CAMBRIDGE BIOLOGICAL SERIES
FOSSIL PLANTS
CAMBRIDGE UNIVERSITY PRESS
C. F. CLAY, +Manager+
=London=: FETTER LANE, E.C.
=Edinburgh=: 100 PRINCES STREET
=London=: H. K. LEWIS AND CO. +Ltd.+, 136, GOWER STREET, W.C. =London=: WILLIAM WESLEY AND SON, 28, ESSEX STREET, STRAND =New York=: G. P. PUTNAM’S SONS =Bombay, Calcutta and Madras=: MACMILLAN AND CO., +Ltd.+ =Toronto=: J. M. DENT AND SONS, +Ltd.+ =Tokyo=: THE MARUZEN-KABUSHIKI-KAISHA
All rights reserved
CHARLES RENÉ ZEILLER Membre de l’Institut Inspecteur général des Mines Professeur à l’École Natˡᵉ Supérieure des Mines (1847–1915)
FOSSIL PLANTS
A TEXT-BOOK FOR STUDENTS
OF BOTANY AND GEOLOGY
BY
A. C. SEWARD
M.A., F.R.S., +Hon. Sc.D. Dublin+
PROFESSOR OF BOTANY IN THE UNIVERSITY;
MASTER OF DOWNING COLLEGE AND HONORARY
FELLOW OF EMMANUEL COLLEGE, CAMBRIDGE
WITH 253 ILLUSTRATIONS
VOLUME III
PTERIDOSPERMEAE, CYCADOFILICES, CORDAITALES,
CYCADOPHYTA
CAMBRIDGE:
AT THE UNIVERSITY PRESS
1917
TO THE MEMORY OF MY FRIEND
CHARLES RENÉ ZEILLER
ILLUSTRIOUS AS A MAN OF SCIENCE
AND A NOBLE-HEARTED GENTLEMAN
WHOM TO KNOW WAS TO REVERE
PREFACE
In the Preface to Volume II published in 1910 I rashly stated that it was my intention “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,” also that Volume III would be completed with as little delay as possible. Though nearly seven years have elapsed since the publication of the second volume it may fairly be said that the delay is not entirely due to causes which it was in my power to control. The subject of geographical distribution receives no connected treatment in Volumes III and IV for the simple reason that I underestimated the space required for the description of the Gymnosperms. The alternatives were either to insert a greatly compressed survey of the successive floras of the world at the end of Volume IV or to attempt a fuller and less technical treatment of the subject in a separate book. In choosing the latter course I am conscious that a further obligation is undertaken which it may not be possible to fulfil; but the risk is deliberately taken. Volume IV is in the press and will, it is hoped, be published before the end of 1917.
It is a pleasant duty to repeat my thanks to many friends who have helped me in various ways. Dr Kidston generously and without reserve allowed me access to his splendid collection of Palaeozoic plants, and the frequent occurrence of his name in the list of illustrations shows how freely I have availed myself of his kindness. He has read some of the chapters and greatly assisted me by his friendly criticism and encouragement. By reading the proofs of this volume Dr Scott has further increased my already large debt to him. It is impossible to thank him adequately; he not only corrected many careless mistakes but by wise counsel and advice he rendered me a service which I greatly appreciate.
The exchange of views with Prof. Zeiller has been a constant source of profit and enjoyment, and it is hard to realise that the completed book will not receive his kindly criticism. He was a singularly unselfish and generous colleague, always ready to help fellow workers, and he had the faculty in an unusual degree of influencing those who had the privilege of his friendship by his sound advice and lovable personality.
The death of Count Solms-Laubach has deprived Palaeobotany of one of its most learned and strongest supporters. In common with all students of fossil plants I owe much to the critical treatment of the subject in the Einleitung in die Paläophytologie. Prof. Jeffrey has very kindly given me several photographs and sections which have been of great service, and I am similarly indebted to Prof. Zalessky. To Prof. Nathorst my thanks are due for the great interest he has taken in my work and for his generosity in providing drawings and showing to me many of the treasures in the famous Stockholm Museum. Prof. Bertrand and Prof. Lignier freely supplied photographs and drawings of specimens in their possession, and I am particularly grateful to them for the willingness with which they always responded to my requests.
Through the death of Prof. Lignier in March 1916 Palaeobotany has been deprived of another original thinker who devoted himself with whole-hearted enthusiasm to botanical research and for many years faithfully served the University of Caen: he was a generous friend to whom one never appealed in vain for assistance. Through the kindness of the Director of the Indian Geological Survey I have been able to examine several fossils from the Calcutta Museum described by Oldham and Morris and by Feistmantel. With the Director’s permission several photographs and drawings made for a forthcoming paper to be published by the Indian Survey are reproduced in this volume. I take this opportunity of thanking friends in Australia who recently afforded me facilities for examining fossil plants in their charge, and I would especially thank Mr A. B. Walkom of the University of Brisbane, who has recently undertaken an investigation of the rich plant-beds in the Ipswich district, for all that he did to enable me to make the most of a very short time available for palaeobotanical work.
For the loan of specimens and for other help I am indebted to Prof. Bayly Balfour, Prof. Bower, Prof. Margaret Benson, Prof. Oliver, Sir David Prain, Dr Smith Woodward, Prof. Weiss, the Director of the Geological Survey, Dr A. H. Church, Dr Arber, and other friends. I would also acknowledge a debt, by no means inconsiderable, to my Colleague Mr Hamshaw Thomas. Among younger friends in the Cambridge Botany School to whom I am indebted I wish particularly to thank Miss Ruth Holden, Miss Bancroft, Mr Sayers, Mr Dutt and others who have rendered me willing help.
In the List of Illustrations mention is made of Corporate Bodies and individuals from whom blocks have been obtained, and I am grateful to them for readily responding to my applications.
My Wife, though prevented by more urgent calls in the later stages of my task from giving as much time to the illustrations as in the two former volumes, has contributed several drawings, and my daughter Phyllis Seward has also given me much help in preparing drawings from previously published figures.
In spite of the vigilance and wise counsel of many friends numerous blemishes remain and for these the author is alone responsible.
