364 



AUGUSTO BONAZZI 



To 250 cc. of the filtered solution were added 0.316 gram 

 Ca(N03)2 + 4H2O and 50 cc. were pipetted into each of several 

 250 cc. Erlenmeyer flasks of Jena glass, containing 0.5000 gram 

 of CaCOa weighed on an analytical balance. After steriUzation 

 and inoculation with a pure culture of Azotohacter chroococcum 

 the flasks were incubated at 30°C. for varying periods of time. 



Sugar determinations were made as wefl as determinations of 

 the dry matter in the cultures after acidifying with HCl; the 

 dry matter reckoned on the basis of the substance at 110°C. in 

 vacuum over P2O5. 



TABLE 24 



Although the evidence seems at first sight to throw a shadow 

 of doubt on the theory of phosphorus hunger in the filtered 

 cultures, closer analysis shows it to corroborate the conclusions 

 of Allen. 



The nitrate used was tested for phosphorus by means of the 

 ammonium molybdate reagent and found to be phosphorus free. 

 The attempt was also made to avoid secondary reactions on any 

 phosphates which might have passed through the paper by using 

 Ca(N03)2 instead of any other nitrate, but the aim might not 

 have been fully reached. And this in spite of the work of Cam- 

 eron and Hurst (1904) in which they found calcium nitrate to 

 depress the concentration of the PO4 ions in a solution of Ca3(P04)2 

 in presence of the sohd phase. 



III. DISCUSSION AND CONCLUSIONS 



Azotohacter chroococcum Beij. when grown in synthetic solu- 

 tions presents a complicated physiology. Its carbon relations 

 seem to vary with the age of the culture, and are deeply affected 



