Abstract:Microscopic examination shows that Robinia pseudoacacia seedlings inoculated with rhizobia produces a variety of root hair forms. Part of the root is much swollen with long and thick root hairs around until form of nodules. Observation of TEM on the ultrastructure of swollen root parts indicated that there is a large amount of wall ingrowths which are well developed on the extangential wall of common epidermal cells among hairy cells. It is verified that these epidermal cells with wall ingrowths are transfer cells induced by rhizobia on root epidermal cells of Robinia pseudoacacia.