Japan Flora: The submersed leaves with blades linear-lanceolate, elongate, the floating leaves long-petiolate, oblanceolate to elliptic, 10-15 cm. long, rounded and decurrent at base, the stipules 5-10 cm. long; peduncles 10-15 cm. long, thickened above, bearing densely flowered spikes; nutlets 4, about 5 mm. long, narrowly winged on dorsal ridge. Apr.-Aug. Ponds.