p. 176, Pl. vii. fig. 7.
[241] Rothpletz (96).
[242] A term applied to a certain facies of Eocene and Oligocene rocks in Central Europe.
[243] Hall (47) Pl. lxviii. 1 and 2, p. 261.
[244] Nathorst (83) p. 453.
[245] Seward (942) p. 4.
[246] Kidston (83) Pl. xxxii. fig. 2. Specimens of this form may be seen in the British
Museum collection.
[247] Cf. Matthew, G. F. (89). Hall called attention in 1852 to the prevalent habit of
describing ‘algae’ from the older strata, without any evidence for a vegetable origin. (Hall
[52] p. 18.)
[248] Credner (87) p. 431.
[249] Saporta (84) p. 45, Pl. vii.
[250] Solms-Laubach (91) p. 51.
[251] A monograph on the Diatomaceae has recently been written by Schütt for Engler and
Prantl’s systematic work. See also Murray, G. (97) and Pfitzer (71).
[252] Darwin (90) p. 5.
[253] Weed (87).
[254] Wilson (87).
[255] Ehrenberg (54).
[256] Noll (95) p. 248.
[257] Hooker, J. D. (44) vol. i. p. 503.
[258] Murray, J. and Renard (91) p. 208.
Page 514
[259] Nansen, Daily Chronicle, Nov. 2, 1896.
[260] Schütt (93) p. 10.
[261] Ehrenberg (36) p. 77.
[262] Cayeux (92), (97).
[263] Shrubsole and Kitton (81).
[264] I am indebted to Mr Murton Holmes for specimens of these London Clay Diatoms.
[265] Rothpletz (96) p. 910, fig. 3, Pl. xxiii. fig. 203.
[266] Schütt (96) p. 62.
[267] Castracane (76).
[268] Heer (76) p. 66, Pl. xxiii. and (53) p. 117, Pl. vi.
[269] Stefani (82) p. 103.
[270] The Chlorophyceae have recently been exhaustively dealt with by Wille (97) in
Engler and Prantl’s Pflanzenfamilien.
[271] Vide p. 142.
[272] Murray G. (95) p. 123.
[273] Göppert (60) p. 439. Pl. xxxiv. fig. 8.
[274] Zeiller (84).
[275] Murray G. (92) p. 11; also (95) p. 127.
[276] Damon (88) Pl. xix. fig. 12.
[277] Vide also Rothpletz (96) p. 894.
[278] Ellis (1755) Pl. xxxiii. α p. 86.
[279] Fuchs (96) Pl. viii. fig. 3.
[280] Murray G. (95) Pl. iii. figs. 1 and 2.
[281] Rothpletz (90), and (91) Pls. xv. and xvi.
[282] Bornemann (87) p. 17, Pl. ii. pp. 1–4.
[283] Lamouroux (21) Pl. xxv. fig. 5, p. 23.
[284] Munier-Chalmas (79).
[285] For references to genera of calcareous algae previously referred to Foraminifera,
vide Sherborn (93).
[286] Lamarck (16) p. 193.
[287] Defrance (26) Pl. xlviii. fig. 2, and Pl. l. fig. 6.
[288] Carpenter (62) p. 179, Pl. xii. figs. 9 and 10.
[289] Michelin (40–47) Pl. xlvi. fig. 24.
[290] Munier-Chalmas (79).
[291] Lamouroux (21) Pl. xxv. fig. 6, p. 23.
[292] Harvey (58) Vol. I. Pl. xxii. fig. 3.
[293] Fuchs (94).
[260] Schütt (93) p. 10.
[261] Ehrenberg (36) p. 77.
[262] Cayeux (92), (97).
[263] Shrubsole and Kitton (81).
[264] I am indebted to Mr Murton Holmes for specimens of these London Clay Diatoms.
[265] Rothpletz (96) p. 910, fig. 3, Pl. xxiii. fig. 203.
[266] Schütt (96) p. 62.
[267] Castracane (76).
[268] Heer (76) p. 66, Pl. xxiii. and (53) p. 117, Pl. vi.
[269] Stefani (82) p. 103.
[270] The Chlorophyceae have recently been exhaustively dealt with by Wille (97) in
Engler and Prantl’s Pflanzenfamilien.
[271] Vide p. 142.
[272] Murray G. (95) p. 123.
[273] Göppert (60) p. 439. Pl. xxxiv. fig. 8.
[274] Zeiller (84).
[275] Murray G. (92) p. 11; also (95) p. 127.
[276] Damon (88) Pl. xix. fig. 12.
[277] Vide also Rothpletz (96) p. 894.
[278] Ellis (1755) Pl. xxxiii. α p. 86.
[279] Fuchs (96) Pl. viii. fig. 3.
[280] Murray G. (95) Pl. iii. figs. 1 and 2.
[281] Rothpletz (90), and (91) Pls. xv. and xvi.
[282] Bornemann (87) p. 17, Pl. ii. pp. 1–4.
[283] Lamouroux (21) Pl. xxv. fig. 5, p. 23.
[284] Munier-Chalmas (79).
[285] For references to genera of calcareous algae previously referred to Foraminifera,
vide Sherborn (93).
[286] Lamarck (16) p. 193.
[287] Defrance (26) Pl. xlviii. fig. 2, and Pl. l. fig. 6.
[288] Carpenter (62) p. 179, Pl. xii. figs. 9 and 10.
[289] Michelin (40–47) Pl. xlvi. fig. 24.
[290] Munier-Chalmas (79).
[291] Lamouroux (21) Pl. xxv. fig. 6, p. 23.
[292] Harvey (58) Vol. I. Pl. xxii. fig. 3.
[293] Fuchs (94).
Page 515
[294] Lamouroux gives a figure of Acetabularia, and includes this genus with several
other algae in the animal kingdom (Lamouroux [21] p. 19), Pl. lxix.).
[295] Solms-Laubach (953).
[296] D’Archiac (43) p. 386, Pl. xxv. fig. 8.
[297] Solms-Laubach loc. cit. p. 33, Pl. iii.
[298] D’Archiac (43) p. 386, Pl. xxv. fig. 8.
[299] Michelin (40) p. 176, Pl. xlvi. fig. 14.
[300] Carpenter (62) p. 137, Pl. xi. figs. 27–82.
[301] Solms-Laubach loc. cit. p. 32.
[302] Ibid. p. 34, Pl. iii. fig. 13.
[303] Andrussow (87).
[304] Solms-Laubach (953) p. 11.
[305] Carpenter (62) Pl. xi. fig. 32.
[306] Reuss (61) p. 8, figs. 5–8.
[307] Ellis (1755) Pl. xxv. C.
[308] Solms-Laubach (91) p. 38 gives a detailed description with two figures of a recent
species of Cymopolia.
[309] Murray G. (95).
[310] Wille (97).
[311] Munier-Chalmas (77).
[312] Cramer (87) (90).
[313] Solms-Laubach (91) (93) (953).
[314] Church (95).
[315] Gümbel (71).
[316] Benecke (76).
[317] Defrance (26) p. 453.
[318] Munier-Chalmas (77) p. 815.
[319] Munier-Chalmas ibid.
[320] Defrance (26) Pl. xlviii. fig. 1.
[321] Stolley (93).
[322] Deecke (83).
[323] Benecke (76) Pl. xxiii.
[324] Solms-Laubach (91) p. 42.
[325] Rothpletz (94) p. 24.
[326] Lamarck (16) p. 188.
[327] Carpenter (62) Pl. x.
[328] Gümbel (71). Vide also Solms-Laubach (91) p. 39.
[329] Stolley (93).
other algae in the animal kingdom (Lamouroux [21] p. 19), Pl. lxix.).
[295] Solms-Laubach (953).
[296] D’Archiac (43) p. 386, Pl. xxv. fig. 8.
[297] Solms-Laubach loc. cit. p. 33, Pl. iii.
[298] D’Archiac (43) p. 386, Pl. xxv. fig. 8.
[299] Michelin (40) p. 176, Pl. xlvi. fig. 14.
[300] Carpenter (62) p. 137, Pl. xi. figs. 27–82.
[301] Solms-Laubach loc. cit. p. 32.
[302] Ibid. p. 34, Pl. iii. fig. 13.
[303] Andrussow (87).
[304] Solms-Laubach (953) p. 11.
[305] Carpenter (62) Pl. xi. fig. 32.
[306] Reuss (61) p. 8, figs. 5–8.
[307] Ellis (1755) Pl. xxv. C.
[308] Solms-Laubach (91) p. 38 gives a detailed description with two figures of a recent
species of Cymopolia.
[309] Murray G. (95).
[310] Wille (97).
[311] Munier-Chalmas (77).
[312] Cramer (87) (90).
[313] Solms-Laubach (91) (93) (953).
[314] Church (95).
[315] Gümbel (71).
[316] Benecke (76).
[317] Defrance (26) p. 453.
[318] Munier-Chalmas (77) p. 815.
[319] Munier-Chalmas ibid.
[320] Defrance (26) Pl. xlviii. fig. 1.
[321] Stolley (93).
[322] Deecke (83).
[323] Benecke (76) Pl. xxiii.
[324] Solms-Laubach (91) p. 42.
[325] Rothpletz (94) p. 24.
[326] Lamarck (16) p. 188.
[327] Carpenter (62) Pl. x.
[328] Gümbel (71). Vide also Solms-Laubach (91) p. 39.
[329] Stolley (93).
Page 516
[330] Schlüter (79).
[331] Saporta (91) Pl. xxxii. &c.
[332] Solms-Laubach (93), Pl. ix. figs. 1, 8.
[333] Cramer (90).
[334] Rothpletz (922) p. 235.
[335] Steinmann (80).
[336] Solms-Laubach (91), p. 40. fig. 3. Vide also Deecke (83) Pl. i. fig. 12.
[337] Brongniart (28) p. 211.
[338] Bornemann (91) p. 485. Pls. 42 and 43.
[339] Seward (952) p. 367.
[340] Report of the Trial (62).
[341] Bertrand and Renault (92) p. 29.
[342] Bertrand (93), Bertrand and Renault (92) (94), Bertrand (96), Renault (96).
Additional references may be found in these memoirs.
[343] Batters (92). Vide also Schmitz (97) p. 315.
[344] Hauck (85) in Rabenhorst’s Kryptogamen Flora, vol. ii.
[345] Kent (93) p. 140.
[346] Agassiz (88) vol. i. p. 82.
[347] Walther (85).
[348] Ibid. (88) p. 478.
[349] Philippi (37) p. 387.
[350] Rosanoff(66) Pl. vi. fig. 10.
