Japan Flora: Rhizomes nearly wanting; culms 30-60 cm. long, slender, smooth; basal sheaths obliquely truncate at apex, bladeless; inflorescence of 1-3(-5) radiate sessile spikelets, pseudolateral, headlike; bract 1, decurrent on the culm, erect, 5-8 cm. long, shallowly sulcate in front; spikelets ovoid to narrowly ovoid, 8-12 mm. long, 5-6 mm. across; scales ovate-orbicular, rounded at apex; achenes dark brown, lustrous, compressed-trigonous, broadly obovate, 2 mm. long, rugose; stigmas 3; bristles shorter or slightly longer than the achene, 6, retrorsely scabrous, brownish. Rather common in wet places; Hokkaido, Honshu, Shikoku, Kyushu. Korea and Manchuria.

var. ohwianus (T. Koyama) T. Koyama Culms terete, rather soft, opaque, indistinctly obtuse-angled; inflorescence of 3-9(^12) short- cylindric spikelets; achenes lenticular, unequally convex; style bifid; otherwise with the characters of var. hotarui.  Hon­shu, Shikoku, Kyushu. Ryukyus, Formosa, and China.