Smooth Jointtail Grass

No specimens are known from China with paired sessile spikelets. There is some geographic division between forms that regularly have only a single sessile spikelet on each raceme segment and those with a pair. Forms from India to W Indonesia usually have paired sessile spikelets, whereas those from east of this area have single sessile spikelets. However, specimens from the west occasionally have few or no paired spikelets and are then indistinguishable from the eastern form. There is also much variation in the degree of fusion of the pedicel with the rachis internode.

Perennial. Culms tufted, erect, slender, 15–70 cm tall, usually unbranched. Leaf sheaths glabrous, often keeled; leaf blades linear, 8–25 × 0.1–0.4 cm, glabrous, apex abruptly acute; ligule 0.5–1 mm, glabrous. Racemes solitary, either terminal or also axillary, cylindrical, 5–10 cm × ca. 1.5 mm, sessile spikelets paired at each joint and separated by a pedicel, or triads present only at raceme base, or whole raceme with single sessile spikelets; rachis internodes clavate, 3.5–4 mm. Sessile spikelet 3–5 mm; lower glume oblong, smooth, or slightly sunken between lower part of veins, or ribbed throughout, rarely pitted, margins not winged, apex obtuse; upper glume boat-shaped, membranous, equal to lower glume; lower lemma slightly shorter than glumes, palea absent; upper lemma ca. 2.5 mm. Pedicelled spikelet minute or absent; pedicel linear, adnate to rachis internode, when paired sessile spikelets present the pedicel between them often adnate only at apex.

Shortly rhizomatous perennial; culms 20-100 cm high. Leaf-blades flat, 3-25 cm long, 2-5 mm wide, abruptly acute. Racemes terminal and axillary, 5-15 cm long. Sessile spikelet 3-4 mm long; lower glume narrowly oblong-elliptic, smooth, wingless. Pedicelled spikelet absent, the pedicel fused to the internode at its upper end.

Fujian, Guangdong, Guangxi, Hainan, Taiwan [India, Indonesia, Pakistan, Philippines, Sri Lanka, Thailand, Vietnam; Pacific Islands (Polynesia)].

Distribution: Pakistan (Punjab & N.W.F.P.); Afghanistan through India to Sri Lanka, Burma, Thailand and Indonesia.

Meadows, grassy hill slopes; 100–1000 m.