464 BOTANICAL GAZETTE [December 



reaction system (for example, X equilibrium), which arises as 

 the result of an inevitable sequence of events, determines what 

 general type of reaction shall take place at a given phase in the 

 life history. The by-product (for example, x 3 ) merely decides 

 which of a number of possible reactions within this general type 

 shall be the one chosen. . 



The origin of a given by-product was accounted for by chance 

 environmental conditions. The environment referred to may well 

 have been the external environment in the case of the simpler 

 organisms, but must be the internal environment in the more 



com 



sufficient 



inherit 



said to take place. 



University of Chicago 



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