Division of peribacteroid membranes in root nodules of white clover

Division of peribacteroid membranes in the cytoplasm of root nodules of white clover was found, from a study of serial thin sections prepared for electron microscopy, to accompany division of the bacteroids. It was also observed that the peribacteroid membranes appeared to have adhered to various sites on the surface of the bacteroid envelope outer membranes. Wherever peribacteroid membranes were constricted as though undergoing division in the region of the cleft formed by partial division of the bacteroids, these constrictions could be related to the point of adhesion of the peribacteroid membranes to the surface of the bacteroids within the cleft. It was concluded that adhesion of the peribacteroid membranes to the bacteroid envelope outer membranes is likely to be a critical element in the process of division of the peribacteroid membranes. Differences in the degree of adhesion between peribacteroid membranes and the bacteroid envelope outer membranes may explain variations in the number of bacteroids enclosed by peribacteroid membranes in nodules of different legumes.