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..
Mostly annual grasses with narrow leaf-blades and contracted or open panicles. Spikelets small, 2-flowered, both flowers perfect. Scales 4; the 2 lower empty, thin-membranous, acute, subequal, persistent; the flowering scales usually contiguous, hyaline, mucronate or 2-toothed, deciduous, bearing a delicate dorsal awn inserted below the middle; palet a little shorter than the scale, hyaline, 2-nerved. Stamens 3. Stigmas plumose. Grain enclosed in the scale and palet, and often adhering to them. [Greek, from Theophrastus.]
Six or seven species, natives of Europe. Type species: Aira praecox L.
Panicle contracted; flowering scales about 1 1/2' long; plants 2'-4' tall.
Aira caryophyllea L. Sp. PI. 66. 1753.
Smooth and glabrous throughout, culms 5'-10' tall, erect from an annual root, simple, slender. Sheaths mostly basal; ligule 1 1/2" long; blades 1/2'-2' long, involute-setaceous; panicle 1'-4' in length, silvery, shining, open, the branches spreading or ascending, the lower 1' long or less; spikelets 1"-1 1/4" long, the empty scales acute; flowering scales very acute, 2-toothed, 1" long, bearing an awn 1 1/2"-2" long.
In fields and waste places, eastern Massachusetts to Ohio and Virginia. Also on the Pacific Coast. Local. Naturalized from Europe. Mouse-grass. May-July.
Aira praecox L. Sp. PI. 65. 1753.
Glabrous and smooth throughout, culms 2'-4' tall, erect, from an annual root, simple, rigid. Sheaths clothing the whole culm, the upper one often enclosing the base of the panicle; ligule about 1 1/2" long; blades 1' long or less, involute-setaceous; panicle contracted, strict, 1/2-1' in length; spikelets about 1 1/2" long, the empty scales acute; the flowering scales acuminate, 2-toothed, about 1 1/2" long, bearing an awn \\"-2" long.
In dry fields, southern New Jersey and Pennsylvania to Virginia. Naturalized from Europe. May-July.