Avenastrum Jess.
Caespitose perennials. Leaf-blades linear, flat or folded, sometimes setaceous. Inflorescence a narrow panicle, erect or nodding. Spikelets 2-6-flowered, the florets similar, bisexual, or the uppermost ± reduced; rhachilla disarticulating below each floret, slender, hairy, produced as a short bristle or ending with a rudimentary lemma; glumes unequal, keeled, hyaline to herbaceous, the lower 1-3-nerved, the upper 3-5-nerved, acute; lemmas narrowly lanceolate in profile, enclosed by or more often exserted from the glumes, herbaceous with hyaline tips and margins, sometimes becoming indurated, 5-11-nerved, bind, geniculately awned from the upper part of the back; palea shorter than the lemma, 2-keeled; stamens 3; stigmas 2.
A genus of about 60 species chiefly in the temperate regions of the northern hemisphere, extending through the African mountains to South Africa and Madagascar; 1 species on mountains in Java and Sumatra; 2 species occur in Pakistan.
The genus resembles Avena, in which it is often included, but the latter are annuals with larger pendulous spikelets and 7-11-nerved glumes. Also similar is Arrhenatherum, but this has mostly 2-flowered spikelets with the lower floret male, and the florets falling together at maturity. Helictotrichon is distinguished from Trisetum by its larger spikelets (over 9 mm) and hairy ovary.
