1	"Auricles large, well-developed on both lower and upper leaves; body of lateral spikelets at least 8 mm long; glumes of central spikelets distinctly flattened"	2
1	"Auricles usually lacking or present but inconspicuous on the lower leaves; body of lateral spikelets up to 5 mm long; glumes of central spikelets flattened or not"	4
2	"Plants perennial; culms with a bulbous swelling at the base"	"Hordeum bulbosum"
2	"Plants annual; culms not swollen at the base; lateral spikelets with awns up to 2 mm long"	3
3	"Central spikelets sessile, at least 3 mm wide, its awn, if present, 2-15 cm long"	"Hordeum vulgare"
3	"Central spikelets pedicellate to subsessile or sessile, up to 2 mm wide, its awn 2-4 cm long"	"Hordeum murinum"
4	"Plants annual"	5
4	"Plants perennial"	14
5	"Glumes of central spikelets 1.5-4 cm long"	6
5	"Glumes of central spikelets shorter than 1.5 cm long"	8
6	"Glumes not strongly spreading at maturity"	"Hordeum marinum"
6	"Glumes strongly spreading at maturity"	7
7	"Glumes of central spikelets more or less flattened, 1.5-2 cm long"	"Hordeum arizonicum"
7	"Glumes of central spikelets not flattened, usually much longer than 2 cm"	"Hordeum jubatum"
8	"Lemmas of lateral spikelets with awns 5-10 mm long"	9
8	"Lateral spikelets unawned or with awns 1-2 mm long"	10
9	"Glumes of the lateral spikelets heteromorphic, the lower glumes distinctly flattened and winged, the upper glumes scarcely flattened, almost setaceous"	"Hordeum marinum"
9	"Glumes of the lateral spikelets isomorphic, the lower glumes sometimes slightly flattened but never conspicuously winged"	"Hordeum geniculatum"
10	"Glumes of central spikelets setaceous or somewhat flattened"	"Hordeum depressum"
10	"Glumes of central spikelets distinctly flattened"	11
11	"Plants forming dense or loose tufts; basal leaf sheaths becoming fibrous; lemma awns of central spikelets shorter than 5 mm; glumes usually shorter than 9 mm, flattened portion of lower glume of lateral spiekelts often with distinct shoulders or teeth; rachillas more or less flattened"	"Hordeum flexuosum"
11	"Plants forming loose tufts; basal leaf sheaths not becoming fibrous; lemma awns of central spikelets longer than 5 mm; glumes usually longer than 9 mm, flattened portion of lower glumes of lateral spikelets without distinct shoulders or teeth; rachillas round in cross-section"	12
12	"Lateral florets 2.8-5.7 mm long (excluding the awns), aristulate to aristate (rarely muticous); glumes not spreading at maturity"	"Hordeum pusillum"
12	"Lateral florets 1.7-4.4 mm long, obtuse or, rarely, muticousglumes usually spreading at maturity"	13
13	"Culm nodes glabrous; only the lower or sometimes also the middle, leaf sheaths pubescent; lower glume of lateral spikelets more than 0.4 mm wide, upper glumes setaceous"	"Hordeum euclaston"
13	"Culm nodes and leaf sheaths more or less pubescent; lower glumes of lateral spikelets leass than 0.4 mm wide, upper glumes often flattened but sometimes setaceous"	"Hordeum intercedens"
14	"Glumes of central spikelets distinctly flattened in the lower portion"	15
14	"Glumes of central spikelets not flattened in the lower portion"	22
15	"Glumes spreading at maturity"	16
15	"Glumes not spreading at maturity"	17
16	"Glumes scabrous; lower glume of lateral spikelets distinctly flattened at the base, with a sharp demarcation line at the base; rachillas thick, flattened"	"Hordeum chilense"
16	"Glumes somewhat hairy; lower glume of lateral spikelets not distinctly flattened at the base and without a sharp demarcation line; rachillas thin, setaceous"	"Hordeum arizonicum"
17	"Lemmas with (5) 7 or 9 conspicuous veins"	"Hordeum cordobense"
17	"Lemmas with 5 (rarely more) inconspicuous veins"	18
18	"Lemmas glabrous"	19
18	"Lemmas pubescent, at least towards their tip"	21
19	"Flattened portion of lower glumes of lateral spikelets often with distinct shoulders or teeth"	"Hordeum flexuosum"
19	"Flattened portion of lower glumes of lateral spikelets without distinct shoulders or teeth"	20
20	"Lemma awns 1-2 mm long; rachillas thin, setaceous"	"Hordeum patagonicum"
20	"Lemma awns 5-10 mm long; rachillas thick, flattened"	"Hordeum chilense"
21	"Lower glume of lateral spikelets distinctly flattened; spikes pale green; rachillas more or less thick; lemmas usually pubescent throughout, rarely glabrous"	"Hordeum stenostachys"
