This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Tufted annual or perennial grasses, with flat or setaceous leaf-blades and mostly spikelike panicles. Spikelets 2-5-flowered. Two lower scales empty, narrow, acute, unequal, keeled, scarious on the margins; the flowering scales 3-5-nerved. Palet hyaline, acute, 2-keeled. Stamens 3. Styles very short. Stigmas plumose. Grain free, enclosed in the scale and palet. [In honor of Georg Ludwig Koeler, German botanist.]
About 15 species of wide geographic distribution. The following, which may contain two forms, occurs in North America. Type species: Poa nitida Lam.
Aira cristata L. Sp. PI. 63. 1753.
Koeleria cristata Pers. Syn. 1: 97. 1805.
Koeleria nitida Nutt. Gen. 1: 74. 1818.
Koeleria cristata var. gracilis A. Gray, Man. 591. 1848.
Culms 1°-2 1/2° tall, erect, simple, rigid, smooth, often pubescent just below the panicle. Sheaths often shorter than the internodes, smooth or scabrous, sometimes hirsute; ligule 1/2" long; blades 1'-12' long, 1/2"-1 1/2" wide, erect, flat or involute, smooth or rough, often more or less hirsute; panicle 1'-7' in length, pale green, usually contracted or spike-like, the branches erect or rarely ascending, 1' long or less; spikelets 2-5-flowered, 2"-3' long, the scales rough, acute, the empty ones unequal; flowering scales 1 1/2"-2" long, shining.