A. C. SEWARD.
+Downing College Lodge+,
February 10, 1917.
* * * * *
+Note.+ The letters A and B added to references in the footnotes indicate that the works will be found in the Bibliographies at the end of Volumes I and II.
TABLE OF CONTENTS
CHAPTER XXVIII
CYCADALES (Recent). Pp. 1–34.
CHAPTER XXIX PTERIDOSPERMEAE (continued from Volume II). Pp. 35–85.
PAGE
I. =LYGINOPTERIDEAE= 35–85 =Lyginopteris= 35–70 Telangium 54, 55; Lagenostoma 55–64; Lagenospermum 64–66; Pterispermostrobus 66, 67.
=Heterangium= 70–85 Sphaerostoma 78–81.
CHAPTER XXX
II. =MEDULLOSEAE= 86–165 i. Medullosa 86–109, 156–163 Myeloxylon 106–110; Neuropteris 110–117; Alethopteris and Linopteris 113; Trigonocarpus 117–124; Codonotheca 124–126; Schützia 126–128; Whittleseya 128–131; Dolerophyllum 132–139; Ottokaria 139–141; Strobilites 141, 142. ii. =Colpoxylon= 142–145 iii. =Rhexoxylon= 146–149 iv. =Sutcliffia= 149–156 General considerations suggested by the anatomical features of Medullosa 156–163
II. =A. STELOXYLEAE= 163–165 =Steloxylon= 163–165
CHAPTER XXXI PTERIDOSPERMEAE. (Foliage and seeds.) Pp. 166–174.
Pecopteris Pluckeneti 166–168; Eremopteris artemisaefolia 169–172; =Wardia= 172, 173; Adiantites bellidulus and Lagenospermum Arberi 173, 174.
CHAPTER XXXII
CYCADOFILICES. Pp. 175–213.
I. =MEGALOXYLEAE= 175–180 =Megaloxylon= 175–180
II. =RHETINANGIEAE= 181–183 =Rhetinangium= 181–183
III. =STENOMYELEAE= 183–185 =Stenomyelon= 183–185
IV. =CYCADOXYLEAE= 185–190 =Cycadoxylon= 185–187 =Ptychoxylon= 187–190
V. =CALAMOPITYEAE= 190–200 =Calamopitys= 190–196 Kalymma 194–196 =Eristophyton= 197–200
VI. =CLADOXYLEAE= 200–210 =Cladoxylon= 201–207 =Völkelia= 208–210
VII. =PROTOPITYEAE= 210–213 =Protopitys= 210–213
CHAPTER XXXIII
CORDAITALES. Pp. 214–299.
A. =POROXYLEAE= 214–219
=Poroxylon= 214–219
B. =CORDAITEAE= 219–284
=Cordaites= 219–265
Noeggerathiopsis 238–243; Rhiptozamites 244,
245; Phylladoderma 244; Euryphyllum 245;
Artisia 246–248; Dadoxylon 248–260;
Metacordaites 260, 261; Cordaianthus 264–270;
=Mesoxylon= 270–275; =Pelourdea= 277–281;
=Niponophyllum= 282, 283; =Titanophyllum= 283, 284.
CHAPTER XXXIV
C. =PITYEAE= 285–299 =Pitys= 285–289 =Archaeopitys= 290 =Callixylon= 291–293 =Coenoxylon= 293, 294 =Parapitys= 294, 295 =Mesopitys= 295, 296 =Antarcticoxylon= 296–299
CHAPTER XXXV
PALAEOZOIC GYMNOSPERMOUS SEEDS. Pp. 300–365.
I. +Lagenostomales+ 308–318 =Physostoma= 309–312; =Conostoma= 313–316; =Sphaerostoma= 316; =Lagenostoma= 316; =Gnetopsis= 317, 318.
II. +Trigonocarpales+ 318–332 =Trigonocarpus= 319–321; =Tripterospermum= 321; =Ptychotesta= 321; =Hexapterospermum= 321–323; =Polypterospermum= 323; =Pachytesta= 323–326; =Stephanospermum= 326–329; =Polylophospermum= 329, 330; =Codonospermum= 330, 331; =Aetheotesta= 331, 332; =Eriotesta= 332; =Gaudrya= 332.
III. +Cardiocarpales+ 332–356 =Cardiocarpus= 338–340; =Cyclospermum= 340, 341; =Cycadinocarpus= 341; =Rhabdocarpus= and =Rhabdospermum= 341–345; =Mitrospermum= 345, 346; =Diplotesta= 346; =Leptocaryon= 346, 347; =Taxospermum= 347; =Compsotesta= 347, 348; =Samaropsis= 348–354; =Cordaicarpus= 354–356.
IV. +Miscellaneous Seeds+ 356–365 i. =Hexagonocarpus= 356,357; =Decagonocarpus= 357; =Polypterocarpus= 357, 358; =Rhynchogonium= 358–360; =Boroviczia= 360; =Diplopterotesta= 360, 361; =Musocarpus= 361; =Holcospermum= 361–363.
ii. =Malacotesta= 363; =Thysanotesta= 364;
=Carpolithus= 364, 365; Microspermum 365.
CHAPTER XXXVI
CYCADOPHYTA (+Fossil+). Pp. 366–420.
=BENNETTITALES= 367–420 =Cycadeoidea= 367–417 =Cycadella= 417, 418 =Amphibennettites= 418 =Vectia= 419, 420
CHAPTER XXXVII
=BENNETTITALES= (continued) 421–477 =Williamsonia= 421–463 =Wielandiella= 463–467 =Williamsoniella= 467–473 =Cycadocephalus= 473–475 =Weltrichia= 475–477
CHAPTER XXXVIII
CYCADOPHYTA. Pp. 478–506.
i. =Bucklandia= 480–490; =Cycadeomyelon= 490, 491; =Colymbetes= 491–494; =Cycadeolepis= 494–496.
ii. =Carpolithus= 497–500; =Cycadospadix= 500, 501; =Beania= 502; =Zamiostrobus=, =Cycadeostrobus= 503–505; =Androstrobus= 505, 506.
CHAPTER XXXIX
CYCADOPHYTA (+Fronds+). Pp. 507–591.
