H. B. Hutchinson 



101 



received in addition a similar quantity of a suspension of a pure culture 

 of Azotobader chroococcum. The bottles were stored in the laboratory 

 at 15-20°, with occasional shaking, for six weeks, and their contents 

 were then returned to the corresponding vegetation pots. From this 

 time no special precautions against infection were observed excepting 



■a 



o 



Spring application. 

 1907-1909 



Autumn application. 

 1910 and 1911 



□1 



Straw 



Grain 



Fig. 1. Effect of carbohydrates on the yield of barley. 

 1907-1911. Relative yields. 



Hoos Field experiments, 



that any seeds sown in the pots were previously treated with dilute 

 mercuric chloride solution and only sterilised water was used for main- 

 taining the water content of the sand. 



Barley was grown as a first crop, five seeds being sown in each pot on 



