矮小沿沟草 ai xiao yan gou cao

Aira humilis M. Bieberstein, Fl. Taur.-Caucas. 1: 57. 1808; Catabrosa humilis (M. Bieberstein) Trinius; Cata-brosella humilis (M. Bieberstein) Tzvelev; C. humilis subsp. songorica Tzvelev; C. songorica (Tzvelev) Czerepanov.

Perennial, densely tufted; roots hairy. Culms tuberously thickened at base, clothed in fibrous sheath remnants, erect or geniculate at lowest node, 10–30 cm tall, 2–3-noded. Leaf sheaths closed in lower 1/6; leaf blades usually flat, 1–6 cm × 1–2 mm, glabrous; ligule 1–2 mm. Panicle pyramidal, open, 3.5–7 × 2–5 cm; branches 2–6 per node, ascending or spreading, smooth. Spikelets 3–5 mm, florets 2–3(–4), purplish brown or purplish green; glumes shorter than spikelet, unequal, lower glume ovate, 1.5–2 mm, upper glume broadly ovate, 2–2.3 mm, acute; lemmas ovate-oblong, 2.5–3 mm, keel and marginal veins densely silky villous below middle, intermediate veins inconspicuous or absent, apex truncate-erose; palea keels densely silky villous below middle; rachilla extension 0.3–0.8 mm. Stamens 3; anthers 1.5–1.8 mm. Fl. Apr–Jun. 2n = 10.

Sandy steppe, mountain valleys, roadsides; 400–1700 m. Xinjiang [Kazakhstan, Kyrgyzstan, Russia, N Uzbekistan; SW Asia (Caucasus, N Iran)].

This is a rather widespread species showing variation over its range, especially in lemma hairiness and venation, and several subspecies have been described. The Chinese material, with mainly 3-veined lemmas, and any weak intermediate veins glabrous, corresponds to Catabrosella humilis subsp. songorica. Typical Colpodium humile has distinctly 5-veined lemmas densely pilose on the proximal part of all veins.