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 flat leaf-blades and terminal cylindric spikes. Spikelets 1-flowered, rarely 2-flowered, usually in 3's at each joint of the rachis, the lateral short-stalked and imperfect, rarely perfect; rachilla produced beyond the flower, the lower empty scales often reduced to awns and forming an apparent involucre around the spikelets. Empty scales rigid; flowering scales rounded on the back, 5-nerved at the apex, awned; palet scarcely shorter than the scale, 2-keeled. Stamens 3. Styles very short, distinct. Grain usually adherent to the scale, hairy at the summit. [Latin name for Barley.]
About 20 species, widely distributed in both hemispheres. Type species: Hordeum vulgare L.
Lateral spikelets abortive.
Flowering scales, exclusive of awns, 3"-4" long.
Awn of the flowering scale 1/2' long or less.
All the empty scales of each cluster bristle-like.
Four of the empty scales of each cluster dilated above the base.
Awn of the flowering scale 1' long or more.
Flowering scales, exclusive of awns, about 6" long.
Lateral spikelets with perfect flowers.
Hordeum nodosum L. Sp. PI. Ed. 2, 126. 1762. Hordeum pratense Huds. Fl. Angl. Ed. 2, 56. 1762.
Culms 6'-2° tall, erect, or sometimes decumbent, simple, smooth and glabrous. Sheaths shorter than the internodes; ligule 1/4" long, truncate; blades 1 1/2'-5' long, 1"-3' wide, flat, rough; spike 1'-3 1/2 in length; spikelets usually in 3's, the central one containing a palet and perfect flower, the lateral enclosing a staminate or rudimentary flower, or a palet only; empty scales of each cluster awn-like; flowering scale of the central spikelets 3"-4" long exclusive of the awn, which is 3"-6" long, the corresponding scale in the lateral spikelets much smaller and short-stalked.
In meadows and waste places, Indiana to Minnesota, Alaska, Texas and California. Also in Europe and Asia. June-July.
Hordeum pusillum Nutt. Gen. 1: 87. 1818.
Culms 4'-15' tall, erect, or decumbent at the base, smooth and glabrous. Sheaths loose, usually shorter than the internodes, smooth and glabrous, the upper often enclosing the base of the spike; ligule very short; blades 1/2'-3' long, i"-2" wide, erect, smooth beneath, rough above; spike I-3' in length; spikelets usually in 3's, the central one containing a palet and perfect flower, the lateral imperfect; scales awned, the empty ones scabrous, those of the central spike-let and the lower ones of the lateral spikelets dilated above the base; flowering scale smooth, that of the central spikelet 3"-4" long, short-awned, the corresponding scale in the lateral spikelets smaller and very short-stalked.
In dry soil, Indiana to Tennessee, Wyoming, California, Texas and Louisiana; also sparingly introduced along the coast from Virginia to Florida. June-July.