360 



AUGUSTO BONAZZI 



Experiment 1^7. A solution prepared according to Gerlach 

 and Vogel constituted the basal medium. 



Deep well water 500.00 cc. 



K2HPO4 0.25 gram 



NaCl 0.25 gram 



FeS04 + 7H2O 0.01 gram 



Glucose 5.00 grams 



To 250 cc. of this medium 0.316 gram Ca (N03)2 + 4H2O 

 were added. Fifty cubic centimeters of the nitrate solution 

 and of the nitrate-free solution were placed in very large petri 



TABLE 21 

 Nitrate attack by Azotobacter chroococcum 



* Calculated from experiments 46 and 49 made with the same solutions. 



dishes which had been sterilized with 0.5 gram CaCOa. Inocu- 

 lation of some of the dishes with a pure culture of Azotobacter 

 chroococcum was followed by incubation for twenty-four days at 

 25°C. The analytical results obtained are summarized in 

 table 21. 