[351] Rothpletz (91) Pl. xvii. fig. 4.
[352] Früh (90) fig. 12.
[353] Kjellman (83).
[354] Holmes and Batters (90) p. 102.
[355] Hauck (85). Rosanoff (66). Rosenvinge (93) p. 779. Kjellman (83) p. 88. Solms-
Laubach (81).
[356] Unger (58).
[357] A microscopic section of the Vienna Leithakalk is figured in Nicholson and
Lydekker’s Manual of Palæontology (89) vol. ii. p. 1497.
[358] Gümbel (71) Pl. ii. fig. 7, p. 41.
[359] Hauck (85) p. 272.
[360] Rothpletz (91) Pl. xvii. fig. 4.
[361] Vide Walther (88) p. 499; also Jukes-Browne and Harrison (91) passim. I am
indebted to Mr G. F. Franks, who has studied the Barbadian reefs, for the opportunity of
examining sections of West-Indian coral-rock.
[362] Brown A. (94).
[363] Brown A. (94) p. 147.
[331] Saporta (91) Pl. xxxii. &c.
[332] Solms-Laubach (93), Pl. ix. figs. 1, 8.
[333] Cramer (90).
[334] Rothpletz (922) p. 235.
[335] Steinmann (80).
[336] Solms-Laubach (91), p. 40. fig. 3. Vide also Deecke (83) Pl. i. fig. 12.
[337] Brongniart (28) p. 211.
[338] Bornemann (91) p. 485. Pls. 42 and 43.
[339] Seward (952) p. 367.
[340] Report of the Trial (62).
[341] Bertrand and Renault (92) p. 29.
[342] Bertrand (93), Bertrand and Renault (92) (94), Bertrand (96), Renault (96).
Additional references may be found in these memoirs.
[343] Batters (92). Vide also Schmitz (97) p. 315.
[344] Hauck (85) in Rabenhorst’s Kryptogamen Flora, vol. ii.
[345] Kent (93) p. 140.
[346] Agassiz (88) vol. i. p. 82.
[347] Walther (85).
[348] Ibid. (88) p. 478.
[349] Philippi (37) p. 387.
[350] Rosanoff(66) Pl. vi. fig. 10.
[351] Rothpletz (91) Pl. xvii. fig. 4.
[352] Früh (90) fig. 12.
[353] Kjellman (83).
[354] Holmes and Batters (90) p. 102.
[355] Hauck (85). Rosanoff (66). Rosenvinge (93) p. 779. Kjellman (83) p. 88. Solms-
Laubach (81).
[356] Unger (58).
[357] A microscopic section of the Vienna Leithakalk is figured in Nicholson and
Lydekker’s Manual of Palæontology (89) vol. ii. p. 1497.
[358] Gümbel (71) Pl. ii. fig. 7, p. 41.
[359] Hauck (85) p. 272.
[360] Rothpletz (91) Pl. xvii. fig. 4.
[361] Vide Walther (88) p. 499; also Jukes-Browne and Harrison (91) passim. I am
indebted to Mr G. F. Franks, who has studied the Barbadian reefs, for the opportunity of
examining sections of West-Indian coral-rock.
[362] Brown A. (94).
[363] Brown A. (94) p. 147.
Page 517
[364] ibid. p. 200.
[365] e.g. Saporta (82) p. 12.
[366] Turner (11) vol. ii. p. 51.
[367] Rothpletz (96).
[368] Penhallow (96) p. 45.
[369] Dawson (59).
[370] Vide ‘Academy’ 1870, p. 16.
[371] Carruthers (72).
[372] Penhallow (89).
[373] Barber (92).
[374] Solms-Laubach (952).
[375] Penhallow (96).
[376] loc. cit. p. 83.
[377] Dawson (59), also (71) p. 17.
[378] Penhallow (89) and (96) p. 46.
[379] Barber (92) p. 336.
[380] Penhallow (89) and (93).
[381] Dawson (81) p. 302.
[382] Barber (92).
[383] Hicks (81) p. 490.
[384] Lake (95) p. 22.
[385] Solms-Laubach (952).
[386] A similar method of fossilisation has been noted by Rothpletz in the case of the
Lower Devonian alga Hostinella. [Rothpletz (96) p. 896.]
[387] Penhallow (96) p. 47.
[388] Carruthers (72) p. 162 regards this species as identical with N. Logani.
[389] Seward (953).
[390] Strickland and Hooker (53).
[391] Hicks (81) p. 484.
[392] Dawson (82) p. 104.
[393] Barber (89) and (90).
[394] Murray G. (953).
[395] Hooker J. D. (89).
[396] loc. cit.
[397] Solms-Laubach (952) p. 81.
[398] Seward (942) p. 4.
[399] An excellent monograph on the Mycetozoa has lately been issued by the Trustees of
the British Museum under the authorship of Mr A. Lister (94). Vide also Schröter (89) in
[365] e.g. Saporta (82) p. 12.
[366] Turner (11) vol. ii. p. 51.
[367] Rothpletz (96).
[368] Penhallow (96) p. 45.
[369] Dawson (59).
[370] Vide ‘Academy’ 1870, p. 16.
[371] Carruthers (72).
[372] Penhallow (89).
[373] Barber (92).
[374] Solms-Laubach (952).
[375] Penhallow (96).
[376] loc. cit. p. 83.
[377] Dawson (59), also (71) p. 17.
[378] Penhallow (89) and (96) p. 46.
[379] Barber (92) p. 336.
[380] Penhallow (89) and (93).
[381] Dawson (81) p. 302.
[382] Barber (92).
[383] Hicks (81) p. 490.
[384] Lake (95) p. 22.
[385] Solms-Laubach (952).
[386] A similar method of fossilisation has been noted by Rothpletz in the case of the
Lower Devonian alga Hostinella. [Rothpletz (96) p. 896.]
[387] Penhallow (96) p. 47.
[388] Carruthers (72) p. 162 regards this species as identical with N. Logani.
[389] Seward (953).
[390] Strickland and Hooker (53).
[391] Hicks (81) p. 484.
[392] Dawson (82) p. 104.
[393] Barber (89) and (90).
[394] Murray G. (953).
[395] Hooker J. D. (89).
[396] loc. cit.
[397] Solms-Laubach (952) p. 81.
[398] Seward (942) p. 4.
[399] An excellent monograph on the Mycetozoa has lately been issued by the Trustees of
the British Museum under the authorship of Mr A. Lister (94). Vide also Schröter (89) in
Page 518
Engler and Prantl’s Natürlichen Pflanzenfamilien.
[400] Renault (96) p. 422, figs. 75 and 76.
[401] Schröter (89) p. 32, fig. 18 B.
[402] Cash and Hick (782) Pl. vi. fig. 3.
[403] Göppert and Menge (83) Pl. xiii. fig. 106.
[404] Harper (95).
[405] e.g. Ludwig (57) Pl. xvi. fig. 1.
[406] Potonié (93) p. 27, Pl. i. fig. 8.
[407] References are given by Potonié to illustrations by Zeiller (922) Pl. xv. fig. 6, Grand’
Eury (77) Pl. xxxiii. fig. 7, and others in which possible fungi are represented.
[408] Engelhardt (87).
[409] For figures of the Coccineae, see Comstock (88), Maskell (87), Judeich and Nitsche
(95) &c.
[410] Massalongo (59) Pl. i. fig. 1, p. 87.
[411] Meschinelli (92).
[412] James, J. F. (932).
[413] Lesquereux (87).
[414] Herzer (93).
[415] Conwentz (90) Pl. xii. fig. 5.
[416] Feilden, H. W. (96); Seward (962) p. 62, appendix to Feilden’s paper. I am indebted
to Dr Bonney for an opportunity of examining the plant remains from the Feilden
collection.
[417] Hartig (78).
[418] Conwentz (80) Pl. v. fig. 17.
[419] Carruthers (70) Pl. xxv. fig. 3.
[420] Renault (96) p. 427, fig. 80, d.
[421] ibid. p. 427, fig. 80, a–c.
[422] p. 127.
[423] Etheridge (92) Pl. vii.
[424] Hartig (78) and (94), Göppert and Menge (83).
[425] Renault (96) p. 425, fig. 78.
[426] Fischer in Rabenhorst, vol. i. (92) p. 144.
[427] Carruthers (76) p. 22, fig. 1.
[428] Smith, W. O. (77) p. 499.
[429] Williamson (81) Pl. xlviii. p. 301.
[430] Renault (96) p. 439, figs. 88 and 89.
[431] Cash and Hick (782).
[432] Cash and Hick, Pl. vi. fig. 3.
[400] Renault (96) p. 422, figs. 75 and 76.
[401] Schröter (89) p. 32, fig. 18 B.
[402] Cash and Hick (782) Pl. vi. fig. 3.
[403] Göppert and Menge (83) Pl. xiii. fig. 106.
[404] Harper (95).
[405] e.g. Ludwig (57) Pl. xvi. fig. 1.
[406] Potonié (93) p. 27, Pl. i. fig. 8.
[407] References are given by Potonié to illustrations by Zeiller (922) Pl. xv. fig. 6, Grand’
Eury (77) Pl. xxxiii. fig. 7, and others in which possible fungi are represented.
[408] Engelhardt (87).
[409] For figures of the Coccineae, see Comstock (88), Maskell (87), Judeich and Nitsche
(95) &c.
[410] Massalongo (59) Pl. i. fig. 1, p. 87.
[411] Meschinelli (92).
[412] James, J. F. (932).
[413] Lesquereux (87).
[414] Herzer (93).
[415] Conwentz (90) Pl. xii. fig. 5.
[416] Feilden, H. W. (96); Seward (962) p. 62, appendix to Feilden’s paper. I am indebted
to Dr Bonney for an opportunity of examining the plant remains from the Feilden
collection.
[417] Hartig (78).
[418] Conwentz (80) Pl. v. fig. 17.
[419] Carruthers (70) Pl. xxv. fig. 3.
[420] Renault (96) p. 427, fig. 80, d.
[421] ibid. p. 427, fig. 80, a–c.
[422] p. 127.
[423] Etheridge (92) Pl. vii.
[424] Hartig (78) and (94), Göppert and Menge (83).
[425] Renault (96) p. 425, fig. 78.
[426] Fischer in Rabenhorst, vol. i. (92) p. 144.
[427] Carruthers (76) p. 22, fig. 1.
[428] Smith, W. O. (77) p. 499.
[429] Williamson (81) Pl. xlviii. p. 301.
[430] Renault (96) p. 439, figs. 88 and 89.
[431] Cash and Hick (782).
