西藏须芒草 xi zang xu mang cao

Andropogon gyirongensis L. Liu; A. hookeri Munro ex Hackel; A. tristis Nees ex Hackel; A. yunnanensis Hackel; Cym-bopogon hookeri (Munro ex Hackel) Stapf ex Bor; C. tibeticus Bor.

Perennial from tough rootstock, rhizomatous; basal sheaths crowded, pale yellow, papery, strongly keeled. Culms tufted, 30–100 cm tall. Leaf sheaths glabrous; leaf blades narrowly linear, flat or folded, tough, 15–25 × 0.2–0.4 cm, scaberulous, often with scattered long tubercle-based hairs especially on adaxial surface, midrib white, apex finely acuminate; ligule 1.5–4 mm. Inflorescence a sparse spathate panicle, spathate clusters few, often purplish; spatheoles very slender, terete, 2.5–4 cm; racemes paired or frequently branching, then subdigitate along a short axis, 2–4 cm, finally reflexing, lowest spikelet pair homogamous; peduncle glabrous or pilose; rachis internodes and pedicels slender, ciliate, tips cupular, irregularly toothed. Sessile spikelet narrowly oblong, 4.5–6.5 mm; lower glume leathery, deeply to shallowly concave, keels rounded below middle, sharp and scabrid above, glabrous or puberulous in groove, veinless or 1-veined above groove, apex 2-toothed; upper glume awnless; upper lemma 2-lobed, lobes filiform; awn 1–1.6 cm. Pedicelled spikelet 4.5–6 mm, awnless. Fl. and fr. Jun–Nov.

Mountainsides, dry open places in scrub; 2000–4500 m. Sichuan, S Xizang, Yunnan (Yongsheng, Ninglang) [Bhutan, N India, Nepal, Pakistan].

This species lies on the boundary between Andropogon and Cym-bopogon and is sometimes placed in the latter genus on account of its reflexing racemes and homogamous spikelets. However, the slender, unequal raceme bases and frequently subdigitate, longer racemes are typical of Andropogon. As far as is known, the leaf blades do not contain aromatic oils. The yellowish, strongly keeled basal sheaths are characteristic of this species.

Robust specimens, often with several racemes per spathe, a hairy peduncle, and shallowly grooved sessile spikelets, have been separated as Andropogon tristis. However, there are many intermediates, which make a division into two species impracticable.