ORGANIC MATTER AND NITROGEN 225 



agricultural significance, because they develop only in the absence 

 of free oxygen. 



Third, is the azotobacter, an aerobic group described by Beijer- 

 inck in 1901, of which Lipman has recently found some additional 

 species, one of which (Azotobacter vinelandii) appears to be quite 

 active in the fixation of free nitrogen when the best artificial condi- 

 tions are provided. (See Lipman's " Bacteria in Relation to Coun- 

 try Life," page 199.) 



Beijerinck has found, " as a result of improved technique for the 

 determination and study of the distribution of the organism, that 

 azotobacter fixes nitrogen, and that there is a distinct relation 

 between the distribution of this organism and leguminous plants." 

 The author questions if there may not be a relationship between the 

 legume bacteria and the azotobacter. (See Experiment Station 

 Record, 1909, Vol. 20, page 920.) 



Whether any of these nonsymbiotic bacteria are of appreciable 

 agricultural importance under practical conditions, is not fully 

 established. It is known, however, that a supply of organic matter 

 is essential for their development, and the organic matter of the 

 soil which must be decomposed in order to furnish their necessary 

 supplies of carbonaceous food may also furnish part or all of the 

 nitrogen which they require. (See also pages 434-440.) 



