34 T O R R E Y A 



would be an understanding of the complex organic system in which they work 

 and which determines their effect. About this we still know ver}^ little. 



The problem may perhaps be stated somewhat more vividly by comparing 

 the operation of a developing organic mechanism with that of others more 

 familiar to us. A nickel inserted into a slot, for example, will activate a 

 turnstile or a juke box or a coin telephone. There is but little specificity in the 

 "stimulus'" but a great deal in the mechanism which it activates. If one knew 

 even.-thing about nickels and ho^\• the}' differ from other coins he still would 

 fail to understand how a nickel could produce these results, for an answer 

 to this question lies in the character of the reacting mechanism. In somewhat 

 the saine way, auxin produces one effect in one part of the developing organism 

 or under one set of conditions, and quite another elsewhere ; and the principle 

 of minimal surfaces may determine the position of new cell walls at one region 

 of the meristem but may be overruled by other factors in another. 



The developing organism is a patterned whole, the parts and activities of 

 which derive their particular character from their relation to this whole, 

 and should be studied in this relation and not only as independent structures 

 or processes. An understanding of this organized pattern and the way in which 

 it controls development and differentiation is the chief task of the science of 

 morphogenesis. 



osborx botaxical laboratory 



Yale Uxivtjisity 



Xew Ha\-ex, Coxxecticut 



