Part 1

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INTRODUCTION

TO THE STUDY OF

PALÆONTOLOGICAL BOTANY

INTRODUCTION

TO THE STUDY OF

PALÆONTOLOGICAL BOTANY

BY

JOHN HUTTON BALFOUR, A.M. M.D. EDIN. F.R.S., SEC. R.S.E., F.L.S.

PROFESSOR OF MEDICINE AND BOTANY IN THE UNIVERSITY OF EDINBURGH, REGIUS KEEPER OF THE ROYAL BOTANIC GARDEN, AND QUEEN'S BOTANIST FOR SCOTLAND

WITH FOUR LITHOGRAPHIC PLATES, AND UPWARDS OF ONE HUNDRED WOODCUTS

EDINBURGH

ADAM AND CHARLES BLACK

1872

_Printed by_ R. & R. CLARK, _Edinburgh_.

TO

PROF. HEINRICH ROBERT GOEPPERT, M.D.,

DIRECTOR OF THE BOTANIC GARDEN, BRESLAU;

ONE OF THE MOST EMINENT PALÆONTOLOGICAL BOTANISTS OF EUROPE,

The following Treatise

IS DEDICATED, WITH BEST RESPECTS, BY HIS OBLIGED FRIEND

THE AUTHOR.

PREFACE.

The subject of Fossil Botany or Palæophytology has formed a part of the Course of Botany in the University of Edinburgh for the last twenty-five years, and the amount of time devoted to the exposition of it has increased. The recent foundation of a Chair of Geology and of a Falconer Palæontological Fellowship in the University seems to require from the Professors of Zoology and Botany special attention to the bearings of their departments of science on the structure of the animals and plants of former epochs of the Earth's history. No one can be competent to give a correct decision in regard to Fossils, unless he has studied thoroughly the present Fauna and Flora of the globe. To give a well-founded opinion in regard to extinct beings, it is essential that the observer should be conversant with the conformation and development of the living ones now on the earth; with their habits, modes of existence and reproduction, the microscopic structure of their tissues, their distribution, and their relation to soil, the atmosphere, temperature, and climate.

There can be no doubt that to become a good Fossil Geologist a student must begin with living animals and plants. The study of Geology must be shared by the Petralogist, who looks at the condition of the rocks of the globe, the minerals forming them, and their mode of formation; the Chemist, who determines the materials which enter into the composition of minerals and rocks; the Naturalist, who examines the plants and animals found in the various strata; and perhaps also the Natural Philosopher, who calculates from independent sources the phases of the Earth's history. It may be said thus to combine all these students of Science in one brotherhood. Much has been done by the efforts of such men as Hutton and Werner, who were engaged chiefly in considering the mineral department of Geology; but it is clear that the Science could not have attained its present position without the continued labours of those who have been examining fossils in their relations to time and space. Had it not been for the researches of Palæontologists, Geology could not have made its present advance.

In my Class Book of Botany I have given an introduction to Palæophytology, and it occurred to me that it might be useful to students to publish this in a separate form, with additions in both the letterpress and the illustrations. The institution of the Palæontological Fellowship, in memory of my former friend Dr. Falconer, has brought the subject specially under my notice. The Fellowship has been promoted chiefly by my friend and former pupil Dr. Charles Murchison, a gentleman fond of science and of his Alma Mater, the University of Edinburgh, where he and Falconer studied and took their degrees.

The first award of the Fellowship has been made to a distinguished student, who acquitted himself with the greatest credit during the three days of examination on Geology, Zoology, and Botany. I trust that the Fellowship will continue to stimulate our eminent students in future years.

Having been a student of Natural Science along with Dr. Falconer, I feel a peculiar interest in doing what I can to promote the study of a subject to which he so successfully devoted his energies. In my endeavour to do so I have been encouraged by my friend and former pupil, Mr. William Carruthers, at the head of the Botanical Department of the British Museum, and a former student in Edinburgh under the late Professor Fleming. He has done much to advance our knowledge of Fossil Botany, and to him I am indebted for two of the plates and some of the woodcuts which illustrate this publication. He has given me most efficient assistance, and I have to return my best thanks for his kind aid. I am also indebted to my colleague, Professor Geikie, for his valued assistance.

