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HORDEUM L. Barley
Plants hermaphoditic, caespitose (some solitary), annual or perennial. Culms erect or ascending or geniculate, glabrous;
internodes hollow, terete. Leaves cauline, not distinctly distichous; sheaths terete, margins open; auricles present or absent;
ligules membranous; blades flat or involute, linear, lax. Spicate racemes (or spikes in H. vulgare)
bilateral, rachis disarticulating or persistent. Spikelets in three's at inflorescence nodes, 1 central sessile and
fertile, and 2 lateral pedicellate and sterile; ascending, laterally compressed, disarticulation below the glumes with spikelet
cluster, awned. Central (sessile) spikelets perfect; glumes usually 1-veined, subulate extending into awns, many appearing as
awns; florets 1, reduced floret absent, callus glabrous to scabrous, rachilla extending beyond the floret as a naked bristle;
lemmas 5-veined, coriaceous, glabrous; apex entire or bifid or trifid, extending into an awn; paleas 2-veined, awnless
glabrous. Stamens 3; anthers yellow. Caryopses adnate to lemma and/or palea or free, dorsiventrally compressed. Lateral
(pedicellate) spikelets sterile or neuter; glumes usually reduced to awns; florets bract like or awn like, lemma extending into
an awn; awn straight. Base chromosome number x=7.
A genus of about 40 species in temperate areas of North and South America. These species are commonly
found in open habitats as weedy species. Barley (H. vulgare) in a major cereal crop.
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