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..
Perennial grasses with flat or involute leaf-blades, and contracted or open panicles. Spikelets 2-flowered, both flowers perfect, the hairy rachilla extended beyond the flowers.or rarely terminated by a staminate one. Scales 4 (rarely more), the 2 lower empty, keeled, acute, membranous, shining, persistent; the flowering scales of about the same texture, deciduous, bearing a dorsal awn, the apex toothed. Palet narrow, 2-nerved. Stamens 3. Styles distinct. Stigmas plumose. Grain oblong, free, enclosed in the scale. [In honor of J. C. A. Loiseleur-Deslongchamps, 1774-1849, French physician and botanist.]
About 20 species, inhabiting cold and temperate regions, a few occurring in the high mountains of the tropics. Besides the following, some 6 others occur in the western parts of Nort America. Type species: Aira caespitosa L.
Upper flowering scale reaching or extending beyond the apex of the empty scales.
Flowering scales about 1 1/4" long, erose-truncate; leaves flat.
Flowering scales about 2" long, acute or obtuse; leaves involute.
Empty scales extending much beyond the upper flowering scale.
Aira caespitosa L. Sp. PI. 64. 1753.
D. caespitosa Beauv. Agrost. 160. pl. 18. f. 3. 1812.
Culms 2°-4° tall, erect, simple, smooth and glabrous. Sheaths much shorter than the internodes; ligule 1"-3" long; blades flat, 1"- 1 1/2" wide, smooth beneath, strongly scabrous above, the basal ones numerous, one-quarter to one-half as long as the culm, those of the culm 2'-6' long; panicle open, 3'-9' in length, the branches widely spreading or ascending, often somewhat flexu-ous, naked at the base, the lower 2'-5' long; spikelets 1 3/4"-2" long; flowering scales about 1 1/4" long, erose-truncate at the apex, the awns somewhat shorter or a little longer, the upper scale reaching to or extending beyond the apices of the empty ones.
Newfoundland to Alaska, south to New Jersey, Illinois, Minnesota and in the Rocky Mountains and Sierra Nevada to New Mexico and California, mostly in wet soil. Also in Europe and Asia. Hassock-grass, Bull-poll, Bullpates, Windlestraw. July-Aug.
Aira flexuosa L. Sp. PI. 65. 1753.
Deschampsia flexuosa Trin. Bull. Acad. Sci. St. Petersb. 1: 66. 1836.
Glabrous throughout, culms l°-2 1/2° tall, erect, slender, simple, smooth. Sheaths much shorter than the internodes; ligule 1" long or less; blades involute-setaceous, smooth beneath, scabrous above, the basal very numerous, one-fifth the length of the culm or less, those of the culm 1'-3' long; panicle open, 2'-8' in length, the branches ascending or erect, sometimes widely spreading, naked at the base, flexuous, the lower 1 1/2'-5' long; spikelets 2 1/4"-2 1/2" long; flowering scales about 2" long, acutely toothed at the apex; awns bent and twisted, much exceeding the scale; upper scale reaching to or extending beyond the apices of the empty ones.
In dry soil, Greenland and Newfoundland to Ontario, south to North Carolina and Tennessee. Ascends to 5100 ft. in the Adirondacks. Also in Europe. Wood Hair-grass. July-Aug.
Glabrous and smooth or very nearly so, culms 6'-18' tall, erect, simple, rigid. Sheaths shorter than the internodes; ligule 1" long or less, truncate; blades l"-2" wide, erect, sometimes slightly scabrous above, the basal 2 1/2'-5' long, those of the culm shorter; panicle contracted, usually purple or purplish, 1'-2' in length, the branches erect, or sometimes ascending, the lower 1/2'-1 1/2' long; spikelets 2 1/2" long; flowering scales about 1 1/4" long, erose-truncate at the apex; awns bent and much longer than the scales; upper scale much exceeded by the very acute outer ones.