Description from Flora of China
Annuals or perennials. Culms mostly tufted. Leaf blades narrow; ligule a line of hairs. Inflorescence of racemes inserted singly along an axis; racemes unilateral, 1–80, short, deciduous or persistent; spikelets sessile, few to numerous, biseriate, sometimes pectinate; rachis narrow, flat, ending in a straight or forked point. Spikelets subterete or laterally compressed, fertile floret 1, usually 2nd sterile floret present, rarely this reduced to a rachilla extension; glumes unequal, narrow, membranous, 1-veined, keeled, acuminate to awn-pointed; lemma of fertile floret ± as long as upper glume, rounded or keeled on back, thinly leathery, 3-veined, veins excurrent into 3 short awns, central awn sometimes flanked by 2 teeth, less often apex simply acute; palea veins sometimes excurrent; sterile floret variable within a species or even an individual specimen, usually lemma body reduced and prominently awned. Caryopsis ellipsoid. x = 7, 10.
About 40 species: Canada to Argentina, centered on Mexico; two species (both introduced) in China.
(Authors: Sun Bixing (孙必兴 Sun Bi-sin); Sylvia M. Phillips)