I. +Bennettitales+ 512–566 =Ptilophyllum= 512–529; =Zamites= 529–537; =Otozamites= 537–545; =Dictyozamites= 546–548; =Pterophyllum= 548–558; =Cycadites= and =Pseudocycas= 558–566.
II. +Nilssoniales+ 566–587 =Nilssonia= 566–578; =Ctenis= 578–583; =Pseudoctenis= 584–587.
III. +Incertae sedis+ 587–591 =Sphenozamites= 587–589; =Plagiozamites= 589, 590; =Cycadorachis= 590, 591.
+List of Works referred to in the Text+ (Vols. III & IV). 592–639
+Index+ 640–656
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. The names of donors of photographs or drawings are added after the descriptions of the figures.
+Frontispiece.+ Charles René Zeiller. From a photograph given to me by Madame Zeiller.
FIG. PAGE
377. Cycas circinalis. A. Malins Smith 2
378. Cycas revoluta. [G. R. Wieland.] 3
379. Encephalartos horridus 3
380. Cycas circinalis. [Encyclopaedia Britannica.] 4
381. Cycas revoluta and Zamia Loddigesii 5
382. Encephalartos Ghellinckii. [Camb. Phil. Soc.] 11
383. Cycas siamensis. [Encyclopaedia Britannica.] 12
384. Cycas circinalis 13
385. Cycas Micholitzii and Zamia angustifolia 14
386. Encephalartos Altensteinii; Dioon edule. S. M. Wadham. 15
387. Cycadean Fronds 16
388. Zamia Wallisii 17
389. Zamia integrifolia. [Camb. Univ. Press.] 18
390. Zamia Loddigesii 18
391. Bowenia spectabilis. [Encyclopaedia Britannica.] 20
392. Cycas pectinata, C. Riuminiana, C. angulata, Encephalartos, and Stangeria 21
393. Stangeria, Encephalartos, and Ceratozamia 22
394. Macrozamia Preissii. [Camb. Univ. Press.] 23
395. Zamia floridana. [G. R. Wieland.] 24
396. Dioon edule, Cycas circinalis, etc., Encephalartos, Bowenia, Macrozamia, Microcycas 26
397. Stangeria paradoxa. [New Phytologist; A. G. Tansley.] 29
398. Macrozamia 29
399. Cycadean foliar bundles 31
400. Cycas Micholitzii. [Camb. Phil. Soc.] 33
401. Lyginodendron Landsburgii. R. Kidston 37
402. Lyginopteris oldhamia. [Camb. Phil Soc.] 39
403–405. Lyginopteris oldhamia 41, 44, 48
406. Lyginopteris oldhamia. F. W. Oliver 49
407. Crossotheca Hoeninghausi. R. Kidston and other sources 53
408. Lagenospermum Sinclairi; Lagenostoma; Calymmatotheca Stangeri; Crossotheca Hoeninghausi 57
409. Lagenostoma 58
410. Lyginopteris oldhamia 69
411, 412. Heterangium Grievii 73, 76
413. Sphenopteris elegans 78
414. Sphaerostoma ovale 79
415. Heterangium Grievii; H. tiliaeoides; Lyginopteris root 82
416. Medullosa (stem-anatomy) 92
417. Medullosa centrofilis 96
418. Myeloxylon radiatum; Medullosa stellata; M. Leuckarti 103
419. Medullosa Leuckarti 104
420. Myeloxylon radiatum; Medullosa anglica, and Medullosa sp. 107
421. Potoniea adiantiformis; Linopteris obliqua; Neuropteris heterophylla 111
422. Neuropterocarpus Kidstoni. [Edinburgh Royal Society.] 114
423–426. Trigonocarpus Parkinsoni 118, 120, 121
427. Codonotheca caduca. [New Phytologist.] 125
428. Whittleseya elegans; W. brevifolia 128
429. Whittleseya elegans 130
430–432. Dolerophyllum Goepperti 133, 134, 137
433. Ottokaria bengalensis. [Indian Geol. Survey.] 140
434. Strobilites Milleryensis 141
435, 436. Colpoxylon aeduense 143
437, 438. Rhexoxylon africanum 146, 148
439, 440. Sutcliffia insignis 150, 151
441. Steloxylon Ludwigii 163
442. Pecopteris Pluckeneti 167
443. Eremopteris artemisaefolia; Samaropsis acuta 170
444. Samaropsis acuta. R. Kidston 171
445. Wardia fertilis 172
446–448. Megaloxylon Scotti. [Camb. Phil. Soc.] 176–178
449, 450. Rhetinangium Arberi. W. T. Gordon 182
451. Stenomyelon tuedianum 183
452. Stenomyelon tuedianum. R. Kidston 185
453. Ptychoxylon Levyi; Cycadoxylon Fremyi; C. robustum 188
454, 455. Calamopitys Saturni. M. Zalessky 191, 192
456. Kalymma grandis 195
457. Eristophyton fasciculare 197
458. Eristophyton Beinertianum. M. Zalessky 199
459. Cladoxylon mirabile; C. dubium; C. taeniatum; Syncardia pusilla 202
460. Cladoxylon Kidstoni; C. mirabile 206
461. Völkelia refracta 209
462. Protopitys Buchiana 211
463. Poroxylon Edwardsii. C. E. Bertrand and F. W. Oliver 216
464. Poroxylon Edwardsii; P. Boysseti. C. E. Bertrand 218
465. Cordaites leaf. (C. Felicis.) R. Kidston 228
466. Cordaites principalis; Artisia transversa. R. Kidston 231
467. Cordaites lingulatus 234
468. Cordaites (Rhizo-Cordaites); Cordaites circularis; Cordaites sp. cf. C. Lacoei; C. crassifolius 237
469. Cordaites aequalis; C. Clerci. M. Zalessky 239
