LEGUMES IN GENERAL 249 



for many leguminous crops. Under certain conditions 

 the partnership between the plant and the bacteria, even 

 though the latter are present, is not perfected. When 

 the soil contains nitrogen in large amounts, the plant 

 draws its supply from the soil, and the bacteria lose many 

 of their activities and put forth little effort to penetrate 

 the plant root. It is not usually desirable, therefore, to 

 use nitrogenous fertilizers in connection with leguminous 



Fig. 87. — Applying lime to the land. 



crops. Sometimes, however, when the soil is especially 

 deficient in this element, a light apphcation of nitrate 

 of soda is beneficial in starting the plants so that they may 

 make suflicient growth for the forming of symbiotic re- 

 lations with the bacteria. 



The bacteria are distributed over the country in various 

 ways. The most important agencies are wind, water, and 

 the transportation of hay and seeds. The diminutive 

 size of the bacteria makes possible their wide distribution 

 by the wind in connection with small particles of soil, 

 leaves, and other vegetation. The water also carries 

 them long distances in the time of high water. The ship- 



