Japan Flora: Stems elongate; floating leaves broadly lanceolate to ovate-elliptic, 5-10 cm. long, (1.5-)2-4 cm. wide, petioles 6-10 cm. long, the submersed leaves lanceolate, long-petiolate, acute at both ends, minutely serrulate with projecting marginal cells; stipules 3-4.5 cm. long, thinly membranous, soon decaying; peduncles not thickened above; spikes 2-5 cm. long; nutlets 3-3.5 mm. long, ridged on the dorsal margin, the style short. June-Sept. Ponds and paddy fields.

Hokkaido, Honshu, Shikoku, Kyushu. Korea and China.