Hemarthria compressa (L. fil.) R. Br.

Usually the culms are straggling among bushes or hedges. It is grazed and liked by all stock. It is a very variable species as to height and shape of the plant.

Hemarthria compressa is not completely distinct from H. altis-sima, but is generally a more slender plant with smaller spikelets.

Hemarthria altissima (Poir.) Stapf & Hubbard in Kew Bull. 1934: 109. 1934, is a species closely related to Hemarthria compressa which is centred upon Africa and the Mediterranean; it also occurs in America and there are a few isolated records from Burma, Thailand and Borneo. It is a rather more robust plant than Hemarthria compressa with the lower glume of the sessile spikelet 4-6 mm long. The callus is triangular and thus the species overlap to some extent, sometimes being difficult to separate with certainty. So far the identity of Pakistani material has not been open to question, but ,Hemarthria altissima may be expected to occur in Pakistan and should be looked for.

Culms ascending, basal part branching and rooting, creeping; the flowering culms up to 1 m high. Blade obtuse, glabrous, 5-10 cm long; ligule of a ring of short hairs; sheath glabrous, shorter than the internode. Spike single, terminal or axillary, sometimes several aggregated, 5-10 cm long; rachis and pedicel united, nearly as long as the sessile spikelet. Spikelets paired, one pedicelled and the other sessile. Sessile spikelets about 4 mm long, with a distinct callus of about 1 mm long, the spikelet sunken in a cavity tormed by the adnation of the rachis and the pedicel; glumes coriaceous; lower glume ovate-lanceolate, dorsally flat; upper glume boat-shaped, nearly as long as the spikelet; lower lemma about 3 mm long, membranous, epaleate, neutral; upper lemma slightly shorter than the lower lemma, enclosing a small upper palea; anthers about 2 mm long. Caryopsis ovate-orbicular, about 2 mm long. Distributed widely throughout India, Ceylon, Burma, Malaysia, China and Japan.

Stoloniferous perennial; culms up to 1 m long or more, postrate and rooting at the nodes below. Leaf-blades flat, 2-15 cm long, 2-5 mm wide. Racemes 2-8 cm long; internodes obliquely articulated. Sessile spikelet narrowly elliptic-oblong with a triangular callus; lower glume 3-4 mm long, obtuse to obscurely bidentate; upper glume acute, as long as the lower.

Perennial. Culms decumbent to long-stoloniferous, rooting at lower nodes, up to 1 m or more, much branched from base, nodes conspicuous, dark, glabrous. Leaf sheaths loose, compressed, keeled, glabrous or hairy along mouth, often shorter than internodes; leaf blades linear, 2–15 × 0.2–0.5 cm, base rounded, apex subacute; ligule 0.3–1 mm. Racemes solitary or few per node, lightly compressed, 2–10 cm, articulation line oblique, tardily disarticulating. Sessile spikelet slightly longer than adjacent internode, 3–5 mm; callus broadly triangular, 0.5–1 mm; lower glume narrowly oblong, leathery, flat or subconvex on back, abruptly constricted into obtuse or emarginate apex; upper glume adnate to rachis, equaling lower glume, thin, acute; lower floret 2.4–3.3 mm; upper floret 2–3.2 mm, palea small, rarely absent. Pedicelled spikelet 2.4–5 mm, lower glume narrowly obtuse, upper glume acuminate-caudate. Fl. and fr. Jul–Sep. 2n = 18, 27, 36.

Nepal, India, Ceylon, Burma, China, Malaysia.

Distribution: Pakistan (Sind, Punjab, N.W.F.P. & Kashmir); Iraq and Afghanistan through India to China, Taiwan, Indo-China and Thailand.

Fujian, Guangdong, Guangxi, Guizhou, Hainan, Nei Mongol, Shaanxi, Sichuan, Taiwan, Yunnan [Afghanistan, Bangladesh, Bhutan, India, Japan, Laos, Malaysia, Myanmar, Nepal, Pakistan, Sri Lanka, Thailand, Vietnam; SW Asia (Iraq)].

700-900 m

Fl. & Fr. Per.: July-September.

Marshes, wet places, coasts; below 2000 m.

Rottboellia compressa Linnaeus f., Suppl. Pl. 114. 1782 ["1781"]; Hemarthria coromandelina Steudel, nom. illeg. superfl.; H. glabra (Roxburgh) Blatter & McCann; H. laxa Nees ex Steudel; Manisuris compressa (Linnaeus f.) Kuntze; Rottboellia glabra Roxburgh.

Rottboellia compressa l. f., Suppl. 114. 1781; Honda, Monogr. 369. 1930.
Manisuris compressa O. Ktze., Rev. Gen. Pl. 2: 779. 1891.

Hemarthria compressa là một loài thực vật có hoa trong họ Hòa thảo. Loài này được (L.f.) R.Br. mô tả khoa học đầu tiên năm 1810.

扁穗牛鞭草（学名：Hemarthria compressa）为禾本科牛鞭草属下的一个种。