FOSSIL PLANTS
CAMBRIDGE UNIVERSITY PRESS
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Part of a transverse section of a Permian Osmundaceous Fern stem, Thamnopteris Schlechtendalii (Eichwald). a, outer xylem; b, inner xylem. For description, see page 329. (After Kidston and Gwynne-Vaughan. Very slightly reduced.)
FOSSIL PLANTS
A TEXT-BOOK FOR STUDENTS
OF BOTANY AND GEOLOGY
BY
A. C. SEWARD, M.A., F.RS. PROFESSOR OF BOTANY IN THE UNIVERSITY; FELLOW OF ST JOHN’S COLLEGE AND HONORARY FELLOW OF EMMANUEL COLLEGE, CAMBRIDGE
WITH 265 ILLUSTRATIONS
VOL. II
CAMBRIDGE:
AT THE UNIVERSITY PRESS
1910
~Cambridge~:
PRINTED BY JOHN CLAY, M.A.
AT THE UNIVERSITY PRESS.
PREFACE
I regret that pressure of other work has prevented the completion of this Volume within a reasonable time since the publication of Volume I. Had Volume II been written ten years ago, the discoveries made in the course of the last decade would have given an out-of-date character to much of the subject-matter. It is more especially in regard to the Ferns and the extinct members of the Gymnosperms that our outlook has been materially altered by recent contributions to Palaeobotany. It is, however, some satisfaction to be able to add that recent progress has been relatively slight in that part of the subject dealt with in the first volume.
The original intention was to complete the whole work in two volumes. Soon after the second volume was begun, it became evident that the remaining divisions of the plant-kingdom could not be included within the compass of a single volume. I decided, therefore, to take the consequences of having embarked on too ambitious a plan of treatment, and to preserve uniformity of proportion by reserving the seed-bearing plants for a third volume. The third volume will include the Pteridosperms, other than those briefly described in the final chapter of the present volume, and other classes of Gymnosperms. I propose also to devote such space as is available within the limits of a text-book to the neglected subject of the geographical distribution of plants at different stages in the history of the earth. It is my intention to complete Volume III with as little delay as possible. As I have written elsewhere, the past history of the Flowering plants needs special treatment, and anything more than a mere compilation can be adequately attempted only after considerable research and with the assistance of botanists possessing a special knowledge of different families of Angiosperms. The need of a critical examination of available data in regard to the geological history of this dominant group will not be lost sight of.
I am well aware that while certain genera have received an undue share of attention in the present volume, others have been ignored or treated with scant consideration. For this inconsistency I have no excuse to offer, beyond the statement that the subject is a large one, and selection is necessary even though the work consists of three volumes.
The publication in 1909 of a collection of excellent photographs of Palaeozoic Plants, with brief descriptive notes, by Mr Newell Arber, as one of a series of popular “Nature Books,” bears striking testimony to the remarkable spread of interest in the study of the vegetation of the past, which is one of the outstanding features in the recent history of botanical science.
In the list of illustrations I have mentioned the source of all figures which have been previously published. I would, however, supplement the statement of fact with an expression of thanks to corporate bodies and to individuals who have allowed me to make use of blocks, drawings, or photographs.
I wish to thank my colleague, Mr A. G. Tansley, for placing at my disposal several blocks originally published in the pages of the New Phytologist. To Professor Bertrand of Lille and to his son Dr Paul Bertrand I am indebted for several prints and descriptive notes of specimens in their possession. My friends Dr Nathorst of Stockholm and Dr Zeiller of Paris have generously responded to my requests for information on various points. I wish especially to thank Dr Kidston for several excellent prints of specimens in his collection and for the loan of sections. I have profited by more than one examination of his splendid collection at Stirling. Professor Weiss has generously allowed me to borrow sections from the Manchester University collections, more especially several which have been reproduced in the chapter devoted to the genus Lepidodendron. To Professor F. W. Oliver my thanks are due for the loan of sections from the collection under his charge at University College. I have pleasure also in thanking Dr Scott, not only for lending me sections of a Lepidodendron and for allowing me to use some drawings of Miadesmia originally made by Mrs Scott for reproduction in his invaluable book, Studies in Fossil Botany, but for kindly undertaking the laborious task of reading the proofs of this volume. It would be unfair to express my gratitude to Dr Scott for many helpful suggestions and criticisms, without explicitly stating that thanks to a friend for reading proofs must not be interpreted as an attempt to claim his support for all statements or views expressed. The General Editor of the Series, Mr A. E. Shipley, has also kindly read the proofs. I am under obligations also for assistance of various kinds to Prof. Thomas of Auckland, New Zealand, to Mr Boodle of Kew, to Mr D. M. S. Watson of Manchester, to Mr T. G. Hill of University College, and to Mr Gordon of Emmanuel College, Cambridge. I am indebted to the kind offices of Miss M. C. Knowles for the photograph of the specimen of Archaeopteris hibernica in the Irish National Museum, Dublin, reproduced on page 561.
Many of the illustrations are reproduced from drawings by my wife: those made from the actual specimens are distinguished by the addition of the initials M. S. I am grateful to her also for some improvements in the letter-press. For the drawings made from sections and for some of the outline sketches I am responsible. I have availed myself freely of the facilities afforded by Professor McKenny Hughes in the Sedgwick Museum of Geology for the examination of specimens under the charge of Mr Newell Arber, the University Demonstrator in Palaeobotany. It is a pleasure to add that, as on former occasions, I am indebted to the vigilance of the Readers of the University Press for the detection of several errors which escaped my notice in the revision of the proofs.
A. C. SEWARD.
BOTANY SCHOOL, CAMBRIDGE.
