Rhizobia entered the root via root hairs and formed infection threads. The nodules were exogenous in origin. A mature nodule consisted of four regions, namely apical meristem, bacteroid region, vascular region and nodule cortex. The vascular supply of the nodule consisted of 1-2 strands which branched and encircled the bacteroid zone as a skeletal mantle. The vascular bundles were amphicribral. The cortex of 8 week old nodules showed a layer of sclerids with heavily lignified walls. Degeneration of the nodule occurred due to the formation of a layer of suberized cells and appearance of tannin oodles at the base of the nodule.