CURRENT LITERATURE 



BOOK REVIEWS 

 Fossil plants 



The third volume of Seward's Fossil plants^ will be welcomed alike by- 

 students of paleobotany and by those whose primary interest is in the mor- 

 phology and phylogeny of the living vascular plants. The volume, comprising 

 chapters xxvii-xxxix of the complete work, is devoted to Gymnosperms, 

 the space being distributed as follows: Cycadales (recent) 34 pages, Pterido- 

 spermae 140, Cycadofilices 39, Cordaitales 86, Paleozoic gymnospermous seeds 

 66, Cycadophyta (fossil) 226, Bibliography of Vols. Ill and IV 48, Index 17, 

 making a total of 656 pages. There are 252 figures, many of which are original. 



The account of the living cycads, from the standpoint of a competent paleon- 

 tologist, is particularly interesting and suggestive to one who, like the reviewer, 

 is somewhat familiar with those forms, but is dependent upon investigators like 

 Seward for descriptions of their extinct predecessors. This introductory 

 chapter is a fitting introduction to the more detailed treatment of paleozoic and 

 mesozoic members of the phylum. The practical advantage of such an intro- 

 duction is sufficient excuse for treating the living cycads first instead of consider- 

 ing them in their natural place at the end of their phylum. The author believes 

 the antiquity of that part of the cycadophyte phylum represented by the living 

 cycads cannot be determined, but it is probable that if cycads, apart from Ben- 

 nettitales, existed in the Jurassic and lower Cretaceous beds, they occupied a 

 very subordinate place in comparison w'ith the Bennettitales. While the living 

 cycads resemble the Bennettitales in many vegetative features, we believe that 

 the reproductive structures show a kind of difference which would make it 

 impossible to derive the living cycads from any forms of the Cycadeoidea type; 

 while, on the other hand, the Cycadofilicales, which Seward prefers to call 

 Pteridospermae, have reproductive structures from which the cones of living 

 cycads might easily be derived. If the living cycads have come from Ben- 

 nettitales, they must have come from ancient types in which the mega- 

 sporophylls still retained a distinct leaflike character. Whether they have come 

 from the Bennettitales or directly from the Cycadofilicales, they must have 

 greater antiquity than is indicated by any material yet discovered. We agree 

 with Seward that the afiinities are still in doubt, but we hope that Triassic 

 material which can be sectioned will be found and that it will clear up relation- 

 ships, for, it seems to us, the differentiation must have taken place long ago. 



' Seward, A. C, Fossil plants, a textbook for students of botany and geology. 

 Vol. III. Pteridospermae, Cycadofilices, Cordaitales, Cycadophyta. 8vo. pp. xviii-|- 

 656. figs. 25J. Cambridge University Press. 1917. 



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