AIRA L. Hairgrass
Plants hermaphroditic, caespitose, annual. Culms erect or ascending (delicate), glabrous to scabrous; internodes hollow,
terete. Leaves basal, not distinctly distichous; sheaths terete, margins open; auricles absent; ligules membranous;
blades flat (narrow to filiform) or folded, lax. Panicles open or contracted; primary branches spreading or
ascending. Spikelets solitary, laterally compressed, disarticulation above glumes; awned, pedicellate;
florets 2, reduced floret absent, callus hairy, rachilla extending beyond upper floret or not extended above upper
floret; glumes 1-(occasionally 3-) veined, nearly equal, longer than florets, glabrous or scabrous,
awnless; lemmas 5-veined, membranous or chartaceous, scabrous, apex bifid, lower lemma awnless, upper lemma
with a geniculate dorsal awn; paleas present, 2-veined, awnless. Stamens 3; anthers yellow.
Caryopses small, fusiform, dorsiventrally compressed. Base chromosome number x=7.
A genus of about 10 species that were native to Europe. These taxa are from mesic to xeric sites where they are frequently adventive.