944 



SOIL PHYSICS, CHEMISTRY AND MICROBIOLOGY 



C'ltyvcs showing the Fixation of Nitrogen and Decomposition of Sugar in mix- 

 ed cultures of Azotohacter chroococcum, and Clostridium Pasteurianum. 



i:r " 15 " 10 f5 30 



Gradual increase of the nitrogen fixed 

 Increase of the sugar decomposed. 



35 



^0 



to the quantity of sugar consumed, it represents the greatest degree of 

 efficiency. The efficiency of the bacteria dechnes rapidly during the three 

 following periods, after which, during the final period, it remains at nearlj^ 

 the same level. It may be said therefore that during the first periods of 

 growth of the bacteria in question in the non- nitrogenous medium, that is 

 to say, when the cells of the nitrogen fixers multiply energetically, their work 

 is most efficient. The im]:)ression of the low efficiency of the work of these 



+ N 

 microbes gained from examining the ratio — - at the close of the experi- 

 ment must be due tc the depressing influence resulting from the process 

 being in its last stages. 



TV .Physiology and Biology of Nitrogen- fixing Bacteria. — M. Omelianskij 

 has endeavoured to make a digest of the large amount of information contain- 

 ed in the literature, not systematised hitherto, in relation to the physiology 

 and biology of Azotohacter chroococcum, supplementing them by his own 

 researches. He deals with the following questions : methods of accumula- 



