281. Carex japonica Thunberg in Murray, Syst. Veg., ed. 14. 845. 1784.
日本薹草 ri ben tai cao
Rhizome short, with slender stolons. Culms laxly tufted, 20-40 cm tall, rather slender, compressed triquetrous, scabrous on upper angles, clothed with few brownish and bladeless sheaths at base, sheaths usually split into reticulate fibers. Upper leaves longer than culm, basal leaves usually shorter than culm, blades 3-4 mm wide, slightly stiff, flat, distinctly 2-veined laterally, scabrous on margins, sheathed. Involucral bracts leaflike, lower involucral bracts longer than subtending spike, upper 1 or 2 involucral bracts shorter than subtending spike, not sheathed. Spikes 3 or 4, rather remote; terminal spike male, linear, 2-4 cm, pedunculate; lateral spikes female, oblong-cylindric or oblong, 1-2.5 cm, densely many flowered, lower ones shortly pedunculate, upper ones sessile or nearly sessile. Male glumes pale, lanceolate, ca. 5 mm, membranous, 3-veined, greenish between veins, apex acuminate; female glumes pale or brownish, narrowly ovate, 2.5-3 mm, membranous, 3-veined, greenish between veins, apex acuminate. Utricles yellowish green or stramineous, obliquely patent, elliptic-ovate or ovate, slightly inflated trigonous, 4-4.5 mm, papery, glabrous, slightly shiny, obscurely veined, base broadly cuneate, apex abruptly contracted into a medium-sized to long beak, orifice hyaline-membranous on margins, shortly 2-toothed. Nutlets brownish, slightly loosely enveloped, elliptic or obovate-elliptic, trigonous, ca. 2 mm; style base slightly thickened; stigmas 3. Fl. and fr. May-Aug.
Shady and wet areas in forests, forest margins, ditch sides in valleys; 1200-2000 m. Hebei, Henan, Hubei, Jiangsu, Liaoning, Nei Mongol, Shaanxi, Shanxi, Sichuan, Yunnan [Japan, Korea].