Glabrous, glaucous perennial with short rhizome, or annual in unfavourable circumstances. Stems densely tufted, erect, rigid, quadrangular, strongly ribbed, smooth, 10-60 cm by ½-1 mm. Leaves of the flowering stems reduced to 2-3 obliquely truncate, membranous, ferrugineous or fuscous, 3-10 cm long sheaths, bladeless or the uppermost with a short, lanceolate blade; those of the sterile shoots filiform, c. ½ mm wide. Inflorescence consisting of a single terminal spikelet. Spikelet erect, ebracteate, globose, ovoid or oblong-ovoid, terete, obtuse, very densely many-flowered, dull brown, 6-15 by 4-6 mm; rachilla ragged by narrow wings. Glumes spiral, closely imbricate, membranous, oblong-ovate or oblong, very obtuse, with rounded apex, muticous, concave, faintly many-nerved (3 central nerves more prominent), 3-5 by 2-3 mm. Stamens 1-3; anthers linear, 1¼-1½ mm. Style subpersistent on the nut, flat, slightly dilated at the base which is nearly as wide as the nut, sparsely ciliate, dark brown, 2-3 mm; stigmas 2 or 3, much shorter than the style. Nut plano-convex or subterete, oblong-cylindrical, slightly curved, conspicuously stipitate, trabeculate by the hexagonal or transversely elliptic, slightly impressed epidermal cells in c. 9 vertical rows on either face, stramineous, 1½-2 by ½ mm; gynophore (stipe) spongious, (⅓-)½-1 long.
More
Annuals or short-lived perennials. Rhizomes poorly developed. Culms densely tufted, (8-)18-50(-60) cm tall, 4-angled, smooth, with few leaf sheaths at base. Leaves bladeless; sheath margin brown membranous, mouth obliquely truncate. Involucral bracts absent. Inflorescences reduced to a single terminal spikelet, ovoid to ellipsoid, 5-10 × 3-6 mm, many flowered, apex obtuse to rounded. Glumes densely spirally imbricate, pale brownish yellow, oblong, 3.5-5 mm, membranous, many veined, middle 3 veins thicker but abaxially not forming a keel, base sometimes narrower, apex not mucronate. Stamens 3; anthers linear, 1.2-1.5 mm. Style long and compressed, sparsely ciliate, basally gradually broader and nearly as wide as nutlet; stigmas 2 or 3. Nutlet pale brown, with a ca. 0.7 mm stipe, narrowly oblong, ca. 2.5 mm, biconvex, shiny and with obvious hexagonal reticulation. Fl. and fr. Sep-Oct.
On heavy soil in open, wet places: swamps, swampy grasslands, wet rice-fields, at low altitudes (usually below 300 m, in Sumba at 500 m, in Sumatra up to 1000 m).
Home
