Japan Flora: Culms 5-40 cm long, often densely tufted, green, capillary or filiform, ribbed, 0.2-1 mm. wide, the sheaths somewhat reddish; spikelets lanceolate to narrowly ovoid, 3-8 mm. long, 1.5-2.5 mm. thick, sometimes proliferous at base; scales membranous, oblong to elliptic, 15-2.5 mm. long, obtuse, reddish; achenes obovoid, 0.7- 0.8 mm. long, obtusely 3-angled, yellowish green, lustrous, nearly smooth, the style base compressed, trigonous, 1/3-1/2 as broad as and 1/5니/3 as long as the achene, the bristles 6} usually slighdy longer than the achene, retrorsely scabrous. June-Oct. Common in wet places.

Hokkaido, Honshu, Shikoku, Kyushu. Korea, Manchuria, China, Formosa, and Philippines.

var. congesta. Plant more robust, achenes larger, 1-1.2 mm. long, with firm brisdes more or less densely scabrous, 1.5 times as long as the achene.  Honshu, Kyushu. India and Indochina.

var. thermalis (Hult.) T. Koyama. Culms short, spikelets very rarely proliferous, rather loosely flowered, scales somewhat keeled, dark sanguineous-fuscous; achenes olive-colored, 1.2 mm. long.  Hokkaido, Honshu, Shikoku, Kyushu; rather rare. Kamchatka.

var. nipponica (Makino) Ohwi Spikelets linear, sharp-tipped, 7-17 mm. long, 1.5-2.5 mm. thick; scales more obtuse than in the typical phase; achenes 1-1.3 mm. long, the style base ovate-deltoid, 炎-샀 as wide as the body of the achene；Honshu, Kyushu; rare.