Japan Flora: Peren­nial, terrestrial or sometimes aquatic; aerial stems terete, red­dish, pubescent, the basal stems creeping and branched, 10-30 cm. long or much longer in the aquatic phase; aerial leaves verticillate in 5’s to 8’s, spreading, the pinnatifid segments linear or narrowly lanceolate, 1-2 cm. long, 3-7 mm. wide, acute, glabrate; aquatic leaves 2 or 3 times pinnately dissected into filiform segments; flowers solitary in axils, sessile or nearly so; calyx 5-7 mm. long, 5-cleft, loosely pubescent at base, the lobes lanceolate; corolla rose-purple, 6-10 mm. long, tubular; capsules ovoid-globose, about 4 mm. long; seeds oblong, terete, about 0.6 mm. long. Paddy fields, shallow ponds, and ditches in lowlands.

Honshu, Shikoku, Kyushu; common. Korea, Ryukyus, Formosa, China to India.