21	"Lower glume of lateral spikelets somewhat flattened to setaceous; spikespurple or bluish; rachillas thin or absent; lemmas usually scabrous to hairy  only in the distal portion, rarely pubescent throughout"	"Hordeum muticum"
22	"Glumes spreading at maturity"	23
22	"Glumes not spreading at maturity"	32
23	"Awn of central spikelets 4-8 mm long"	24
23	"Awn of central spikelets at least 10 mm long"	25
24	"Lemmas and paleas 4-5.5 mm long; lemma awns distinctly subulate"	"Hordeum roshevitzii"
24	"Lemmas and pales 6.5-9.5 mm long; lemma awns not distinctly subulate"	"Hordeum fuegianum"
25	"Glumes of central spikelets more or less flattened"	"Hordeum arizonicum"
25	"Glumes of central spikelets not flattened"	26
26	"Lateral spikelets aristate, the awns 1.5-3 cm long, more than half as long as the glumes"	"Hordeum comosum"
26	"Lateral spikelets acute to shortly aristate, the awns always less than 1.5 cm long, less than half as long as the glumes"	27
27	"Lemma of central spikelets scabrous all over; spikes long, more or less terete, greenish"	"Hordeum procerum"
27	"Lemmas of central spikelets smooth or scabrous-hairy only distally; spikes rather short, terete or laterally compressed, often purplish"	28
28	"Spikes terete or more or less laterally compressed; glumes 1-2.5 cm long; glumes and lateral spikelets glabrous, scabrous, or conspicuously hairy"	29
28	"Spikes not laterally compressed; glumes 2.5-7 cm long; glumes and lateral spikelets usually not hairy"	31
29	"Spikes greenish, terete; lemmas and glumes smooth of shortly scabrous"	"Hordeum capense"
29	"Spikes reddish or blackish-purple, more or less laterally compressed; glumes usually scabrous to distinctly pubescent distally, occasionally glabrous"	30
30	"Triplets often more than 2 cm long; lemmas of central spikelets 7-10 mm long; rachillas as long as the paleas; spikes often blackish-purple"	"Hordeum pubiflorum"
30	"Triplets often shorter than 2 cm; rachilla extensions usually less than half as long as the paleas; spikes often reddish"	"Hordeum halophilum"
31	"Lateral spikelets aristulate, 7-15 mm long; anthers 1-1.5 mm long"	"Hordeum lechleri"
31	"Lateral spikelets shortly aristulate, 4-6 mm long; anthers 0.6-1 mm long"	"Hordeum jubatum"
32	"Culms very short, usually 15-20 cm long"	"Hordeum patagonicum"
32	"Culms usually more than 30 cm long"	33
33	"Anthers longer than (2.7) 3 mm"	34
33	"Anthers shorter than 2.7(3) mm"	36
34	"Lemma awn of central spikelets longer than 6 mm; glumes of central spikelets usually longer than 10 mm"	"Hordeum secalinum"
34	"Lemma awn of central spikelets shorter than 5 mm; glumes of central spikelets up to 10 mm long"	35
35	"Culm nodes hairy or glabrous; anthers always hanging freely at anthesis; self-incompatible; lateral spikelets usually with a distinct awn up to 3 mm long; plants native to Asia"	"Hordeum brevisubulatum"
35	"Culm nodes glabrous; anthers emerging but not hanging freely at anthesis; self compatible; lateral spikelets obtuse to acute, not aristate; plants native to South America"	"Hordeum tetraploidum"
36	"Lemmas more or less pubescent"	37
36	"Lemmas glabrous"	38
37	"Rachises usually not brittle; lemmas with short, more or less sparse hairs; lemma awns longer than 5 mm"	"Hordeum bogdanii"
37	"Rachises brittle; lemmas with obtuse long hairs; lemma awns shorter than 5 mm"	"Hordeum patagonicum"
38	"Glumes of central spikelets 7-15 mm long; awn of central spikelets 1.5-8 mm long"	"Hordeum parodii"
38	"Glumes of central spikelets 8-23 mm long; awn of central spikelets 7-21 mm long"	39
39	"Plants tufted but somewhat rhizomatous; glumes of central spikelets 5-9 mm long; awn of central spikelets 2.5-8.5 mm long"	"Hordeum guatemalense"
39	"Plants cespitose; glumes of central spikelets 8-23 mm long; awn of central spikelets 7-12 mm long"	40
40	"Leaves narrow, glaucous, erect; spikes glaucous and laterally compressed"	"Hordeum erectifolium"
40	"Leaves not narrow, not glabrous, not erect; spikes neither glaucous nor laterally compressed"	41
41	"Glumes of central spikelets 13-23 mm long, about the length of the glumes of the lateral spikelets; lower glumes of lateral spikelets more or less flattened near the base"	"Hordeum capense"
41	"Glumes of central spikelets 7-17 mm lon, shorter than those of the lateral spikelets; lower glumes of lateral spikelets setaceous throughout"	"Hordeum brachyantherum"