[432] Cash and Hick, Pl. vi. fig. 3.
Page 519
[433] Felix (94) p. 276, Pl. xix. fig. 1.
[434] ibid. p. 274, Pl. xix. figs. 5 and 6.
[435] Williamson (78) and (80).
[436] Conwentz (90) p. 119, Pl. xi. pp. 2, 3, Pl. xv. fig. 8.
[437] Migula (90) in Rabenhorst’s Kryptogamen Flora, vol. v.
[438] Vaillant (1719) p. 17.
[439] Migula (90) p. 53.
[440] Knowlton (892).
[441] Meek (73) p. 219.
[442] Saporta (73) p. 214, Pl. ix. figs. 8–11.
[443] Seward (942) p. 13, fig. 1.
[444] Woodward, H. B. (95) pp, 234, 261, etc.
[445] Forbes, E. (56) p. 160, Pl. vii.
[446] Vide p. 69, fig. 10.
[447] Lyell (29).
[448] Skertchly (77) p. 60.
[449] Schiffner and Müller in Engler and Prantl (95), Campbell (95), Dixon and Jameson
(96) are among the best of modern writers on the Bryophyta.
[450] Hooker, J. D. (91) p. 513.
[451] Schiffner (95) p. 140.
[452] Hooker, W. J. (20) Pl. clxiii.
[453] Bennett and Brown (38), Pl. v.
[454] Bennett and Brown (38) p. 35.
[455] Nathorst (90) Pl. ii. fig. 3.
[456] Lindenberg (39) Pl. ix. fig. 1.
[457] Zeiller (922) Pl. i. figs. 7 and 8.
[458] Fliche and Bleicher (81).
[459] Brongniart (49) p. 12.
[460] Seward (942) p. 17.
[461] Leckenby (64) Pl. xi. fig. 3.
[462] Seward loc. cit. p. 18, Pl. i. fig. 3.
[463] Raciborski (94) p. 10, Pl. vii. figs. 1–3.
[464] Brongniart (49) p. 12.
[465] Saporta (68) p. 308, Pl. i. figs. 1–8. Vide also Watelet (66) p. 40, Pl. xi. fig. 6.
[466] Göppert and Berendt (45) Pl. vi. and (53).
[467] Gottsche (86).
[468] Schimper (65) Pl. iii.
[434] ibid. p. 274, Pl. xix. figs. 5 and 6.
[435] Williamson (78) and (80).
[436] Conwentz (90) p. 119, Pl. xi. pp. 2, 3, Pl. xv. fig. 8.
[437] Migula (90) in Rabenhorst’s Kryptogamen Flora, vol. v.
[438] Vaillant (1719) p. 17.
[439] Migula (90) p. 53.
[440] Knowlton (892).
[441] Meek (73) p. 219.
[442] Saporta (73) p. 214, Pl. ix. figs. 8–11.
[443] Seward (942) p. 13, fig. 1.
[444] Woodward, H. B. (95) pp, 234, 261, etc.
[445] Forbes, E. (56) p. 160, Pl. vii.
[446] Vide p. 69, fig. 10.
[447] Lyell (29).
[448] Skertchly (77) p. 60.
[449] Schiffner and Müller in Engler and Prantl (95), Campbell (95), Dixon and Jameson
(96) are among the best of modern writers on the Bryophyta.
[450] Hooker, J. D. (91) p. 513.
[451] Schiffner (95) p. 140.
[452] Hooker, W. J. (20) Pl. clxiii.
[453] Bennett and Brown (38), Pl. v.
[454] Bennett and Brown (38) p. 35.
[455] Nathorst (90) Pl. ii. fig. 3.
[456] Lindenberg (39) Pl. ix. fig. 1.
[457] Zeiller (922) Pl. i. figs. 7 and 8.
[458] Fliche and Bleicher (81).
[459] Brongniart (49) p. 12.
[460] Seward (942) p. 17.
[461] Leckenby (64) Pl. xi. fig. 3.
[462] Seward loc. cit. p. 18, Pl. i. fig. 3.
[463] Raciborski (94) p. 10, Pl. vii. figs. 1–3.
[464] Brongniart (49) p. 12.
[465] Saporta (68) p. 308, Pl. i. figs. 1–8. Vide also Watelet (66) p. 40, Pl. xi. fig. 6.
[466] Göppert and Berendt (45) Pl. vi. and (53).
[467] Gottsche (86).
[468] Schimper (65) Pl. iii.
Page 520
[469] Greville (47) Pl. xii.
[470] Brown, R. (11) Pl. xxiii.
[471] Hooker, W. J. (20) Pl. clxii.
[472] Limpricht (90) p. 67.
[473] Brongniart (282) p. 93.
[474] Renault and Zeiller (88) p. 84, Pl. xli. figs. 2–4.
[475] Solms-Laubach (91) p. 186.
[476] Lesquereux (79) Pl. lxii. fig. 1.
[477] Heer (65) p. 89.
[478] Buckman (50) 1.
[479] Gardner (86) p. 203.
[480] Ludwig (59) p. 165, Pl. lxiii. fig. 9.
[481] Schimper and Schenk (90) p. 75.
[482] e.g. the Fern Trichomanes Goebelianum Gies. Giesenhagen (92) p. 157.
[483] Scott (96) a text-book for elementary students; a full account is given of Equisetum
and other genera of primary importance. Vines (95) Part iii. Campbell (95), Luerssen (89)
in Rabenhorst’s Kryptogamen-Flora, vol. iii., Van Tieghem (91), de Bary (84), Baker (87).
[484] Wallace (86) p. 117.
[485] Baker (87) p. 4. Hooker, W. J. (61) Pl. lxxiv. Vide also Milde (67) for figures of
Equisetum.
[486] Seeman (65).
[487] Duval-Jouve (64) Pl. i. fig. 5.
[488] Milde (67) Pl. xix. fig. 8.
[489] ibid. Pl. xxxi. fig. 3.
[490] Cormack (93) p. 71.
[491] Williamson and Scott (94) p. 877. These authors, in referring to Cormack’s
description of the secondary nodal wood of E. maximum, express doubts as to the
existence of such secondary growth in all species of the genus.
[492] Pfitzer (67).
[493] Strasburger (91) p. 443.
[494] Strasburger (91) p. 435.
[495] Bower (94) p. 495.
[496] Sternberg (38) p. 43.
[497] Scott (97). This genus will be described in Volume ii.
[498] Potonié (93) Pl. xxv. fig. 1a.
[499] ibid. p. 179. Vide also Potonié (92).
[500] Zeiller (922) p. 56, Pl. xii. Other similar leaf-sheaths have been figured by Germar
(44) Pl. x., Schimper (74) Pl. xvii. and others.
[501] Grand’Eury (90) p. 223, Pl. xv. fig. 16.
[470] Brown, R. (11) Pl. xxiii.
[471] Hooker, W. J. (20) Pl. clxii.
[472] Limpricht (90) p. 67.
[473] Brongniart (282) p. 93.
[474] Renault and Zeiller (88) p. 84, Pl. xli. figs. 2–4.
[475] Solms-Laubach (91) p. 186.
[476] Lesquereux (79) Pl. lxii. fig. 1.
[477] Heer (65) p. 89.
[478] Buckman (50) 1.
[479] Gardner (86) p. 203.
[480] Ludwig (59) p. 165, Pl. lxiii. fig. 9.
[481] Schimper and Schenk (90) p. 75.
[482] e.g. the Fern Trichomanes Goebelianum Gies. Giesenhagen (92) p. 157.
[483] Scott (96) a text-book for elementary students; a full account is given of Equisetum
and other genera of primary importance. Vines (95) Part iii. Campbell (95), Luerssen (89)
in Rabenhorst’s Kryptogamen-Flora, vol. iii., Van Tieghem (91), de Bary (84), Baker (87).
[484] Wallace (86) p. 117.
[485] Baker (87) p. 4. Hooker, W. J. (61) Pl. lxxiv. Vide also Milde (67) for figures of
Equisetum.
[486] Seeman (65).
[487] Duval-Jouve (64) Pl. i. fig. 5.
[488] Milde (67) Pl. xix. fig. 8.
[489] ibid. Pl. xxxi. fig. 3.
[490] Cormack (93) p. 71.
[491] Williamson and Scott (94) p. 877. These authors, in referring to Cormack’s
description of the secondary nodal wood of E. maximum, express doubts as to the
existence of such secondary growth in all species of the genus.
[492] Pfitzer (67).
[493] Strasburger (91) p. 443.
[494] Strasburger (91) p. 435.
[495] Bower (94) p. 495.
[496] Sternberg (38) p. 43.
[497] Scott (97). This genus will be described in Volume ii.
[498] Potonié (93) Pl. xxv. fig. 1a.
[499] ibid. p. 179. Vide also Potonié (92).
[500] Zeiller (922) p. 56, Pl. xii. Other similar leaf-sheaths have been figured by Germar
(44) Pl. x., Schimper (74) Pl. xvii. and others.
[501] Grand’Eury (90) p. 223, Pl. xv. fig. 16.
Page 521
[502] Renault (93) Pl. xlii. figs. 6 and 7.
[503] Kidston (92).
[504] Zeiller (95).
[505] Potonié (93) p. 179, Pl. xxv. figs. 2–4.
[506] Renault and Zeiller (88) p. 396, Pl. lvii. fig. 7.
[507] Lindley and Hutton (31) Pl. cxiv.
[508] Schoenlein and Schenk (65) Pl. v. fig. 1.
[509] Schimper and Mougeot (44) p. 58, Pl. xxix.
[510] Jäger (27).
[511] Schimper (74) Pls. ix–xi.
[512] Schimper and Koechlin-Schlumberger (62).
[513] Schoenlein and Schenk (65) Pls. i–iv.
[514] Brongniart (28) p. 115, Pl. xiii.
[515] Young and Bird (22) p. 185, Pl. iii. fig. 3.
[516] König, in Murchison (29) p. 293, Pl. xxxii.
[517] Murchison (29) p. 368.
[518] Bunbury (51) p. 189.
[519] Schimper (69) p. 267.
[520] Zigno (56) Pl. iii. fig. 1, p. 45.
[521] Gardner (86) Pl. ix. fig. 3.
[522] Williamson (83) p. 4.
[523] Williamson and Scott (94) p. 889, Pl. lxxix. fig. 19.
[524] Phillips J. (29) Pl. x. fig. 13.
[525] Lindley and Hutton (31) Pl. clxxxvi.
[526] Bunbury (51) p. 189.
[527] Zigno (56) Pl. iii. fig. 3, p. 46.
