viii Preface 



not be restricted to small consolidations of already known phenomena. 

 Nor will it be restricted only to occasional and accidental discoveries 

 of really new applications. Instead technology may advance in a rapid 

 and orderly manner toward greater and greater efficiency in agricul- 

 ture at a time, now, when greater agricultural productivity is vital to 

 the peaceful progress of our overpopulated world. 



Grateful acknowledgment is made to Drs. J. van Overbeek and F. 

 Skoog for reading all of the manuscript critically, as well as to Drs. 

 J. Bonner, J. C. Crane, E. L. Rice, L. M. Rohrbaugh and G. F. Warren 

 and Professors C. L. Burkholder and R. Klackle for assistance and 

 suggestions concerning individual chapters. Special thanks are due 

 to Dr. S. P. Sen for much of the preparative work on the section 

 dealing with paper chromatography, to Mrs. Frances Scott Guernsey 

 for her abundant and enthusiastic help with the first draft, to Dr. 

 N. K. Ellis for encouragement, and to my wife, Keena, for being so 

 patient. 



The literature review for this book was concluded in June, 1954. 



Department of Horticulture A. Carl Leopold 



Purdue University 

 Lafayette, Indiana 

 July 14. 1954 



