BIOCHEMIK DBR PFLANZEN 49 



the problems of vital organization and metabolism. In con- 

 cluding this section, in which the amazing progress of biochemistry 

 is more strikingly reflected than in any other part of the book, 

 the author considers the chemical aspects of heredity, variation, 

 evolution, pointing out that in the light of the recent work of 

 Keeble, Armstrong, and others, various colour varieties and 

 mutants in flowers may be regarded as cases of " chemical 

 mutation," and that many other morphological characters will 

 doubtless be shown by future work to be the outw^ard and visible 

 signs of inner biochemical changes taking place in the cell. 



The remainder of this volume is devoted to the carbohydrates 

 (in the widest sense) and the lipoids (fats, waxes, phosphatides). 

 It is impossible here to indicate, even by a bare enumeration of 

 the chapter headings, the extraordinarily detailed and compre- 

 hensive nature of the author's treatment of these groups of 

 substances in their various relations to each other and to metabolic 

 processes. Many will doubtless be inclined to consider the 

 amount of condensation to which these chapters have been 

 subjected as somewhat ruthless, so much that appeared in the 

 first edition having been excised altogether in order to make room 

 for new matter based on recent investigations. In many cases, 

 for instance, in the sections dealing with chlorophyll and allied 

 substances, the older work — largely based on impure extracts — 

 has very pi'operly been omitted or relegated in severely condensed 

 form to the valuable historical introductions which preface the 

 main sections throughout the book. In other cases, however, one 

 is inclined to wonder whether the author has not gone rather too 

 far in his fixed determination to condense or omit material dealt 

 with in other text-books, despite the fact that what the work has 

 lost in encyclopasdic fullness (and perhaps dullness) it has cer- 

 tainly gained in other directions. The outstanding feature of the 

 work is the remarkable width of its range, the author having 

 thoroughly ransacked the literature of pure and applied chemistry 

 and botany in his brilliantly successful efforts to sort out and 

 piece together a vast number of scattered observations which 

 thus acquire a significance which would have escaped a writer 

 less critical and less able to estimate relative values, while, on the 

 other hand, a good deal of work which has formed the basis of 

 uncritical and even extravagant theories is here dismissed with 

 scant ceremony. Although the references to literature prior to 

 1905 have been greatly cut down, this volume contains some 6000 

 citations. It is almost incredible that any one author can have 

 actually consulted every one of these thousands of books and 

 papers. Hence, it is hardly surprising that one can detect a 

 sHght slip here and there. For instance, in the section deahng 

 with light intensity and its measurement, a footnote reference is 

 given, following the heading " Messende Methodik " (p. 534), to a 

 paper by Wiesner {Flora, Band 105, p. 127), which certainly does 

 not deal with methods of light measurement, though its title 

 (" Ueber die Photometrie von Laubsprossen ") might imply that it 

 does. p ^ 