470. Cordaites (Noeggerathiopsis) Hislopi. G. R. Wieland. 241
471. Cordaites (Noeggerathiopsis) Hislopi. [Geological Society.] 241
472. Cordaites (Noeggerathiopsis) Hislopi. [Geol. Surv. India.] 242
473. Cordaites stem 246
474, 475. Dadoxylon materiarum 257
476. Dadoxylon Pedroi 259
477. Cordaites root 262
478. Cordaites? root. T. N. Leslie 263
479. Cordaianthus. F. E. Weiss 265
480. Cordaianthus Pitcairniae; C. Volkmanni 266
481. Cordaianthus Grand’Euryi; C. Williamsoni; C. Zeilleri. C. E. Bertrand 268
482. Cordaianthus microsporangia 270
483. Mesoxylon Sutcliffii 272
484. Pelourdea vogesiaca. [Geologists’ Assoc.] 279
485. Titanophyllum Grand’Euryi 284
486, 487. Pitys antiqua 286, 287
488. Pitys primaeva 288
489. Callixylon Trifilievi. M. Zalessky 292
490. Mesopitys Tchihatcheffi 296
491. Antarcticoxylon Priestleyi 298
492. Diagram of a synthetic type of seed 303
493. Lagenostoma ovoides; L. Lomaxi; Physostoma elegans; Telangium Scotti; Stephanospermum akenioides 311
494. Stephanospermum akenioides; Conostoma oblonga; Gnetopsis elliptica; Physostoma elegans; Mitrospermum compressum 314
495. Polypterospermum Renaultii; Ptychotesta tenuis; Polylophospermum stephanense; Hexapterospermum stenopterum; Diplotesta avellana; D. Grand’Euryana; Taxospermum Grüneri 322
496. Pachytesta incrassata; Polypterocarpus anglicus 324
497. Pachytesta 325
498. Codonospermum olivaeforme; Aetheotesta elliptica 330
499. Samaropsis emarginata 337
500. Cardiocarpus drupaceus var. expansus 339
501. Cardiocarpus sclerotesta; Rhabdocarpus cyclocaryon 340
502. Samaropsis fluitans; S. emarginata; S. bicaudata; S. Seixasi; S. barcellosa; S. Newberryi; Cordaicarpus Cordai 350
503. Samaropsis Leslii 352
504. Samaropsis Milleri. [Geol. Surv. India.] 353
505. Cordaicarpus Cordai 355
506. Holcospermum sulcatum; Codonospermum anomalum; Diplopterotesta spitzbergensis; Gnetopsis elliptica; Thysanotesta sagittula; Rhynchogonium costatum; Boroviczia Karpinskii; Hexagonocarpus Noeggerathi; Rhabdospermum tunicatum 359
507. Cycadeoidea marylandica. [G. R. Wieland.] 373
508, 509. Cycadeoidea Wielandi [G. R. Wieland.] 375, 376
510. Cycadeoidea sp. 377
511. Cycadeoidea Gibsoniana 377
512. Cycadeoidea ingens. [G. R. Wieland.] 378
513–515. Cycadeoidea. [G. R. Wieland.] 380–383
516. Cycadeoidea Dartoni 384
517–523. Cycadeoidea Gibsoniana 387–394
524–527. Cycadeoidea (Bennettites) Morierei. [O. Lignier.] 397–402
528–532. Cycadeoidea dacotensis. [G. R. Wieland.] 404–408
533. Cycadeoidea colossalis. [G. R. Wieland.] 410
534. Cycadeoidea Reichenbachiana. [A. Rothpletz.] 411
535–537. Cycadeoidea gigantea. [Geological Soc.] 413, 414
538. Cycadeoidea micromyela 415
539. Cycadeoidea Jenneyana (?) [G. R. Wieland.] 416
540. Vectia luccombensis. [Trustees of the British Museum.] 419
541–543. Williamsonia gigas 424–427
544. Williamsonia gigas. [Yorkshire Nat. Union.] 428
545. Williamsonia gigas. A. G. Nathorst. 429
546, 547. Williamsonia gigas 430, 431
548. Williamsonia gigas. O. Lignier. 432
549, 550. Williamsonia gigas. [Cambridge Phil. Soc.] 435, 436
551. Williamsonia spectabilis. A. G. Nathorst. 437
552. Williamsonia spectabilis. [Geological Soc.] 438
553, 554. Williamsonia Leckenbyi. A. G. Nathorst. 439, 440
555, 556. Williamsonia whitbiensis. A. G. Nathorst. 441
557. Williamsonia sp. [Indian Geol. Survey.] 444
558. Williamsonia Blandfordi. [Indian Geol. Survey.] 446
559. Williamsonia Carruthersi 447
560. Williamsonia Bucklandi 449
561. Williamsonia scotica 450
562–564. Williamsonia scotica. [Royal Society.] 451–453
565. Williamsonia spectabilis; W. whitbiensis; W. mexicana 459
566, 567. Wielandiella angustifolia 463, 464
568. Wielandiella angustifolia. A. G. Nathorst. 466
569–573. Williamsoniella coronata. [Royal Society.] 468–471
574. Cycadocephalus Sewardi. A. G. Nathorst. 474
575. Bucklandia anomala 482
576. Bucklandia Milleriana 484
577. Bucklandia Yatesii 485
578. Bucklandia buzzardensis. [Trustees of the British Museum.] 486
579. Bucklandia indica. [Trustees of the British Museum.] 488
580, 581. Colymbetes Edwardsi 492, 493 [Trustees of the British Museum.]
582, 583. Cycadolepis sp. 495
584, 585. Carpolithus conicus 498 [Trustees of the British Museum.]
586. Beania gracilis. [W. G. Carruthers.] 502
587. Ptilophyllum pecten. [Trustees of the British Museum.] 513
588, 589. Ptilophyllum pecten 514, 516 [Geological Surv. India.]