[528] Heer (77) p. 43, Pl. iv.
[529] Schimper (69) p. 284. Vide also Nathorst (80) p. 54.
[530] Andrae (53) Pl. vi. figs. 1–5.
[531] Solms-Laubach (91) p. 180.
[532] cf. p. 283.
[533] There is a similar specimen in the Oxford Museum.
[534] Since this was written I have found a specimen of Equisetites lateralis in the
Woodwardian Museum, in which a diaphragm like that in fig. 64, C, occurs in the centre of
a flattened leaf-sheath similar to that of fig. 64, B.
[535] Buckman (50) p. 414.
[536] Schenk (67).
[503] Kidston (92).
[504] Zeiller (95).
[505] Potonié (93) p. 179, Pl. xxv. figs. 2–4.
[506] Renault and Zeiller (88) p. 396, Pl. lvii. fig. 7.
[507] Lindley and Hutton (31) Pl. cxiv.
[508] Schoenlein and Schenk (65) Pl. v. fig. 1.
[509] Schimper and Mougeot (44) p. 58, Pl. xxix.
[510] Jäger (27).
[511] Schimper (74) Pls. ix–xi.
[512] Schimper and Koechlin-Schlumberger (62).
[513] Schoenlein and Schenk (65) Pls. i–iv.
[514] Brongniart (28) p. 115, Pl. xiii.
[515] Young and Bird (22) p. 185, Pl. iii. fig. 3.
[516] König, in Murchison (29) p. 293, Pl. xxxii.
[517] Murchison (29) p. 368.
[518] Bunbury (51) p. 189.
[519] Schimper (69) p. 267.
[520] Zigno (56) Pl. iii. fig. 1, p. 45.
[521] Gardner (86) Pl. ix. fig. 3.
[522] Williamson (83) p. 4.
[523] Williamson and Scott (94) p. 889, Pl. lxxix. fig. 19.
[524] Phillips J. (29) Pl. x. fig. 13.
[525] Lindley and Hutton (31) Pl. clxxxvi.
[526] Bunbury (51) p. 189.
[527] Zigno (56) Pl. iii. fig. 3, p. 46.
[528] Heer (77) p. 43, Pl. iv.
[529] Schimper (69) p. 284. Vide also Nathorst (80) p. 54.
[530] Andrae (53) Pl. vi. figs. 1–5.
[531] Solms-Laubach (91) p. 180.
[532] cf. p. 283.
[533] There is a similar specimen in the Oxford Museum.
[534] Since this was written I have found a specimen of Equisetites lateralis in the
Woodwardian Museum, in which a diaphragm like that in fig. 64, C, occurs in the centre of
a flattened leaf-sheath similar to that of fig. 64, B.
[535] Buckman (50) p. 414.
[536] Schenk (67).
Page 522
[537] Tenison-Woods (83), Pl. vi. figs. 5 and 6. Specimen no. V. 3358 in the British
Museum.
[538] Dunker (46) p. 2, Pl. v. fig. 7.
[539] Seward (942) p. 30.
[540] Seward (942) p. 33.
[541] Heer (55) vol. iii. p. 158, Pl. cxlv.
[542] Heer (77) p. 99, Pl. xxii.
[543] Vide Saporta (73) p. 227.
[544] The distribution will be dealt with in Volume ii.
[545] Brongniart (28) p. 151.
[546] Schmalhausen (79) p. 12, Pl. i. figs. 1–3.
[547] Solms-Laubach (91) p. 181.
[548] Zeiller (96).
[549] Zeiller (962).
[550] ibid. (96).
[551] Letter, July 30, 1897.
[552] On this character of Annularian leaves, vide p. 337.
[553] Göppert (45) p. 379, Pl. xxv. figs. 1, 2.
[554] Schmalhausen (79) p. 12.
[555] McCoy (47) Pl. xi. fig. 7.
[556] Bunbury (61) Pl. xi. fig. 1.
[557] Seward (972) p. 324, Pl. xxiv. fig. 1.
[558] Feistmantel (81) Pl. ix. A. fig. 7, &c.
[559] ibid. (90) Pl. xiv. fig. 5.
[560] Bunbury (61) Pl. xi. fig. 1.
[561] Solms-Laubach (91) p. 181, fig. 17.
[562] Heer (82) p. 9.
[563] Potonié (962) p. 115, fig. 3.
[564] Zigno (56) Pl. vii. p. 59.
[565] Bunbury (61).
[566] Feistmantel (81), Pl. xii. A.
[567] Brongniart (28) p. 152.
[568] Bunbury (61).
[569] Grand’Eury (90) p. 221.
[570] Etheridge (95).
[571] Weiss (76) p. 88.
[572] Heer (77) p. 43, Pl. iv. (78) p. 4, Pl. i.
Museum.
[538] Dunker (46) p. 2, Pl. v. fig. 7.
[539] Seward (942) p. 30.
[540] Seward (942) p. 33.
[541] Heer (55) vol. iii. p. 158, Pl. cxlv.
[542] Heer (77) p. 99, Pl. xxii.
[543] Vide Saporta (73) p. 227.
[544] The distribution will be dealt with in Volume ii.
[545] Brongniart (28) p. 151.
[546] Schmalhausen (79) p. 12, Pl. i. figs. 1–3.
[547] Solms-Laubach (91) p. 181.
[548] Zeiller (96).
[549] Zeiller (962).
[550] ibid. (96).
[551] Letter, July 30, 1897.
[552] On this character of Annularian leaves, vide p. 337.
[553] Göppert (45) p. 379, Pl. xxv. figs. 1, 2.
[554] Schmalhausen (79) p. 12.
[555] McCoy (47) Pl. xi. fig. 7.
[556] Bunbury (61) Pl. xi. fig. 1.
[557] Seward (972) p. 324, Pl. xxiv. fig. 1.
[558] Feistmantel (81) Pl. ix. A. fig. 7, &c.
[559] ibid. (90) Pl. xiv. fig. 5.
[560] Bunbury (61) Pl. xi. fig. 1.
[561] Solms-Laubach (91) p. 181, fig. 17.
[562] Heer (82) p. 9.
[563] Potonié (962) p. 115, fig. 3.
[564] Zigno (56) Pl. vii. p. 59.
[565] Bunbury (61).
[566] Feistmantel (81), Pl. xii. A.
[567] Brongniart (28) p. 152.
[568] Bunbury (61).
[569] Grand’Eury (90) p. 221.
[570] Etheridge (95).
[571] Weiss (76) p. 88.
[572] Heer (77) p. 43, Pl. iv. (78) p. 4, Pl. i.
Page 523
[573] Tenison-Woods (83) Pl. ix. fig. 2.
[574] Brongniart (28) p. 128.
[575] Schimper and Mougeot (44) p. 48, Pls. xxiv–xxvi.
[576] Feistmantel (81) p. 59, Pls. i. A–x. A.
[577] ante, p. 284.
[578] Schimper and Mougeot (44) p. 50, Pls. xxiv–xxvi.
[579] Seward (972).
[580] Scheuchzer (1723), p. 19, Pl. iv. fig. 1.
[581] Volkmann (1720), p. 110, Pl. xiii. fig. 7.
[582] Woodward, J. (1728), Pt. ii. p. 10.
[583] Schulze, C. F. (1755), Pl. ii. fig. 1.
[584] Suckow (1784), p. 363.
[585] Steinhauer (18), Pls. v. and vi.
[586] Martin (09), Pls. viii. xxv. and xxvi.
[587] Artie (25).
[588] Brongniart (22), p. 218.
[589] Brongniart (28), p. 34.
[590] Lindley and Hutton (31).
[591] Cotta (50). I am indebted to Prof. Stenzel of Breslau for calling my attention to the
fact that Cotta’s work appeared in 1832, but in 1850 the same work was sold with a new
title-page bearing this date.
[592] Unger (40).
[593] Petzholdt (41).
[594] Unger (44).
[595] Brongniart (49), p. 49.
[596] E.g. Isoetes, Botrychium, &c.
[597] Mougeot (52).
[598] Göppert (64), p. 183.
[599] ἄρθρον, joint; πίτυς, Pine-tree.
[600] The original specimens described by Göppert are in the rich palaeobotanical
Collection of the Breslau Museum.
[601] Williamson (713), p. 174.
[602] vide Solms-Laubach (96).
[603] Letter, November 1897.
[604] Vide p. 310.
[605] Hick (94), Pl. ix. fig. 1.
[606] On this point vide Williamson and Scott (94), p. 869.
[607] Williamson and Scott, loc. cit. p. 876.
[574] Brongniart (28) p. 128.
[575] Schimper and Mougeot (44) p. 48, Pls. xxiv–xxvi.
[576] Feistmantel (81) p. 59, Pls. i. A–x. A.
[577] ante, p. 284.
[578] Schimper and Mougeot (44) p. 50, Pls. xxiv–xxvi.
[579] Seward (972).
[580] Scheuchzer (1723), p. 19, Pl. iv. fig. 1.
[581] Volkmann (1720), p. 110, Pl. xiii. fig. 7.
[582] Woodward, J. (1728), Pt. ii. p. 10.
[583] Schulze, C. F. (1755), Pl. ii. fig. 1.
[584] Suckow (1784), p. 363.
[585] Steinhauer (18), Pls. v. and vi.
[586] Martin (09), Pls. viii. xxv. and xxvi.
[587] Artie (25).
[588] Brongniart (22), p. 218.
[589] Brongniart (28), p. 34.
[590] Lindley and Hutton (31).
[591] Cotta (50). I am indebted to Prof. Stenzel of Breslau for calling my attention to the
fact that Cotta’s work appeared in 1832, but in 1850 the same work was sold with a new
title-page bearing this date.
[592] Unger (40).
[593] Petzholdt (41).
[594] Unger (44).
[595] Brongniart (49), p. 49.
[596] E.g. Isoetes, Botrychium, &c.
[597] Mougeot (52).
[598] Göppert (64), p. 183.
[599] ἄρθρον, joint; πίτυς, Pine-tree.
[600] The original specimens described by Göppert are in the rich palaeobotanical
Collection of the Breslau Museum.
[601] Williamson (713), p. 174.
[602] vide Solms-Laubach (96).
[603] Letter, November 1897.
[604] Vide p. 310.
[605] Hick (94), Pl. ix. fig. 1.
[606] On this point vide Williamson and Scott (94), p. 869.
[607] Williamson and Scott, loc. cit. p. 876.
Page 524
[608] Renault (93), Pl. xlvii. fig. 4.
[609] Stur (87).
