Japan Flora: culms 30-60 cm. long, 1-2 nun. thick; spikelets ellipsoid to broadly lanceolate, 7-15 mm. long, 3-4 mm. thick, ferrugineous; scales many, mem­branous, erect, deltoid-lanceolate, 3-4 mm. long, acute; achenes obovate, inflated-biconvex, 1-1.2 mm. long, the style-base del­toid, half as broad as the achene or narrower, the bristles 4, pale, rather firm, nearly 3 times as long as the body of the achene, not flexuous, somewhat densely scabrous. July-Oct. Wet places and shallow ponds in lowlands.

Honshu (Kanto Distr.)