发草 fa cao

Aira cespitosa Linnaeus, Sp. Pl. 1: 64. 1753.

Perennial, densely tufted. Culms erect, slender to stout, 30–150 cm tall, 1–3 mm in diam., 1–3-noded. Leaf sheaths loose, glabrous; leaf blades linear, flat or folded, up to 30 cm, 1–5 mm wide, abaxial surface smooth, adaxial surface with coarse sharp ridges, densely scabrid; ligule obtuse to acuminate, 2–7(–12) mm. Panicle usually open, often nodding, infrequently loosely contracted, ovate to narrowly oblong in outline, up to 30 cm or more, greenish or purplish sometimes with golden sheen; branches slender, bearing spikelets on distal part. Spikelets 2.5–7 mm, florets (1–)2(–3), rachilla internode ca. 1 mm; glumes slightly longer to slightly shorter than florets, lower glume slightly shorter than or equaling upper glume, 1-veined, upper glume 3-veined, apex acute; callus hairs ca. 1/3 lemma length; lemmas 2.5–3.5 mm, awned from near base to near middle, rarely awnless, apex broad, toothed or erose; awn straight or slightly bent, slightly shorter to longer than lemma. Anthers 1.2–2 mm. Fl. and fr. Jul–Sep.

Wet meadows, river sand and gravel, among bushes, wet places; 1500–4500 m. Gansu, Heilongjiang, Nei Mongol, Qinghai, Shaanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan [Bhutan, India (Sikkim), Japan, Kazakhstan, Korea, Kyrgyzstan, Mongolia, Pakistan, Russia, Tajikistan, Uzbekistan; SW Asia, Europe, North America; introduced elsewhere].

Deschampsia cespitosa is an extremely polymorphic, widely distributed grass. Many regional and local variants have been accorded separate status, either at specific or infraspecific rank. Variation is complex due to polyploidy and introgression, and morphological and cytological variation often do not coincide. There is extensive overlapping of diagnostic characters leading to a lack of clear boundaries between taxa. Variation is nowadays usually consigned to subspecies, mostly strongly linked to geographic distribution. The main variants reported in China are given below.

The position of the awn on the lemma back refers to the lowest lemma. In general the awn arises higher up on the second lemma, and short awns arise higher on the lemma back than do longer awns. A specimen collected at 2800 m on a grassy spur in Shennongjia, Hubei, has been described as Deschampsia cespitosa var. exaristata Z. L. Wu (Acta Biol. Plateau Sin. 2: 15. 1984). In this plant the lower lemma has a ca. 0.5 mm awn arising from the upper 1/5, or both lemmas are awnless. It is not possible from the protologue to assign it to a subspecies.