1	"Plants perennial"	2
1	"Plants annual"	6
2	"Culms usually with a bulbous swelling at the base; auricles to 5.5 mm long, well developed"	"Hordeum bulbosum"
2	"Culms not bulbous-based; auricles absent or no more than 1 mm long"	3
3	"Glumes of the central spikelet flattened near the base"	"Hordeum arizonicum"
3	"Glumes of the central spikelet usually setaceous throughout, rarely flattened near the base"	4
4	"Glumes 15–85 mm long, divergent to strongly divergent at maturity"	"Hordeum jubatum"
4	"Glumes 7–19 mm long, divergent or not at maturity"	5
5	"Anthers of the central spikelet 0.8–4 mm long; auricles absent"	"Hordeum brachyantherum"
5	"Anthers of the central spikelet 3.5–5 mm long; auricles present on the basal leaves"	"Hordeum secalinum"
6	"Auricles to 8 mm long, well developed even on the upper leaves; lemmas of the lateral florets 6–15 mm long"	7
6	"Auricles usually absent or to 0.3 mm long; lemmas of the lateral florets 1.7–8.5 mm long"	8
7	"Rachises disarticulating at maturity; glumes of the central spikelets ciliate; lemmas of the central florets to 2 mm wide, with awns 20–40 mm long; lateral spikelets staminate"	"Hordeum murinum"
7	"Rachises usually not disarticulating at maturity; glumes of the central spikelets pubescent; lemmas of the central florets at least 3 mm wide, unawned or with awns 30–180 mm long; usually 1 or both lateral spikelets at a node seed-forming"	"Hordeum vulgare"
8	"Glumes bent, strongly divergent at maturity"	9
8	"Glumes straight, ascending to slightly divergent at maturity"	10
9	"Glumes of the central spikelets not flattened, (15)35–85 mm long"	"Hordeum jubatum"
9	"Glumes of the central spikelets slightly flattened towards the base, 11–28 mm long"	"Hordeum arizonicum"
10	"Lemmas of the lateral spikelets with awns 3–8 mm long"	"Hordeum marinum"
10	"Lemmas of the lateral spikelets unawned or with awns no more than 3 mm long"	11
11	"Glumes of the central spikelets setaceous to slightly flattened near the base"	12
11	"Glumes of the central spikelets distinctly flattened near the base"	13
12	"Spikes 4–8 mm wide; lemmas of the central spikelets with awns 3–12 mm long; ligules 0.3–0.8 mm long"	"Hordeum depressum"
12	"Spikes 6–20 mm wide; lemmas of the central spikelets with awns 10–22 mm long; ligules 0.6–1.8 mm long"	"Hordeum arizonicum"
13	"Lemmas of the lateral spikelets 1.7–4.4 mm long, usually unawned, rarely with awns to 1.2 mm long; sheaths with stripes of hairs"	"Hordeum intercedens"
13	"Lemmas of the lateral spikelets 2.5–5.7 mm long, usually awned, with awns to 1.8 mm long; sheaths glabrous"	"Hordeum pusillum"