毛轴异燕麦 mao zhou yi yan mai

Avena pubescens Hudson, Fl. Angl. 42. 1762; Avenastrum pubescens (Hudson) Opiz; Avenula pubescens (Hudson) Dumortier.

Perennial, shortly rhizomatous. Culms solitary or few, erect, 30–120 cm tall, 3–4-noded. Leaf sheaths of lower leaves pubescent, upper and infrequently also lower glabrous, closed to above middle; leaf blades linear-lanceolate, flat, 10–30 cm, 4–10 mm wide, usually pubescent on both surfaces, abaxial surface with thin midrib, margins only slightly thickened, apex subacute; ligule lanceolate, 3–6 mm. Panicle lax, oblong in outline, 8–15 cm or more; branches 4–6 per node, up to 5 cm, fine, scaberulous. Spikelets 1.2–1.7 cm, pale green or variegated purple, florets 2–4; rachilla hairs 4–6 mm; glumes hyaline, lower glume 10–11 mm, 1–3-veined, upper glume 13–17 mm, 3-veined; lemmas firmly herbaceous, hyaline above awn insertion, lowest 9–11 mm, scabrid, apex irregularly 2-denticulate; awn 1.5–2 cm, geniculate, column twisted, terete; palea subequal to lemma, keels close together, smooth, glabrous, hyaline between keels. Anthers 5–7 mm. Fl. and fr. Jun–Sep.

Grassy mountain slopes, forest margins, among shrubs; 1000–2600 m. Xinjiang [Kazakhstan, Kyrgyzstan, Mongolia, Russia, Tajikistan; SW Asia (Caucasus, Turkey), Europe; introduced in North America].

This is a widespread, polymorphic species, varying especially in the degree of hairiness of the leaves and the width of the blades. The Chinese population probably corresponds to a broad-leaved, rather sparsely hairy form found in neighboring parts of Russia and C Asia, Helictotrichon pubescens var. latifolium (Printz) Tzvelev. The typical variety has hairy leaves usually up to 5 mm wide.

Helictotrichon pubescens is distinguished from all other species in the genus by its palea with close, smooth keels. Molecular studies place it close to the group of species including H. dahuricum (see the comment under that species). However, it differs morphologically from those species in several characters besides the palea, including unthickened leaf blade margins, an evenly bearded (vs. laterally bearded) callus, and a hilum as long as the caryopsis (vs. half as long).