白羊草 bai yang cao

Andropogon ischaemum Linnaeus, Sp. Pl. 2: 1047. 1753; Amphilophis ischaemum (Linnaeus) Nash; Andropogon ischae-mum var. songaricus Ruprecht ex Fischer & Meyer; Bothrio-chloa ischaemum var. songarica (Ruprecht ex Fischer & Meyer) Celarier & J. R. Harlan.

Perennial, tussocky from a branching rootstock. Culms slender, erect or geniculately ascending, 25–70 cm tall, 3–6-noded, nodes glabrous or appressed bearded. Leaf sheaths keeled, congested at plant base; leaf blades linear, 5–16 × 0.2–0.3 cm, usually sparingly hairy with tubercle-based hairs, apex acuminate; ligule ca. 1 mm. Inflorescence composed of 5–15 racemes, subdigitate or inserted on a brief axis; racemes 3–7 cm, silvery-green or tinged purplish brown; rachis internodes and pedicels ciliate with long white or pinkish silky hairs. Sessile spikelet 4–5 mm; lower glume oblong-lanceolate, usually cartilaginous, sometimes herbaceous, back flat to slightly concave, 5–7-veined, silky-pilose below middle, lacking a pit, margins keeled and stiffly ciliate near apex; awn of upper lemma 1–1.5 cm. Pedicelled spikelet male or barren, subequal to sessile spikelet, glabrous. Fl. and fr. autumn. 2n = 40, 50, 60.

Rocky and sandy slopes, roadsides, disturbed places. Anhui, Fujian, Guangdong, Guizhou, Hainan, Hebei, Henan, Hubei, Hunan, Jiangxi, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, N India, Kazakhstan, Korea, Kyrgystan, Mongolia, Nepal, Pakistan, Russia, Tajikistan, Turkmenistan, Uzbekistan; N Africa, SW Asia, Europe; introduced in United States].

Dichanthium annulatum is similar, but can be distinguished by its conspicuously bearded nodes with spreading hairs and by the broadly obtuse sessile spikelet with long hairs on the upper margins. It also lacks a purple stripe on the pedicels.

Bothriochloa ischaemum introgresses with B. bladhii, leading to a range of intermediates. The name Andropogon taiwanensis Ohwi (J. Jap. Bot. 12: 652. 1936), described from Taiwan, has been applied to one of these intermediates. The name "Bothriochloa taiwanensis" (Ohwi, loc. cit.) was not validly published because it was merely cited as a synonym of A. taiwanensis.