March 12, 1910.
TABLE OF CONTENTS
CHAPTER XII =SPHENOPHYLLALES= (continued from Volume I.). Pp. 1–16.
PAGE
Sphenophyllum 1–7 Cheirostrobus 7–12 =Sphenophyllales and Psilotaceae= 12–16
CHAPTER XIII
=PSILOTALES.= Pp. 17–29.
Psilotum and Tmesipteris 17–24 Fossils described by authors as being closely allied to Psilotum 24–26 Psilophyton 26–29
CHAPTER XIV
=LYCOPODIALES.= Pp. 30–91.
=Recent Lycopodiales= (General) 30–33 Lycopodiaceae (Recent) 33–49 Selaginellaceae (Recent) 49–58 Isoetaceae (Recent) 58–66 =Fossil Lycopodiales= 66–91 Isoetaceae (Fossil) 66–68 Pleuromeia 68–73 Herbaceous fossil species of Lycopodiales 73–91 Lycopodites 76–84 Selaginellites 85–88 Lycostrobus 88–91 Poecilitostachys 91
CHAPTER XV
=ARBORESCENT LYCOPODIALES.= Pp. 92–195.
=Lepidodendron= 93–181
i. General 93–97
ii. Leaves and Leaf-cushions 97–105
iii. Lepidophloios 105–109
iv. The anatomy of Lepidodendron vasculare 109–123
v. Lepidodendron stems as represented by casts and impressions of partially decorticated specimens 123–128 a. Knorria 124–126; b. Bergeria 126, 127; c. Aspidiaria 127, 128.
vi. Lepidodendroid axes known as Ulodendron and Halonia 128–139 a. Ulodendron 128–135; b. Halonia 135–139.
vii. Anatomical characters of vegetative Lepidodendron shoots 139–181 1. Lepidodendron esnostense 139, 140; 2. L. rhodumnense 140; 3. L. saalfeldense 141; 4. L. fuliginosum 141–160; 5. L. Harcourtii 160–163; 6. L. Wünschianum 163–171; 7. L. macrophyllum 171; 8. L. Veltheimianum 171–177; 9. L. Pedroanum 177, 178; 10. L. australe 178–181.
viii. Fertile shoots of Lepidodendreae 181–195 A. Lepidostrobus 181–191. i. Lepidostrobus variabilis 187, 188; ii. L. oldhamius 188–190; iii. L. Brownii, etc. 190, 191. B. Spencerites 192–195.
CHAPTER XVI
=SIGILLARIA.= Pp. 196–226.
i. General 196–210; ii. Leaves 210–215; iii. Fertile shoots 215–218; iv. The structure of Sigillarian stems 218–224; v. Sigillaria Brardi 224–226.
CHAPTER XVII
=STIGMARIA.= Pp. 227–247.
CHAPTER XVIII
=BOTHRODENDREAE.= Pp. 248–270.
Bothrodendron 248–264. a. B. minutifolium 251–253; b. B. punctatum 254, 255; c. B. kiltorkense 255–259. Anatomy of vegetative shoots of Bothrodendron 260–262; Cones of Bothrodendron 262–264. Pinakodendron 264 Omphalophloios 264–266 General considerations 266–270
CHAPTER XIX
=SEED-BEARING PLANTS CLOSELY ALLIED TO
MEMBERS OF THE LYCOPODIALES.= Pp. 271–279.
i. Lepidocarpon 271–275; ii. Miadesmia 275–279.
CHAPTER XX
=FILICALES.= Pp. 280–323.
I. =Leptosporangiate Filicales= 283–316 Eufilicineae 284–316. Osmundaceae 285, 286; Schizaeaceae 286–291; Matonineae 291–293; Loxsomaceae 293; Hymenophyllaceae 294; Cyatheaceae 294–296; Dennstaedtiinae 296; Polypodiaceae 296; Parkeriaceae 297; Dipteridinae 298. The habit, leaf-form, and distribution of ferns 300–309; The anatomy of ferns 309–316.
II. =Marattiales= 316–321
III. =Ophioglossales= 321–323
CHAPTER XXI
=FOSSIL FERNS.= Pp. 324–394.
=Osmundaceae= 324–346; =Schizaeaceae= 346–351; =Gleicheniaceae= 351–355; =Matonineae= 355–363; =Hymenophyllaceae= 363–365; =Cyatheaceae= 365–375; =Polypodiaceae= 375–380; =Dipteridinae= 380–394.
CHAPTER XXII
=MARATTIALES (FOSSIL).= Pp. 395–411.
Ptychocarpus 397; Danaeites 398; Parapecopteris 398; Asterotheca 398–400; Hawlea 400; Scolecopteris 401, 402; Discopteris 402–404; Dactylotheca 404–406; Renaultia 406; Zeilleria 407; Urnatopteris 407; Marattiopsis 407–409; Danaeopsis 409; Nathorstia 410, 411.
CHAPTER XXIII
=PSARONIEAE.= Pp. 412–426.
CHAPTER XXIV
=OPHIOGLOSSALES (FOSSIL).= Pp. 427–431.
CHAPTER XXV
=COENOPTERIDEAE.= Pp. 432–472.
I. Botryoptereae 434–443
II. Zygoptereae 443–470
CHAPTER XXVI =HYDROPTERIDEAE AND SAGENOPTERIS.= Pp. 473–483.
Marsiliaceae 473–475; Salviniaceae 475–477; Sagenopteris 477–483.
CHAPTER XXVII
=GENERA OF PTERIDOSPERMS, FERNS, AND=
PLANTAE INCERTAE SEDIS. Pp. 484–580.
