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..
Annual or perennial grasses, with usually flat leaf-blades and panicled spikelets. Spike-lets 2-many-flo\vered, or rarely 1-flo\vered; lower flowers perfect, the upper often staminate or imperfect. Scales 4-many (rarely 3); the 2 lower empty, somewhat unequal, membranous, persistent; flowering scales deciduous, rounded on the back, acute, generally bearing a dorsal awn, the apex often 2-toothed. Palet narrow, 2-toothed. Stamens 3. Styles short, distinct. Stigmas plumose. Grain oblong, deeply furrowed, enclosed in the scale and palet, free or sometimes adherent to the latter. [Old Latin name for the Oat.]
About 50 species, widely distributed in temperate regions, chiefly in the Old World. Type species: Avena sativa L.
Spikelets, exclusive of the awns, 8" long or more; annuals.
Flowering scales more or less hispid, the awn with a pronounced spiral column; rachilla hispid.
Flowering scales glabrous, awnless or with a straight awn slightly spiral at the base.
Spikelets, exclusive of the awns, less than 8" long; perennials.
Empty basal scales much shorter than the spikelet; flowering scales, herbaceous, with the awn inserted near the apex.
Flowering scales with a ring of hairs at the base; awn equalling or exceeding the scale.
Flowering scales naked at the base; awn not more than 1/2 as long as the scale.
Empty scales, at least the second one, as long as the spikelet or nearly so; flowering scales scari-
ous and hyaline above, the awn inserted about the middle.
Avena fatua L. Sp. PI. 80. 1753.
Culm 1°-4° tall, erect, simple, stout, smooth and glabrous. Sheaths smooth, or scabrous at the summit, sometimes sparingly hirsute, the lower often overlapping; ligule 1"-2" long; blades 3'-8' long, 1"-4" wide; panicle open, 4'-12' in length, the branches ascending; spikelets 2-4-flowered, drooping; outer scales 3/4'-1' in length, smooth, enclosing the flowering scales; flowering scales 6"-9" long, with a ring of stiff brown hairs at the base, pubescent with long rigid brown hairs, bearing a long bent and twisted awn.
In fields and waste places, Ontario and Ohio (according to Hitchcock) and westward to Missouri; abundant on the Pacific Coast. Naturalized from Europe or Asia. Haver-corn. Poor Oat. Hever. Drake. July-Sept.
Avena sterilis L., a native of Europe, is reported as occurring sparingly as an adventive plant in New Jersey and near Philadelphia, Penn. It can be distinguished from the above by its larger spikelets and longer awns.