The rhizobia from Robinia pseudoacacia, Sophora viciifolia, Wisteria sinensis and Amorpha fructicosa were peritrichously flagellated and fast growing, with a serum zone formed in litmus milk culture and acid produced on YEM media. The host legumes are of temperate zone origin. Those from Acacia auriculaefor-mis, Dalbergia odorifera, Albizia chinensis, A. julibrissin and Samanea saman were of polar or subpolar flagellum and grew slowly, with their strains forming no serum zone in litmus milk and no acid produced on YEM media. The host legumes are of tropical origin.Therefore, the root nodule bacteria of tree legumes should also belong to two different genera: Rhizobium and Bradyrhizobium. This classification is generally in keeping with the new one put forward by Sordan.