Taeniopteris 485–494; Weichselia 494–496; Glossopteris 496–512; Gangamopteris 512–517; Lesleya 517–519; Neuropteridium 519–523; Cardiopteris 523–525; Aphlebia 525–529; Sphenopteris 529–532; Mariopteris, Diplotmema, Palmatopteris 532–537; Cephalotheca 537; Thinnfeldia 537–544; Lomatopteris 544–546; Cycadopteris 546; Ptilozamites 546–548; Ctenopteris 548–550; Dichopteris 550–552; Odontopteris 552–556; Callipteris 557–559; Callipteridium 560; Archaeopteris 552–565; Neuropteris 565–571; Cyclopteris 571, 572; Linopteris 572, 573; Alethopteris 573–576; Lonchopteris 576; Pecopteris 576–580.
INDEX Pp. 609–624
LIST OF ILLUSTRATIONS
Several of the illustrations are printed from blocks for which I am indebted to learned societies or to individuals. The sources from which clichés were obtained are mentioned within square brackets.
FRONTISPIECE. Thamnopteris Schlechtendalii (Eich.). From a photograph given to me by Dr Kidston and Mr Gwynne-Vaughan. (Page 329.)
FIG. PAGE 112. Sphenophyllostachys 2 113. ╭ Sphenophyllostachys Römeri 3 ┤ Sphenophyllum trichomatosum ╰ S. majus 114, 115. Sphenophyllostachys fertilis 4, 5 [Council of the Royal Society of London.] 116. Sphenophyllostachys Dawsoni 6 [Mr A. G. Tansley, Editor of the New Phytologist.] 117. ╭ Cheirostrobus pettycurensis 8 ╰ Pseudobornia ursina 118. Psilotum triquetrum 18 119. Psilotum triquetrum (anatomy) 20 120. Tmesipteris tannensis 22 121. Lycopodium (seven species) 35 122. Lycopodium squarrosum 36 123. Lycopodium cernuum 37 124. Lycopodium obscurum 38 125. Lycopodium (anatomy of stem) 41 126. Lycopodium (anatomy of cones) 45 127–129. Lycopodium cernuum (cone) 47–49 [Council of the Royal Society of Edinburgh.] 130. Selaginella grandis 50 131. Selaginella (anatomy) 52 132. ╭ Isoetes echinospora 59 ╰ I. lacustris 133. Isoetes lacustris (anatomy) 62 134. Pleuromeia Sternbergi 70 135. Selaginellites and Lycopodites 80 136. Lycopodites lanceolatus 81 [Council of the Geological Society of London.] 137. Lycopodites falcatus 83 138. Selaginellites primaevus 86 139. Lycostrobus Scotti 89 140. Picea excelsa 94 141. Lepidodendron Sternbergii 97 142. Sigillaria (leaves) 98 143. Lepidodendron (leaves) 99 144. Lepidodendron Veltheimianum 101 145. Lepidodendron leaf-cushion 102 146. Lepidodendron and Lepidophloios leaf-cushions 104 147. Lepidophloios leaf-cushion 108 148–155. Lepidodendron vasculare 112–122 156. Knorria mirabilis 125 157. Lepidodendron Veltheimianum (Ulodendron) 129 158. Diagrammatic section illustrating the branch-theory of the Ulodendroid scar 132 [Council of the Manchester Literary and Philosophical Society.] 159. Pinus clausa 134 160. Lepidophloios scoticus 135 161. Halonia tortuosa 136 162–167. Lepidodendron fuliginosum 143–147 [Council of the Cambridge Philosophical Society.] 168. Lepidodendron vasculare and L. fuliginosum 148 169. Lepidodendron fuliginosum 149 170–172. L. fuliginosum 150–152 173. Lepidodendron obovatum 154 174–176. Lepidodendron aculeatum 155, 156 [Oxford University Press: Annals of Botany.] 177. Stigmaria radiculosa 157 178. Stigmarian rootlet 158 179. Lepidodendron Harcourtii and L. fuliginosum 162 180. Lepidodendron Wünschianum 163 181, 182. L. Wünschianum 165, 166 183, 184. L. Wünschianum 168, 169 [Editor of the New Phytologist.] 185. Lepidodendron Veltheimianum 173 186. L. Veltheimianum and L. macrophyllum 176 187. Lepidodendron australe 179 [Dr H. Woodward, Editor of the Geological Magazine.] 188, 189. Lepidostrobus 183, 184 190. Lepidodendron and Lepidostrobi 186 191. Lepidostrobus 188 192. Spencerites insignis 193 [Oxford University Press: Annals of Botany.] 193. Sigillaria elegans, S. rugosa, S. tessellata, Omphalophloios anglicus 197 194. Sigillaria McMurtriei 199 195. Sigillaria mammillaris 199 196. Sigillaria Brardi, S. laevigata, and Lepidodendron Wortheni 200 197. Carica sp. 202 198, 199. Sigillaria 205, 206 200. Sigillaria Brardi 212 201. Sigillariostrobus 216 202. Sigillaria elegans and S. elongata 220 203. Sigillaria Brardi 225 204, 205. Stigmaria ficoides 227, 228 206. Cyperus papyrus 230 207, 208. Stages in the development of Sigillaria 236 209. Stigmariopsis 237 210. Stigmaria 241 211. Bothrodendron punctatum 250 212. Bothrodendron minutifolium, B. punctatum, B. kiltorkense and Lepidostrobus Olryi 252 213. Bothrodendron minutifolium 254 214. Bothrodendron Leslei 258 [Trustees of the British Museum.] 215. Bothrodendron mundum 259 216. Bothrostrobus 263 [Council of the Manchester Literary and Philosophical Society.] 