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Bromus
See list of 20 species in this genusReference: Pavlick (1995).
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1a. Lobes of the lemma apex 0.1–0.5 mm long [Fig. 196]; plants perennial
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2a. Lower glume 3- or 5-nerved; upper glume 5- to 9-nerved
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3a. Lemmas compressed and strongly keeled; ligules 2–3.5 mm long; first and second glumes 7–9 and 9–11 mm long, respectively
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3b. Lemmas convex, neither strongly compressed nor keeled; ligules 0.5–1 mm long; first and second glumes 5–7.5 and 6.5–8.5 mm long, respectively
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2b. Lower glume 1-nerved; upper glume 3-nerved
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4a. Plants with long rhizomes; lemmas awnless or with awns up to 3 mm long [Fig. 198]
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4b. Plants without rhizomes; lemmas always awned, the awns 3–7 (–8) mm long
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5a. Panicle contracted, usually narrower than 2 cm, with erect to ascending branches; anthers 4–6.5 mm long; leaf blades often involute
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5b. Panicle open, usually wider than 2 cm, with spreading to drooping branches (rarely ascending); anthers 1–4 (–5) mm long; leaf blades flat
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6a. Lemmas conspicuously pubescent along the margins [Fig. 196], glabrous or scabrous over the abaxial surface; anthers 1–2 mm long
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6b. Lemmas sparsely to densely pubescent over the abaxial surface; anthers 2–4 (–5) mm long
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7a. Leaf sheaths overlapping and concealing the nodes, the densely pubescent apex prominently outward-flanged and auriculate [Fig. 199]; leaves 9–20 per stem; anthers 2–3 mm long
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7b. Leaf sheaths not overlapping, at least the upper nodes exposed, the glabrous to pubescent apex neither outwardly flanged nor auriculate; leaves 4–6 per stem; anthers (2–) 2.5–4 (–5) mm long
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8a. First glume 1 (–3)-veined; second glume 3 (–5)-veined; lemmas narrow from a side view, 1–1.5 mm deep; spikelets oblong to obtriangular in outline, usually wider toward the apex; lemma awns (8–) 10–50 mm long, often longer than the associated lemma
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9a. Lemmas 22–28 mm long, with awns 30–50 mm long emerging between 2 apical lobes 3–5 mm long
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9b. Lemmas 9–20 mm long, with awns 10–30 mm long emerging between 2 apical lobes 0.8–3 mm long [Fig. 201]
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10a. Panicle with crowded, ascending to erect branches, 2–10 cm tall; pedicels usually shorter that associated spikelets; ligules pubescent (as well as lacerate at the apex)
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10b. Panicle with loose, nodding to ascending branches, 5–20 cm tall; pedicels usually longer than associated spikelets excluding the awns; ligules glabrous (though lacerate at the apex)
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11a. Lemmas 9–12 mm long; anthers 0.5–1 mm long; awns 10–18 mm long; lower panicle branches bearing 4–8 spikelets
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11b. Lemmas 14–20 mm long; anthers 1–1.4 mm long; awns 15–30 mm long; panicle branches bearing 1–3 spikelets
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8b. First glume 3- or 5-veined; second glume 5- or 7-veined; lemmas wider from side view, 1.2–2.2 mm deep; spikelets ovate to lanceolate in outline, usually widest below the middle; lemma awns absent or up to 13 mm long, usually as long as or shorter than the associated lemma
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12a. Lemmas awnless or with awns up to 0.8 mm long; spikelets ovate in outline
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12b. Lemmas with awns 2–13 mm long; spikelets narrow-ovate to lanceolate in outline
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13a. Lemmas 4.5–6.5 mm long, the margins with a sharp bend where the lemma begins to taper toward the apex from its widest point [Fig. 200]; caryopsis longer than the palea
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13b. Lemmas 6.5–11.5 mm long, the margins rounded or with a bluntly angled bend where the lemma begins to taper toward the apex from its widest point; caryopsis as long as or shorter than the palea
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14a. Lemmas with prominently raised veins and concave regions between the veins; anthers 0.6–1 (–1.5) mm long; pedicels mostly shorter than their spikelets [Fig. 197]; inflorescence compact, erect, 3–10 cm tall
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14b. Lemmas with obscure to distinct, but not raised, veins; anthers 1–5 mm long; pedicels as long as or longer than their associated spikelets excluding the awns (usually shorter in B. squarrosus); inflorescence open, ascending to drooping (narrow and erect in B. racemosus), 4–20 cm tall
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15a. Margin of the lemma involute at maturity, tightly enclosing the caryopsis and exposing the rachilla
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16a. Ligules 2–3 mm long, glabrous; anthers 1–2 mm long; awns straight or flexuous, 3–6 (–9.5) mm long
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16b. Ligules 1–1.5 mm long, pubescent; anthers 3–5 mm long; awns straight, 6–11 mm long (in part)
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15b. Margin of the lemma not tightly involute, overlapping the caryopsis and concealing the rachilla
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17a. Anthers 3–5 mm long; panicle 15–30 cm tall (in part)
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17b. Anthers 1–3 mm long; panicle 4–22 cm tall
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18a. Branches of the panicle erect, straight or nearly so, usually 2 per node; lemmas 6.5–8 mm long; anthers 1.5–3 mm long
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18b. Branches of the panicle ascending to, more commonly, spreading or even drooping, flexuous or arching, 2–6 per node; lemmas 7–11.5 mm long; anthers 1–2 mm long
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19a. Awns terete or narrow and flattened at the base, not or only slightly divergent; apical lobes of lemma up to 1.5 mm long; palea up to 1.5 mm shorter than its associated lemma; branches of the panicle rather stiffly ascending to spreading
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19b. Awns broad and flattened at the base, divergent at maturity; apical lobes of lemma 1.5–3 mm long; palea 1–2.5 mm shorter than its associated lemma; branches of the panicle lax, often arched or drooping
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20a. Panicle not secund, with compound lower branches; spikelets with 6–12 florets; lemmas 7–9 mm long, 1.2–2.2 mm deep in side view, the margins with a long, obscure bend where the lemma begins to taper toward the apex from its widest point
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20b. Panicle ± secund, often with simple branches; spikelets with 8–30 florets; lemmas 8–11 mm long, 2.5–3.5 mm deep in side view, the margins with an obtusely angled bend where the lemma begins to taper toward the apex from its widest point
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Each photo represents one species in this genus.