Preface viii 



some unavoidable repetition of material but this has been reduced by fre- 

 quent use of cross references. The book is designed primarily for reference, 

 though by means of such a presentation more teachers may be encouraged 

 to offer courses in this field. 



To many individuals the author is indebted for good counsel and as- 

 sistance in many ways. His thanks are due especially to his former col- 

 league Dr. Robert Bloch, who for some years collaborated with him in 

 the present project. Professor Ralph H. Wetmore has read a portion 

 of the manuscript and made valuable suggestions, as has the author's 

 colleague Prof. Arthur W. Galston for the chapter on Growth Substances. 

 Various problems have been discussed with many others, and to all 

 these the author is grateful. For the positions taken on particular issues 

 and the opinions expressed, however, he assumes full responsibility, as 

 he does for any errors of fact, attribution, or citation which may appear 

 and which are hard to eliminate completely from a book of this sort. 



For several years Mrs. Charlotte Reeder has assisted in compiling 

 information, in abstracting papers, and, through her genius for orderli- 

 ness, in keeping the project from bogging down under the sheer weight 

 of its material. To her the author is greatly indebted. Other assistants have 

 been associated with the work from time to time, and their help is 

 here thankfully acknowledged. 



For financial assistance, and especially for grants from the Eugene 

 Higgins Trust, the author wishes to express his gratitude to Yale Uni- 

 versity and its Provost, Edgar S. Furniss. 



The illustrations have been taken from the work of many individuals. 

 In every case the source from which they come has been acknowledged 

 in the caption, but the author here offers his further thanks for the privi- 

 lege of using them. For specific figures he is indebted to the editors of 

 Endeavour, the authorities of the Boyce Thompson Institute for Plant 

 Research, the Department of Plant Pathology of the University of Wis- 

 consin, Triarch Botanical Products, the W. Atlee Burpee Company, Dr. 

 G. R. Zundel, and Rutherford Piatt. 



This book has been a long time in the making. It proved to be such a 

 time-consuming task that the author was not able to bring it to com- 

 pletion until his retirement from academic duties a few years ago. He 

 hopes that this long period of ripening may have improved its quality 

 and increased its value to those who use it. 



Edmund W. Sinnott 