[610] The term primary ray may be conveniently restricted to the truly primary
interfascicular tissue, and the term principal ray may be used for the outward extension of
the primary rays by the cambium [Williamson and Scott (94), p. 878].
[611] Binney (68).
[612] Ettingshausen (55).
[613] The sections of fossil plants described by Binney were presented to the
Woodwardian Museum, Cambridge, by his son (Mr J. Binney).
[614] Vide footnote, p. 311.
[615] Williamson (832), Pl. xxxiii. fig. 19.
[616] Williamson (78), p. 323, Pl. xx. figs. 14 and 15.
[617] Williamson and Scott (94), p. 888.
[618] Hartig (94), pp. 149, 297, etc.
[619] Renault (96), p. 91.
[620] Williamson and Scott, loc. cit. p. 893. Vide specimens 133*–135* in the Williamson
Collection.
[621] E.g. specimen 132*** in the Williamson Collection.
[622] Vide Williamson (71), Pl. xxviii. fig. 38; (712), Pl. iv. fig. 15; (78), Pl. xxi. figs. 26–
28. Williamson and Scott (94), Pl. lxxii. figs. 5 and 6. Renault (93), Pl. xlv. figs. 4–6, etc.
Felix (96), Pl. iv. figs. 2 and 3.
[623] Strasburger (91), Pl. ii. fig. 40.
[624] Williamson (78).
[625] Williamson (71), p. 507.
[626] Williamson (712), Pl. i. fig. 1; (78), Pl. xxi. fig. 31.
[627] Lyell (55), p. 368.
[628] Williamson (96), p. 194.
[629] Vide specimens 15–17, etc. in the Williamson Collection.
[630] The stem of fig. 83 is an example of Arthrodendron, but the appearance of the
secondary xylem agrees with that in some forms of Arthropitys.
[631] For figures of this type of stem vide Göppert (64); Cotta (50), Pl. xv. (specimens
13787 in the British Museum Collection); Mougeot (52), Pl. v.; Stur (87), pp. 27–31;
Renault (93), Pls. xliv. and xlv. etc.
[632] Williamson (71), (712), (87), fig. 5.
[633] Williamson and Scott (94), p. 879
[634] Vide Williamson (872). In this paper Williamson compares the three subgenera of
Calamite stems. Renault and Zeiller (88), Pl. lxxv. Renault (93), Pls. lviii. and lix.
[635] Renault (96), p. 125; (93), Pl. lix. fig. 2.
[636] Lindley and Hutton (31), Pls. cxiv., cxc. etc. Most of the specimens figured by these
authors are in the Newcastle Natural History Museum. For notes on the type-specimens of
[609] Stur (87).
[610] The term primary ray may be conveniently restricted to the truly primary
interfascicular tissue, and the term principal ray may be used for the outward extension of
the primary rays by the cambium [Williamson and Scott (94), p. 878].
[611] Binney (68).
[612] Ettingshausen (55).
[613] The sections of fossil plants described by Binney were presented to the
Woodwardian Museum, Cambridge, by his son (Mr J. Binney).
[614] Vide footnote, p. 311.
[615] Williamson (832), Pl. xxxiii. fig. 19.
[616] Williamson (78), p. 323, Pl. xx. figs. 14 and 15.
[617] Williamson and Scott (94), p. 888.
[618] Hartig (94), pp. 149, 297, etc.
[619] Renault (96), p. 91.
[620] Williamson and Scott, loc. cit. p. 893. Vide specimens 133*–135* in the Williamson
Collection.
[621] E.g. specimen 132*** in the Williamson Collection.
[622] Vide Williamson (71), Pl. xxviii. fig. 38; (712), Pl. iv. fig. 15; (78), Pl. xxi. figs. 26–
28. Williamson and Scott (94), Pl. lxxii. figs. 5 and 6. Renault (93), Pl. xlv. figs. 4–6, etc.
Felix (96), Pl. iv. figs. 2 and 3.
[623] Strasburger (91), Pl. ii. fig. 40.
[624] Williamson (78).
[625] Williamson (71), p. 507.
[626] Williamson (712), Pl. i. fig. 1; (78), Pl. xxi. fig. 31.
[627] Lyell (55), p. 368.
[628] Williamson (96), p. 194.
[629] Vide specimens 15–17, etc. in the Williamson Collection.
[630] The stem of fig. 83 is an example of Arthrodendron, but the appearance of the
secondary xylem agrees with that in some forms of Arthropitys.
[631] For figures of this type of stem vide Göppert (64); Cotta (50), Pl. xv. (specimens
13787 in the British Museum Collection); Mougeot (52), Pl. v.; Stur (87), pp. 27–31;
Renault (93), Pls. xliv. and xlv. etc.
[632] Williamson (71), (712), (87), fig. 5.
[633] Williamson and Scott (94), p. 879
[634] Vide Williamson (872). In this paper Williamson compares the three subgenera of
Calamite stems. Renault and Zeiller (88), Pl. lxxv. Renault (93), Pls. lviii. and lix.
[635] Renault (96), p. 125; (93), Pl. lix. fig. 2.
[636] Lindley and Hutton (31), Pls. cxiv., cxc. etc. Most of the specimens figured by these
authors are in the Newcastle Natural History Museum. For notes on the type-specimens of
Page 525
Lindley and Hutton, vide Howse (88) and Kidston (902).
[637] Weiss (88), Stur (87), etc.
[638] Vide, p. 367.
[639] Ante, p. 260.
[640] Hick (95).
[641] Brongniart (22), p. 235.
[642] Schlotheim (20).
[643] Brongniart (28), p. 159.
[644] Lindley and Hutton (31), Pl. cxc.
[645] Ettingshausen (55).
[646] Schimper (69), p. 323.
[647] Grand’Eury (90).
[648] Martin (09), Pl. xx. figs. 4 and 6.
[649] Schlotheim (20), p. 397.
[650] Sternberg (25), p. xxviii.
[651] Brongniart (28), p. 154.
[652] Lindley and Hutton (31), Pl. cxci.
[653] Ettingshausen (55), p. 28.
[654] Schimper (69), Pls. xxii. and xxvi. fig. 1.
[655] For other lists and synonyms, vide Zeiller (88), p. 368, and Kidston (86), p. 38 and
(93), p. 316, also Potonié (93), p. 162.
[656] Sternberg (20).
[657] Brongniart (28), p. 155.
[658] Lehmann (1756), p. 127. Vide also Volkmanns (1720), Pl. XV. p. 113.
[659] Potonié (93), pp. 169 et seq., Pl. xxiv.
[660] Dawson (71).
[661] Nicholson (69) Pl. xviii. B. Nicholson’s specimens are in the Woodwardian Museum,
Cambridge.
[662] Schlotheim (20), p. 397.
[663] Sternberg (26), p. xxviii.
[664] Brongniart (28), p. 156.
[665] Lindley and Hutton (31), Pl. cxxiv.
[666] Binney (68), Pl. vi. fig. 3.
[667] Stur (87), Pl. xvi b, and Pls. iv b and xiii.
[668] Scheuchzer (1723), p. 63, Pl. xiii. fig. 3.
[669] Potonié (93), p. 166.
[670] Vide pp. 351 et seq.
[671] Renault (96), p. 66; (93), Pl. xxviii.
[637] Weiss (88), Stur (87), etc.
[638] Vide, p. 367.
[639] Ante, p. 260.
[640] Hick (95).
[641] Brongniart (22), p. 235.
[642] Schlotheim (20).
[643] Brongniart (28), p. 159.
[644] Lindley and Hutton (31), Pl. cxc.
[645] Ettingshausen (55).
[646] Schimper (69), p. 323.
[647] Grand’Eury (90).
[648] Martin (09), Pl. xx. figs. 4 and 6.
[649] Schlotheim (20), p. 397.
[650] Sternberg (25), p. xxviii.
[651] Brongniart (28), p. 154.
[652] Lindley and Hutton (31), Pl. cxci.
[653] Ettingshausen (55), p. 28.
[654] Schimper (69), Pls. xxii. and xxvi. fig. 1.
[655] For other lists and synonyms, vide Zeiller (88), p. 368, and Kidston (86), p. 38 and
(93), p. 316, also Potonié (93), p. 162.
[656] Sternberg (20).
[657] Brongniart (28), p. 155.
[658] Lehmann (1756), p. 127. Vide also Volkmanns (1720), Pl. XV. p. 113.
[659] Potonié (93), pp. 169 et seq., Pl. xxiv.
[660] Dawson (71).
[661] Nicholson (69) Pl. xviii. B. Nicholson’s specimens are in the Woodwardian Museum,
Cambridge.
[662] Schlotheim (20), p. 397.
[663] Sternberg (26), p. xxviii.
[664] Brongniart (28), p. 156.
[665] Lindley and Hutton (31), Pl. cxxiv.
[666] Binney (68), Pl. vi. fig. 3.
[667] Stur (87), Pl. xvi b, and Pls. iv b and xiii.
[668] Scheuchzer (1723), p. 63, Pl. xiii. fig. 3.
[669] Potonié (93), p. 166.
[670] Vide pp. 351 et seq.
[671] Renault (96), p. 66; (93), Pl. xxviii.
Page 526
[672] One of the finest specimens of Annularia stellata is figured by Stur (87), Pl. xvi b; it
is in the Leipzig Museum. Vide also Schenk (83), Pl. xxxix.; Germar (44), Pl. ix.; Renault
and Zeiller (88), Pls. xlv. and xlvi. There are some well-preserved impressions of A.
stellata in the British Museum from Radstock, Newcastle and elsewhere.
[673] Zenker (33), Pl. v. pp. 6–9.
[674] Heer (65), fig. 6, p. 9, and other authors.
[675] Weiss (76), p. 27, Pl. iii. fig. 2.
[676] Lhwyd (1699), Pl. v. fig. 202.
[677] Sterzel (82).
[678] Vide Weiss (76), Pl. iii. and Weiss (84), p. 178.
[679] Williamson (71), p. 487, Pls. xxv. and xxvi.
[680] Ibid. (78), p. 319, Pl. xix.
[681] Cash and Hick (81), p. 400.
[682] Williamson (81), vide also Spencer (81).
[683] Spencer (83), p. 459.
[684] Williamson (83), p. 459, Pls. xxvii.–xxx.
[685] Renault (85).
[686] Lindley and Hutton (31), Pls. lxxviii. and lxxix. (The specimens are figured in a
reversed position.)
[687] Binney (68), p. 5, fig. 1.
[688] Grand’Eury (77), Pls. i. and ii.; (87), Pls. xxvii., xxviii.
