354 AUGUSTO BONAZZI 



We thus see that the sugar lost from a culture in the early 

 stages of development passes through the cells in large quantities 

 and is transformed into compounds which do not form integral 

 part of the cells themselves but are dissolved in the medium. 

 The curves of CO2 production given by Krainsky (1908, 1910) 

 might indicate the close relation between this function and 

 growth, which is pointed to by the values of the ferment power 

 here obtained. 



This conception constitutes the conclusion to be drawn from 

 the discussion and closes, temporarily, the chapter on carbon 

 relations of Azotobacter. That it appears contrary to the con- 

 clusions of Krzmieniewsky and Omeliansky and Prazmowsky is 

 evident, but it should be remembered that their search for 

 soluble by-products was performed ten days after the start of 

 the experiments, — probably when they had been already utilized. 

 This is significant in view of the fact that we failed to find vola- 

 tile acids in our cultures in conformity with the findings of the 

 above mentioned investigators. 



Nitrogen relations — Attack on nitrates by Azotobacter 



The organism with which these investigations were undertaken 

 was an organism from the Wooster soils that when grown in 

 twenty-five cubic centimeters of Ashby solution (1 per cent 

 mannitol) in 150 cc. Erlenmeyer flasks and incubated for fifty- 

 nine days at a temperature of 28°C. possessed a low nitrogen 

 fixing capacity. 



Experiment 15. 



B-l check uninoculated (mgm. N2 found) 0.65 



B-3 inoculated culture (mgm. N2 found) 2.78 



Nitrogen fixed (mgm. ) 2 . 13 



Thus fixation calculated to the basis of 1 liter of solution 

 would give 85.2 mgm. fixed nitrogen; a quantity that represents 

 a fixation of 8.5 mgm. of nitrogen per gram of mannitol if we 

 assume all the mannitol to be utilized during the experiment. 



