82. Aira Linnaeus, Sp. Pl. 1: 63. 1753.
银须草属 yin xu cao shu
Authors: Zhen-lan Wu & Sylvia M. Phillips
Annuals, small. Leaf blades rolled. Inflorescence an open or contracted panicle. Spikelets small, laterally compressed, florets 2, both alike, bisexual, separated by very short internode, disarticulating below each floret; rachilla not extended beyond upper floret; glumes persistent, equal, enclosing florets, ovate, membranous, shining, 1(–3)-veined, apex acute; floret callus small, usually shortly bearded laterally, rarely glabrous; lemmas ovate, rounded on back, membranous becoming firm at maturity, indistinctly 5-veined, glabrous, upper part scaberulous to scabrid, awned from lower back or lower floret awnless, apex 2-toothed; awn geniculate with twisted column; palea slightly shorter than lemma. Anthers small. Caryopsis fusiform. 2n = 14, 28.
Eight species: centered on the Mediterranean region, extending northward to Scandinavia and eastward to Iran and Afghanistan; introduced in other temperate regions; one species in China.