[689] Weiss (84), Pls. ii.–iv., viii. and ix.
[690] Stur (87), Pls. iii., vi., vii., etc.; Zeiller (86), Pl. liv.
[691] Weiss (76), (84).
[692] For references, vide Kidston (86), p. 58.
[693] Artis (25), Pl. v.
[694] Williamson and Scott (95), p. 694.
[695] Williamson (832), Pl. xxix. fig. 7.
[696] Williamson and Scott (95), Pls. xv.–xvii.
[697] For figures vide Williamson, loc. cit., Williamson and Scott, and Renault (85), (93).
[698] E.g. Schenk (90) in Zittel’s Handbuch, p. 237.
[699] Williamson and Scott, loc. cit. p. 689.
[700] de Bary (84), p. 474; van Tieghem (91), p. 720.
[701] Renault (96), pp. 118, 126; (93), Pl. lv.
[702] Carruthers (67), Pl. lxx.
[703] Sternberg (25), Pl. xlviii. and li.
[704] Brongniart (49), p. 51.
[705] Binney (68), p. 23, Pls. iv. and v.
is in the Leipzig Museum. Vide also Schenk (83), Pl. xxxix.; Germar (44), Pl. ix.; Renault
and Zeiller (88), Pls. xlv. and xlvi. There are some well-preserved impressions of A.
stellata in the British Museum from Radstock, Newcastle and elsewhere.
[673] Zenker (33), Pl. v. pp. 6–9.
[674] Heer (65), fig. 6, p. 9, and other authors.
[675] Weiss (76), p. 27, Pl. iii. fig. 2.
[676] Lhwyd (1699), Pl. v. fig. 202.
[677] Sterzel (82).
[678] Vide Weiss (76), Pl. iii. and Weiss (84), p. 178.
[679] Williamson (71), p. 487, Pls. xxv. and xxvi.
[680] Ibid. (78), p. 319, Pl. xix.
[681] Cash and Hick (81), p. 400.
[682] Williamson (81), vide also Spencer (81).
[683] Spencer (83), p. 459.
[684] Williamson (83), p. 459, Pls. xxvii.–xxx.
[685] Renault (85).
[686] Lindley and Hutton (31), Pls. lxxviii. and lxxix. (The specimens are figured in a
reversed position.)
[687] Binney (68), p. 5, fig. 1.
[688] Grand’Eury (77), Pls. i. and ii.; (87), Pls. xxvii., xxviii.
[689] Weiss (84), Pls. ii.–iv., viii. and ix.
[690] Stur (87), Pls. iii., vi., vii., etc.; Zeiller (86), Pl. liv.
[691] Weiss (76), (84).
[692] For references, vide Kidston (86), p. 58.
[693] Artis (25), Pl. v.
[694] Williamson and Scott (95), p. 694.
[695] Williamson (832), Pl. xxix. fig. 7.
[696] Williamson and Scott (95), Pls. xv.–xvii.
[697] For figures vide Williamson, loc. cit., Williamson and Scott, and Renault (85), (93).
[698] E.g. Schenk (90) in Zittel’s Handbuch, p. 237.
[699] Williamson and Scott, loc. cit. p. 689.
[700] de Bary (84), p. 474; van Tieghem (91), p. 720.
[701] Renault (96), pp. 118, 126; (93), Pl. lv.
[702] Carruthers (67), Pl. lxx.
[703] Sternberg (25), Pl. xlviii. and li.
[704] Brongniart (49), p. 51.
[705] Binney (68), p. 23, Pls. iv. and v.
Page 527
[706] Schimper (69), p. 330.
[707] For figures and descriptions of this type of cone vide Williamson (73), (80), (89);
Hick (93), (94) and Williamson and Scott (94).
[708] Weiss (84), Pls. xxii.—xxiv.
[709] Williamson and Scott (94), p. 911, Pls. lxxxi. and lxxxii.
[710] Vide Heinricher (82); Bower (94), p. 495; Campbell (95), pp. 396, 503.
[711] Williamson (81), Pl. liv.
[712] An excellent figure illustrating the co-existence of heterospory and secondary
thickening is given by Williamson and Scott, loc. cit., Pl. lxxxii. fig. 36.
[713] Weiss (76), p. 103.
[714] Williamson (712).
[715] Ibid. (882).
[716] Williamson and Scott (94), p. 900.
[717] Weiss (84), Pl. xxi. fig. 4.
[718] Williamson (74), Pl. v. fig. 32.
[719] Williamson (882), Pl. ix. fig. 20.
[720] E.g. Renault (82), Pl. xix. fig. 1; (96), Pl. xxix. figs. 1 and 4.
[721] Williamson (882), Pl. viii. figs. 1 and 4.
[722] Renault (93), Pl. xxix. fig. 7.
[723] Solms-Laubach (91), p. 325.
[724] Weiss (84) p. 161. Solms-Laubach, loc. cit. p. 326.
[725] E.g. Volkmannia Ludwigi Carr., also Volkmannia elongata Presl. [Solms (91), p. 332
and Weiss (76), p. 108].
[726] E.g. Brukmannia Grand’Euryi Ren. [Renault (76)].
[727] Weiss (84), p. 190.
[728] Weiss (76), p. 1.
[729] Weiss (84), p. 161.
[730] Renault (82), p. 139; (76).
[731] Solms-Laubach (91), p. 330.
[732] Schenk (88), p. 132; (83), p. 232.
[733] Weiss (84), p. 161.
[734] E.g. Volkmannia gracilis Sternb. [Renault (76), Pl. ii.].
[735] Schimper (69), p. 332. Vide also Renault and Zeiller (88), p. 420.
[736] Renault (82), p. 120, Pl. xix.; (93), Pl. xxix. figs. 8–14; (96), p. 77.
[737] Weiss (84), p. 98, Pl. xx. etc.
[738] Sterzel (82).
[739] Renault and Zeiller (88), Pl. xlvi. fig. 7.
[740] Kidston (86), p. 47; (93), p. 319. Vide also Renault (93), Pl. xxviii.
[707] For figures and descriptions of this type of cone vide Williamson (73), (80), (89);
Hick (93), (94) and Williamson and Scott (94).
[708] Weiss (84), Pls. xxii.—xxiv.
[709] Williamson and Scott (94), p. 911, Pls. lxxxi. and lxxxii.
[710] Vide Heinricher (82); Bower (94), p. 495; Campbell (95), pp. 396, 503.
[711] Williamson (81), Pl. liv.
[712] An excellent figure illustrating the co-existence of heterospory and secondary
thickening is given by Williamson and Scott, loc. cit., Pl. lxxxii. fig. 36.
[713] Weiss (76), p. 103.
[714] Williamson (712).
[715] Ibid. (882).
[716] Williamson and Scott (94), p. 900.
[717] Weiss (84), Pl. xxi. fig. 4.
[718] Williamson (74), Pl. v. fig. 32.
[719] Williamson (882), Pl. ix. fig. 20.
[720] E.g. Renault (82), Pl. xix. fig. 1; (96), Pl. xxix. figs. 1 and 4.
[721] Williamson (882), Pl. viii. figs. 1 and 4.
[722] Renault (93), Pl. xxix. fig. 7.
[723] Solms-Laubach (91), p. 325.
[724] Weiss (84) p. 161. Solms-Laubach, loc. cit. p. 326.
[725] E.g. Volkmannia Ludwigi Carr., also Volkmannia elongata Presl. [Solms (91), p. 332
and Weiss (76), p. 108].
[726] E.g. Brukmannia Grand’Euryi Ren. [Renault (76)].
[727] Weiss (84), p. 190.
[728] Weiss (76), p. 1.
[729] Weiss (84), p. 161.
[730] Renault (82), p. 139; (76).
[731] Solms-Laubach (91), p. 330.
[732] Schenk (88), p. 132; (83), p. 232.
[733] Weiss (84), p. 161.
[734] E.g. Volkmannia gracilis Sternb. [Renault (76), Pl. ii.].
[735] Schimper (69), p. 332. Vide also Renault and Zeiller (88), p. 420.
[736] Renault (82), p. 120, Pl. xix.; (93), Pl. xxix. figs. 8–14; (96), p. 77.
[737] Weiss (84), p. 98, Pl. xx. etc.
[738] Sterzel (82).
[739] Renault and Zeiller (88), Pl. xlvi. fig. 7.
[740] Kidston (86), p. 47; (93), p. 319. Vide also Renault (93), Pl. xxviii.
Page 528
[741] Renault and Zeiller (88), Pl. xlv.
[742] Solms-Laubach (91), p. 339. Weiss (84), p. 159.
[743] Weiss (84), Pl. xx. fig. 6.
[744] Weiss (84), Pl. xx. fig. 7; Pl. xxi. fig. 4.
[745] Ibid. Pls. xiv. and xv. Cf. also Stur (87), Pls. vi. and vii b, and Lesquereux (84), Pl.
xc. fig. 1.
[746] Grand’Eury (90), pp. 205, 208. Renault and Zeiller (88), Pl. li.
[747] Vide Unger (50), p. 63.
[748] Weiss, loc. cit.
[749] Solms-Laubach (91), p. 328.
[750] Schenk (83), p. 234.
[751] Weiss (76), p. 88; (84), p. 162. Solms-Laubach, loc. cit. p. 334, fig. 47.
[752] Renault (96), p. 132.
[753] Zeiller (88), Pl. liv. fig. 4.
[754] Stur (87), p. 17.
[755] Lindley and Hutton (31), Pl. cxlii b. The original specimen is in the University
College Collection, London.
[756] Nathorst (94), p. 56, Pl. xv. figs. 1 and 2.
[757] Seward (88).
[758] Weiss (84), p. 54.
[759] Zeiller (88), p. 329.
[760] Weiss (76), p. 117; (84), p. 55.
[761] Weiss (84), p. 93, Pl. xi. fig. 1.
[762] Vide Weiss (84), Pl. xxv. fig. 2; Pl. xvi a, etc.
[763] Weiss (76), Pl. xvii. fig. 1.
[764] Weiss (84), Pl. i.
[765] Grand’Eury (90), p. 208, and (77), Pl. v.
[766] Lindley and Hutton (31), Pl. cxc.
[767] Stur (87), Pl. v. fig. 1.
[768] Grand’Eury (77), Pl. iv.
[769] Stur (87), Pl. xvii.
[770] Renault (82), Pl. xvii. fig. 2.
[771] Renault and Zeiller (88), Pt. ii. p. 434, Pls. lii. and liii.
[772] Stur (87), p. 37, fig. 17. Vide also Grand’Eury (90), p. 208.
