51. Elymus tridentatus (C. Yen & J. L. Yang) S. L. Chen, Novon. 7: 229. 1997.
三齿披碱草 san chi pi jian cao
Roegneria tridentata C. Yen & J. L. Yang, Novon 4: 310. 1994.
Culms tufted, erect or slightly procumbent geniculate at base, 40–65 cm tall, 1.5–2 mm in diam., 2- or 3-noded, smooth, glabrous. Leaf sheath glabrous; ligule ca. 0.5 mm, scarious, apex truncate; leaf blade involute or subinvolute, 5–7 × ca. 0.2 cm, abaxial surface glabrous, adaxial surface pubescent. Spike erect, 5–11.5 × ca. 0.5 cm, with 6–14 spikelets; rachis usually glabrous. Spikelets 1 per node, purple or greenish purple, 10–13 × ca. 2 mm, with 4 or 5 florets; rachilla internodes 1.5–2 mm, appressed puberulent. Glumes oblong or oblong-elliptic, slightly oblique, unequal, prominently 3(–5)-veined, glabrous, sometimes sparsely shortly spinulose along veins, apex rounded-obtuse, rarely acute; proximal glume 4–5 mm; distal glume 5–6.5 mm. Lemma oblong-lanceolate, (7–)8–9 mm, appressed white pubescent proximally and laterally, apex truncate and 3-toothed, teeth 0.5–1 mm; callus obtuse, puberulent along sides. Palea shorter to longer than lemma, scabrous between keels, setulose-ciliate on distal 1/3–1/2 of keels, apex truncate. Anthers black, ca. 2 mm. 2n = 42*.
* Rocky slopes, roadsides; ca. 3700–3800 m. Qinghai.