Studies of Bacillus Radicicola of Canada Field Pea 35 



was to use pure cultures of the organisms for inoculation purposes, and 

 not the soil infusions as was done by a number of previous investigators. 



In a subsequent paper, Nobbe, Hiltner and Schmid (1895) arrived at 

 the following important conclusions on the relation of nodule-forming 

 organisms to the different species of legumes: 



" The infecting power of the nodule bacteria of the various groups 

 and species of legumes cannot be differentiated absolutely, but only in 

 degree. The pure cultures from nodules of different species of legumes 

 do not represent different species, but only different forms. We have 

 not the least doubt that all the nodule bacteria of the different legumes 

 we have studied, even those of Mimosse, are one species, all belonging 

 to Bacillus radicicola of Beyerinck. These bacteria, however, are 

 influenced by the plants in whose roots they live to such a degree that 

 their descendants are able to infect readily only that species of legumes 

 to which the former host plant belonged, at the same time losing partly 

 or completely the power to infect other species of legumes. When the 

 legume is grown in a suitable soil, nodules will develop on the roots 

 only when either those nodule bacteria are present which have lived 

 previously on that legume species, or when the neutral nodule bacteria 

 are present. The latter will be found in the soil where legumes have never 

 been grown or where they have not been grown for a long time. If one 

 legume is preponderantly grown in a soil, most of the neutral bacteria 

 become influenced by this legume, and when a different legume is planted 

 which is not closely related to the former no nodules will be formed, or 

 only very few and faulty ones, and these will appear so late that they 

 will be of very little value to the plants."^ 



By means of extensive experiments (Nobbe and Hiltner, 1896) it has 

 been demonstrated that effective inoculation is obtamed only when the 

 plants are inoculated with bacteria from the nodules of the same species 

 of legumes. 



Moore (1905) conducted extensive cross-inoculation experiments, and 

 maintains that "it is possible to cause the formation of nodules upon 

 practically all legumes, no matter what was the source of the original 

 organisms, provided they were cultivated for some time upon a synthetic 

 nitrogen-free medium." He states further: "It is undoubtedly true that 

 the long adaptation of the bacteria to the special conditions obtaining 



^ TranslatioQ from the original German. 