217. Omphalophloios 265 218. Lepidocarpon Lomaxi 273 219. Miadesmia and Bothrodendron 276 220. Angiopteris evecta and Cycas revoluta 283 221. Osmunda cinnamomea, O. regalis, and Todea barbara 286 222. Schizaea elegans 287 223. Aneimia rotundifolia 288 224. Aneimia flexuosa, A. phyllitidis, Hymenophyllum, Matonia pectinata, Thyrsopteris elegans, Gleichenia 289 225. Gleichenia dicarpa 290 226. Gleichenites Rostafinskii, Gleichenia dicarpa, G. dichotoma 290 227. Matonia pectinata 292 [Council of the Royal Society.] 228. Matonia pectinata 293 229. Thyrsopteris elegans, Cyathea spinulosa, Dicksonia coniifolia, D. culcita, Davallia concinna, Alsophila excelsa 294 230. Dicksonia Bertervana 295 [Trustees of the British Museum.] 231. Dipteris quinquefurcata, D. conjugata, D. Wallichii, and Polypodium quercifolium 297 232. Davallia aculeata 299 233. Polypodium Billardieri 302 234. Polypodium quercifolium 303 235. Hemitelia capensis 304 236 a, 236 b. Pteris aquilina 305, 306 [Council of the Linnean Society of London.] 237. Matonia pectinata, Matonidium, Gleichenia dicarpa, and Trichomanes reniforme (anatomy) 310 238. Trichomanes scandens 311 [Editor of the New Phytologist.] 239. Platyzoma microphylla 312 [Editor of the New Phytologist.] 240. Cyathea Imrayana 313 [Editor of the New Phytologist.]. 241. Angiopteris evecta and Marattia fraxinea 317 242. Angiopteris evecta and Danaea 318 243, 244. Angiopteris evecta 319 245. Marattia fraxinea, M. Kaulfussii, Kaulfussia, and Marattiopsis Münsteri 320 246. Ophioglossum vulgatum 322 247. Botrychium virginianum 322 248. Zalesskya gracilis 327 249. Zalesskya diploxylon 328 250. Thamnopteris Schlechtendalii 330 251. Lonchopteris virginiensis 331 252. Osmundites Dunlopi 333 253, 254. Osmundites Kolbei 334, 335 [Editor of the Geological Magazine.] 255. O. Kolbei 336 256. Cladophlebis denticulata, Todites Williamsoni, Discopteris Rallii, Kidstonia heracleensis, and Todeopsis primaeva 340 257, 258. Cladophlebis denticulata 342, 345 259. Klukia exilis 348 [Council of the Cambridge Philosophical Society.] 260. Ruffordia Goepperti 349 261. Chrysodium lanzaeanum, Lygodium Kaulfussi, Marattia Hookeri 350 262. Gleichenites longipennis, G. delicatula, G. Nordenskioldi and G. Zippei 354 263. Gleichenites hantonensis 356 [Council of the Palaeontographical Society.] 264. Laccopteris elegans 357 [Council of the Royal Society.] 265. Matonidium Wiesneri, Marattiopsis marantacea, Gleichenites gracilis, Laccopteris Goepperti, and L. Muensteri 358 266. Laccopteris polypodioides 359 [Trustees of the British Museum.] 267. Laccopteris 359 [Trustees of the British Museum.] 268. ? Laccopteris polypodioides 360 [Trustees of the British Museum.] 269. Matonidium Goepperti 362 [Editor of the Encyclopaedia Britannica.] 270. Senftenbergia elegans, Oligocarpia Brongniartii, Trichomanes sp., Hymenophyllum tunbridgense, Sphenopteris (Hymenophyllites) quadridactylites 364 271. Coniopteris hymenophylloides 368 [Council of the Manchester Literary and Philosophical Society.] 272. C. hymenophylloides 369 273. Coniopteris quinqueloba 370 274. Coniopteris arguta 371 275. Coniopteris arguta and C. hymenophylloides 372 276. Oncopteris Nettvalli 373 277. Protopteris punctata 373 278. Laccopteris polypodioides, L. Muensteri, Dicksonia, Onychiopsis Mantelli, Hausmannia Sewardi, H. Kohlmanni, and Protopteris Witteana 374 279. Adiantides antiquus and A. lindsayoides 376 280. Onychiopsis Mantelli 379 281. Dictyophyllum exile 381 282. Dictyophyllum Nilssoni, Rhizomopteris Schenki, Camptopteris spiralis, and D. exile 382 283. Dictyophyllum rugosum 384 [Trustees of the British Museum.] 284. Thaumatopteris Münsteri 386 285. Clathropteris meniscoides 387 286. Clathropteris egyptiaca 388 [Editor of the Geological Magazine.] 287. Camptopteris spiralis 389 288. Hausmannia dichotoma 391 289. Hausmannia sp. 393 290. Alethopteris lonchitica, Lonchopteris rugosa, Sphenopteris Hoeninghausi, Parapecopteris neuropteroides,and Pecopteris (Dactylotheca) plumosa 399 291. Ptychocarpus unita, Asterotheca Sternbergii, Danaeites sarepontanus, Hawlea Miltoni, H. pulcherrima, Scolecopteris elegans 400 292. Dactylotheca plumosa 405 293. D. plumosa 406 294. Nathorstia angustifolia and N. latifolia 410 295. Psaronius 414 296. Psaronius infarctus, P. coalescens, P. musaeformis, and P. asterolithus 416 297. Pecopteris Sterzeli 419 298. Caulopteris peltigera and Megaphyton insigne 421 299. Ptychopteris 423 300. Dicksonia antarctica 424 301. Rhacopteris sp. 427 302. Noeggerathia foliosa 429 303. Chiropteris Zeilleri 430 [Annals of the South African Museum.] 