87. Hordeum (barley)

(Baum and Bailey, 1990; von Bothmer et al., 1991)

Plants annual or perennial (short‑lived), lacking rhizomes, forming tufts. Flowering stems erect to ascending or spreading, glabrous. Leaf sheaths glabrous or hairy, the ligule short, membranous. Leaf blades flat, glabrous or roughened to hairy, sometimes with a pair of auricles at the base. Inflorescences erect or arched to nodding, often with the base enclosed in the uppermost leaf sheath, with numerous erect to ascending or spreading spikelets spaced densely along opposite sides of the axis, the internodes 1.5–3.0 mm long. Spikelets in clusters of 3 at each node, the central spikelet fertile, with 1 perfect floret, the 2 lateral spikelets sterile and with reduced, small florets (except sometimes in Hordeum vulgare, with all 3 spikelets perfect), linear in outline, disarticulating at the nodes of the inflorescence axis (except in Hordeum vulgare), the joints shed as a unit with the attached spikelets. Glumes similar in size and appearance, linear or awnlike, usually somewhat hardened at the base, the tip with a long or short, roughened awn (except sometimes in H. vulgare), glabrous or roughened to hairy. Lemmas with the tip awned (except sometimes in H. vulgare), rounded on the back, faintly 5‑nerved, the body thickened and hard, glabrous or roughened. Paleas lanceolate, as long as or slightly shorter than the body of the lemmas. Fruits, linear to elliptic, usually slightly flattened and grooved, hairy at the tip, yellowish brown. About 32 species, North America, South America, Europe, Asia, Africa.

A number of intergeneric hybrids between Hordeum and Elymus species have been reported in the literature, but only one of these has been found in Missouri thus far (see discussion under the treatment of E. trachycaulus). Other hybrids are to be expected in Missouri.