44 LUTHER BURBANK 



vital activities of animals and plants that the 

 sprinkling of the soil with bacteria seems almost 

 as commonplace a deed as the sowing of seed. 



This method, however, is obviously only an 

 accessory to the methods of the plant developer. 



It has exceptional interest as illustrating the 

 application of science to the art of agriculture, 

 but it has no direct association with the work of 

 the experimenter who develops plants by hybrid- 

 izing and selection. 



Just how the leguminous plants came to de- 

 Jvelop this anomalous habit of serving as hosts for 

 the particular types of bacteria that can aid them 

 by the extraction of nitrogen from the air, it is 

 difficult to understand. But the fact that they 

 have developed the habit is of very great im- 

 portance, because it enables these plants to enrich 

 the nitrogen content of the soil in which they 

 grow, instead of impoverishing it. 



By turning the clover under with a plow, the 

 farmer is enabled to restore to the soil an equiva- 

 lent of the nitrogen that was taken from it in a 

 preceding season by other crops. 



The importance of this will be obvious to any- 

 one who is aware that nitrogen is an absolute 

 essential as a constituent of a soil on which good 

 crops of any cultivated plant are to be grown, 

 and who further understands that the available 



