358 



AUGUSTO BONAZZI 



inoculated with a pure culture of Azotohacter chroococcum. After 

 an incubation of nineteen daj^s at 30°C. the cultures were ana- 

 lyzed and found to give the values summarized in table 18. 

 Reference to the cultural notes shows that by far the better 

 growth was found in the nitrate cultures during the whole period 

 of incubation. 



An attack on the nitrate is here evident, without a quantita- 

 tive corresponding increase in the organic nitrogen. Further- 

 more a certain amount of nitrogen (that quantity w^hich failed 

 to be organized) is actually lost from solution. Although the 

 data are not quantitatively conclusive, their qualitative signifi- 

 cance is paramount. They establish an actual loss from the 

 solution in direct corroboration of the results of Hills. Since 

 the depth of the solution layer may be responsible for the low 

 nitrogen changes obtained, trials were made with extensive 

 surfaces of exposure. 



Experiment 32. Four large Fernbach flasks received 100 cc. 

 of Ashby's solution together with 0.5 gram CaCOs; two of these 



TABLE 19 

 Nitrogen fixed or lost by Azotobacter in absence or presence of nitrates 



flasks received 5 cc. of water while the other two received 5 cc. 

 of a 2.532 per cent solution of Ca(N03)2 + 4H2O. The flasks 

 intended for inoculation were sterilized and all the flasks then 

 received as infecting material equal amounts of a suspension of 

 Azotobacter chroococcum. After this the controls were sterilized 

 at the same temperature and pressure as the others. 