The neighbourhood of Edinburgh is rich in Fossils of the Carboniferous epoch, and much yet remains to be done to illustrate its Palæontology. Such labourers as Geikie and Peach may be expected to give great assistance in the furtherance of our knowledge of Scottish Geology, so as to form a school which shall revive the reputation enjoyed by Edinburgh in the days of Hutton and Jameson. If I can be useful in encouraging students to take up the study of Palæontological Botany, and to prosecute it with vigour, I shall feel that this introductory treatise has not been issued in vain. As one of the few surviving relations of Dr. James Hutton, I am glad to be able to show an interest in a science which may aid in elucidating the "Theory of the Earth."

In writing this work I have taken for granted that the reader is acquainted with the Elements of Botany, and knows the general structure of plants of the present day. I have not, therefore, hesitated to use the ordinary Botanical terms without explanation. I am satisfied that no one can study Fossil Botany properly unless he has studied Modern Botany.

Those readers who may find any difficulty as to technical terms I would refer to my Botanist's Companion, where a full Glossary is given.

27 INVERLEITH ROW, _May 1872_.

TABLE OF CONTENTS.

PAGE

INTRODUCTORY REMARKS 1

DETERMINATION OF FOSSIL PLANTS 3

MODE OF PRESERVATION OF FOSSIL PLANTS 8

EXAMINATION OF THE STRUCTURE OF FOSSIL PLANTS 12

FOSSILIFEROUS ROCKS 20

NATURAL ORDERS TO WHICH FOSSIL PLANTS BELONG 22

PERIODS OF VEGETATION AMONG FOSSIL PLANTS 25

FOSSIL FLORA OF THE PRIMARY OR PALÆZOIC PERIOD 26

REIGN OF ACROGENS 26

FLORA OF THE CARBONIFEROUS EPOCH 36

FLORA OF THE PERMIAN EPOCH 71

FOSSIL FLORA OF THE SECONDARY OR MESOZOIC PERIOD 72

REIGN OF GYMNOSPERMS 72

FLORA OF THE TRIAS AND LIAS EPOCHS 77

FLORA OF THE OOLITIC EPOCH 80

FLORA OF THE WEALDEN EPOCH 84

FOSSIL FLORA OF THE TERTIARY OR CAINOZOIC PERIOD (INCLUDING THE CRETACEOUS EPOCH) 87

REIGN OF ANGIOSPERMS 87

FLORA OF THE CHALK 87

FLORA OF THE EOCENE EPOCH 90

FLORA OF THE MIOCENE EPOCH 92

FLORA OF THE PLIOCENE EPOCH 98

GENERAL CONCLUSIONS 101

RECAPITULATION 103

WORKS ON FOSSIL BOTANY 105

EXPLANATION OF PLATES 111

INDEX 113

LIST OF WOODCUTS.

