PREFACE TO THE SECOND EDITION. 



THE great advances made in the chemistry of Plant 

 Pigments since the issue of the first edition have neces- 

 sitated the re-writing of the section dealing with this 

 subject. For the rest, we have confined ourselves to 

 making a few minor additions and corrections and 

 adding a number of further references to the literature. 



P. H. 



July, 1916. T. G. H. 



PREFACE TO THE FIRST EDITION. 



THE importance to the botanist of a working knowledge 

 of chemistry can hardly be overestimated, since vege- 

 table physiology is replete with problems awaiting 

 solution by the combined application of botanical and 

 chemical methods. 



Teachers of vegetable physiology, however, not in- 

 frequently find that their students' knowledge is deficient 

 in just those branches of chemistry which are of parti- 

 cular importance to the botanist, which is, no doubt, 

 largely due to the fact that those compounds which are 

 of interest to the botanist do not necessarily fit into the 

 scheme of instruction of the chemist. 



The present work is an attempt to provide such 

 students, who are assumed to have some acquaintance 

 with chemistry, with an introductory account of the 

 chemistry and biological significance of some of the 

 more important substances occurring in plants. 



In compiling this book various sources of informa- 

 tion have been laid under contribution, and although 

 the point of view is, in the main, purely chemical and 

 botanical, the economic aspect has not been lost sight of, 

 and, where possible, mention has been made of the uses 

 of plant products and of the manufacturing processes 

 employed in their preparation. 



P. H. 



December. 1912. T. G. H. 