590. Ptilophyllum pecten and Williamsonia Blandfordi 517 [Geological Surv. India.]
591. Ptilophyllum cutchense. [Geological Society.] 518
592. Ptilophyllum pecten 519
593. Ptilophyllum pecten. [Geological Society.] 519
594. Ptilophyllum pecten 520
595. Ptilophyllum pecten 523
596. Ptilophyllum pecten. [Trustees of the British Museum.] 523
597. Ptilophyllum boreale. A. G. Nathorst. 526
598. Ptilophyllum antarcticum; P. Anderssoni 527
599. Zamites gigas. [Encyclopaedia Britannica.] 533
600. Zamites recta 534
601. Zamites Buchianus; Z. Carruthersi; Z. Zitteli 535
602. Zamites Buchianus 536
603. Otozamites Goeppertianus; O. Bechei 538
604. Otozamites Bechei 539
605. Otozamites Bechei 541
606. Otozamites Beani; O. Bunburyanus [Encyclopaedia Britannica.] 542
607. Otozamites bengalensis. [Geological Surv. India.] 542
608. Otozamites Kliptsteini. [Geological Society.] 545
609. Dictyozamites Hawelli 548
610. Pterophyllum Jaegeri 549
611. Pterophyllum Nilssoni; Nilssonia mediana 551
612. Pterophyllum Fayoli 552
613. Pterophyllum Braunianum 554
614. Pterophyllum Nathorsti; Nilssonia tenuicaulis 556 [Royal Society of Scotland.]
615. Pterophyllum Nilssoni [Trustees of the British Museum.] 557
616. Pterophyllum Lyellianum [Trustees of the British Museum.] 557
617. Pseudocycas insignis 562
618. Pseudocycas Saportae. [Encyclopaedia Britannica.] 564
619. Nilssonia pterophylloides; N. brevis; N. polymorpha 567
620. Nilssonia brevis; N. saighensis 570
621. Nilssonia rajmahalensis. [Geological Surv. India.] 571
622. Nilssonia compta. [Trustees of the British Museum.] 574
623. Nilssonia princeps. [Geological Surv. India.] 577
624, 625. Ctenis sp. [Manchester Phil. Lit. Society.] 579
626. Ctenis sulcicaulis 583
627. Pseudoctenis eathiensis [Trustees of the British Museum.] 584
628. Sphenozamites Rochei 588
629. Sphenozamites Belli. [Trustees of the British Museum.] 588
CHAPTER XXVIII.
CYCADALES (+recent+).
Among the fossil genera described in the last chapter of the second volume some were spoken of as true Ferns though most of them, it was added, ‘may safely be regarded as plants which will ultimately be shown to belong to some other group, in most cases that of the Pteridosperms.’ Since this was written additional evidence has been obtained in favour of the inclusion of certain genera in the Pteridosperms. In the case of Taeniopteris, one of the genera already described, there is reason to believe that at least one species is a member of the Cycadales and not a true Fern as formerly supposed.
The Pteridosperms so far described are represented for the most part by sterile leaves preserved as impressions, the genera founded on more satisfactory material having been reserved for treatment in this volume. As these genera are founded to a large extent on anatomical characters oscillating in their essential features between recent Ferns and Cycads, it is important that the student should be in possession of the anatomical characteristics of both of these classes; and for this reason a general account of recent Cycads is intercalated between the Pteridosperms already described and those reserved for treatment in this volume.
* * * * *
The section of the Gymnosperms known as the Cycadales, represented by nine recent genera and less than 100 species, is of exceptional importance phylogenetically and demands special attention from palaeobotanical students. Familiarity with the morphology of recent forms is essential not only in relation to extinct cycadean plants but also to types which, though not sufficiently close to surviving species to be included with them in one class, exhibit features regarded by many botanists as indications of an affinity either to true Cycads or to some generalised stock of which they are an offshoot. The Cycads of to-day may fairly be spoken of as anachronisms, plants appropriate to a former age but out of harmony with the present. They are confined to tropical and sub-tropical regions in both the old and new world. In habit many of them resemble tree-ferns, but the columnar stem, which may live to a great age and attain a height of 20 metres, differs from that of ferns in its gradually tapered form consequent on the presence of one or more cambial cylinders. Though often unbranched (fig. 377) branching of the main trunk is by no means unusual (fig. 378; fig. 381, B). Many Cycads are geophilous and have short tuberous stems (figs. 383, 395, 1_a_; 396, E): the genus Zamia includes a few epiphytic forms[1]. The typical cycadean stem is covered with persistent petiole-bases with or without an admixture of smaller scale-leaf bases (figs. 379, 380), while in several species a transversely wrinkled or irregularly fissured periderm forms the superficial tissue (figs. 381, B; 383). The foliage-leaves are relatively large and, with the exception of the bipinnate fronds of Bowenia (fig. 391), they are always pinnate. The fronds usually form a terminal crown (figs. 377, 379) and as many as 100 may be produced from one bud. In _Zamia pygmaea_[2] the fronds are only 10–12 cm. long, but in some cycads they reach a length of several metres. On both young foliage-leaves and scale-leaves long and very rarely branched[3] unicellular hairs (fig. 396, N) form a characteristic feature and take the place of the ramental scales of the majority of ferns. The apex of the stem shown in fig. 386, A is covered with a mass of woolly hairs and several scale-leaves are seen on the lower part of the bud.
Fig. 377. Cycas circinalis. From a photograph taken by Mr A. Malins Smith at Teldeniya (Ceylon).
Fig. 378. Cycas revoluta, as grown by Japanese horticulturalists. (After Wieland.)
Fig. 379. Encephalartos horridus.
Fig. 380. Cycas circinalis. Stem showing alternate zones of leaf-bases (F) and scale-leaf bases (S). (From the Encyclopaedia Britannica.)
Fig. 381. A. Cycas revoluta, megasporophylls. B. Zamia Loddigesii, branched stem.
