BACTERIA FIXING ATMOSPHERIC NITROGEN 135 



On the basis of serological investigation, Klimmer and Kruger 156 

 formed nine groups of legume bacteria: (1) Lupinus and Ornithopus, 

 (2) Melilotus, Medicago, and Trigonella, (3) Vicia (V. sativa), (4) 

 Pisum, (5) Vicia faba, (6) Trifolium pratense, (7) Phaseolus vulgaris, 

 (8) Soja hispida, and (9) Onobrychis sativa. 157 Other serological 

 studies 158 confirmed the general conclusion that the nodule bacteria 

 include more than one organism. 



The agar test-tube method may be used for the study of nodule forma- 

 tion on the roots of legumes by different strains of bacteria. 159 On the 

 basis of the cultural method, the nodule bacteria were divided into the 

 following groups: (1) alfalfa organism inoculating also Medicago lupu- 

 lina, M. denticulata and Melilotus, (2) clover organism inoculating all 

 species of Trifolium, (3) vetch and garden pea, (4) cowpea, (5) soybean, 

 (6) garden bean. Burrill and Hansen 160 demonstrated, by cross-inocula- 

 tion studies, eleven kinds of bacteria divided into three groups, namely: 

 (1) thin, scant, slow growth on ash-agar slant; little gum formed, 

 flagella easily demonstrated — Vigna, Cassia, Acacia, Glycine, etc.; (2) 

 more rapid and more abundant growth; glistening, opaque and pearly 

 white; considerable gum formed which interferes with attempt of 

 staining flagella — Melilotus, Medicago, Trigonella; (3) very fast, 

 spreading growth; watery and semi-translucent; very slimy and sticky, 

 due to excess of gum — Vicia, Pisum, Lens, Lathyrus, Trifolium, 

 Phaseolus and Strophostyles. 



Lohnis and Hansen 161 divided the bacteria of the leguminous plants 

 into two groups, the representatives of which differ both morphologi- 

 cally and physiologically. The first group shows all the features of 

 Bad. radicicola; it is peritrichic, grows relatively fast on agar plates and 



156 Klimmer, M., and Kruger, R. Sind die bei den verschiedenen Legumino- 

 sen gefundenen Knollchenbakterien artverschieden? Centrbl. Bakt. II, 40: 

 256-265. 1914; Klimmer, M. Zur Artverschiedenheit der Leguminosen-Knoll- 

 chenbakterien festgestellt auf Grund serologischer Untersuchungen. Centrbl. 

 Bakt. II, 55: 281-283. 1922. 



157 Simon, J. Uber die Verwandtschaftsverhaltnisse der Leguminosen-Wurzel- 

 bakterien. Centrbl. Bakt. II, 41: 470-479. 1914. 



168 Stevens, J. W. Can all strains of a specific organism be recognized by agglu- 

 tination? Jour. Inf. Dis. 33: 557. 1923; A study of various strains of Bacillus 

 radicicola from nodules of alfalfa and sweet clover. Soil Sci. 20: 45-66. 1925. 



169 Garman, H., and Didlake, M. Six different species of nodule bacteria. 

 Ky. Agr. Exp. Sta., Bui. 184: 343-363. 1914. 



160 Burrill and Hansen, 1917 (p. 126). 



161 Lohnis and Hansen, 1921 (p. 126). 



