FOREWORD 



It is with the greatest satisfaction that I follow the increasing 

 interest in America and England in the investigations concerning 

 growth substances in plants; indeed, a series of important con- 

 tributions to our knowledge about these substances originate 

 from laboratories in these countries. It is, therefore, a great 

 delight for me to have American friends translate my book 

 "Die Wuchsstofftheorie " into English. I want to express my 

 most sincere thanks to Professor George S. Avery, Jr., Dr. Paul 

 R. Burkholder, Dr. Harriet B. Creighton, and Miss Beatrice 

 A. Scheer, who have undertaken the troublesome and ungrateful 

 work, and who have likewise revised the text and brought it up 

 to date. I hope that the translation and revision may make 

 the book more easily available to American and English 

 colleagues and that it may also stimulate new studies on these 

 promising problems, as there are still so many points needing 

 further investigation. 



P. BoYSEN Jensen. 

 Copenhagen, 

 June, 1936. 