All recent Cycads are dioecious. The reproductive shoots, except the megasporophylls of Cycas—which have departed to a less extent than those of other genera from the foliage-leaf plan (fig. 381, A; fig. 392, A–C) and are borne in a terminal cluster through which the stem subsequently pushes its way—consist of a varying number of micro- or mega-sporophylls in dense spirals on the axis of an elongated or oval strobilus (figs. 386, B, 393, 394). The microsporophylls are occasionally verticillate[4]. The strobili are sometimes though rarely branched[5] and generally but by no means invariably[6] terminal on the main stem which branches sympodially[7]. A striking example of lateral strobili has recently been described by Chamberlain[8] who figures a stem of Macrozamia Moorei with fertile shoots wedged among the persistent petiole-bases, a condition very similar to that in the Mesozoic Bennettitales. Pearson has also described clear cases of laterally-borne cones in Encephalartos. Cycas exhibits two kinds of branching, the female plants being monopodial while in the male the branching is sympodial. The microspores are produced in sporangia grouped in more or less well defined sori (figs. 389, A; 392, E–G). There is no definite annulus, but in the occurrence of groups of thick-walled cells some microsporangia recall those of certain ferns[9]. The ovules vary considerably in size, sometimes exceeding 5 cm. in diameter: there are usually two on each megasporophyll (figs. 393, C; 394; 395, 1_d_) but in most species of Cycas (fig. 392, B) and occasionally in other genera the number is larger[10]. A thick integument encloses the nucellus with which it is fused except in the apical region (fig. 396, A, B). Below the comparatively long micropylar tube is a well-developed pollen-chamber (fig. 396, B′, p), a striking feature of Cycadean ovules, immediately above the megaspore; the latter is filled with prothallus-tissue and bears a small apical group of archegonia on the floor of a depression (fig. 396, A–B′). In _Microcycas_[11] as many as 200 archegonia are recorded—a very exceptional case—and these are not confined to the apical region, though only the apical archegonia are functional. Each archegonium is characterised by a very large oval egg-cell and a much reduced neck[12]. The microspores usually produce a single prothallus-cell, a stalk-cell, and body-cell, and from the body-cell are developed two spirally ciliated spermatozoids (fig. 396, M). In this respect also the monotypic genus Microcycas is peculiar: it may have as many as 8 body-cells and 16 male gametes in a single pollen-tube (fig. 396, G), while in _Ceratozamia_[13] 4 gametes have been seen in one tube. The pollen-tube grows like a fungal mycelium into the nucellar tissue and the male gametes are formed in the distended proximal end which on bursting liberates the motile sperms with the watery cell-sap. Fertilisation is succeeded by the development of a homogeneous proembryo partially or completely filling the zygote (fertilised egg): by the formation of long suspensors the embryo is brought into contact with the food-store of the prothallus. In some Cycads, e.g. Encephalartos, the embryogeny exhibits a close resemblance to that of _Ginkgo_[14]. The embryo is dicotyledonous[15].
The single stele of the stem is characterised by a large pith which in some genera (e.g. Encephalartos, Macrozamia) contains an anastomosing system of collateral bundles. The vascular tissue of a cycadean stem forms a cylinder of secondary xylem and phloem, the primary xylem being represented only by a few, usually crushed, protoxylem elements on the inner margin of the reticulately pitted or scalariform tracheids. Both xylem and phloem are traversed by numerous broad and deep medullary rays[16]. The looser texture and more parenchymatous structure of Cycadean wood afford a ready means of distinguishing it from the wood of Conifers: for the Cycadean type the term manoxylic is proposed and pycnoxylic for the more compact coniferous wood[17]. Rims (or ‘bars’) of Sanio, of which much has been said in discussions on the phylogeny of Conifers, have recently been described in the petiolar xylem of Cycas revoluta: the rims are short and ‘cling closely to the borders of the pits,’ features which also characterise the rims found in the cones of the Araucarineae and in the root- and cone-wood of certain Pines[18]. In some Cycads the secondary xylem and phloem form a single cylinder, but in others (Cycas, Encephalartos, Macrozamia, Bowenia) the cambium is succeeded by one or several concentric cylinders of meristem which have their origin in the pericycle. The spasmodic occurrence of separate arcs of inversely orientated secondary xylem and phloem between the normal cylinders is a feature of importance from the point of view of comparison with the Palaeozoic Medulloseae[19]. The occurrence of concentric cauline strands in the cortex of Cycas is also a peculiarity worthy of notice. Successive bands of periderm, and occasionally a considerable amount of phelloderm[20], are formed in the peripheral region of the stem.
The leaf-traces in an adult stem exhibit a striking feature in their indirect or girdle-like course to the leaves (fig. 396, H, g) and in the gradual change from an endarch (fig. 396, O) to an apparently mesarch structure (fig. 400) as they pass from the perimedullary zone to the petiole: except at the base of the petiole the vascular bundles of the frond-axis consist of (i) centripetally developed xylem with a median protoxylem and a much smaller amount of centrifugal xylem (fig. 400) separated by a few parenchymatous elements from the centripetal xylem, (ii) an external arc of protophloem and within this metaphloem and parenchyma[21]. In the slender petiole of Bowenia there are a few collateral bundles arranged in the form of a circle or ellipse[22]; in Cycas and some other genera the more numerous bundles form a pattern like an inverted U, and in some species of Encephalartos the number is greater and the strands more irregularly scattered[23]. In the vegetative stems there is no centripetal xylem in the stele, but scattered centripetal tracheids occasionally occur internal to the protoxylem in the steles of the peduncles[24].
* * * * *
=Cycadeae.= Megasporophylls each bearing 2–8 ovules, borne separately like foliage-leaves and not in strobili. Pinnae have a midrib but no lateral veins (figs. 384, 387, A). Cycas (fig. 377).
=Zamieae.= Both kinds of sporophylls form strobili. Pinnae have several dichotomously branched, more or less parallel veins. Zamia (figs. 388–390), Macrozamia, Encephalartos (figs. 379, 386, C), Ceratozamia, Dioon (fig. 386, B), Microcycas.
=Stangerieae.= Strobili as in Zamieae. Pinnae fern-like, numerous dichotomously branched lateral veins given off from a midrib. Stangeria.
=Bowenieae.= Leaves bipinnate (fig. 391), strobili as in Zamieae. Bowenia.
