on the three climatic factors here dealt with in a definite 

 way and apparently not subject to large variation due to in- 

 ternal conditions of the plants. Another possible method by 

 means of which to elimin ite the internal peculiarities of the 

 standard plant would be to grow the standard plant and plants 

 whose reaction to external conditions was to be expressed in 

 terms of the standard ujider the same set of environmental con- 

 ditions and to compare the growth rates. In this way ratios 

 between the standard plant and the plant 'vhose reaction to the 

 given set of environmental conditions is unknown would be se- 

 cured. We might then grow the standard plants in various en- 

 vironments and predict what growth would be made in those en- 

 vironments by plants whose relations to the standard plant 

 were known. 



