抄録
In order to obtain further knowledge on the irregularities existing between soybean-and cowea-group, inoculation experiments, in which soybean plants were inoculated with strains of rhizobia isolated from various legumes belonging to cowpea group, were made. The type B of cowpea bacteria is added to the strains which infect soybean. That such various types as A, B, D and F of cowpea bacteria infect soybean shows the intimate relation between soybean and cowpea-group, but the proposal that both groups may be brought under one group is hardly acceped, because there are not few strains which are unable to infect soybean, and moreover, the type A of cowpea bacteria which is usually found in cowpea nodules is hardly isolated from soybean in the field. Concerning the finding that there are strains which are able to infect soybean in the type B of cowpea bacteria, it is considered that the strains of soybean bacteria (type A) may be isolated from cowpea nodule, because as described in the previous paper, some plants of cowpea group are easily infected with soybean bacteria (type A). And since it is proved that the infective power of rhizobia is not easily altered by first passage through plant other than their original hosts, the adoption of such strain as type B of cowpea bacteria which corresponds to type A of soybean organisms will make the relation between soybean-and cowpea-group be reciprocal. Consequently, it is easy to understand that one of the factors determining whether the relation between the two groups is reciprocal or not is the strains used as cowpea bacteria. When such strains as types A, B, D, and F which infect soybean as well as cowpea are used, the reciprocal relation will undoubtedly be established. The kinds of plants included in cowpea group are so diverse and each of them seems, more or less, differ in the range of strains of rhizobia with which they symbiose, respectively. The relation of soybean and the plants of cowpea group to the range of rhizobia is the other important factor.
