8. Microstegium vimineum (Trinius) A. Camus, Ann. Soc. Linn. Lyon, N.S. 68: 201. 1921.
柔枝莠竹 rou zhi you zhu
Andropogon vimineus Trinius, Mém. Acad. Imp. Sci. St.-Pétersbourg, Sér. 6, Sci. Math. 2: 268. 1833; Arthraxon nodosus Komarov; Eulalia cantonensis (Rendle) Hitchcock; Microstegium cantonense (Rendle) A. Camus; M. dilatatum Koidzumi; M. imberbe (Nees ex Steudel) Tzvelev; M. nodosum (Komarov) Tzvelev; M. vimineum subsp. nodosum (Komarov) Tzvelev; M. vimineum var. imberbe (Nees ex Steudel) Honda; M. vimineum var. willdenowianum (Nees ex Steudel) Sur; M. willdenowianum Nees ex Steudel; Pollinia cantonensis Rendle; P. imberbis Nees ex Steudel; P. imberbis var. willdenowiana (Nees ex Steudel) Hackel; P. viminea (Trinius) Merrill; P. willdenowiana (Nees ex Steudel) Bentham.
Annual. Culms decumbent, up to 1 m long. Leaf sheaths shorter than internodes, upper usually enclosing cleistogamous spikelets; leaf blades narrowly elliptic, 4–9 × 0.5–0.8 cm, pubescent, often sparsely, midvein white, apex acuminate; ligule ca. 0.5 mm. Racemes 1–6, ascending, 4–6 cm; rachis internodes linear-clavate, ciliate, shorter than spikelet. Sessile spikelet 4–5.5 mm; lower glume narrowly lanceolate-oblong, back deeply grooved, puberulous-scaberulous or occasionally hispidulous, 0–4-veined between keels, veins connected by veinlets below apex, apex subtruncate; upper glume scabrid on keel, acuminate; lower floret reduced to an inconspicuous linear-lanceolate scale or absent; upper lemma lanceolate or oblong, 1–1.5 mm, acute or bidenticulate, awnless or shortly awned; awn weakly geniculate, often included within spikelet, up to 6(–9) mm; upper palea ovate, ca. 1 mm. Anthers 3, 0.5–1.5 mm. Fl. and fr. Aug–Nov.
Forest margins, moist grassy places. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [Bhutan, NE India, Japan, Korea, Myanmar, Nepal, Philippines, Russia, Vietnam; SW Asia (Iran); introduced in America and elsewhere].
This is a variable species, usually with apparently awnless spikelets, where in fact a weakly developed awn is enclosed within the glumes. Sometimes the awn is exserted and obvious; rarely it is completely absent. The fertile lemma is accompanied by an ovate upper palea, clasping the opposite side of the caryopsis. Additionally an inconspicuous, linear-filiform remnant of the lower floret is often present.