1	Spikelets strongly laterally compressed, lemmas 7–13-veined, keeled (B. sect. Ceratochloa (P. Beauvois) Grisebach)		(2)
+	Spikelets slightly laterally compressed to ± cylindrical, lemmas 5–9-veined, rounded on back		(4)
2 (1)	Perennial; leaf sheaths retrorsely pubescent; lemmas often hairy, awn 5–7 mm.		53 B. marginatus
+	Annual; leaf sheaths glabrous; lemmas mostly glabrous, mucronate or awned		(3)
3 (2)	Lemmas awnless or with mucro, ca. 1 mm; palea 1/2 lemma length.		54 B. catharticus
+	Lemmas with ca. 10 mm awn; palea subequal to lemma.		55 B. carinatus
4 (1)	Perennials, tufted or rhizomatous		(5)
+	Annuals		(37)
5 (4)	Glumes subequal to lower florets; awn stout, recurved, mostly as long as lemma; panicle narrow, branches simple (B. sect. Sinobromus Keng ex P. C. Keng)		(6)
+	Glumes conspicuously shorter than lower florets; awn slender, straight, mostly shorter than lemma; panicle contracted to effuse (B. sect. Bromopsis Dumortier)		(10)
6 (5)	Lower glume 5–8 mm, upper glume 7–12 mm; lemmas 8–10 mm.		24 B. himalaicus
+	Lower glume 8–15 mm, upper glume 11–17 mm; lemmas 9–16 mm		(7)
7 (6)	Glumes glabrous		(8)
+	Glumes pubescent		(9)
8 (7)	Culms 50–70 cm tall, nodes 3; lemmas glabrous.		26 B. epilis
+	Culms up to 100 m tall, nodes 7–8; lemmas marginally and distally pubescent.		27 B. mairei
9 (7)	Panicle branches each with 1–5 spikelets; spikelets 12–20 mm; awn arising near lemma apex.		28 B. sinensis
+	Panicle branches each with 1 apical spikelet; spikelets 18–25 mm; awn arising between apical lobes.		25 B. porphyranthos
10 (5)	Plants usually more than 1 m tall; lemma with long or short awn		(11)
+	Plants less than 1 m tall (if more than 1 m, then lemma awn shorter than 3 mm, sometimes absent)		(24)
11 (10)	Plants tufted, without rhizomes or stolons; culms with 6–9 nodes		(12)
+	Plants rhizomatous; culms often with fewer than 6 nodes		(16)
12 (11)	Lemma 3–5-veined; rachilla clearly visible from side in mature spikelet		(13)
+	Lemma often 7-veined; rachilla not visible from side of intact mature spikelet		(14)
13 (12)	Rachilla internodes 3–4 mm; lemma 5-veined, ca. 12 mm.		1 B. magnus
+	Rachilla internodes 1–2 mm; lemma 3-veined, ca. 10 mm.		2 B. plurinodis
14 (12)	Panicles contracted; lemmas 10–12 mm.		3 B. erectus
+	Panicles spreading; lemmas 12–15 mm		(15)
15 (14)	Panicle branches 3–5 cm, with 1–3 spikelets.		4 B. pseudoramosus
+	Panicle branches up to 20 cm, with 2–9 spikelets.		5 B. ramosus
16 (11)	Plants with long creeping rhizomes		(17)
+	Plant with short rhizomes		(20)
17 (16)	Panicles spreading.		7 B. pumpellianus
+	Panicles narrow		(18)
18 (17)	Panicles racemelike; lemmas glabrous.		6 B. stenostachyus
+	Panicles narrowly contracted; lemmas pubescent on veins		(19)
19 (18)	Lemma pubescent along keel and marginal veins to middle or slightly above; awn 1–5 mm.		8 B. sibiricus
+	Lemma pubescent on marginal veins almost to apex; awn up to 2 mm.		14 B. korotkiji
20 (16)	Panicle branches (2–)6–9 per node		(21)
+	Panicle branches 2–5 per node		(22)
21 (20)	Awns 1–1.5 mm; rachilla not visible from side, internodes very short.		13 B. inermis
+	Awns 5–10 mm; rachilla clearly visible from side, internodes 3–4 mm.		12 B. remotiflorus
22 (20)	Leaf blades 3–5 mm wide.		9 B. staintonii
+	Leaf blades 5–12 mm wide		(23)
23 (22)	Lemmas 11–14 mm; anthers 2.5–3 mm.		10 B. benekenii
+	Lemmas 10–12 mm; anthers 1–1.2 mm.		11 B. ciliatus
24 (10)	Awns absent or less than 2(–4) mm; plants with long rhizomes		(25)
+	Awns more than 2 mm; plants tufted or rhizomatous		(26)
