6/4 SCIENCE PROGRESS 



choice of a word to describe "the characteristic of logical propositions" — 

 namely, " tautology." The present writer cannot help feeling that the 

 emphasis on the tautological aspect of mathematics arises from Mr. Russell's 

 present attitude towards infinity : he tends to be unduly sceptical about 

 infinity, much as he was in 1896, when he hastily denied the validity of 

 Cantor's work. There is, it seems, a failure to grasp what was sound in the 

 contentions of such men as Poincare, who maintained that the infinity in 

 the principle of mathematical induction avoided tautology. 



This book is a lamentable performance. Lamentable because many of 

 us have a vivid recollection of good service which Mr. Russell has done in 

 the past to the cause of logic, before he took to journalism in 1912. 



The book is pleasantly written. But if the symbolic language of Dr. 

 Whitehead and Mr. Russell really does express anything that is both true 

 and not trivial, that Mr. Russell has utterly failed to express in ordinary 

 words. 



THE FAL-ffiONTOLOGICAL HISTORY OF THE GYMNO- 

 SFERMS on : Fossil Plants. A Textbook for Students of Botany and 

 Geology. Vol. 4, Ginkgoales, Coniferales, Gnetales. By A. C. Seward, 

 M.A., F.R.S., Master of Downing College, Cambridge. (Pp. x\i + 54i, 

 with 190 illustrations.) (Cambridge : at the University Press, 1919. 

 Price £1 is. net.) 



The fourth volume of Prof. Seward's monumental book on Paleobotany is 

 the final one of the series. On its title-page, however, it reveals the dis- 

 appointing fact that the work ceases with the Gymnosperms, and it does not 

 touch the Angiospermic flora at all. As the present-day flora which catches 

 the eye consists almost entirely of members of the Angiospermic family, it 

 may seem as though it were impossible to complete a book on the history 

 of plants and leave out the flowering plants. Nevertheless, owing to the 

 nature of the material on which the science is based, and owing to the com- 

 paratively short history of the flowering plants (which did not appear 

 until well on in the Cretaceous), the reputable data of Paleobotany are 

 almost all to be found concerning the Coniferse and lowlier groups. 



The author himself says : " It is with a keen sense of the incomplete- 

 ness of my task that Volume IV is concluded without any attempt to deal 

 with the abundant, if, in very many cases, undecipherable records of Angio- 

 sperms. . . . What is needed ... is the co-operation of trained systematists." 

 The difficulty, however, in obtaining this co-operation of trained systematists 

 is that the modern botanist bases his classification on the floral details and 

 fructifications of plants, whereas one may safely say that 95 per cent, of 

 the remains of fossil Angiosperms consist of foliage leaves in varying degrees 

 of incompleteness. The points on which classification must therefore depend 

 are primarily venation and the marginal outline of the leaf. By an unfor- 

 tunate chance even the " cuticle preparations " which are now so useful, 

 particularly in specimens from the Lower Mesozoic, are extremely rare 

 for the Higher Mesozoic and the Tertiary deposits containing dicotyledonous 

 and other leaves, and they have not yet been used with any practical effect 

 in work on dicotyledons. In recent years the only output of work of any 

 magnitude on the Angiosperm fossil flora comes from America, where the 

 deposits are of first-rate geological importance ; but we do not lack excel- 

 lent fossil material in this country, were workers in this field to arise. By 

 the untimely death of Clement Reid, research on the late Tertiary Angio- 

 sperms was prematurely cut off, and the earlier Tertiary collections in this 

 country are still lying as undescribed specimens awaiting the research worker 

 to handle them. However, in the middle of last century, much has been 

 published by various European scientists, such as Heer, Ettingshausen, and 

 others, so that there will be a very voluminous critical work awaiting 