Distribution. The most widely spread genus, Cycas, occurs in Siam, India, the Nicobar Islands, Ceylon, Madagascar, and Australia, in many of the islands in the Indian and Pacific oceans, in New Guinea, Borneo, New Caledonia, New Britain, China and Japan[25]. Zamia, the most northerly genus, extends from North Mexico and Florida through Central America and some of the West Indian islands to Ecuador, Bolivia, Chile, and Peru. Dioon and Ceratozamia are confined to South Mexico, and Microcycas flourishes on the Cuban mountains. The continent of Africa possesses two endemic genera Encephalartos and Stangeria. Encephalartos extends from Cape Colony through Natal and Zululand to Zanzibar and Mombasa[26]: a specimen in the Kew Herbarium (probably E. Hildebrandti) is said to have been collected as far north as the Soudan. Two species are recorded from the Congo[27] and E. Barteri, discovered by Barter in Central Africa, is recorded from the Gold Coast[28]. Stangeria has a much more limited range in S.E. Africa[29]; Australia possesses Macrozamia, represented by several species in Western Australia, New South Wales and Queensland, Cycas in Queensland and the Northern territory and the Queensland genus Bowenia. There are no Cycads in New Zealand. As a whole Cycads have a limited range and with the exception of Cycas and Zamia none of them extend beyond the limits of a single continent. They are as a rule not gregarious plants and play a subordinate part in the facies of the vegetation. Macrozamia forms dense thickets[30] in some districts and occurs both in exposed situations and in association with Palms in damp Queensland forests. Chamberlain[31] speaks of 100 plants of Dioon edule as visible in one view in South Mexico where the species forms a mountain forest. In Florida _Zamia pumila_[32] grows in dense moist woods, a habitat in contrast to that of many Cycads. The Mexican Ceratozamia is associated with luxuriant vegetation, while its compatriot _Dioon_[33] lives in blazing sunshine. Sir Joseph Hooker[34] speaks of Cycas living in the deepest and hottest valleys in Sikkim. Encephalartos is essentially a xerophilous genus. Stangeria paradoxa is said to be confined to forests in Cape Colony, and another species grows among the grass of the Park-lands in open country[35]. While it is true that many Cycads are characteristic of dry regions some species flourish in places where shade and moisture are abundant.
Though it is impossible in many cases to form an estimate of the age of individual plants, there are clear indications that some specimens afford notable instances of longevity. Chamberlain estimates the age of some plants of Dioon spinulosum as exceeding 400 years and mentions an example of D. edule that is probably 1000 years old. An unusually tall plant of Encephalartos in the Botanic Garden of Amsterdam is believed by Prof. de Vries to have reached the venerable age of 2000 years[36]. The restricted range and in many cases the solitary existence of recent Cycads, with their tall stems clothed with the persistent cork-covered stumps of thousands of fronds, deepens the impression of antiquity derived from a study of the geological history of this dwindling race.
Stems. The tall columnar stems of some species of Cycas, often branched or bearing numerous ovoid buds like enlarged bulbils[37], are characterised by the regular alternation of large and small leaf-bases as seen in the stem of C. circinalis reproduced in fig. 380. In older stems of this species the leaf-bases are exfoliated and the stem is covered with wrinkled and fissured cork; but in Cycas revoluta the leaf-bases are even more persistent. The columnar but relatively stout stems of Encephalartos (figs. 379, 382, 386, A) and Ceratozamia are similarly encased in a covering of petiole-bases, but in these genera the differences between foliage-leaves and bud-scales is much less obvious and there is no zonal alternation. On the stems of Macrozamia the rhomboidal leaf-bases are more uniform in size and there are no scale-leaves. The tall and often palm-like stems of Microcycas sometimes show transverse rings on the bark marking the position of former terminal buds, and in older trunks these may disappear, leaving a fissured bark[38]. In Cycas siamensis the tuberous stem is similarly covered with a rough bark (fig. 383) and the stems of Zamia are also characterised by an absence of persistent leaf-bases (figs. 381, B; 395, I_a_, a). It is pertinent to remind the palaeobotanical student of the occurrence of flowering plants with stems closely simulating those of some Cycads. Prof. Bower[39] in describing Rhynchopetalum montanum, an Abyssinian Lobeliaceous plant, drew attention to the similarity in surface-features and to some extent in anatomical structure to cycadean stems. The resemblances are further emphasised in a more recently published account of the same species under a different name, _Lobelia Rhynchopetalum_[40].
Fig. 382. Encephalartos Ghellinckii. (¹⁄₁₁ nat. size.)
Fig. 383. Cycas siamensis. (From the Encyclopaedia Britannica.)
Fronds. A general acquaintance with the various types of fronds illustrated by recent Cycads is important to the student of fossils not only to enable him to compare existing and extinct forms but as affording safeguards against possible sources of error in the description and identification of impressions[41]. The vernation exhibits less uniformity than in Ferns: in Cycas the rachis is straight and the pinnae circinately coiled (fig. 220, B, vol. +ii.+ p. 283); in Zamia and Stangeria the rachis is bent and the pinnae straight, while in Ceratozamia and other genera both the axis and leaflets are straight. As Braun pointed out, there is as a rule no terminal leaflet, or it may be pushed to one side giving a forked appearance to the frond apex[42].
Fig. 384. Cycas circinalis, abnormal frond. (From a specimen in the British Museum.)
Cycas. The presence of a strong midrib and the absence of lateral veins are distinguishing features: the lower margin of the lamina is frequently decurrent (fig. 387, A). In C. circinalis the pinnae may reach 40 cm. in length with a fairly uniform breadth of 2 cm. A frond of this species in the British Museum, not quite complete, has a length of 112 cm.: on the lower part of the rachis strong spines replace the leaflets and near the apex of the leaf concrescent pinnae form a continuous lamina traversed by seven ribs and dissected at the margin into acuminate teeth (fig. 384): some of the pinnae are forked as in _Cycas Micholitzii_[43] (fig. 385). Several years ago I noticed a similar instance of concrescence in a small plant of C. circinalis in the Royal Gardens, Kew (fig. 387, I). In Cycas Micholitzii the pinnae, reaching a length of 20 cm., are repeatedly and deeply forked (fig. 385, A, B; fig. 400): the pinnae of C. Rumphii var. _bifida_[44] are also deeply dissected. Cycas Beddomei has very narrow pinnae (15 cm. × 2 mm.) similar to those of the Wealden species Cycadites Saportae, and it is noteworthy that narrow leaflets with a strongly revolute lamina would produce casts with two parallel ribs (the grooves between the midrib and the edge of the lamina) simulating the double midrib of the fossil genus Pseudocycas. In some fronds, e.g. C. Cairnsiana, the midrib is hardly visible on the upper face of a dried pinna which shows a longitudinal wrinkling simulating parallel venation.
