134 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



chemistry of vital products that more than two -thirds of the volume are de- 

 voted to substances belonging to this category. Few will disagree with the 

 author in welcoming this return to nature, but we must differ from him when 

 he states that "It is surprising to find how many subjects for research have 

 been unearthed among the substances which go to build up animal and vegetable 

 structures " (p. 2). Subjects for research do not need unearthing in this field, 

 which on the contrary simply bristles with them. It is rather the complexity 

 of most vital products and the intricacy of vital processes which in the past 

 have hindered the prosecution of fruitful research in biochemistry. Indeed, 

 recent triumphs in the synthesis of vital products have been achieved only as a 

 result of the earlier work on the manifold reactions of the simpler carbon com- 

 pounds. Moreover, it is doubtful whether any real advance will be made in 

 elucidating the mechanism and nature of vital reactions until the physical chemist 

 has won a clearer insight into the properties of colloids, to quote a conspicuous 

 example. 



The first chapter is now devoted to a survey of the main lines of research 

 in the present century. The chapters on the terpenes do not differ sensibly 

 from those in the previous edition. The chapter on rubber contains a trenchant 

 criticism of Harries' work and theories, while the large amount of new work 

 on the alkaloids is clearly reviewed in the chapter on these bodies. After a 

 short account of the polypeptides, twenty pages are devoted to Willstatter's 

 researches on chlorophyll, of which a lucid account is given, though the subject is 

 too complex for really satisfactory treatment in so short a space. After a chapter 

 on Willstatter's remarkable researches on the anthocyanins, we come to what 

 is in many ways the most fascinating chapter in the book. This is based largely 

 on a private communication from Prof. Collie, and in it the author shows in detail 

 how the course of the natural syntheses of the various classes of vital products 

 can be formulated in the light of present-day knowledge of organic chemistry. 

 Succeeding chapters deal with the organic chemistry of arsenic and with the struc- 

 ture of triphenyl methyl. Perhaps the least satisfactory chapter is that headed 

 " Other elements which exhibit abnormal valency." The subject is undoubtedly 

 an important one, but the present state of our knowledge scarcely justifies the 

 space devoted to some of the inconclusive work recorded. The author is again 

 at his best in the final chapter, in which he gives an illuminating and suggestive 

 account of the limitations of existing structural formulae as an expression of the 

 reactions and reactivity of organic substances. 



We have found very few errors, and the only one which calls for comment 

 occurs at the top of p. 263, where the need for a reduction at one stage of the 

 reaction has been overlooked. With regard to the choice of subjects, it is 

 suggested that in a subsequent edition an account should be given of recent 

 important work on the structure of the nucleic acids and of the lipins. 



Prof. Collie says in his Introduction : " The text-book is rare that stimulates 

 its reader to ask, Why is this so ? or How does this connect with what 

 has been read elsewhere ? " Dr. Stewart's book undoubtedly falls into this 

 category. 



" A Dictionary of Flowering Plants and Ferns." By J. C. Willis, M.A., Sc.D., 

 F.R.S. Ed. 4. 8vo. xii + 712 -f- lv pp. (University Press, Cambridge, 191 9.) 

 205. net. 



It is with a certain amount of regret that we find this new edition of Dr. 

 Willis' well-known Dictionary does not contain the valuable introductory 

 summary that made the earlier editions something more than a mere dictionary 

 — made them indeed interesting as textbooks dealing with some aspects of botany 

 too often neglected. It is with regret too that we find the serviceable dark blue 

 cover of the earlier replaced by a light blue-grey one in this last edition. These 

 regrets are only not quite turned to whole-hearted approbation when we investi- 

 gate the contents of the Dictionary itself and find that all the genera of flowering 

 plants are noted, and the book is thus much more complete than in the earlier 

 editions where only the principal ones found a place. The style of the book is too 

 well known to need description, for as a handy book of reference it has been 

 in constant use by botanists and those who need to refer to plant names and 

 uses for many years, and we can confidently predict a wider usage now it is 

 more complete. 



" The Preparation of Substances Important in Agriculture." By C. A. 

 Peters, Ph.D. Ed. 3. 8vo. vii -f 81 pp. (Chapman and Hall, London, 1919 ) 

 45. net. 



This is best described as a series of laboratory exercises with notes upon the 

 preparation of manures and insecticides, and is to be used by students working 

 in the laboratory, not as a guide to the manufacturer. 



