How the Legumes Aid Us 269 



them have acquired characters that make it necessary that 

 that particular legume shall be their home and they do not 

 readily Hve on other species, though in some nearly allied 

 species the bacteria will transfer from one species to an- 

 other as it has been found that the bacteria that Hve 

 on the roots of the Medicago denticulata will also hve on 

 Medicago sativa^ or alfalfa, and that the form that lives on 

 the roots of Melilotus alba will also thrive on the alfalfa 

 roots. The bacteria that affect the vetches will also be 

 transferred from the garden pea, and all the true clovers 

 seem to be the home of a distinct form common to all of 

 them. 



A great deal has been written of late years in regard to 



the artificial culture of the various forms of bacteria that 



are parasitic on the roots of the different 



Artificial species of legumes. It was thought for a 



Inoculation ^ , , , i u t 



time that these laboratory cultures could be 



used in the inoculation of the seed or the soil for the 

 various legume plants with success. The Department of 

 Agriculture in Washington undertook the work of pre- 

 paring the cultures and distributing them to the farmers in 

 all parts of the country. Placed in sterilized raw cotton, 

 and with nutrient materials for promoting their growth 

 after being received by the farmers, many thousands of 

 cultures were distributed. 



But unfortunately, it was found that the bacteria on the 

 cotton were very short Hved, and there were more failures 

 than successes. Hence the use of the artificial cultures 

 has been generally abandoned, it being found more prac- 

 ticable to use the soil from a field that has already been 

 inoculated by long cultivation of the particular legume 



