34 Martin J. Prucha 



soil, all the plants developed nodules except the serradella and the lupine. 

 From this Helhiegel inferred that important differences must exist between 

 the nodule bacteria of the different legumes. 



Bej'erinck (1888) was of the opinion that the nodule-forming organisms 

 of the legumes belonged to one species, but that there were several groups 

 and in each group a number of varieties. From the results of his sub- 

 sequent investigation (1890) he was forced to change his former opinion. 

 He considered the organism of Ornithopus and that of Vicia to be two 

 distmct species. 



Frank's mvestigations (1899) led hmi to believe that there was only 

 one species among the nodule-forming orgamsms. 



Salfeld (1888) grew peas and horse beans in " Hochmoorboden," and 

 inoculated one part of them with sandy soil in which peas were gro^^^^ 

 and the other part with sandy soil in which lupines were grown. Both 

 the peas and the horse beans inoculated wdth the pea soil developed 

 nodules, while those inoculated with the lupine soil were free from nodules. 



Laurent (1901) could produce nodules on dwarf peas by inoculating 

 them with material from nodules of thirty different leguminous species, 

 but he claimed that the number, size, and appearance of the nodules 

 was influenced by the moculating material of the different sources. 



Kirchner (1896) grew about one hundred different species of legumes 

 in the Hohenheimer botanical garden. He observed that all the different 

 species of legumes developed nodules in the garden soil except the so}^ 

 beans, although these had been grown in the garden for ten years. The 

 soy beans did not produce nodules until they were moculated with soil 

 on which Japanese soy beans had been groT^^l. 



The investigations of Maze (1898) led liim to divide the nodule-forming 

 organisms into two groups — those adapted to a neutral or an alkaline 

 soil, and those adapted to an acid soil; the former infecting the plants 

 that favor neutral and alkalme soil, and the latter infecting the plants 

 that favor acid soil. 



Nobbe, Schmid, Hiltner, and Hotter (1891) undertook a very extensive 

 series of investigations on the general subject of nitrogen assimilation by 

 leguminous plants. Much of the present information on this subject is 

 due to these men, especially to Hiltner and Nobbe. Thej' showed that 

 the only way to study the relations between the nodule-forming organisms 

 of the different legumes and the different species and varieties of legumes 