FIG. PAGE

1. Section of Peuce Withami, Lindley and Hutton 3

2. Bark of Araucaria 5

3. Markings on Araucaria bark 6

4. " " 7

5. " " 7

6. Leaf of Araucaria 7

7. Nicolia Owenii (Carr.) 11

8. Bryson's instrument for slitting Fossils 14

9. Tree-fern 27

10. Asplenium 28

11 _a._ Bifurcating Trunk of a Tree-fern (Alsophila Perrottetiana) 29

11 _b._ Rhizome of Lastrea Filix-mas 29

12. Transverse section of stem of a Tree-fern (Cyathea) 29

13. Scalariform vessels from Tree-fern 30

14. Sporangia of a Fern 30

15. Lycopodium clavatum 30

16. Spore-case, containing Microspores of Lycopodium 30

17. " " Macrospores of Selaginella 30

18. Fructification of Equisetum maximum 31

19. Polygonal scale of Equisetum 32

20. Spore of Equisetum--filaments contracted 32

21. " " " expanded 32

22. Marsilea Fabri 33

22 _bis._ Adiantites Lindseæformis 41

23. Pecopteris (Alethopteris) aquiline 43

24. " (Alethopteris) heterophylla 43

25. Neuropteris Loshii 43

26. " gigantean 43

27. " acuminate 43

28. Sphenopteris affinis 43

29. Cyclopteris dilatata 43

30. Stem of Caulopteris macrodiscus 44

31. " " Balfouri (Carr.) 44

32. " " Morrisi (Carr.) 44

33. " Sigillaria pachyderma 45

34. Sigillaria reniformis 45

35. " pachyderma 46

36. " (Favularia) tessellate 46

37. " pachyderma 46

38. Stigmaria ficoides 47

39. " " (S. anabathra of Corda) 47

40. Bifurcating stem of Lepidodendron obovatum (elegans) 49

41. Stem of Lepidodendron crenatum 49

42. Fructification of Lepidodendron 50

43. Longitudinal section of Fructification of Triplosporites 50

44. (1). Fruit of Selaginella spinulosa, A. Braun (Lycopodium selaginoides, Linn.) 51 (2). Scale and sporangium from the upper part of cone 51 (3). Antheridian microspores from ditto 51 (4). Macrospore 51 (5). Scale and sporangium from lower part of cone, containing macrospores 51 (6). Fruit of Lepidostrobus ornatus (Hooker) 51 (7). Three scales and sporangia of ditto 51 (8). Microspores from sporangia of the upper part of the cone of Triplosporites Brownii, Brongn. 51 (9). Macrospore from the sporangia of the lower part 51 (10). Scales and sporangia of a cone of Flemingites 51

45 _a._ Calamites Suckovii 57 45 _b._ Septum or Phragma of a Calamite 57

46. Vertical stems of Calamites--in coal-measures of Treuil, near St. Etienne 58

47. Fruits of Equisetum and Calamites 60 (1). Equisetum arvense, L. 60 (2). Portion of sporangium wall 60 (3, 4). Spores--elaters free 60 (5). Longitudinal section of part of one side of cone 60 (6). Transverse section of cone 60 (7). Calamites (Volkmannia) Binneyi (Carr.) 60 (8). Portion of sporangium wall 60 (9). Two spores 60 (10). Longitudinal section of part of one side of cone 60 (11). Transverse section of cone 60

48. Foliage and fruits of Calamites 62 (1, 2). Asterophyllites 62 (3, 4). Annularia 62 (5, 6). Sphenophyllum 62

49. Araucarioxylon Withami, Krauss (Pinites Withami) 63

50. Trigonocarpum olivæforme 63

51. Cardiocarpum Lindleyi (Carr.) 65

52. " " 65

53. Cardiocarpum anomalum (Carr.) 66

54. Pothocites Grantoni (Paterson) 67

55, 56. Walchia piniformis (Sternb.) 72

57. Pinus sylvestris 73

58. Abies excelsa 73

59. Larix Europæa 73

60. Cedrus Libani 73

61. Araucaria excelsa 74

62. Woody tubes of fir--single rows of discs 74

63. " " --double and opposite rows of discs 74

64. Woody tubes of Araucaria excelsa--double and triple and alternate rows of discs 74

65. Longitudinal section of stem of a Gymnosperm 74

66. Linear leaves of Pinus Strobus 75

67. Cone of Pinus sylvestris 75

68. " Cupressus sempervirens 75

69. Scale of mature cone of Pinus sylvestris 75

70. Fruiting branch of Juniperus communis 76

71. Branch of Taxus baccata 76

72. Male flower of Yew 76

73. Fruit of Yew 76

74. Cycas revoluta 77

75. Encephalartos (Zamia) pungens 77

76. Schizoneura heterophylla 78

77. Zamites 79

78. Pterophyllum Pleiningerii 80

79. Nilssonia compta (Pterophyllum comptum of Lindley and Hutton) 80

80. Palæozamia pectinata (Zamia pectinata of Brongniart, and Lindley and Hutton) 80

81. Brachyphyllum mammillare 81

82. Equisetum columnare 81

83. Araucarites sphærocarpus (Carr.) 82

84. Termination of a scale of ditto 82

85. Section of a scale of ditto 82

86. The Dirt-bed of the island of Portland 83

87. Cycadoidea megalophylla (Mantellia nidiformis of Brongniart) 83

88. Kaidacarpum ooliticum (Carr.) 84

89. Pandanus odoratissimus 84

90. Fossil wood, Abietites Linkii 85

91. Sequoiites ovalis 88

92. Pinites ovatus (Zamia ovata of Lindley and Hutton) 89

93. Palmacites Lamanonis 90

95. Comptonia acutiloba 92

96. Acer trilobatum 93

97. Ulmus Bronnii 93

98. Rhamnus Aizoon 94

99. Alnus gracilis 95

100. Taxites or Taxodites Campbellii 95

101. Rhamnites multinervatus 95

102. Equisetum Campbellii 96

PALÆONTOLOGICAL BOTANY.

