230 Bacteria in Relation to Country Life 



but, also, on cultivated soils on which these crops have 

 been raised more or less extensively. The latter fact is 

 of considerable significance because it shows that the 

 introduction of artificial cultures into the soil may add 

 to it not only a large number of organisms, but also the 

 kind that are more vigorous and more efficient than those 

 already present there. In other words, there is every 

 indication that we may develop in the laboratory 

 strains of tubercle-bacteria of a higher degree of viru- 

 lence than is possessed by the bacteria in the soil. Future 

 investigations will teach us to utilize soil-inpculation 

 more extensively and more profitably by pointing out 

 to us the best condition and treatment for any particular 

 soil or crop. 



Soil-inoculation in the United States. — The history 

 of soil-inoculation efforts in the United States is, in 

 many respects, unique. As in Germany, the first at- 

 tempts at inoculation involved the application of legume- 

 earth as inoculating material. Crops like clovers, cow- 

 peas, field-peas, beans, and even vetches did not appar- 

 ently require any inoculation. As a rule, they grew on 

 new soils rather vigorously and produced the character- 

 istic nodules, thus indicating that the proper bacteria 

 are present in most soils. It was otherwise with at 

 least two leguminous crops, soybeans and alfalfa. Soy- 

 beans, originally introduced into the United States from 

 Japaii, did not do very well. They frequently failed to 

 develop that healthy, dark green color characteristic 

 of vigorous leguminous plants. Careful examination 

 showed their roots to be devoid of tubercles. Soybean 

 earth, straw and chaff were obtained from Japan and 



