Bromus Linnaeus 1753

Key to Bromus of México and Central America 1 Spikelets strongly flattened laterally; lemmas strongly keeled (sect. Ceratochloa) ........................................................... 2 – Spikelets not strongly flattened laterally; lemmas rounded over the mid-rib, not strongly keeled ..................................... 4 2 Awns 0–3.5(–4) mm long; upper glumes 9(–11)-nerved, lemma nerves usually raised ............................. 6. B. catharticus – Awns 4–15 mm long; upper glumes 5–7-nerved, lemma nerves not raised ......................................................................... 3 3 Upper glumes ca. equal in length to the lowermost lemma; lemmas generally hairy along the margins, backs hairy or glabrous, marginal hairs generally longer than those on lemma backs; panicles with 1–2 spikelets per branch; spikelets 1.5–2.5(–2.7) cm long; plants annual ............................................................................................................ 2. B. arizonicus – Upper glumes shorter than the lowermost lemmas; lemmas scabrous or variously hairy, marginal hairs if present similar in length to those on lemma backs; panicles with 1–3(–9) spikelets per branch; spikelets 2–4 cm long; plants perennial ........ .......................................................................................................................................................................... 5. B. carinatus 4 Lemma apices conspicuously bidentate, teeth hyaline, awn-liketoacuminate; largestlemmasgenerally <2 mm wide ... 5 – Lemma apices entire or inconspicuously bidentate, teeth usually not hyaline; largest lemmas generally> 2 mm wide .. 10 5 Awns geniculate and/or twisted; spikelets elliptic to lanceolate (sect. Neobromus) .................................. 4. B. berteroanus – Awns straight, not twisted; spikelets linear-elliptic to cuneate (sect. Genea) ...................................................................... 6 6 Lemmas mostly> 20 mm long; awns 30–65 mm long; upper glumes 18–35 mm long .................................. 8. B. diandrus – Lemmas mostly <20 mm long; awns 8–30 mm long; upper glumes 7–21 mm long .......................................................... 7 7 Inflorescences open, branches spreading to nodding, usually one-sided, often sinuous, usually longer than the spikelets; spikelets 1.5–2(–2.5) cm long (2.5–3.5 cm including awns) ......................................................................... 22. B. tectorum – Inflorescences dense, branches ascending to spreading, not one-sided or sinuous, usually shorter than the spikelets; spikelets 2–4.5 cm long (3–6.5 cm including awns) ..................................................................................................................... 8 8 Inflorescence internodes gradually reduced distally, some branches usually longer than spikelets, shortest branch on lowest inflorescence node 6–24 mm long, longest branch on lowest node 0–1 times branched; culms glabrous below the inflorescences; florets not overlapping at maturity .............................................................................................. 16. B. madritensis – Inflorescence internodes abruptly reduced distally, branches shorter than spikelets, shortest branch on lowest inflorescence node ≤ 6 mm long, longest branch on lowest node 2–5 times branched; culms pubescent below the inflorescences; florets overlapping at maturity ..................................................................................................................................... 20. B. rubens 10 Plants annual; lower glumes 3(5)-nerved; upper glumes 5–9-nerved (sect. Bromus) ......................................................... 11 – Plants perennial; lower glumes 1(3)-nerved; upper glumes 3(5)-nerved ........................................................................... 13 11 Awns inserted 1.5–5 mm below lemma apex, straight to strongly divergent .............................................. 14. B. japonicus – Awns inserted <1.5 mm below lemma apex, straight ........................................................................................................ 12 12 Lemmas densely pubescent, nerves raised; glumes sparsely to densely pubescent; lower glumes 5.2–7 mm long; upper glumes 6–8.5 mm long; lemmas 7.5–9 mm long; spikelets not widening substantially by divergence of the florets as the fruit forms, lemmas continuing to obscure most rachillas; caryopses flat or crescent shaped in cross section; panicles usually dense .................................................................................................................................................... 12. B. hordeaceus – Lemmas glabrous, occassionally scabrous distally, nerves smooth, not distinctly raised; glumes glabrous or scabrous; lower glumes 3.6–4.9 mm long; upper glumes 4.2–6.1 mm long; lemmas 6–7.7 mm long; spikelets widening substantially by divergence of the florets as the fruit forms, many rachillas becoming visible as the lemma wraps around the caryopses; caryopses U- and V-shaped in cross section; panicles ± open ...................................................................... 