304. Tubicaulis solenites 435 [Editor of the New Phytologist.] 305. Botryopteris cylindrica 439 306. Botryopteris ramosa 441 307. Botryopteris antiqua 442 308. Clepsydropsis antiqua, Etapteris Scotti, Diplolabis forensis, Zygopteris primaria, Stauropteris oldhamia 444 309. Diplolabis forensis, Botryopteris forensis, Corynepteris coralloides, Schizopteris pinnata 445 310. Metaclepsydropsis duplex, Stauropteris oldhamia, Ankyropteris scandens 450 311. Ankyropteris Grayi 451 312. Thamnopteris Schlechtendalii, Ankyropteris corrugata, A. bibractensis 453 313. Ankyropteris bibractensis 454 314. Ankyropteris corrugata 457 315. Ankyropteris corrugata 458 [Editor of the New Phytologist.] 316, 317. Ankyropteris corrugata 459, 460 318. Etapteris Scotti 462 [Editor of the New Phytologist.] 319. Etapteris, Botryopteris forensis 463 320. Stauropteris oldhamia 464 [Editor of the New Phytologist.] 321. Stauropteris oldhamia 467 322. Stauropteris oldhamia 468 [Editor of the New Phytologist.] 323. Stauropteris 469 [Editor of the New Phytologist.] 324. Asterochlaena laxa 472 [Editor of the New Phytologist.] 325. Sporocarp-like bodies (? Sagenopteris) 478 326. Regnellidium diphyllum, Sagenopteris rhoifolia 479 327. Sagenopteris Phillipsi 480 [Trustees of the British Museum.] 328. Sagenopteris Phillipsi 481 [Council of the Manchester Literary and Philosophical Society.] 329. Taeniopteris multinervis, Lesleya Delafondi 487 330. Taeniopteris Carnoti, T. spatulata, T. coriacea 490 331. Taeniopteris Carruthersi 491 [Annals of the South African Museum.] 332. Taeniopteris vittata 493 333. Weichselia Mantelli, W. erratica 495 334. Glossopteris Browniana 499 [Council of the Geological Society of London.] 335, 336. Glossopteris Browniana 500, 501 [Trustees of the British Museum.] 337. Vertebraria indica 502 338. Vertebraria indica, Onoclea struthiopteris 503 339. Glossopteris fronds attached to rhizome 504 340, 341. Glossopteris indica, G. angustifolia 506, 507 [Trustees of the British Museum.] 342. Glossopteris angustifolia var. taeniopteroides 508 [Council of the Geological Society.] 343. Blechnoxylon talbragarense 509 344. Glossopteris retifera 511 [Trustees of the British Museum.] 345. Gangamopteris cyclopteroides 515 [Trustees of the British Museum.] 346. Arberia sp. 517 347. Lesleya simplicinervis 518 348. Neuropteridium validum 520 [Trustees of the British Museum.] 349. Neuropteridium intermedium 522 350. Cardiopteris frondosa 524 351. Gunnera manicata 527 352. Sphenopteris obtusiloba, Pecopteris arborescens, Sphenopteris furcata 529 353. Sphenopteris affinis 531 354. Palmatopteris, Mariopteris, Diplotmema Zeilleri, Neuropteris macrophylla, N. heterophylla, N. Scheuchzeri, Alloiopteris Essinghii 535 355. Cephalotheca mirabilis 536 356. Thinnfeldia odontopteroides, Ptilozamites 539 [Council of the Geological Society.] 357. Thinnfeldia odontopteroides 540 [Council of the Geological Society.] 358. Thinnfeldia odontopteroides 541 [Annals of the South African Museum.] 359. Thinnfeldia rhomboidalis 542 360. Lomatopteris jurensis, L. Schimperi, Thinnfeldia rhomboidalis 544 361. Ptilozamites Heeri 547 362. Ctenopteris cycadea 549 363. Dichopteris visianica 551 364. Alethopteris lonchitica, Mariopteris muricata, Odontopteris cf. alpina 553 365. Odontopteris minor 554 366. Odontopteris genuina, Callipteridium gigas, Callipteris Pellati, C. lyratifolia 557 367. Callipteris conferta 559 368. Archaeopteris hibernica 561 369. Archaeopteris hibernica, A. archetypus, A.fissilis, A. fimbriata 564 370. Neuropteris with Cyclopteris leaflets 566 [From a block received from Mr Carruthers.] 371. Neuropteris heterophylla 568 372. Neuropteris macrophylla 569 373. Neuropteris Scheuchzeri 570 374. Linopteris neuropteroides 573 375. Alethopteris Serlii 575 376. Pecopteris arborescens 578
ERRATA IN VOL. I
Page 16, line 4. For “The North American Tulip tree” read The Tulip tree of North America and China.
„ 66, line 2 from the bottom. For “Browera” read Berowra.
„ 127, line 3 and 4 from bottom. For Achyla and Palaeachyla read Achlya and Palaeachlya.
„ 145, lines 4 and 5. For “Upper Greensand” read Lower Eocene.
„ 162, line 3 from bottom. For “Corallina barbata” read Cymopolia barbata.
„ 170, line 20. For “sporangiaphore” read sporangiophore.
„ 185, line 2. The genera Udotea and Halimeda, members of the Siphoneae, are incorrectly included under the Corallinaceae.
„ 191, line 11 from bottom. Omit Chondrus crispus, which is one of the Florideae and not a Brown Alga.
„ 202, line 13. For “Halmeda” read Halimeda.
