136 PRINCIPLES OF SOIL MICROBIOLOGY 



changes milk characteristically; it produces nodules on the roots of 

 clover, sweet clover, alfalfa, vetch, pea, navy bean, lupine, black locust, 

 Amorpha and Strophostyles. The second group is characterized by 

 monotrichic flagellation, comparatively slow growth on agar plates, 

 and inability to cause a marked change in milk. It has been isolated 

 from the soybean, cowpea, lima bean, peanut, beggarweed, Acacia, 

 Genista Cassia and Amphicarpa. However, they do not suggest sepa- 

 rating the organism into two new species before the complete life his- 

 tory of the two groups is known. 



Bergey, 162 following the system proposed by the Society of American 

 Bacteriologists placed the Bad. radicicola in a separate genus 

 "Rhizobium," and separated the different forms into two species: 



(1) Rh. leguminosum Frank, inoculating Pisum, Vicia, Lathyrus, etc., 



(2) Rh. radicicolum Beij. of Trifolium, Phaseolus, etc. 



The following is a list of leguminous plants, divided on the basis of inter- 

 inoculation. 163 The different members in any one group are those which can be 

 inoculated by the strain of the Bact. radicicola specific for that group. 



Group I: Group III: 



Trifolium pratense, red clover Vigna sine7isis, cowpea 



Trifolium hybridum, alsike clover Cassia chamaecrista, partridge pea 



Trifolium alexandrinum, bersem Arachis hypogoea, peanut 



clover Lespedeza striata, japan clover 



Trifolium incarnalum, crimson clover Mucuna utilis, velvet bean 



Trifolium repens, white clover Baptisia linctoria, wild indigo 



Trifolium medium, zigzag, or cow Desmodium canescens, tick trefoil 



clover Acacia armata, acacia 



Group II: Genista tinctoria, dyer's greenwood 



Melilotus alba, white sweet clover Phaseolus lunatus, lima bean 



Melilotus officinalis, yellow sweet Group IV: 



clover Pisum sativimi arvense, Canada field 



Mcdicago sativa, alfalfa pea 



Medicago hispida, bur clover Vicia villosa, hairy vetch 



Medicago lupulina, black medick, or Vicia sativa, spring vetch 



yellow trefoil Vicia faba, broad bean 



Trigonella foenum-graccum, fenu- Lens esculenta, lentil 



greek Lathyrus latifolius, sweet pea 



162 Bergey, 1923 (p. x). 



163 Hansen, R. Symbiotic nitrogen-fixation by leguminous plants with special 

 reference to the bacteria concerned. Scientific Agriculture (Canada) 1: 59-62. 

 1921; Whiting, A. L., Fred, E. B., and Helz, G. E. A study of the root nodule 

 bacteria of wood's clover (Dalea alopecuroides). Soil Sci. 22: 467-476. 1926. 



