Studies of Bacillus Radicicola of Canada Field Pea 37 



from one legume does not cause nodules on another legume; (2) that 

 the organism from one legume may be trained to cause nodules on 

 any other legume. The evidence for the latter conclusion, however, is 

 not final. 



About 1895 a German company placed nitragin on the market — a pure 

 culture of the nodule-forming organism for inoculation purposes. The 

 cultures were propagated on gelatin and their preparation was based 

 on the results of the investigations of Nobbe and Hiltner. These cultures 

 were extensively tested both m Germany and in other countries, and, 

 as judged by the reports of these tests, the cultures proved only partially 

 successful. As a result of these adverse reports on nitragin, Nobbe and 

 Hiltner (1899 a) undertook to ascertain the cause of the low efficiency 

 of their cultures. They had already shown that the nodule-forming 

 organism can be trained to infect other legume species than that of its 

 host plant, when they trained the organism from peas to produce nodules 

 on beans and that from beans to cause nodules on peas. They went a 

 step further and demonstrated that the infecting power of the organisms 

 can be altered m degree. They stated that the propagation of the 

 organism on artificial media increases or diminishes the vitality, and 

 that in general nitrogenous media are mjurious to the vitality of the 

 organism. 



Moore (1905) also reports that as a result of numerous trials it has 

 been found that, although the bacteria increase most rapidly on a medium 

 rich in nitrogen, the resulting growth is usually of very much reduced 

 vitality, and when put into the soil these organisms have lost the ability 

 to break up into the minute forms necessary in order to penetrate the 

 root hairs. 



In a further study of this subject, Hiltner (1900) was led to believe that 

 this variableness in the infecting power of the nodule-forming organism 

 is the determining factor of the number and size of the nodules on every 

 plant when grown under otherwise favorable conditions. He took some 

 older plants that already had nodules on their roots, and placed them 

 in a nutrient solution without any nitrogen. Repeated inoculation 

 with its own organism did not produce any nodules on the new rootlets. 

 When fall came, and the leaves began to turn yellow and drop, and the 

 organisms in the nodules became weaker than those in the solution, 

 nodules began to develop on the rootlets. When Hiltner took older 



