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A dwarf-annual with very slender root-system and numerous densely set culms. Culms 1-12 cm long and 0.2-0.3 mm thick, angular, often curved. Sheaths 2 above the prophyll, the basal usually purple and truncate, the upper paler and ending in an arrow lanceolate lobe. Spikelet ovate to broadly lanceolate, 2-4 mm long and 1- wide. Inflorescence-bract lacking and consequently all glumes are fertile. Glumes about 1 mm long, dark reddish brown (but lower glumes sometimes very pale) with a very distinct green midrib ending in or near the obtuse tip, with or without an arrow pale margin; the glumes much spreading at maturity to expose the nutlets. Perianth-bristles usually present, shorter than the nutlet, barbellate with recurved spine-like teeth, usually 4-5 but sometimes lacking. Stamens 2. Style-branches 2. Nutlet about 0.5 mm long and 0.4 mm wide, broadly obovate, flattened, smooth and very shiny; when young whitish-yellow or pale brown, when mature black; appendage greyish, minute, flattened.
Dwarf annual. Stems tufted, erect or curved, capil-lary, angular-sulcate, smooth, 4-15 cm by ¼-⅓ mm. Sheaths appressed, purplish or brownish at the base, the apex of the uppermost oblique, often attenuate. Spikelet oblong-ovoid, obtusish, somewhat angular, densely many-flowered, 2-4 (finally lengthening to 8) by 1½-2 mm. Glumes membranous, at length more or less spreading, elliptic, obtuse, keeled, 1-nerved, with green keel and pale or more or less purplish sides, 9/10-1⅓ by ½-7/10 mm. Bristles 3-4(-6), slender, minutely retrorsely scabrous to almost smooth, shorter than to about as long as the nut, whitish, translucent, not rarely vestigial or absent. Stamens 1-2; anthers linear or oblong-linear, mi-nutely apiculate, ¼-⅓ mm long. Style 2-fid. Nut biconvex, obovate, smooth, shining, black, ½-⅔ by ⅓-2/5 mm epidermal cells very inconspicuous. Style-base minute, flattened, strongly depressed, disciform or depressed-conical, ¼-⅓ as wide as the nut.
Plants tufted, without creeping rhizomes. Culms 2–12(–19) cm × 0.2–0.4 mm. Leaves: distal leaf sheaths firm, distally tightly sheathing, apex acute. Spikelets ovoid to ellipsoid, 2–6(–8) × 1–2.5 mm, apex acute; proximal scale with or without flower, not amplexicaulous; floral scales to 100, 15–19 per mm of rachilla, often loosely appressed, dark red-brown to stramineous, ovate to elliptic, 0.6–1.3 × 0.3–0.7 mm, membranous, apex rounded to acute. Flowers: perianth bristles (0–)4–6, typically 4, colorless to whitish, vestigial to 1/2 as long as achene, smooth or spinuliferous; styles 2-fid. Achenes black, obovoid, biconvex, 0.3–0.5 × 0.3–0.4 mm, apex often constricted proximal to tubercle, smooth at 40X. Tubercles stramineous to whitish, umbonate to subconic, 0.1–0.2 × 0.1–0.2 mm, apex acute. 2n = 20.
