SUMMARY: Strains of from a wide variety of host plants were found to possess either a complete or a reduced life cycle. In the former, which was characteristic of strains from certain wild legumes and garden flowers, the bacteroids within the nodule were branched and septate; the free-living stages included small Bacterium-like forms which were responsible for infection of the host plant, and large, occasionally Gram-positive forms resembling , which produced both specialized, coceoid swarmers and resistant endospores. The reduced cycle was commonly found in from cultivated field crops. The bacteroids were single cells of irregular outline; the free-living stages were reduced to the Bacteriumlike stage alone, sometimes so actively motile as to perform the function of swarmers. This condition is regarded as degenerate and due to a parasitic habit. The mode of formation of the endospores, which differs in detail from that of , is described. The morphology of various stages in the life cycle and a slight tendency to Gram-positivity render it apparent that is a specialized genus of Bacillaceae. probably related to the plant parasitic group, with which it also has biochemical affinities.


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