21. B. secalinus 13 Lemmas 3(–5)-nerved (sect. Mexibromus) ........................................................................................................................ 14 – Lemmas 5–7-nerved (sect. Bromopsis) .............................................................................................................................. 16 14 Awns 7–13 mm long; lemmas 14–20 mm long; anthers 1.1–2(–3) mm long ......................................... 9. B. dolichocarpus – Awns <5 mm long; lemmas <14 mm long; anthers> 3 mm long .................................................................................... 15 15 Anthers 6–6.5 mm long; widest leaf blades 2–3 mm wide, blades not narrowing towards their base; awns (1–) 2–3.5 mm long; auricles usually absent (sometimes present in plants from Cerro Potosí, NL); plants densely tufted, often with a conspicuous, corm-like rootstock .............................................................................................................................. 7. B. densus – Anthers 3.5–5.5 mm long; widest leaf blades 6–16 mm, blades narrowing towards their base; awns 2.5–4.5(–5) mm long; auricles present; plants tufted, conspicuous corm-like rootstock absent ....................................................... 3. B. attenuatus 16 Plants with rhizomes; awns absent or up to 3 mm long; longest anthers> 4 mm long ................................... 13. B. inermis – Plants caespitose, rhizomes absent; awns 1.5–11 mm long; all anthers <4 mm long ....................................................... 17 17 Most lower glumes on a plant 1-nerved ............................................................................................................................. 18 – Most lower glumes on a plant 3-nerved ............................................................................................................................. 22 18 Lower leaf sheaths densely lanate, the hairs matted at the tips .................................................................... 15. B. lanatipes – Lower leaf sheaths pubescent, pilose, or glabrous, never lanate ....................................................................................... 19 19 Lower glumes (7–) 9–11 mm long, linear-lanceolate; lemmas 12–16 mm long, linear-lanceolate, gradually narrowed to apices; spikelets moderately laterally compressed .............................................................................................. 10. B. exaltatus – Lower glumes 4.9–9.5(–12) mm long, lanceolate; lemmas 7–13.5(–15) mm long, elliptic to lanceolate; spikelets terete to moderately laterally compressed ........................................................................................................................................ 20 20 Auricles usually present; awns 1–3 mm long; leaf blades 2–4 mm wide; lemmas 7–10 mm long; ligules 0.2–1.6 mm long ......................................................................................................................................................................... 1. B. anomalus – Auricles absent; awns 3.1–8 mm long; leaf blades (3–)4–10.5(–13) mm wide; lemmas (9–)10–13.5(–15) mm long; ligules 1.5–4 mm long ................................................................................................................................................................... 21 21 Anthers 1–2.6(–3.4) mm long; awns 3.1–6.5 mm; panicle branches lax, ascending to nodding; plants widespread in México ................................................................................................................................................................... 19. B. richardsonii – Anthers (3–) 3.5–4 mm long; awns (6–) 6.5–8 mm long; panicle branches stiff, erect to ascending; plants endemic to Coahuila, México ............................................................................................................................................... 17. B. pinetorum 22 Upper glumes 5-nerved; anthers 3.5–5.5 mm long .............................................................................. 18. B. pseudolaevipes – Upper glumes 3-nerved; anthers 1.5–3.5 mm long ............................................................................................................ 23 23 Lower glumes (7–) 9–11 mm long; upper glumes (9–) 11–14 mm long; lemmas 12–16 mm long, linear-lanceolate, gradually narrowed to apices; spikelets moderately laterally compressed .............................................................. 10. B. exaltatus – Lower glumes 4.9–8.5 mm long; upper glumes 6–10.5 mm long; lemmas 7–12(–13) mm long, elliptic to lanceolate, apices acute, obtuse or truncate; spikelets terete to moderately laterally compressed .............

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