„ 250, line 11. For “three” read the.
„ 381, line 10. For “Calamopytus” read Calamopitys.
CHAPTER XII[1].
SPHENOPHYLLALES (concluded).
Sphenophyllum.
The account of the Sphenophyllales given in the first volume[2] of this work must be extended and somewhat modified in the light of recent work on the fertile shoots of Sphenophyllum.
Sphenophyllostachys Dawsoni (Will.) was described as consisting of an axis bearing superposed whorls of bracts connate at the base in the form of a shallow funnel-shaped collar giving off from the upper surface and close to the axis of the cone two concentric series of sporangiophores. Occasionally there are three series, as represented in fig. 112. In another type of strobilus, _Sphenophyllostachys Römeri_[3] each sporangiophore terminates in two pendulous sporangia (fig. 113, A; see also fig. 107, C, vol. I.). It has already been pointed out that the common occurrence of detached strobili necessitates their description under distinct specific names; it is only by a rare accident that we can assign fossil cones to their vegetative shoots. There are, however, reasons for believing that Sphenophyllostachys Dawsoni is the strobilus of the plant originally described by Sternberg[4] from impressions of foliage-shoots as Rotularia cuneifolia. Another difficulty presented by petrified material is that of determining, with certainty, whether two imperfect specimens, differing from one another in features which do not appear to be of sufficient importance to warrant specific separation, are forms of one species or portions of specifically distinct cones. It has been pointed out by Scott[5] that the strobilus known as Sphenophyllostachys Dawsoni probably includes two distinct species, one being the cone of Sphenophyllum cuneifolium Sternb., and the other the cone of S. myriophyllum Crép[6]. The stem of S. myriophyllum agrees anatomically with the type known as Sphenophyllum plurifoliatum Will. and Scott[7].
FIG. 112. Sketch of a radial longitudinal section of Sphenophyllostachys. There are usually two concentric series of sporangia on the sporophylls, not three as shown in the figure. The upper figure (after Zeiller) shows the linear bracts in surface-view.
In addition to the two types of cone already mentioned, Sphenophyllostachys Dawsoni and S. Römeri, others have been described by Kidston from carbonised impressions. One of these is the fertile branch of _Sphenophyllum majus_[8]. The basal portions of the bracts of each whorl form a narrow collar round the axis of the cone; the free portion of each bract consists of a lamina divided into two equal bifid lobes bearing on its upper surface one group, or possibly two groups, of four sessile sporangia between the narrow coherent bases of the laminae and the sinus between the terminal lobes (fig. 113, C). Another characteristic feature is the greater length of the internodes; this renders the cone less compact and less sharply differentiated from the vegetative shoots than those of other species. A specimen in Dr Kidston’s collection illustrates the peculiar character of the fertile portion of this species; it consists of an axis bearing a succession of lax sporophylls succeeded above and below by whorls of sterile leaves. In this species, therefore, we cannot speak of a compact strobilus at the end of a shoot of limited growth, but of axes in which sterile and fertile leaves are borne alternately[9], a condition recalling the alternation of foliage leaves and sporophylls in Tmesipteris and in Lycopodium Selago.
FIG. 113. A. Sphenophyllostachys Römeri. (Solms-Laubach.) B. Sphenophyllum trichomatosum Stur. C. Sphenophyllum majus. Bronn. (A–C. After Kidston.)
Another form of cone, also from the Middle Coal Measures, is referred by Kidston to Sphenophyllum trichomatosum Stur[10] (fig. 113, B): this is characterised by the more horizontal position of the bracts, which “do not appear to be so much or so suddenly bent upwards in their distal portion as in some other species of Sphenophyllum,” and by sessile sporangia borne singly on the upper face of each bract.
FIG. 114. Sphenophyllostachys fertilis (Scott). (After Scott.) Diagram of a node in longitudinal section, showing one sporophyll and the base of the opposite one. v.l. ventral lobe of sporophyll; v.s. one of the segments into which it divides; v.s′. stump of another segment; d.l. dorsal lobe; d.s., d.s′. segments of dorsal lobe.
A more recent addition to our knowledge of the fertile shoots of Sphenophyllum is due to Scott who has described a new type of cone under the name _Sphenophyllum fertile_[11]. The petrified specimen on which the species was founded was discovered by Mr James Lomax in the Lower Coal Measures of Lancashire; it represents a portion of a cone 6 cm. long and approximately 12 mm. broad. The axis contains a single vascular cylinder agreeing in essentials with the type of stem structure known as Sphenophyllum plurifoliatum. The nodal regions, which exhibit the slight swelling characteristic of the genus, bear several (probably twelve) appendages connate at the base and forming a narrow flange encircling the axis. Each bract, the base of which forms part of the narrow collar surrounding the axis, consists of two lobes, ventral and dorsal, divided palmately into several (sometimes four) segments or sporangiophores (fig. 115). Each sporangiophore terminates distally in an oblong or oval lamina bearing two sporangia on its adaxial face (fig. 114). The space between the axis and the periphery of the cone is thus occupied by crowded peltate laminae, each with its pair of sporangia. A single vascular bundle supplies each sporangiophore and bifurcates in the distal lamina into two branches which extend to the bases of the sporangia. The sporangia agree in structure with those of other species of Sphenophyllum: the spores are of one size and elliptical, characterised by the presence of several sharp ridges or flanges encircling the spore-wall in the direction of the major-axis. Sphenophyllostachys fertilis differs from all previously recorded types in the absence of sterile bracts. The appendages of the cone-axis are all fertile, a striking contrast to the differentiation into protective and sporangia-bearing bracts which constitutes a constant feature in the cones of Sphenophyllum and Calamites. It is possible, as Scott suggests, that the absence of sterile segments is the result of modification of the more usual type of strobilus; instead of the dorsal and ventral lobes of the bracts sharing between them the duties of protection and spore-production, the whole of each bract is constructed on the plan of the maximum spore-output, the laminar terminations of the sporangiophores serving the purpose of protection. The cone may be described as more specialised than the normal type of strobilus for reproductive purposes[12].
