CONCLUSION. 585 



The work of distributional etiology must be carried on in close 

 coordination with the work of plant physiology. A knowledge of the 

 fundamental physiological features of a plant should go hand in hand 

 with an effort to investigate the features of physiological and ecological 

 behavior that do not lend themselves to laboratory experimentation. A 

 substantial advance in the investigation of the etiology of plant dis- 

 tribution would provide facts and methods of inestimable value in the 

 practice of agriculture, horticulture, and forestry. 



