Note on the Ability of Certain Strains of Rhizobi from Peas and Clover to Infect Each Other's Host Plants

The ability of nodule bacteria of the pea and of the clover groups to infect each other's host plants has been claimed (Wilson, 1939), but these two groups have usually been regarded as distinct and have indeed been given different specific names. The existence in each inoculation group of strains serologically related to some from the other group suggested that certain strains having a specific ability to cross-infect may exist in the two groups (Kleczkowski and Thornton, 1944). The following experiments were made to examine this possibility.