光脊荩草 guang ji jin cao

Arthraxon guizhouensis S. L. Chen & Y. X. Jin; A. xina-nensis S. L. Chen & Y. X. Jin; A. xinanensis var. laxiflorus S. L. Chen & Y. X. Jin.

Perennial with spreading branching rhizomes. Culms stiff, erect or decumbent, 30–70 cm long. Leaf sheaths glabrous or tuberculate-hispid; leaf blades lanceolate, firm, green or glaucous, 3–10 cm × 4–15 mm, glabrous or sparsely hispid, base subcordate, margins serrulate, pectinate-setose near base, apex slenderly acuminate; ligule 0.5–1.5 mm. Racemes 2–6, 3–10 cm, yellowish green, lax, slightly flexuous; rachis internodes slightly shorter to equaling sessile spikelets, margins villous. Sessile spikelet 5–7 mm; lower glume linear-lanceolate, herbaceous, shallowly convex, laterally keeled, margins inflexed, glabrous, 5–7-veined between keels, veins visible along length of glume, keels scabrid to tuberculate in a single row, tubercles spinescent toward apex; upper lemma awned from 0.75–1.3 mm above base, apex subentire or 2-denticulate, teeth (0.1–) 0.5–0.7 mm; awn 7.5–13 mm; palea 0.5–1 mm. Anthers 3, 2.4–3.5 mm. Pedicelled spikelet narrowly lanceolate, 4.5–6 mm, staminate; pedicel villous. Fl. and fr. Jul–Nov.

Grassy slopes, among rocks, roadsides; 700–2500 m. Gansu (Wenxian), Guizhou, Shaanxi, Sichuan, Yunnan [Bhutan, Nepal].

This grass is easily confused with Arthraxon prionodes when the base is absent. However, besides the key characters of the lower glume, A. epectinatus is also distinguished by some less obvious differences. The leaf blades are usually a little narrower with the cartilaginous margin serrulate (vs. smooth) between the tubercle-based bristles, the awn arises slightly higher up the back of the upper lemma, and an upper palea is present. The apex of the upper lemma is not deeply 2-toothed as reported in Chinese literature. The delicate hyaline tissue is easily split down the midline during dissection.

Like Arthraxon prionodes, this grass has often been misidentified as the S Indian species A. lanceolatus (Roxburgh) Hochstetter, which has flatter, lower glumes with fewer, more prominent intercarinal veins, and a sub-basally awned upper lemma.