Japan Flora: Rhizomes short-creeping; culms 3-angled, sparingly scabrous above, 30-50 cm. long; leaves overtopping the culm, blades 1.5-2.5 mm. wide, slightly involute, sulcate, the basal sheaths bladeless, partially dark reddish purple, splitting into fibers; spikes 3 or 4, the upper 2-4 staminate, approximate, linear, 2-4 cm. long, pale to red­dish brown, the lower 1 or 2 pistillate, oblong, 1-2 cm. long, nearly sessile, the lowest bract leaflike, longer than the in­florescence, sheathless; pistillate scales deltoid-ovate, acute, pale ferrugineous; perigynia longer than the scales, 6-8 mm. long, oblong-ellipsoidal, ligneous, slenderly nerved, glabrous, the beak short, erect, thick, shallowly bilobed; stigmas 3, short.   Apr.-July. Wet places near tidal zone at mouth of rivers or in lagoons, below high tide level.

Hokkaido, Honshu, Shi­koku, Kyushu; common. Korea, Manchuria, Ussuri, Ryukyus, Formosa, and China.