25 (24)	Lemmas glabrous, scabrid near base; anthers 3–4 mm.		13 B. inermis
+	Lemmas pilose, at least on keel and marginal veins; anthers 5–6 mm.		14 B. korotkiji
26 (24)	Plants with long downwardly extending rhizomes.		15 B. formosanus
+	Plants tufted or with short rhizomes		(27)
27 (26)	Plants loosely tufted, or with short inconspicuous rhizomes		(28)
+	Plants densely tufted		(32)
28 (27)	Plants ca. 20 cm tall; panicle contracted, lower branches crowded.		20 B. variegatus
+	Plants 20–60 cm tall; panicle open, lower branches not crowded, spreading		(29)
29 (28)	Plants ca. 60 cm tall, with short rhizomes.		21 B. confinis
+	Plants ca. 20–50 cm tall, tufted		(30)
30 (29)	Awns ca. 3 mm.		17 B. paulsenii
+	Awns 8–12 mm		(31)
31 (30)	Panicle branches each with 2–4 spikelets; spikelets 2–2.5 cm.		22 B. morrisonensis
+	Panicle branches each with 1 or 2 spikelets; spikelets 3–4 cm.		23 B. nepalensis
32 (27)	Plants 40–90 cm tall		(33)
+	Plants up to 40(–50) cm tall		(34)
33 (32)	Lower glume 8–10 mm, upper glume 10–12 mm.		17 B. paulsenii
+	Lower glume 5–6 mm, upper glume 7–8 mm.		19 B. tyttholepis
34 (32)	Awns 6–8 mm.		16 B. riparius
+	Awns 3–5 mm		(35)
35 (34)	Leaf blades ca. 5 mm wide; panicles 10–12 cm.		17 B. paulsenii
+	Leaf blades 1.5–2 mm wide; panicles 5–9 cm		(36)
36 (35)	Panicle branches scabrid, shorter than spikelet; lemmas glabrous, often scabrid.		17 B. paulsenii
+	Panicle branches slender, flexuous, often longer than spikelets; lemmas pubescent.		18 B. cappadocicus
37 (4)	Spikelets broadened upward, wedge-shaped; glumes narrow, lower glume 1(–3)-veined, upper glume 3(–5)-veined		(38)
+	Spikelets narrowed upward, oblong-lanceolate; glumes broad, lower glume 3–5-veined, upper glume 5–9-veined (B. sect. Bromus)		(44)
38 (37)	Awn 4–6 times length of lemma; lemma apex minutely 2-toothed (B. sect. Nevskiella (Kreczetowicz & Vvedensky) Tournay).		35 B. gracillimus
+	Awn 1–3 times length of lemma; lemma apex clearly 2-toothed, teeth 3–7 mm (B. sect. Genea Dumortier)		(39)
39 (38)	Panicle lax, branches spreading or drooping		(40)
+	Panicle contracted, branches erect or ascending, never drooping		(41)
40 (39)	Panicle much branched, branches longer or shorter than spikelets, pubescent; spikelets 1–8 per branch, secund.		29 B. tectorum
+	Panicle simple, branches up to 10 cm, with 1 or no branchlets; spikelets sparse, 1 or 2(or 3) per branch.		30 B. sterilis
41 (39)	Lower glume 15–20 mm; lemmas 20–30 mm, awn 30–40 mm.		31 B. rigidus
+	Lower glume 6–10 mm; lemmas 10–15 mm, awn 10–20 mm		(42)
42 (41)	Panicle lax; branches 2–3 cm, scabrid; culms glabrous below inflorescence; stamens 2.		32 B. madritensis
+	Panicle contracted; branches shorter than spikelets, ca. 1 cm, culms pubescent below inflorescence; stamens usually 3		(43)
43 (42)	Plants 5–15 cm tall; panicle ca. 5 cm, branches each with 1 or 2 spikelets; lemmas 13–15 × 1–1.5 mm.		33 B. fasciculatus
+	Plants 30–40 cm tall; panicle ca. 10 cm, branches each with 4 or 5 spikelets; lemmas 10–13 × ca. 2 mm.		34 B. rubens
44 (37)	Lemmas 3-awned.		52 B. danthoniae
+	Lemmas 1-awned		(45)
45 (44)	Spikelets (2–)3–4 cm; lemmas 14–18 mm		(46)
+	Spikelets (1–)1.5–2.5(–3) cm; lemmas 5–11 mm		(49)
46 (45)	Spikelets oblong-lanceolate, ca. 6 mm wide; lemma apex deeply toothed, teeth (1.5–)3–4 mm; panicle open, branches several times longer than spikelets, nodding		(47)
+	Spikelets broadly elliptic, ca. 10 mm wide; lemma apex shallowly toothed, teeth 1–2 mm; panicle slightly contracted, branches not longer than spikelets, obliquely ascending		(48)
