BIOLOGICAL SOIL PROCESSES 



609 



Experiment XII. Nitrogen fixation in solution by pure cultures. Nitrogen in 

 milligrams per 100 cc. of solution. 



Anaerobes (oil) 



Mannite 



Ashby 



Winogradski 



Experiment XIII. Nitrogen fixation in solution by pure cultures. Nitrogen 

 in milligrams per 100 cc. of solution. 



Anaerobes 



Mannite 



Ashby 



Winogradski 



CULTURE NUMBER 



NITROGEN FIXED 

 UNDER OIL 



1.75 

 1.90 

 1.75 

 2.02 

 2.21 



NITROGEN FIXED 

 WITHOUT OIL 



2.63 

 2.63 

 2.32 

 2.39 

 7.21 

 3.54 



More nitrogen is fixed by the anaerobic organisms. More nitro- 

 gen is fixed by the anaerobic organisms when inoculated into 

 media with no oil added to insm-e anaerobic conditions than when 

 oil is added. In the last case more nitrogen is fixed by the anae- 

 robes without oil than is fixed by the aerobes. The Winogradski 

 medium seems to be the best for nitrogen fixation by pure cul- 

 tures. More nitrogen is fixed in Winogradski media than in 

 the other two materials used. 



