水山野青茅 shui shan ye qing mao

Agrostis suizanensis Hayata, Icon. Pl. Formosan. 7: 83. 1918; Calamagrostis filifolia Merrill; C. suizanensis (Hayata) Honda; Deyeuxia biflora Keng; D. chaseana Bor; D. steno-phylla Jansen (1952), not (Handel-Mazzetti) P. C. Kuo & S. L. Lu (1987).

Perennial, densely tufted. Culms slender, erect, up to 65 cm tall, 2–3-noded, retrorsely puberulent below nodes. Leaf sheaths glabrous or retrorsely puberulent toward base; leaf blades filiform, stiff, strongly involute, 6–8(–15) cm, 3–5 mm wide, apex acute; ligule 0.75–2.5 mm, minutely erose. Panicle contracted, narrowly oblong in outline, 5–16 × 0.6–1 cm, axis scaberulous; lowest branches in groups of 2–3(–4), 2.5–5 cm. Spikelets 4–5.5(–6) mm, florets (1–)2, upper floret slightly smaller and bisexual or sometimes rudimentary; glumes lanceolate, slightly unequal with upper glume as long as spikelet, lower glume 1-veined, upper glume 1–3-veined, midvein scabrid, apex acuminate; callus hairs 1/8–1/5 length of lemma; lemma 3.5–4.6(–5.5) mm, scaberulous, apex usually erose; awn arising from lower 1/4–1/3 of lemma, 5–8 mm, geniculate; palea 3/4–7/8 as long as lemma; rachilla 1.6–3 mm including hairs. Anthers 1–2 mm.

Montane grasslands; ca. 3000 m. Taiwan [New Guinea, Philippines].

Specimens from Malesia tend to have longer leaf blades and ligules and a shorter rachilla extension. They have been referred to different varieties from the typical variety in Taiwan: var. stenophylla (Jansen) Veldkamp in the Philippines and var. chaseana (Bor) Veldkamp in New Guinea. Cleistogamous forms with anthers ca. 0.5 mm are known from the Philippines. The name Deyeuxia biflora applies to an aberrant form with a well-developed second floret.