[773] Stur, loc. cit.
[774] Weiss (84), p. 61.
[775] Vide Grand’Eury (77), Pl. v. fig. 5.
[776] Weiss, loc. cit. Pl. xxi. fig. 5.
[742] Solms-Laubach (91), p. 339. Weiss (84), p. 159.
[743] Weiss (84), Pl. xx. fig. 6.
[744] Weiss (84), Pl. xx. fig. 7; Pl. xxi. fig. 4.
[745] Ibid. Pls. xiv. and xv. Cf. also Stur (87), Pls. vi. and vii b, and Lesquereux (84), Pl.
xc. fig. 1.
[746] Grand’Eury (90), pp. 205, 208. Renault and Zeiller (88), Pl. li.
[747] Vide Unger (50), p. 63.
[748] Weiss, loc. cit.
[749] Solms-Laubach (91), p. 328.
[750] Schenk (83), p. 234.
[751] Weiss (76), p. 88; (84), p. 162. Solms-Laubach, loc. cit. p. 334, fig. 47.
[752] Renault (96), p. 132.
[753] Zeiller (88), Pl. liv. fig. 4.
[754] Stur (87), p. 17.
[755] Lindley and Hutton (31), Pl. cxlii b. The original specimen is in the University
College Collection, London.
[756] Nathorst (94), p. 56, Pl. xv. figs. 1 and 2.
[757] Seward (88).
[758] Weiss (84), p. 54.
[759] Zeiller (88), p. 329.
[760] Weiss (76), p. 117; (84), p. 55.
[761] Weiss (84), p. 93, Pl. xi. fig. 1.
[762] Vide Weiss (84), Pl. xxv. fig. 2; Pl. xvi a, etc.
[763] Weiss (76), Pl. xvii. fig. 1.
[764] Weiss (84), Pl. i.
[765] Grand’Eury (90), p. 208, and (77), Pl. v.
[766] Lindley and Hutton (31), Pl. cxc.
[767] Stur (87), Pl. v. fig. 1.
[768] Grand’Eury (77), Pl. iv.
[769] Stur (87), Pl. xvii.
[770] Renault (82), Pl. xvii. fig. 2.
[771] Renault and Zeiller (88), Pt. ii. p. 434, Pls. lii. and liii.
[772] Stur (87), p. 37, fig. 17. Vide also Grand’Eury (90), p. 208.
[773] Stur, loc. cit.
[774] Weiss (84), p. 61.
[775] Vide Grand’Eury (77), Pl. v. fig. 5.
[776] Weiss, loc. cit. Pl. xxi. fig. 5.
Page 529
[777] Stur (87), Pl. xi. fig. 1.
[778] Renault and Zeiller (88), Pt. ii. Pl. li. p. 423.
[779] Lindley and Hutton (31), Pl. cxiv. and Pl. cxc. The original specimens are in the
Natural History Museum, Newcastle-on-Tyne.
[780] Ibid. Pl. cxxx. and Feistmantel (75), Pl. i. fig. 8.
[781] Lesquereux (79), Pl. xiii. fig. 14.
[782] Salter (63), figs. 6 and 7. Vide also Carruthers in Woodward, H. (72), p. 168.
[783] Grand’Eury (69); vide also (77) and (90).
[784] Renault and Zeiller (88), Pt. ii. Pls. lii. and ciii.
[785] Ibid. Pl. li.
[786] Sternberg (21), Pl. xii.
[787] Weiss (84), p. 61.
[788] Ettingshausen (55), Pl. i. fig. 4.
[789] Ettingshausen, loc. cit.
[790] Grand’Eury (69), p. 709.
[791] Feistmantel (75), Pl. i. fig. 8.
[792] Williamson (74), Pl. vii. fig. 45.
[793] Weiss (76), Pl. xvii. figs. 1 and 2.
[794] Weiss (84), Pl. xvi a. figs. 10 and 11.
[795] Ibid. Pl. xxv. fig. 2.
[796] Stur (87), Pl. ii. etc.
[797] Zeiller (88), p. 363, Pl. lvii. fig. 1.
[798] Steinhauer (18), Pl. vi. fig. 1.
[799] Kidston (93), p. 311, Pl. ii.
[800] Kidston (94), p. 248.
[801] Weiss (84), p. 119.
[802] Steinhauer (18), Pl. v. figs. 1 and 2.
[803] Artis (25), Pl. xxiv.
[804] Brongniart (282), Pls. xv. and xvi.
[805] Lindley and Hutton (31), Pl. lxxix.
[806] Kidston (93), p. 314; (86), p. 24.
[807] Zeiller (88), p. 333.
[808] Lindley and Hutton (31), Pl. lxxix.
[809] Weiss (84), Pl. iv. fig. 1.
[810] Renault and Zeiller (88), p. 385.
[811] Grand’Eury (90), p. 214.
[812] Stur (87), p. 160, Pl. ix. fig. 2.
[778] Renault and Zeiller (88), Pt. ii. Pl. li. p. 423.
[779] Lindley and Hutton (31), Pl. cxiv. and Pl. cxc. The original specimens are in the
Natural History Museum, Newcastle-on-Tyne.
[780] Ibid. Pl. cxxx. and Feistmantel (75), Pl. i. fig. 8.
[781] Lesquereux (79), Pl. xiii. fig. 14.
[782] Salter (63), figs. 6 and 7. Vide also Carruthers in Woodward, H. (72), p. 168.
[783] Grand’Eury (69); vide also (77) and (90).
[784] Renault and Zeiller (88), Pt. ii. Pls. lii. and ciii.
[785] Ibid. Pl. li.
[786] Sternberg (21), Pl. xii.
[787] Weiss (84), p. 61.
[788] Ettingshausen (55), Pl. i. fig. 4.
[789] Ettingshausen, loc. cit.
[790] Grand’Eury (69), p. 709.
[791] Feistmantel (75), Pl. i. fig. 8.
[792] Williamson (74), Pl. vii. fig. 45.
[793] Weiss (76), Pl. xvii. figs. 1 and 2.
[794] Weiss (84), Pl. xvi a. figs. 10 and 11.
[795] Ibid. Pl. xxv. fig. 2.
[796] Stur (87), Pl. ii. etc.
[797] Zeiller (88), p. 363, Pl. lvii. fig. 1.
[798] Steinhauer (18), Pl. vi. fig. 1.
[799] Kidston (93), p. 311, Pl. ii.
[800] Kidston (94), p. 248.
[801] Weiss (84), p. 119.
[802] Steinhauer (18), Pl. v. figs. 1 and 2.
[803] Artis (25), Pl. xxiv.
[804] Brongniart (282), Pls. xv. and xvi.
[805] Lindley and Hutton (31), Pl. lxxix.
[806] Kidston (93), p. 314; (86), p. 24.
[807] Zeiller (88), p. 333.
[808] Lindley and Hutton (31), Pl. lxxix.
[809] Weiss (84), Pl. iv. fig. 1.
[810] Renault and Zeiller (88), p. 385.
[811] Grand’Eury (90), p. 214.
[812] Stur (87), p. 160, Pl. ix. fig. 2.
Page 530
[813] Kidston (94), p. 249.
[814] Grand’Eury (89), p. 1087.
[815] Zeiller (88), p. 355.
[816] Weiss (84), p. 96.
[817] Sterzel (93), p. 66.
[818] Zeiller, loc. cit. p. 353.
[819] Sternberg (25), Pl. xlix. fig. 5.
[820] Brongniart (282), p. 128, Pl. xix.
[821] Germar and Kaulfuss (31), p. 221, Pl. xlv. fig. 1.
[822] Lindley and Hutton (31), Pl. ccxvi.
[823] Grand’Eury (77), p. 293.
[824] Zeiller (80), Pl. clxxiv. (expl. plates) fig. 3.
[825] Weiss (84), pp. 112, 113, 114.
[826] Zeiller (88), p. 353.
[827] Kidston (94), p. 249.
[828] Grand’Eury (90), p. 216 (expl. plates).
[829] Stur (87), p. 68.
[830] Stur (87), Pl. x.
[831] Artis (25), Pl. ii.
[832] Weiss, loc. cit. Pls. v. vi. and x.
[833] Grand’Eury (77), (90).
[834] Vide Stur (75), etc. for remarks on the course of the vascular strands.
[835] For good figures of the leaves vide Stur (75), Rothpletz (80), Ettingshausen (66),
Solms (96).
[836] Renault (96), p. 80; (93), Pls. xlii. and xliii. Since the above was written an account
of the internal structure of Archaeocalamites has been published by Solms-Laubach (97);
he describes the wood as being of the Arthropitys type.
[837] Renault, loc. cit. Pl. xlii. figs. 6 and 7.
[838] Stur (75), p. 2, Pls. ii.–v.
[839] An examination of the specimens in the Museum of the Austrian Geology Survey did
not enable me to satisfactorily verify the features of the cone as described by Stur; the
impressions are far from clear.
[840] Kidston (832).
[841] Vide Paterson (41); Lyell (67), vol. i. p. 149 etc.
[842] Volkmann (1720), p. 93, Pl. vii. fig. 2.
[843] Schlotheim (20), p. 402, Pl. xxii. fig. 4.
[844] Sternberg (25).
[845] Brongniart (282), p. 122, Pl. xxvi. figs. 1 and 2.
[846] Paterson (41), Pl. iii.
[814] Grand’Eury (89), p. 1087.
[815] Zeiller (88), p. 355.
[816] Weiss (84), p. 96.
[817] Sterzel (93), p. 66.
[818] Zeiller, loc. cit. p. 353.
[819] Sternberg (25), Pl. xlix. fig. 5.
[820] Brongniart (282), p. 128, Pl. xix.
[821] Germar and Kaulfuss (31), p. 221, Pl. xlv. fig. 1.
[822] Lindley and Hutton (31), Pl. ccxvi.
[823] Grand’Eury (77), p. 293.
[824] Zeiller (80), Pl. clxxiv. (expl. plates) fig. 3.
[825] Weiss (84), pp. 112, 113, 114.
[826] Zeiller (88), p. 353.
[827] Kidston (94), p. 249.
[828] Grand’Eury (90), p. 216 (expl. plates).
[829] Stur (87), p. 68.
[830] Stur (87), Pl. x.
[831] Artis (25), Pl. ii.
[832] Weiss, loc. cit. Pls. v. vi. and x.
[833] Grand’Eury (77), (90).
[834] Vide Stur (75), etc. for remarks on the course of the vascular strands.
[835] For good figures of the leaves vide Stur (75), Rothpletz (80), Ettingshausen (66),
Solms (96).