47 (46)	Lower glume ca. 10 mm; lemma 15–18 mm, awn 20–25 mm, lower part slightly flattened, twisted, conspicuously recurved		48 B. oxyodon
+	Lower glume 5–8 mm; lemma 10–15 mm, awn 8–17 mm, terete, straight, usually erect.		49 B. pectinatus
48 (46)	Lemma scabrid; awn 5–10 mm, straight; anthers 2–3 mm; panicle branches on 1 side of axis.		50 B. grossus
+	Lemma smooth; awn 10–20 mm, conspicuously recurved; panicle branches on all sides on axis.		51 B. lanceolatus
49 (45)	Lemma margins inrolled, not covering adjacent florets; rachilla internodes exposed in mature spikelets.		36 B. secalinus
+	Lemma margins overlapping adjacent florets; rachilla internodes enclosed in mature spikelets		(50)
50 (49)	Lemmas 5–7 mm; awn shorter than lemma body, straight; spikelets 1–1.5(–2.5) cm		(51)
+	Lemmas 8–12 mm, awn as long as or longer than lemma body, straight or recurved; spikelets (1.5–)2–3 cm		(53)
51 (50)	Lemmas 6–11 mm; anthers 1.5–3 mm; caryopsis enclosed by lemma, not exposed.		41 B. racemosus
+	Lemmas 5–6 mm; anthers 0.5–1.5 mm; caryopsis longer than lemma, exposed		(52)
52 (51)	Culms 30–50 cm tall; leaf blades ca. 10 cm; panicle 5–10 cm; lemmas 5.5–6.5 mm.		37 B. lepidus
+	Culms ca. 10 cm tall; leaf blades 3–4 cm; panicle ca. 3 cm; lemmas 4–5 mm.		38 B. brachystachys
53 (50)	Lemmas broadly ovate-elliptic, 3–4 mm wide in side view, margins broadly membranous with a conspicuous obtuse angle about halfway between base and apex; panicle subracemose, branches each with 1 or 2 apical spikelets.		39 B. squarrosus
+	Lemmas elliptic, ca. 2 mm wide in side view, margins without any conspicuous angle; panicle laxly spreading or contracted		(54)
54 (53)	Panicle lax, open, 15–25 cm, branches and pedicels longer than spikelets		(55)
+	Panicle contracted, 3–10 cm, branches and pedicels shorter than spikelets		(58)
55 (54)	Anthers ca. 4 mm; palea subequal to lemma; leaf sheaths glabrous.		40 B. arvensis
+	Anthers 0.5–3 mm; palea conspicuously shorter than lemma; leaf sheaths pubescent		(56)
56 (55)	Awns straight; all awns within a spikelet subequal.		41 B. racemosus
+	Awns curved outward, lower awns within a spikelet shorter than upper awns		(57)
57 (56)	Lemma 10–15 mm, apex deeply 2-lobed, acuminate; awn arising 3–4 mm below apex, terete, spreading.		49 B. pectinatus
+	Lemma 8–10 mm, apex with short, obtuse teeth; awn arising 1–2 mm below apex, base slightly flattened, recurved outward when mature.		42 B. japonicus
58 (54)	Lemmas glabrous; awn as long as or slightly longer than lemma body		(59)
+	Lemmas pubescent; awn slightly shorter than lemma body		(61)
59 (58)	Panicle ca. 10 cm; lower glume ca. 7 mm, awn straight, arising ca. 1 mm below lemma apex; anthers ca. 1 mm.		43 B. sewerzowii
+	Panicle 3–7 cm; lower glume 3–4 mm; awn curved downward, arising 1.5–3 mm below lemma apex; anthers 0.3–0.6 mm		(60)
60 (59)	Panicle with few spikelets, 1-sided; lemmas 8–10 mm, apical teeth 0.5–1 mm.		44 B. tytthanthus
+	Panicle dense, with many clustered spikelets; lemmas 7–8 mm, apical teeth 1.3–2.5 mm.		45 B. scoparius
61 (58)	Plant 40–80 cm tall; culms pubescent on nodes and below panicle, panicle branches and pedicels pubescent; awns slender, straight.		46 B. hordeaceus
+	Plant 20–40(–60) cm tall; culms, panicle branches, and pedicels glabrous; awns conspicuously recurved, base slightly flattened, twisted		(62)
62 (61)	Spikelets 10–15 mm; lower glume 2/3 as long as upper glume; lemma apex with 2–3 mm teeth; anthers ca. 1 mm.		47 B. intermedius
+	Spikelets 15–50 mm; glumes subequal; lemma apex with 1–1.5 mm teeth; anthers 1–1.5 mm.		39 B. squarrosus