2. Avena chinensis (Fischer ex Roemer & Schultes) Metzger, Eur. Cereal. 53. 1824.
莜麦 you mai
Avena nuda Linnaeus var. chinensis Fischer ex Roemer & Schultes, Syst. Veg. 2: 669. 1817; A. sativa subsp. chinensis (Fischer ex Roemer & Schultes) Janchen ex Holub.
Annual. Culms 60–100 cm tall. Leaf blades 8–40 cm, 3–16 mm wide, scabrid. Panicle open, 12–20 cm; branches scabrid. Spikelets 2.5–3.5(–4.5) cm, florets 3–7; rachilla glabrous, not disarticulating at maturity, florets lacking a basal bearded callus, internodes elongate, sinuous, upper sometimes strongly curled; glumes broadly lanceolate, subequal, conspicuously shorter than spikelet, 1.5–2.5 cm, 7–11-veined; lemmas 2–2.5 cm, papery, distinctly veined throughout, glabrous, awned from upper 1/4 of lemma, apex with 2–4 small obtuse teeth; awn 1–2 cm, straight or bent, rarely awnless. Grain ca. 8 mm, free from lemma and palea at maturity (free threshing). Fl. and fr. Jun–Aug.
Cultivated, or naturalized along roadsides and on arable land; 1000–3200 m. Hebei, Henan, Hubei, Xinjiang, Yunnan [Russia; Europe].
More work is needed on Avena chinensis. It is very close to A. nuda, and may not be distinct from it. These naked wheats may be no more than free-threshing forms of A. sativa, caused by occasional mutations, and are perhaps better placed at infraspecific rank within A. sativa.
The name Avena gracillima Keng (Bull. Fan Mem. Inst. Biol., Bot. 7: 36. 1936), described from Hebei, is based on a very depauperate specimen with a panicle of only 1 or 2 spikelets. The spikelets are 1.4–1.8 mm long with herbaceous, glabrous lemmas and rudimentary awns. It is clearly a cultivated species, growing as a weed on grassy slopes, most likely referable to A. chinensis. The type has not been seen.