[836] Renault (96), p. 80; (93), Pls. xlii. and xliii. Since the above was written an account
of the internal structure of Archaeocalamites has been published by Solms-Laubach (97);
he describes the wood as being of the Arthropitys type.
[837] Renault, loc. cit. Pl. xlii. figs. 6 and 7.
[838] Stur (75), p. 2, Pls. ii.–v.
[839] An examination of the specimens in the Museum of the Austrian Geology Survey did
not enable me to satisfactorily verify the features of the cone as described by Stur; the
impressions are far from clear.
[840] Kidston (832).
[841] Vide Paterson (41); Lyell (67), vol. i. p. 149 etc.
[842] Volkmann (1720), p. 93, Pl. vii. fig. 2.
[843] Schlotheim (20), p. 402, Pl. xxii. fig. 4.
[844] Sternberg (25).
[845] Brongniart (282), p. 122, Pl. xxvi. figs. 1 and 2.
[846] Paterson (41), Pl. iii.
Page 531
[847] Göppert (52), Pls. III., V., VI., VIII., XXXVIII.
[848] Ettingshausen (66), Pls. i.–iv.
[849] Feistmantel (73), Pl. xiv. fig. 5.
[850] Zeiller (80), p. 17.
[851] Binney (68), p. 7.
[852] Stur (75), p. 3.
[853] Kidston (86), p. 35.
[854] Schimper and Koechlin-Schlumberger (62), Pl. i. The original specimens of
Schimper’s figures are in the Strassburg Museum.
[855] Feistmantel (73), p. 491, Pl. xxiv. figs. 3 and 4.
[856] Vide specimens 20 A, 20 B, 24 in the Williamson Collection.
[857] Stur (75), p. 17.
[858] Rothpletz (80), p. 8.
[859] Weiss (84), p. 56.
[860] Scheuchzer (1723), p. 19, Pl. iv. fig. 1.
[861] Schlotheim (04), Pl. ii. fig. 24, p. 57.
[862] Sternberg (25), p. 32.
[863] Brongniart (22), Pl. xiii. fig. 8, p. 234.
[864] Ibid. (28), p. 68.
[865] Dawson (66), p. 153, Pl. xii.
[866] For reference vide an excellent monograph by Coemans and Kickx (64), also Potonié
(94).
[867] e.g. Newberry (91).
[868] Renault (73), (762), (96).
[869] Williamson (74), (78).
[870] Williamson and Scott (94), p. 919.
[871] Specimen 929 in the Williamson Cabinet is a longitudinal section of the French
Sphenophyllum, as described by Renault (762).
[872] Williamson and Scott (94), p. 926.
[873] Williamson (91), p. 18.
[874] Williamson and Scott (94), p. 920.
[875] Williamson (91), p. 12.
[876] Ibid. (74).
[877] Felix (86), Pl. Vi. fig. 2.
[878] For figures vide Renault (82), Pl. xvi. fig. 1, (762) Pls. vii. and ix.
[879] Williamson (712).
[880] Weiss (84), p. 200.
[881] Binney (71).
[848] Ettingshausen (66), Pls. i.–iv.
[849] Feistmantel (73), Pl. xiv. fig. 5.
[850] Zeiller (80), p. 17.
[851] Binney (68), p. 7.
[852] Stur (75), p. 3.
[853] Kidston (86), p. 35.
[854] Schimper and Koechlin-Schlumberger (62), Pl. i. The original specimens of
Schimper’s figures are in the Strassburg Museum.
[855] Feistmantel (73), p. 491, Pl. xxiv. figs. 3 and 4.
[856] Vide specimens 20 A, 20 B, 24 in the Williamson Collection.
[857] Stur (75), p. 17.
[858] Rothpletz (80), p. 8.
[859] Weiss (84), p. 56.
[860] Scheuchzer (1723), p. 19, Pl. iv. fig. 1.
[861] Schlotheim (04), Pl. ii. fig. 24, p. 57.
[862] Sternberg (25), p. 32.
[863] Brongniart (22), Pl. xiii. fig. 8, p. 234.
[864] Ibid. (28), p. 68.
[865] Dawson (66), p. 153, Pl. xii.
[866] For reference vide an excellent monograph by Coemans and Kickx (64), also Potonié
(94).
[867] e.g. Newberry (91).
[868] Renault (73), (762), (96).
[869] Williamson (74), (78).
[870] Williamson and Scott (94), p. 919.
[871] Specimen 929 in the Williamson Cabinet is a longitudinal section of the French
Sphenophyllum, as described by Renault (762).
[872] Williamson and Scott (94), p. 926.
[873] Williamson (91), p. 18.
[874] Williamson and Scott (94), p. 920.
[875] Williamson (91), p. 12.
[876] Ibid. (74).
[877] Felix (86), Pl. Vi. fig. 2.
[878] For figures vide Renault (82), Pl. xvi. fig. 1, (762) Pls. vii. and ix.
[879] Williamson (712).
[880] Weiss (84), p. 200.
[881] Binney (71).
Page 532
[882] Williamson (912).
[883] Zeiller (93).
[884] Williamson (92).
[885] Potonié (94), fig. 1.
[886] For a more complete account of this strobilus vide Zeiller (93), and Williamson
(912), etc.
[887] Zeiller (93), p. 37.
[888] Williamson and Scott (94), p. 943.
[889] Scott (97), p. 24.
[890] Solms-Laubach (954).
[891] Ibid. Pl. x. fig. 6.
[892] Kidston (90).
[893] I am indebted to my friend Mr Kidston for an opportunity of examining these
specimens.
[894] Vide Renault (77), (96), p. 158. Zeiller (93), p. 34. Williamson and Scott (94), p. 942.
[895] Brongniart (22), p. 234, Pl. ii. fig. 8.
[896] Brongniart (28), p. 68.
[897] Bischoff (28), Pl. xiii. fig. 1.
[898] Römer, F. (62), p. 21, Pl. v. fig. 2.
[899] Sterzel (86), pp. 26, 27, etc.
[900] Kidston (93), p. 333.
[901] Zeiller (88), p. 414.
[902] Ibid. p. 411.
[903] Weiss (84), p. 201, Pl. xxi. fig. 12.
[904] Solms-Laubach (954), p. 232.
[905] Geinitz (55), Pl. xx. fig. 7.
[906] Zeiller (88), Pl. lxiv. figs. 3–5, and (93), p. 24, Pl. ii. fig. 4.
[907] Stur (75), p. 108.
[908] Stur (87), Pl. xv. and Kidston (90), p. 59, Pl. i.
[909] Zeiller (88), Pl. lxii. figs. 2–4.
[910] Stur (87); Williamson (74); Seward (89), etc.
[911] Renault (82), p. 84, and Newberry (91).
[912] Kidston (90), p. 62.
[913] Stur (75), p. 114, Pl. vii.
[914] Zeiller (93), p. 32.
[915] Mahr (68), Pl. viii.
[916] Zeiller (80), p. 34, Pl. clxi. fig. 9.
[917] Coemans and Kickx (64); Zeiller (80), (88); Schimper (69).
[883] Zeiller (93).
[884] Williamson (92).
[885] Potonié (94), fig. 1.
[886] For a more complete account of this strobilus vide Zeiller (93), and Williamson
(912), etc.
[887] Zeiller (93), p. 37.
[888] Williamson and Scott (94), p. 943.
[889] Scott (97), p. 24.
[890] Solms-Laubach (954).
[891] Ibid. Pl. x. fig. 6.
[892] Kidston (90).
[893] I am indebted to my friend Mr Kidston for an opportunity of examining these
specimens.
[894] Vide Renault (77), (96), p. 158. Zeiller (93), p. 34. Williamson and Scott (94), p. 942.
[895] Brongniart (22), p. 234, Pl. ii. fig. 8.
[896] Brongniart (28), p. 68.
[897] Bischoff (28), Pl. xiii. fig. 1.
[898] Römer, F. (62), p. 21, Pl. v. fig. 2.
[899] Sterzel (86), pp. 26, 27, etc.
[900] Kidston (93), p. 333.
[901] Zeiller (88), p. 414.
[902] Ibid. p. 411.
[903] Weiss (84), p. 201, Pl. xxi. fig. 12.
[904] Solms-Laubach (954), p. 232.
[905] Geinitz (55), Pl. xx. fig. 7.
[906] Zeiller (88), Pl. lxiv. figs. 3–5, and (93), p. 24, Pl. ii. fig. 4.
[907] Stur (75), p. 108.
[908] Stur (87), Pl. xv. and Kidston (90), p. 59, Pl. i.
[909] Zeiller (88), Pl. lxii. figs. 2–4.
[910] Stur (87); Williamson (74); Seward (89), etc.
[911] Renault (82), p. 84, and Newberry (91).
[912] Kidston (90), p. 62.
[913] Stur (75), p. 114, Pl. vii.
[914] Zeiller (93), p. 32.
[915] Mahr (68), Pl. viii.
[916] Zeiller (80), p. 34, Pl. clxi. fig. 9.
[917] Coemans and Kickx (64); Zeiller (80), (88); Schimper (69).
Page 533
[918] Royle (39), p. 431.
[919] For other figures of this plant, vide Feistmantel (81), Pls. xi. a and xii. a.
[920] Zeiller (91).
[921] Vide also Zeiller (922), p. 75.
[922] Feistmantel (81), p. 69.
[923] Scott (97).
[924] Scott (962), p. 15.
[925] Dawson (61), p. 10, fig. 7.
[926] Kidston (94), p. 250.
[927] Kidston (94), p. 250.
[928] Sterzel (93), p. 143.
[929] Zeiller (94), p. 172.
[930] De Bary (84), p. 499.
[931] Westermaier and Ambronn (81).
[932] Schwendener (74), p. 124. Haberlandt (96), p. 165.
[919] For other figures of this plant, vide Feistmantel (81), Pls. xi. a and xii. a.
[920] Zeiller (91).
[921] Vide also Zeiller (922), p. 75.
[922] Feistmantel (81), p. 69.
[923] Scott (97).
[924] Scott (962), p. 15.
[925] Dawson (61), p. 10, fig. 7.
[926] Kidston (94), p. 250.
[927] Kidston (94), p. 250.
[928] Sterzel (93), p. 143.
[929] Zeiller (94), p. 172.
[930] De Bary (84), p. 499.
[931] Westermaier and Ambronn (81).
[932] Schwendener (74), p. 124. Haberlandt (96), p. 165.
Page 534
Transcriber’s Notes:
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Headings and table of contents have been modified to be more consistent, including
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