Reviews — Professor A. C. Seiuard — Fossil Plants. 517 



university may allow of its speedy completion. Like the growing 

 point of a Monocotyledon, the scope of Professor Seward's under- 

 taking has broadened with its growth, and the completed work will 

 form a landmark in the literature of palseobotany. 



The present volume opens with a general account of recent Cycads, 

 the headline to which contains a curious misprint, one of the very 

 few we have noticed in the volume, the general production of which 

 is excellent, with clear and well-arranged text. The account of the 

 Pteridosperms was begun in vol. ii, but the treatment of the better- 

 known genera was reserved for the present volume; "as these 

 genera are founded to a large extent on anatomical characters 

 oscillating in their essential features between recent Ferns and 

 Cycads," this intercalation of a chapter on recent Cycads was a happy 

 thought. In the second chapter the author resumes his descriptive 

 account of the Pteridosperms. These are considered under the 

 headings Lyginopteridese and Medulloseae. Under the former is 

 a full description of Lyginopteris (a name which on principles of 

 nomenclature replaces the somewhat better-known Lyginodendron), 

 including vegetative and reproductive organs, with the seed which 

 was formerly known as Lagenostoma. The subject of nomenclature 

 is a difficult one for the writer of a textbook on palaeobotany. 

 Having pieced together the fragments which have been described 

 under different names at different times, he has to decide what name 

 the more or less perfect entity shall bear ; and it must sometimes 

 happen that a better-known name must give place to one which is 

 for the moment less well known. Professor Seward is wise to be 

 guided by definite principles ; in a book like the one before us, 

 which will be a standard textbook for some time, he has the oppor- 

 tunity of fixing a name for the use of students. 



In this chapter the author discusses the use of the term "seed" 

 for the structure represented by Lagenostoma and other Palaeozoic 

 seeds. The difficulty is the absence of an embryo, a very important 

 feature, the development of the embryo being the outward and visible 

 sign of the process of fertilization. The opinion is expressed that 

 this negative character should not be allowed to outweigh the 

 evidence furnished by morphological features as to the applicability 

 of the term seed (p. 61). Later (p. 301) the writer refers to " the 

 promotion of the megasporangium and niegaspore of the Pteridophyta 

 to the higher stage represented by the integumented megasporangium 

 (nucellus) and single megaspore that in the main fulfil the definition 

 of a seed". How, then, shall we define an ovule ? The seed of the 

 modern phanerogam or seed-plant is so characteristic and morpho- 

 logically well-defined a structure that one somewhat regrets the 

 application of the same term to these early attempts to achieve the 

 same biological function. Professor Seward is not, we think, quite 

 sure of his position, as on each occasion he leans on the stalwart arm 

 of Professor Oliver. As Professor Oliver says, "there is a long 

 chapter in evolution to be deciphered before we can connect . . . the 

 seed of Lyginodendron with the sporangium of any fern at present 

 known to us." We might add, there is a long long trail between 

 Lyginodendron and the modern seed-bearing plant. 



