126 PRINCIPLES OF SOIL MICROBIOLOGY 



of the organism, Beijerinck, termed it Bacillus radicicola. In view of the 

 fact that this is a non-spore forming organism and it is destroyed at 

 60° to 70°C, Prazmowski changed its name to Bacterium radicicola. 

 The fact that a number of races produce only a single polar fiagellum 

 led various investigators 112 ,u3 to classify the organism with the genus 

 Pseudomonas, under the name of Pseudomonas radicicola. E. F. Smith 114 

 and the Committee of the Society of American Bacteriologists (p. 58) 

 decided that the organism described by Frank 115 in 1879 as Schinzia 

 leguminosarum was the nodule forming organism and deserves priority; 

 the name of Bacterium leguminosarum or Rhizobium leguminosarum 

 was therefore suggested. It is doubtful, however, whether Frank 

 ever saw the nitrogen-fixing, nodule-forming organism. 116 According 

 to Lohnis and Hansen, 117 the nodule bacteria do not represent a special 

 genus Rhizobium, but are closely related to Bad. radiobacter, Bact. 

 lactis viscosum, Bact. pneumoniae and Bact. aerogenes, the last three 

 being immotile and the first motile. The species differ only to a slight 

 extent, in their physiological and morphological characters; the 

 branched cell forms (so-called "bacteroids") are common to all mem- 

 bers of the group of capsule bacteria, when tested adequately. These 

 closely related forms are well distributed in the soil and Bact. radio- 

 bacter may actually be present in the root nodules of leguminous plants. 

 On account of its resemblance to Bact. radicicola, it has been mistaken 

 for the nodule-producing organism in the cowpea-soybean group, since 

 it grows rapidly on the plates made from the nodules; however, it can be 

 differentiated from the latter by its brown growth on potato. 



Media. A number of media have been suggested, at various times, 

 for the cultivation of the organism causing the nodules on leguminous 



112 Moore, G. T. Bacteria and the nitrogen problem. Yearb. U. S. Dept. Agr. 

 for 1902, 333-342. 



113 Burrill, T. J., and Hansen, R. Is symbiosis possible between legume bac- 

 teria and non-legume plants? 111. Agr. Exp. Sta. Bui. 202: 115-181. 1917. 

 (Complete bibliography to 1915). 



114 Smith, E. F. Bacteria in relation to plant diseases. Washington, 2: 97- 

 146. 1921. 



118 Frank, B. Uber den gegenwartigen Stand unserer Kenntnis der Assimila- 

 tion elementaren Stickstoffs durch die Pflanze. Ber. deut. bot. Gesell. 7: 234- 

 247. 1889; Landw. Jahrb. 19: 523-640. 1890; also Frank, 1879 (p. 124). 



116 Kellerman, K. F. The present status of soil inoculation. Centrbl. Bakt. 

 II, 34: 42-50. 1912. 



117 Lohnis, F., and Hansen, R. Nodule bacteria of leguminous plants. Jour. 

 Agr. Res. 20: 543-556. 1921. 



