CHAPTER II 



DEVELOPMENT OF THE HORMONE CONCEPT 



A. Correlation and Formative Substances 



The idea that the phenomenon of correlation is brought 

 about by substances or ''saps" is by no means new. No 



detailed consideration 

 need be given to the 

 very vague idea of Mal- 

 pighi (1675) nor to the 

 artistic conceptions of 

 Agricola (1716) of a 

 "materia ad radices pro- 

 movendas." Careful ex- 

 periments, however, 

 were carried out by 

 Duhamel du Monceau 

 (1758), whose sound sci- 

 entific reasoning led him 

 to conceive of correla- 

 tion as brought about 

 by two saps, one mov- 

 ing downward, the other 

 upward. The former 

 was elaborated in the 

 leaves and, after passing 

 downward through the 



Fig. 1. The first published drawings of cor- cortex, waS USed for the 



relations in plants. Swellings occur above but -. •-• f +V, 



not below ring wounds, and in isolated pieces nutrition 01 tne rootS. 



of bark they are most marked when leaves or Jf however this down- 



buds are present. (From Duhamel du ' , . ' x^^^^ 



Monceau, 1758.) ^^^^ Stream were niLei 



cepted by ringing or 

 other means, it caused the swellings, callus, and root forma- 

 tion which he observed above the point of interception (see 



6 