Fig. 385. A, B, Cycas Micholitzii. (After Thiselton-Dyer.) C, Zamia angustifolia.
Encephalartos. The fronds of this genus, in _Encephalartos Laurentianus_[45] reaching the exceptional length of 7 metres, bear alternate pinnae exhibiting a considerable range in form and breadth. In E. longifolius, E. Altensteinii (fig. 386, C), E. Lehmanni, etc., the pinnae are for the most part linear, reaching a length of 20 cm. and a breadth of 2 cm.: in E. caffer (fig. 387, D), E. latifolius, and others the pinnae are broader and shorter and often spinous. A frond of E. longifolius or E. Altensteinii may bear both entire and lobed, spinous pinnae. In E. Frederici-Guilielmi (fig. 387, G) and _E. Ghellinckii_[46] (fig. 382) the pinnae are very narrow and almost filiform, with revolute edges. The thick and leathery pinnae of some species are attached obliquely to the edge or to the upper sloping sides of the rachis which forms a prominent ridge between the rows of leaflets, and characteristic oval scars are left on the fall of the pinnae (fig. 387, D, G′). The lamina in most species contains several veins more or less parallel to the margins and often much more prominent on the lower than on the upper surface.
Fig. 386. A. Encephalartos Altensteinii, apex of stem. B. Dioon edule,megastrobilus. (From a photograph by Mr S. M. Wadham.) C. Encephalartos Altensteinii, frond.
Fig. 387. Cycadean fronds. A, Cycas circinalis; B, Macrozamia Fraseri; C, Macrozamia Denisoni; D, Encephalartos caffer; E, F, Dioon edule from below and above; G, Encephalartos Frederici-Guilielmi, G′, side-view; H, Ceratozamia mexicana; I, Cycas circinalis, lower part of young frond.
Zamia. In Zamia angustifolia (fig. 385, C) and Z. linifolia the pinnae are long and very narrow: the other extreme is represented by _Z. Wallisii_[47] (fig. 388) with broad ovate segments reaching a length of nearly ·5 metre and attached to the rachis by a short stalk; the veins are prominent and dichotomously branched. Other forms of pinnae are represented by Z. integrifolia, Z. floridana, and Z. Loddigesii (figs. 389, 390, 395). The broad and short pinnae of _Z. furfuracea_[48] bear a close resemblance, except in the absence of an auriculate base, to those of some species of the fossil genus Otozamites. The broadly linear pinnae of Z. pseudoparasitica (45 cm. × 3 cm.) often show longitudinal wrinklings on drying which suggest comparison with the corrugated lamina of the fossil species Nilssonia brevis. A basal pad or callosity on the slender bases of the pinnae is characteristic of many Zamia fronds.
Fig. 388. Pinna of Zamia Wallisii. From a drawing after A. Braun in the Kew Herbarium. (⅓ nat. size.)
Fig. 389. Zamia integrifolia bearing a megastrobilus and showing foliage-leaves and scale-leaves. A, microsporophyll; B, megasporophyll. (After Rendle, from Jacquin.)
Fig. 390. Small frond of Zamia Loddigesii. (⅔ nat. size.)
Ceratozamia. The fronds bear a fairly close resemblance to those of Macrozamia: in Ceratozamia mexicana the linear pinnae reach a length of over 30 cm. and a breadth of 2–3 cm.; the lamina tapers to a narrow apex and is more abruptly contracted at the base (fig. 387, H). The veins in Ceratozamia are sub-parallel and dichotomy occurs up to the middle of the lamina[49]. A striking feature is the occurrence of two opposite stipule-like projections a short distance above the base of the petiole.
Macrozamia. A noteworthy feature in some species is the attachment of the linear pinnae along the middle line of the rachis (fig. 387, C); in others (fig. 387, B) the leaflets are attached laterally and may have a basal callosity. The parallel veins, which branch dichotomously near the base of the lamina, are often much more prominent on the lower than on the upper face. In _M. heteromera_[50] (fig. 396, F, F′) the narrow pinnae are deeply forked and strongly revolute. The spirally twisted rachis of M. spiralis, M. heteromera, etc., is a striking feature recalling the Rhaetic fern Camptopteris spiralis Nath[51].
Dioon. The arrangement of the linear pinnae of D. edule (fig. 386, B), D. spinulosum, and _D. Purpusii_[52] forms a ready means of distinguishing the fronds of this genus: the pinnae, often contiguous and at right-angles to the rachis, are attached in a lateral groove by an expanded and slightly decurrent base. The difference between the lower and upper face of a frond (fig. 387, E, F) affords a good illustration of a common source of error in the identification of fossil specimens. The leaflets of D. spinulosum, which except in their spinous margin are very similar to those of D. edule, may reach a length of 15 cm. and a breadth of 8 mm. The parallel veins are unbranched[53].
Microcycas[54]. The pinnae of this genus, very like those of the Wealden species Zamites Buchianus, reach a length of 20 cm. and a breadth of 8 mm.: on falling they leave oblong scars resembling those on the rachis of Encephalartos.
Stangeria. This genus is particularly interesting because of its fern-like habit and venation. The large fronds of _S. paradoxa_[55] bear broadly linear acuminate pinnae with entire, unevenly lobed, serrate, or pinnatifid margins. Some leaflets are so deeply dissected as almost to justify the appellation pinnate. Both entire and dissected leaflets may occur on one frond and the lower ones may be stalked while the upper pinnae are sessile. The venation agrees closely with that of the genus _Taeniopteris_[56].
Bowenia. The large fronds of this genus (fig. 391) are peculiar in being bipinnate; they may reach a length of 2 metres and have a long slender petiole: the asymmetrical lamina of the segments, entire or deeply serrate, is attached by a very short stalk; the veins branch dichotomously[57] and diverge slightly. Both entire and serrate pinnae may occur on the same plant, but Chamberlain has revived André’s specific term serrulata in preference to the generally adopted designation for the serrate forms, B. spectabilis var. _serrata_[58].
Fig. 391. Bowenia spectabilis, frond. (From the Encyclopaedia Britannica.)