BACTERIA OF THE SOIL 



287 



present time, however, efforts in this direction have largely 



failed, and recourse must be had to the transference of these 



bacteria through the natural soil in which they are found 



rather than by means of artificial cultures. Another problem, 



perhaps Utopian in nature, is to adopt these legume bacteria 



to .a life on the roots of 



other kinds of plants. 



For instance, if we 



could teach the legume 



bacteria to grow on 



the roots of corn, there 



seems no reason why 



we could not raise 



three hundred bushels 



of corn to the acre 



FIG. 59. Bacteroids from legumes, (i) From 



where we now raise Melilotus alba ; (2, 3, and 5) from Medicago 



sativa ; (4) from Vicia villosa (Harrison and 



Barlow). After Lipman. 



sixty. 



Some bacteria are 



able to fix the nitrogen of the air independent of any sym- 

 biotic relation with the legumes. It is quite likely that it 

 will develop that these organisms are, or may become, very im- 

 portant agents in the maintenance of soil fertility. Already 

 attempts have been made to cultivate these bacteria and put 

 them up in commercial form. If it should turn out that this 

 is possible, these living nitrogen gatherers could be bought 

 in the market and sown on the field, where they would fix for 

 plants the nitrogen from the inexhaustible supply in the air. 



