Annual, with fibrous roots. Stems solitary or tufted, compressed (elliptic in transverse section), trigonous just below the inflorescence, striate, gla-brous and smooth, 15-40(-75) cm by 1-2 mm. Leaves basal and 1-2 cauline in the lower ⅓ of the stem, ½ as long to about as long as the stems, flat or conduplicate, rigid, gradually attenuate, scaberulous on the margins near the apex, greyish green, 2-4 mm wide. Inflorescence capitate, semiglobose, dense, c. 1-1½ cm across. Bracts 4-6, unequal, patent (the lowest often erect), sheathless, not keeled, densely ciliate at the dilated base, the lowest much overtopping the inflorescence, up to 10(-20) cm long. Spikelets linear-lanceolate, acute, compressed, 2-flowered, ferrugineous, 4-5½ mm long; lower flower ♀, upper one ♂. Glumes 6, distichous, keeled, the 4th and 5th about equal in length. Bristles in the ♀ flower 6, rather thin, antrorsely scabrous, reaching the top of the style-base or slightly exceeding it, 3½-5 mm long, included by the glumes, in the ♂ flower wanting. Stamens 1-2; anthers destitute of pollen at the base, c. 1½ mm. Style shortly bilobed. Style-base strongly compressed, triangular, scabrous, stramineous, decurrent on the shoulders of the nut, c.¾ by ½ mm. Nut oblong, strongly dorsiventrally compressed, slightly concave on the adaxial face, whitish setulose to almost glabrous, blackish, the margins bordered by a whitish line, 2¼-3 by c. ¾ mm; epidermal cells minute, isodiametric.
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Annuals. Roots fibrous. Culms tufted, erect, 10-60 cm tall, slender, 3-angled, smooth. Leaves basal and 1 or 2 cauline in lower 1/3 of culm, 1/4-3/4 as long as culm; leaf blade linear, 2-2.5 mm wide, glabrous or pubescent, margin slightly involute, apex acuminate. Involucral bracts 3-6, leaflike, to 15 cm, base dilated and densely ciliate, apically slightly involute, sheathless, apex acuminate. Inflorescence a single terminal head, 1.2-2 cm in diam. Spikelets narrowly ovoid, 5-6 mm, shiny, 2-flowered. Glumes 6 or 7, rust-colored, ovate-lanceolate to elliptic-lanceolate; basal 3 or 4 empty, ± smaller; middle glumes ca. 4 mm, each with 1 female flower; apical 2 or 3 glumes each with a male flower. Perianth bristles 6, longer than nutlet and style base, antrorsely scabrous. Stamens 2 or 3; anthers linear, ca. 2 mm; connective slightly evident, reddish, pubescent. Nutlet blackish, linear-oblong, ca. 3.5 mm, sub-biconvex, whitish setulose to almost glabrous; persistent style base pale brown, ca. 1/2 as long as nutlet. Fl. and fr. Jun-Oct.
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