The Ritha tree (Sapindus mukorossi) belongs to Sapindaceae (the Soapberry family). It is a tall deciduous tree that is distributed westward from Chubu district of Honshu to Shikoku and Kyushu in Japan, as well as throughtout Asia. This tree can reach about 15 m in height. The barks are pale yellowish-brown, smooth and peel when mature. The leaves are pari-pinnately compound with 4-6 pairs of narrow-oblong leaflets. It is monoecious. The terminal panicles are borne and bloom numerous small yellowish-green flowers in June. The fruits are drupes and ripen in fall. The endocarps contain saponin and used as substitute for soap in former days. In Taiwanese Huayu, it is called "無患子" and in Chinese "無患子" (wu huan zi).