The Scope of this Book 



point of view has been the application of phenyl- butyric acid as 

 a reagent in physiological research. This had not been 

 so employed when the first edition was written. 



The chief changes since the writing of the first edition have 

 been of horticultural value and interest, with one exception. 

 In 1937 the principal application of synthetic growth sub- 

 stances related to the treatment of cuttings; other develop- 

 ments were foreshadowed, but had not been extensively 

 tested. Since then the treatment of seeds with growth- 

 substances has occupied the attention of a number of workers, 

 the use of the synthetics in grafting has become more than a 

 suggestion, and the questions of bud-inhibition and retarda- 

 tion of flowering have assumed practical importance. These 

 developments are at least sketched in the present edition. 



It is hoped, therefore, that the present book may be useful 

 to horticulturists as well as to chemists. The horticulturist 

 will probably get on reasonably well with the book if he skips 

 Chapters X, XIII, and XIV, and some other bits. 



Chapter IV on applications of growth-substances to the 

 rooting of cuttings and the production of such freak results 

 as the formation of roots on stems has been maintained in 

 its original form. Some of the work mentioned in this chapter 

 already has not much more than a historical significance, 

 but it has been felt that, historical as they are, such results 

 provide a fairly easy introduction to the more recent practical 

 uses described in later chapters. 



The first edition was written in November 1937 (which 

 accounts for some omissions), but could not be published until 

 July 1938. Now (May 1940) the book is being revised and 

 extended with a view of the second edition appearing in the 

 early autumn of 1940. It is not possible to mention every 

 application or to keep strictly up-to-date in a book, but 

 because it is desired to give here as good service as possible, a 

 hint may be offered to those who desire to keep fully informed 

 of developments soon after they are made. 



It is possible, though relatively expensive, for an individual 

 to keep up-to-date if he has no access to libraries. Chemists 

 will not need to be reminded of such abstracting journals as 



21 Bl. 



