Twenty Years of Plant Hormone Research 



F. W. WENT 



IN TALKING on the history of plant hormones, I want to trespass first 

 on the era before definite information on the subject was available. 

 It is most illuminating to see how many excellent starts were made 

 experimentally and theoretically before the overwhelming pressure of 

 evidence broke through the inertia of plant science as a whole, and plant 

 hormones became generally accepted as important factors in plant de- 

 velopment. I still remember an afternoon in 1933 when I was discussing 

 plant growth with some students and assistants of one of our big uni- 

 versities. Inadvertently I used the words "plant hormone" which im- 

 mediately illicited the condescending question, "Do you really believe in 

 plant hormones?" 



In and before the eighteenth century the biological sciences were still 

 predominantly descriptive, with only here and there some remarkable 

 inroads by the experimental method, such as were made by Stephen 

 Hale and Jan Ingenhousz. When we find here the first beginnings of the 

 hormone concept, it is merely descriptive without any vestige of experi- 

 mental evidence. Thus Duhamel Du Monceau makes descending sap 

 responsible for root formation, and Agricola is even slightly more specific 

 in that he talks about a "materia," or substance which causes root 

 formation. 



Then in the nineteenth century, after a period of contemplation or 

 Natur philosophic, botany unfolded into an experimental science. It was 

 largely the genius and untiring work of Julius Sachs which led to the 

 creation of a picture of the fife processes in the plant. 



These first years of plant physiology were largely given to analysis, 

 in which many processes inside the plant were studied separately without 

 trying to find links between them. There was so much to be done before 



