CHEMISTRY OF PLAN^T PRODUCTS 371 



hydrogen-Ion concentration. The next three chapters deal respectively 

 with the synthesis of fats, carbohydrates, and proteins ; then follows 

 one on respiration ; the concluding chapter is devoted to a con- 

 sideration of the broad aspects of growth. The diverse problems 

 presented by the process of carl)on assimilation are treated at some 

 length, and the chapter concludes with a critical discussion of the 

 old hypothesis of Baeyer add its more recent interpretations, as well 

 as of that of Willstaetter and StoU. Jiespiration also receives a 

 detailed treatment, including an admirable account of the dehydro- 

 genation theory of oxidation. The authors conclude that there are 

 good grounds for regarding biologicil oxidations as primarily due to 

 enzymes like dehydrax which activate hydrogan in oxidisable sub- 

 stances to be removed by a suitable hydrogen acceptor. This may be 

 the oxygen of the air, or possiblj^ such a compound as glutiatlione 

 which can act altsrnately as Iwdrogen-acceptor or as hj^lrogen- 

 donator. Thg chapter on growth is likewise fully np to date, dealing 

 with such recent asp3cts as the compound interest law, hormones, 

 and vitamins. It is, however, scarcely possible in a brief review to 

 indicate the diversity of subjects touched upon, in spite of the rela- 

 tively small dimensions of the book. 



F. E. Fritsch. 



PJlanzen-terafologie. By O. Pen-ztg, Professor of Botany and 

 Director of the Eoyal Botanic Garden at the University of 

 Grenoa. Second, much enlarged edition. 8vo. Vol. I. pp.xiii, 

 283; Vol. II. pp. 548; Vol. III. pp. 624. Borntraeger, Berlin! 

 1921-2. 



The former edition of Dr. Penzig's work was published from 

 1890-1894, and contained 1134 pages, the present edition comprises 

 1455 pages ; the increase indicates the large number of books and 

 papers dealing with plant-teratology which have appeared in the 

 interval. The first volume is the bibliographical list, in which publi- 

 cations are arranged alphabetically by the author's name; in the 

 original edition this occupied only 1G6 pages : the second and third 

 volumes are the systematic portion. The arrangement adopted is 

 mainly that of Bentham and Hooker's Genera Plantarum, and the 

 Dicotyledons precede the Monocotyledons ; Gymnosperins, Ferns, and 

 Cellular Cryptogams follow in succession after the Monocotyledons. 

 There is an index of families and genera at the end of each volume. 



Under each genus is given a list of species, arranged alpha- 

 betically, in which an abnormality has been noted, with a reference 

 to author and place of publication. 



The whole forms a very useful work of reference to a subject 

 the literature of which is remarkably scattered. 



A. B. R. 



