Japan Flora: Stems elongate, branched, rather densely leafy; floating leaves not developed, the submersed broadly ovate to broadly lanceo­late, 2-6 cm. long, 1-2.5 cm. wide, obtuse to acute, deeply cordate and perfoliate at base, entire and somewhat undulate, 3-nerved and with 2 veinlets between the nerves; stipules thinly membranous, soon withering or caducuos; peduncles slightly thickened above; spikes densely flowered, 1.5-25 cm. long; nutlets about 3 mm. long, broadly obovate, with an en­tire ridge at the back; style short. June-Sept. Ponds and shallow rivers;

Hokkaido, Honshu, Shikoku, Kyushu. Eurasia，North America, Australia, and Argentina.