374 THE JOURNAL OP BOTANY 



Lmks loith the Past in the Plant World. By A. C. Seward, 

 F.K.S. Pp. viii. 142. Cambridge University Press. 1911. 

 Price Is. 



As his title declares, Professor Seward, according to the custom 

 now familiar, concerns himself with the past more than the present 

 and is chiefly anxious to trace the developments through which 

 our existing plants may have attained their present form. The 

 conclusions reached must of course always remain speculative, 

 however reasonable the arguments supporting them may appear, 

 and can never amount to certainty. Nevertheless, when the dis- 

 cussion is conducted, as in this instance, with scientific sobriety 

 and fulness of knowledge, the result is both interesting and in- 

 structive, and may help to enlarge the narrowness of view which 

 is apt to characterise the field botanist. 



The little book is, in fact, full of interest and information, and 

 enables us to realise many vital problems connected with evolu- 

 tionary history, in particular that of geographical distribution, 

 which Darwin considered so supremely important. We are 

 constantly reminded that we must take into account the time 

 when land bridges united countries now separated by water — as 

 Ireland with Great Britain, and both with the Continent ; as also 

 of the part played by the Ice Age in affecting the flora of various 

 regions. In an interesting introductory chapter evidence is given 

 as to the age to which trees attain, and the time their timber 

 endures. As to this it is noted (p. 10) that " the blocks of oak 

 and beech, some of which are as sound as when first felled, 

 recently discovered below the foundations of parts of Winchester 

 Cathedral constructed at the end of the 12th or in the opening of 

 the 13th century, are relics of Norman forests." 



Most curious and striking is the final chapter on the Ginkgo — 

 called from the character of its foliage the " Maidenhair Tree " — 

 a strange growth, the true place of which in the plant-world has 

 but recently been determined, and which in spite of the vast anti- 

 quity it has attained appears now to survive only in cultivated 

 specimens and to be extinct in a wild state. 



Various points may be noted which suggest a useful moral 

 that should teach the necessity of caution in regard of speculations 

 concerning the past course of evolution, the mysteries of which 

 are certainly not rendered less mysterious by such observations as 

 the following (p. 67) : — 



" The plants of the Palseozoic period, though often differing 

 considerably from those of the same class in the floras of to-day, 

 exhibit a remarkably high type of organisation. 



" Some of the most abundant trees in the forest of the Coal Age 

 are decidedly superior in the complexity of their structure, as also 

 in size, to modern survivals of the same stock. ... It is impossible 

 to get away from the conclusion that the oldest Palaeozoic flora 

 of which we have an intimate knowledge must be the product of 

 development of an age which is represented by a chapter in the 

 history of the plant kingdom, at least as far removed from the 

 beginning as it is separated from the chapter now being written. 



