"Mizutama-so" (Circaea mollis) belongs to Onagraceae (the Evening primrose family). It is a perennial herb that is native to various parts of Japan, as well as the Korean Peninsula, China and the Indo-China Peninsula. This herb grows in forests on mountains and fields, it can reach 20-60 cm in height. The nodes are tinged red-brown. The leaves are long-ovate to oblong and opposite with cuneatic bases. The small, white, bipetaled flowers bloom in the racemes atop of stems and axils from August to September. The fruits are broad obovate and covered with dense hooked hairs.