H. B. Hutchinson 



105 



the time the first crop was remov^ed the plants with sugar and Azoto- 

 bacter had merely succeeded in equalling those in the control pots, but 

 the crop in sand and sugar which had been kept free from infection up 

 to the time of sowing was only one-third of the control. The j'ield of 



m 



^ 



Sand alone 



Sand + Hay 

 (sterile) 



Sand -l-Hay + Putrefactive 

 Organisms 



Sand + Hay + Putrefactive 

 Organisms + Azotobacter 



Fig. 3. Pot experiments on the utilisation of bay dust for nitrogen fixation. 

 Production of dry matter by second crop (Rye). 



rye, as a second crop, was distinctly better with Azotobacter, but by far 

 the largest proportion of nitrogen assimilated was found to remain in the 

 sand. It is, however, reasonable to suppose that this is due largely to 

 the fact that putrefactive organisms were not supplied to these sugar 



