Acrachne racemosa (B. Heyne ex Roth) Ohwi

Nile region.

Throughout the Old World tropics.

Introduced weed of maize, naturalized.

Annual.

This species is a good forage grass.

A sporadic monsoon grass, reported to be a good fodder grass for cattle.

Culms tufted, erect or geniculately ascending, 8–50 cm tall. Leaf sheaths glabrous, compressed; leaf blades narrowly lanceolate, 7–20 × 0.3–1 cm, soft, adaxial surface tuberculate-pilose at base, tapering to a setaceous apex. Inflorescence subdigitate or racemes arranged along a central axis up to 15 cm; racemes mainly grouped in pseudo-whorls or pairs, 4–12 cm, ascending. Spikelets densely imbricate, oblong with serrate outline, 6–10 mm, florets 6–20, stramineous at maturity; glumes papery-membranous; lower glume narrowly oblong, 1.2–3 mm, apex acute, mucronate; upper glume lanceolate, 1.5–3 mm, acuminate, awn-pointed; lemmas broadly ovate, 2–3 mm, keel scabrid, shallowly concave above middle and excurrent into a stout 0.5–1 mm awn-point, lateral veins also fractionally excurrent. Grain blackish, rugose, surface finely granular. Fl. and fr. autumn. 2n = 36.

Tufted annual; culms 15-75 cm high, erect or geniculately ascending. Leaf-blades 7-20 cm long, 5-11.5 mm wide, soft, glabrous or sparsely pilose on the upper surface, rounded at the base, tapering to a fine hair-like tip. Inflorescence composed of several to many slender ascending secund spikes 1.5-10 cm long. Spikelets 6-25-flowered, 5.5-13 mm long, closely overlapping, whitish-green or brownish; glumes unequal, the lower 1.2-3.0 mm long, acute and mucronate, the upper 1.5-3.0 mm long, acuminate and awned, the awn one- to two- thirds as long as the glume; lemmas narrowly ovate in profile, 2-2.8 mm long with a stout awn-point 0.3-0.9 mm long.

Hainan, Yunnan [Afghanistan, India, Indonesia, Myanmar, Pakistan, Sri Lanka, Thailand, Vietnam; Africa, SW Asia (S Arabia), N Australia, Pacific Islands; introduced in the West Indies].

Distribution: Pakistan (Punjab, N.W.F.P. & Kashmir); tropical Africa, Southeast Asia and Australia.

Field margins, river banks; 300–900 m.

Eleusine racemosa B. Heyne ex Roemer & Schultes, Syst. Veg. 2: 583. 1817; Acrachne verticillata (Roxburgh) Wight & Arnott ex Chiovenda; Eleusine verticillata Roxburgh; Lepto-chloa racemosa (B. Heyne ex Roemer & Schultes) Kunth; Sclero-dactylon micrandrum P. C. Keng & L. Liu.

Annuals, Terrestrial, not aquatic, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath or blade keeled, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Leaf blades more or less hairy, Ligule present, Ligule a fringed, ciliate, or lobed membrane, Inflorescence terminal, Inflorescence with 2 or more spikes, fascicles, glomerules, heads, or clusters per culm, Inflorescence a panicle with narrowly racemose or spicate branches, Inflorescence a panicle with digitately arranged spicate branches, Inflorescence with 2-10 branches, Inflorescence branches more than 10 to numerous, Inflorescence branches 1-sided, Lower panicle branches whorled, Rachis angular, Flowers bisexual, Spikelets sessile or subsessile, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 3-7 florets, Spikelets with 8-40 florets, Spikelets solitary at rachis nodes, Spikelets paired at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Spikelets secund, in rows on one side of rachis, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes distinctly unequal, Glumes shorter than adjacent lemma, Glumes keeled or winged, Glumes 1 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 3 nerved, Lemma glabrous, Lemma apex acute or acuminate, Lemma mucronate, very shortly beaked or awned, less than 1-2 mm, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea membranous, hyaline, Palea shorter than lemma, Palea about equal to lemma, Palea 2 nerved or 2 keeled, Palea keels winged, scabrous, or ciliate, Palea auriculate or bowed out at base, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Đối với các định nghĩa khác, xem Mần trầu (định hướng).

Mần trầu tầng (danh pháp khoa học: Acrachne racemosa) là một loài thực vật có hoa trong họ Hòa thảo. Loài này được (Heyne ex Roth) Ohwi mô tả khoa học đầu tiên năm 1947.

尖稃草（学名：Acrachne racemosa），为禾本科尖稃草属下的一个植物种。