FIG. 115. Sphenophyllostachys fertilis (Scott). (After Scott.) Diagram of a single sporophyll as it would appear in a transverse section of the cone; showing one lobe (dorsal or ventral). ax, part of axis to which the sporophylls are attached.
FIG. 116. Sphenophyllostachys Dawsoni. (After Thoday.) A. Larger spores; B, abortive spores; C, mature spores showing the characteristic spines.
It has been stated, on evidence which is unsatisfactory, that Sphenophyllum possesses two kinds of spores. While regarding the genus as homosporous on the evidence before us, it is interesting to find that cases occur in which the spores in the same sporangium exhibit a marked difference in size. Attention has been called by Williamson and Scott[13] to variation in the dimensions of spores: a more pronounced difference in size has been recorded by Mr Thoday[14] who gives 120μ as the maximum and 90μ as the minimum diameter of the spores in a cone of Sphenophyllostachys Dawsoni. The presence of several abortive spores in the sporangium (fig. 116) containing the larger spores favours the view that this difference in size may be the first step towards the development of heterospory.
It is clear that the types of strobilus designated Sphenophyllostachys (figs. 112–114) present a divergence of characters too great to be comprised under one genus; but in the absence of fuller information, we cannot do otherwise than follow the only logical custom of grouping them together as examples of strobili borne by plants which, in the present state of our knowledge, are most conveniently referred to the genus Sphenophyllum.
Cheirostrobus.
This generic name was applied by Dr Scott[15] to a calcified cone obtained by Mr James Bennie in 1883 from the Lower Carboniferous plant-beds of Pettycur near Burntisland on the Firth of Forth. Cheirostrobus is distinguished from Sphenophyllostachys by its greater breadth (3.5 cm.); externally it agrees more closely with the fertile shoots of Lepidodendron than with those of Sphenophyllum. A single vascular cylinder having the form of a fluted Doric column (fig. 117, B, x) occupies the axis of the cone: it consists for the most part of reticulate tracheae which tend to assume a short or isodiametric form in the central region; the smaller protoxylem tracheids with the spiral form of pitting constitute the sharp and prominent ridges at the periphery of the xylem-cylinder. In the outer part of the cylinder the metaxylem[16] consists exclusively of tracheae, but towards the centre of the axis these are associated with numerous parenchymatous cells.
The xylem is therefore centripetal in origin as in Sphenophyllum and in nearly all recent and fossil members of the Lycopodiales. In the type-specimen of Cheirostrobus the vascular cylinder of the cone consists entirely of primary xylem, but secondary xylem has been found in a more recently discovered specimen[17]. Secondary xylem occurs also in the peduncle of the cone. No appreciable remains of phloem have been found. The cortex consists of slightly elongated rather thick-walled tissue containing secretory sacs. Crowded superposed whorls of bracts (or sporophylls), usually twelve in each whorl, are borne on the axis and each sporophyll receives a single vascular bundle from one of the vertical ridges of the xylem column (fig. 117, A, lt). The members of each whorl are connate at the base: from this narrow collar each sporophyll branches into an upper or dorsal and a lower or ventral limb (fig. 117, A, f and s). Each limb divides palmately at a short distance from its origin into three slender segments, which extend in a horizontal direction and terminate in large laminar expansions (fig. 117, B, s) to afford a protective covering to the surface of the cone. The upper set of three segments, constituting sporangiophores (fig. 117, A, B, f) or fertile divisions of the sporophyll, expand distally into comparatively bulky laminae; each of these bears on its adaxial face four diagonally placed outgrowths which form the short pedicels of very long and narrow sporangia. The three lower segments—the sterile divisions of the sporophylls—(fig. 117, A, B, s) are similar to the upper set except in their greater length and in the kite-shaped form of their distal laminae which are provided with lateral lobes. The single vascular strand which supplies each sporophyll is represented at lt in fig. 117, B; at lt′ the strand has divided into four, the three upper bundles in the figure supply the sterile segments and the single lower bundle ultimately divides into three which supply the fertile segments. A pair of blunt processes (fig. A, s) extend downwards over the ends of the underlying fertile lamina and two slender prolongations extend upwards through several internodes.
[Illustration: FIG. 117. A, B. Cheirostrobus pettycurensis Scott. (After Scott.) C, D. Pseudobornia ursina Nath. (After Nathorst.)
A. Diagrammatic radial longitudinal section of part of the cone-axis and two sporophylls. lt, bundle passing out to sporophyll; f, fertile segment of sporophyll showing two sporangia; s, sterile (lower) segment. B. Part of transverse section. x, stele; lt, lt′, bundles on their way to sporophylls; a, tips of sterile segments of lower sporophylls. C. Palmately branched leaf (½ natural size). D. Node of stem showing leaf-bases.]