The study of the changes which have taken place in the nature of living beings since their first appearance on the globe till the period when the surface of the earth, having assumed its present form, has been covered by the creation which now occupies it, constitutes one of the most important departments in Geology. It is, as Brongniart remarks, the history of life and its metamorphoses. The researches of geologists show clearly that the globe has undergone various alterations since that "beginning" when "God created the heavens and the earth." These alterations are exhibited in the different stratified rocks which form the outer crust of the earth, and which were chiefly sedimentary deposits produced by the weathering of the exposed rocks. Remains of the plants and animals living on the globe at the time of the formation of the different beds are preserved in them. Elevations and depressions of the surface of the earth affected the organisms on its surface, and gave to successive deposits new faunas and floras. Some of these epochs have been marked by great changes in the physical state of our planet, and they have been accompanied with equally great modifications in the nature of the living beings which inhabited it. The study of the fossil remains of animals is called Palæozoology (παλαιός, ancient, and ζῷον, animal), while the consideration of those of vegetables is denominated Palæophytology (παλαιός and φυτόν, a plant). Both are departments of the science of Palæontology, which has been the means of bringing geology to its present state of advancement. The study of these extinct forms has afforded valuable indications as to the physical state of the earth, and as to its climate at different epochs. This study requires the conjunct labours of the Zoologist, the Botanist, and the Petralogist.

The vegetation of the globe, during the different stages of its formation, has undergone very evident changes. At the same time there is no reason to doubt that the plants may all be referred to the great classes distinguished at the present day--namely, Thallogens, including such plants as Lichens, Algæ, and Fungi; Acrogens, such as Ferns and Lycopods; Gymnosperms, such as Cone-bearing plants and Cycads; Endogens, such as Palms, Lilies, and Grasses; and Exogens, such as the common trees of Britain (excluding the Fir), and the great mass of ordinary flowering plants. The relative proportion of these classes, however, has been different, and the predominance of certain forms has given a character to the vegetation of different epochs. The farther we recede in geological history from the present day, the greater is the difference between the fossil plants and those which now occupy the surface. At the time when the coal-beds were formed, the plants covering the earth belonged to genera and species not existing at the present day. As we ascend higher, the similarity between the ancient and the modern flora increases, and in the latest stratified rocks we have in certain instances an identity in species and a considerable number of existing genera. At early epochs the flora appears to have been uniform, to have presented less diversity of forms than at present, and to have been similar in the different quarters of the globe. The vegetation also indicates that the nature of the climate was different from that which characterises the countries in which these early fossil plants are now found.

DETERMINATION OF FOSSIL PLANTS.

[Sidenote: Fig. 1. Section of _Peuce Withami_, after Lindley and Hutton, a fossil Conifer of the coal epoch. Punctated woody tissue seen.]

Fossil plants are by no means so easily examined as recent species. They are seldom found in a complete state. Fragments of stems, leaves, and fruits, are the data by which the plant is to be determined. It is very rare to find any traces of the flowers. The parts of fossil plants are usually separated from each other, and it is difficult to ascertain what are the portions which should be associated together so as to complete an individual plant. Specimens are sometimes preserved, so that the anatomical structure of the organs, especially of the stem, can be detected by very thin slices placed under the microscope. In the case of some stems the presence of punctated woody tissue (Fig. 1) has proved of great service as regards fossil Botany; this structure, along with the absence of large pitted ducts, serving to distinguish Conifers. The presence of scalariform vessels indicates a plant belonging to the vascular Cryptogams, of which the fern is the best known example. The cautions to be observed in determining fossil plants are noticed by Dr. Hooker in the Memoirs of the Geological Survey of Great Britain (vol. ii. p. 387). At the present day, the same fern may have different forms of fronds, which, unless they were found united, might be reckoned distinct genera; and remarkable examples are seen in Niphobolus rupestris and Lindsæa cordata. Moreover, we find the same form of frond belonging to several different genera, which can only be distinguished by the fructification; and as this is rarely seen in fossil ferns, it is often impossible to come to a decided conclusion in regard to them. A leaf of Stangeria paradoxa was considered by an eminent botanist as a barren fern frond, but it ultimately proved to be the leaf of a Cycad. The leaf of Cupania filicifolia, a Dicotyledon, might easily be mistaken for that of a fern; it resembles much the frond of a fossil fern called Coniopteris. The diverse leaves of Sterculia diversifolia, if seen separately, might easily be referred to different plants. In the same fern we meet also with different kinds of venation in the fronds. Similar remarks may be made in regard to other plants. Harvey has pointed out many difficulties in regard to sea-weeds.

As regards the materials for a fossil flora, the following remarks of Hugh Miller deserve attention:--