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 .. 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 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 .................................................................. 24 24 Awns 3.5–6 mm; auricles absent; leaf blades 4–6 mm wide; lemmas 9–12 mm long; glumes glabrous, scabrous or minutely pubescent; lower glumes lanceolate; leaf sheaths sparsely to densely pilose ................................ 11. B. frondosus – Awns 1–3 mm long; auricles usually present, sometimes absent; leaf blades 2–4 mm wide; lemmas 7–10 mm long; glumes usually pubescent, occassionally glabrous to puberulent; lower glumes triangular or narrowly lanceolate; leaf sheaths glabrous, pubescent or pilose .............................................................................................................................. 1. B. anomalus

Published as part of Saarela, Jeffery M., Peterson, Paul M. & Valdés-Reyna, Jesus, 2014, A taxonomic revision of Bromus (Poaceae: Pooideae: Bromeae) in México and Central America, pp. 1-147 in Phytotaxa 185 (1) on pages 8-9, DOI: 10.11646/phytotaxa.185.1.1, http://zenodo.org/record/10090001