BOOKS AND CURRENT LITERATURE 101 



ence from the stratigraphic or truly historical side. In the present 

 notice, however, designed for botanical readers, I wish to confine what 

 I have to say to the phases of the present volume that are of most 

 interest to them, what I have already said being sufficient to put them 

 in a critical frame of mind toward statements the validity of which 

 need testing. 



The volume opens with a very satisfactory chapter devoted to a 

 discussion of existing cycads, largely an abstract of already published 

 data. Then follow three chapters devoted to the Pteridospermae. 

 These are divided into three families — the Lyginopteridae, Medulloseae 

 and Steloxyleae, and are rather fully and very satisfactorily discussed. 



The remaining structural forms that are probably more or less 

 closely related to the foregoing pteridosperms are considered to repre- 

 sent the following seven families :• — Megaloxyleae, Rhetinangieae, Steno- 

 myeleae, Cycadoxyleae, Calamopityeae, Cladoxyleae and Proto- 

 pityeae, and these are discussed in a separate chapter under the group 

 term of Cycadofilices. These presumable pteridosperms, because of 

 the dearth of conclusive evidence are thus arbitrarily segregated. 

 While caution is to be commended in dealing with fragmentary plant 

 fossils it may be questioned whether judgment may not be suspended 

 until it dies of inanition. It is also questionable how far it is desirable 

 to introduce purely artificial groups, and if it be granted as desirable, 

 it may be pertinent to ask what criteria are to decide such a question. 

 That such a course does not make for clearness and that such questions 

 rest after all upon personal equation rather than upon objective facts 

 may be illustrated by Seward's reference of the genus SteloxyJon to his 

 Pteridospermae and the scarcely to be distinguished genus C ladoxylon 

 to his Cycadofilices. The fact that so many of the so-called families 

 of the latter group are monotypic is convincing enough evidence that 

 they illustrate chance discoveries and the imperfection of the geological 

 record rather than that they were really monotypic. Following the 

 chapter devoted to the Cycadofilices there are two chapters dealing 

 with the Cordaitales, which are described under the three groups of 

 Poroxyleae, Cordaiteae and Pityeae. The statement on page 276 

 that there is no proof of Cordaites in the Arctic may be a statement of 

 opinion — it is hardly a fact. Similarly the statement that it is not 

 certain that Cordaites flourished before the Carboniferous is also a 

 matter of opinion and not of facts. There is abundant proof of the 

 existence of Cordaites-like forms in the Devonian. 



A succeeding chapter of 65 pages is devoted to Paleozoic gymno- 



