BACTERIA IN THE SOIL 



143 



I. The Denitrifying Bacteria. A group whose function 

 has been elucidated in recent years (largely by the investiga- 

 tions of Professor Warington) are held responsible for the 

 breaking down of nitrates. With these may be associated 



A METHOD OF GROWING CULTIVATIONS IN A VACUUM 

 OVER PYROGALLIC SOLUTION 



the Decomposition or Putrefactive Bacteria, which break 

 down complex organic products other than nitrates into 

 simpler bodies. 



2. The Organisms of Nitrification. To this group belong 



