"Saikachi" (Gleditsia japonica) belongs to the Fabaceae (the Legume family). It is a tall deciduous tree that is endemic to Japan, and distributed Chubu district of Honshu south to Shikoku and Kyushu. This tree grows in fields, mountains and stream banks and can reach about 15 m in height. It has acute spines on the trunks and branches. Leaves are alternate, pari-pinnately or bipari-pinnately compound, and the leaflets are oblong. During May to June, racemes with pale yellowish-green flowers are seen on the termial branches. Fruits are legumes 20-30 cm long. The seed contains saponin, it had been used as a soap from old times.