vi PREFACE 



of botanical students with respect to tlie economic aspects of their 

 subject. We have again been at pains to illustrate the subject- 

 matter, as far as possible, by reference to British or commonly 

 cultivated plants, especially in that part of the book dealing with 

 the different groups. 



The index has been compiled with the greatest care, and includes 

 numerous subject-headings with a Adew to rendering the large 

 number of facts dealt with of the widest possible use. Some two- 

 thirds of the illustrations are original, and have been especially 

 prepared for this book. For a number of these we are indebted 

 to Mrs. F. E. Fritch, who is responsible for those initialled H. F. ; 

 the remainder are the work of one or other of the authors. The 

 source of all illustrations that have been copied is acknowledged 

 in the figure descriptions. For the use of the photograph 

 illustrating Fig. 222 we are greatly indebted to Prof. Bateson, 

 F.R.S., and Miss Pellehew. We also have to thank Mr. W. B. 

 Johnson for the photograph illustrating Fig. 200, Prof. F. W. 

 Oliver, F.R.S., for Figs 188-191, Mr. E. M. Cutting, M.A., for 

 Figs. 136- 13Q, the proprietors of the Indiarnhber Journal (through 

 the instrumentality of Mr. H. Wright, A.R.C.S.) for Fig. 79, 

 and Dr. H. C. I. Gwynne-Vaughan for permission to reproduce 

 Figs. 10-12. 



We are glad to have this opportunity of expressing our gratitude 

 to the following specialists, who have kindly read through various 

 sections of the manuscript and ofiered criticisms and suggestions : 

 Prof. A. E. Boycott, F.R.S. (the section on Bacteria), Mr. E. M. 

 Cutting, M.A. (the chapter on Fungi), Prof. F. W. Ohver, F.R.S. 

 (the Cycads and Pteridosperms), and Dr. F. G. Pope (chemical 

 sections). We are also indebted to the works of numerous 

 authorities on special branches of the subject, and, among these, 

 would especially mention that of Haas and Hill on Tlic Chemistry 

 of Plant Products, which we have repeatedly consulted in connec- 

 tion with the chemical matter. 



F. E. F. 

 E. J. S. 



London, 



May 1920. 