An economical arrangement of the long and narrow sporangia and of the sporophyll-segments between the axis and the periphery of the cone is rendered possible by the interlocking of the sterile and fertile segments by means of a groove in the upper face of the latter for the accommodation of the former. The sporangia are characterised by their unusually long and narrow form: the length of a sporangium may reach 1 centimetre. In the structure of the wall the sporangia of Cheirostrobus agree closely with those of _Calamostachys_[18] and Sphenophyllostachys. The spores are of one size only. The vascular cylinder of the peduncle, originally described by Williamson[19] as the peduncle of a large Lepidostrobus (the cone of Lepidodendron), is characterised by the presence of a short radially disposed zone of secondary tracheids, a feature, as Scott points out, which may extend into the axis of the cone. It is noteworthy that the protoxylem elements are not always external, but occasionally occur internal to one or two of the outermost metaxylem tracheae: the usual exarch[20] structure of the central cylinder is not therefore absolutely constant, but may be replaced by a mesarch arrangement.
The presence of a few sterile leaves on the peduncle below the fertile portion of the cone, which agree in their lobed laminae with the sporophylls, is the only fact which we possess as to the form of the vegetative characters of the genus.
The above description is sufficient to indicate the extraordinary complexity and high degree of specialisation of Cheirostrobus. The sporophylls, with their trilobed segments, and the crowded sporangia of exceptional length attached only by a narrow base constitute striking peculiarities of the genus.
It is unfortunate that we are still without any satisfactory evidence as to the nature of the plant the cones of which have been made the type of a new genus and a new family. Cheirostrobus affords an interesting example of a type of reproductive shoot constructed on a plan sui generis, and may be classed with some other extinct genera as instances of the production in the course of evolution of architectural schemes which appear to have been ill adapted for competition with equally efficient though much simpler types. But the discovery of these isolated forms of restricted geological range among the relics of the Palaeozoic vegetation frequently supplies a key to phylogenetic problems. Cheirostrobus by its complex combination of features characteristic of the Equisetales, the Lycopodiales and the genus Sphenophyllum throws a welcome light on the inter-relationships of groups which represent divergent series. The combination of morphological features in this generalised type led the author of the genus to describe it as a descendant of an old stock which existed prior to the divergence of the Equisetales and Lycopodiales.
The discovery of this new type of strobilus naturally led to a search among Lower Carboniferous plants for vegetative shoots exhibiting characters conformable with the whorled and branched leaves of Cheirostrobus. In Sphenophyllum we have a genus obviously comparable with Cheirostrobus as regards the form and disposition of the leaves, but the differences between the cones and the striking similarity of the vascular cylinder of the latter to that of Lepidodendron demonstrate conclusively that we must look elsewhere for the vegetative members of the plant which produced cones of the Cheirostrobus type.
[Sidenote: PSEUDOBORNIA]
In 1902 Professor Nathorst[21] instituted the generic name Pseudobornia for plants of which imperfect examples had previously been referred by Heer[22] to Calamites under the name C. radiatus. Heer’s plants were obtained from Upper Devonian rocks of Bear Island in the Arctic seas and additional specimens were brought from the same locality by the Swedish Polar Expedition of 1898. Pseudobornia possesses jointed stems (fig. 117, D) bearing whorled and shortly stalked leaves, often four in number, at each node. The leaves are palmately branched with fine serrated edges (fig. 117, C). Certain specimens, which are no doubt correctly described by Nathorst as cones, are characterised by a thick axis bearing whorled leaves with sporangia on their lower surfaces, but the material is not sufficiently well preserved to render possible a recognition of structural details. It has been suggested by Scott that Pseudobornia may possibly be referable to the Sphenophyllales and that the stem of Cheirostrobus “may have had something in common with” Nathorst’s genus[23]. The beds in which the stems occur are of Upper Devonian age, while Cheirostrobus was found in Lower Carboniferous rocks: this difference in age is not, however, a serious objection to the validity of the comparison. We cannot do more than express the view that Pseudobornia, so far as can be ascertained without an examination of petrified material or of more perfect impressions of strobili, exhibits vegetative features not inconsistent with the morphological characters of the fertile shoots known as Cheirostrobus.
• • • • •
The institution of a special group-name for the reception of Sphenophyllum is justified by the sum of its morphological features, which do not sufficiently conform to those of any existing group of Pteridophytes to warrant its inclusion in a system of classification based on recent genera. In the case of Cheirostrobus we are limited to the characters of the cone and its peduncle. The suggestion that the Devonian fossils known as Pseudobornia may represent the foliage shoots of a plant closely related to Cheirostrobus has still to be proved correct. Although we may find justification in the highly complex and peculiar structure of Cheirostrobus for the recognition of the genus as a type of still another group of Pteridophytes, it would be unwise to take this step without additional knowledge.
The undoubted similarity between Cheirostrobus and Sphenophyllum coupled with striking points of difference favours the inclusion of the two genera in distinct families placed, for the present at least, in the group Sphenophyllales.
Group =SPHENOPHYLLALES=.
=Sphenophylleae=: genus Sphenophyllum.
=Cheirostrobeae=: genus Cheirostrobus.
It has recently been proposed to include the family Psilotaceae, comprising the two recent genera Psilotum and Tmesipteris, as another subdivision of the Sphenophyllales. This proposal had been made by Professor Thomas[24] primarily on the ground that the sporophylls of Tmesipteris and Psilotum appear to afford the closest parallel among existing plants to the peculiar form of sporophyll characteristic of the Sphenophyllales. The morphological interpretation of the sporophylls of both Sphenophyllum and Cheirostrobus has been the source of considerable discussion[25]. If we regard each sporophyll as a leaf with two lobes, one fertile and one sterile, except in the case of Sphenophyllostachys fertilis in which both are fertile, an obvious comparison may be made with the fern Ophioglossum; but the difference between a single fern frond, consisting of a comparatively large sterile lamina bearing a fertile branch composed of a long axis with two rows of sporangia embedded in its tissues, and the whorled sporophylls of Sphenophyllum is considerable.
[Sidenote: PSILOTACEAE]