1	"Lower stems densely hairy"	"Aristida californica"
1	"Lower stems glabrous"	2
2	Annual	3
2	"Perennial herb"	5
3	"Glumes 10--22 mm; lemma awns generally 10--70 mm"	"Aristida oligantha"
3	"Glumes 3--13 mm; lemma awns 3--20 mm"	4
4	"Central awn straight to curved at base"	"Aristida adscensionis"
4	"Central awn spirally coiled at base"	"Aristida dichotoma"
5	"1&deg; inflorescence branches spreading at base (upper appressed to ascending in <i>Aristida purpurea</i> var. <i>wrightii</i>)"	6
5	"1&deg; inflorescence branches appressed to ascending at base (curving or drooping in <i>Aristida purpurea</i> var. <i>purpurea</i>)"	8
6	"Lower inflorescence branches spreading, upper ascending to appressed"	"Aristida purpurea var. parishii"
6	"All inflorescence branches spreading"	7
7	"Leaf blade base glabrous; lemma tip much twisted; anthers 0.8--1 mm"	"Aristida divaricata"
7	"Leaf blade base sparsely long-hairy; lemma tip slightly twisted or straight; anthers 1--2 mm"	"Aristida ternipes var. gentilis"
8	"Awns generally > 40 mm"	9
8	"Awns generally < 40 mm"	10
9	"Upper glume generally 16--25 mm; lemma 0.3--0.8 mm wide just below awns, awns 0.2--0.5 mm wide at base"	"Aristida purpurea var. longiseta"
9	"Upper glume generally 7--16 mm; lemma 0.1--0.3 mm wide just below awns, awns 0.1--0.3 mm wide at base"	"Aristida purpurea var. purpurea"
10	"1&deg; inflorescence branches and spikelet stalks thread-like, curving to drooping, appearing S- or U-shaped"	"Aristida purpurea var. purpurea"
10	"1&deg; inflorescence branches and spikelet stalks generally stiff, straight, generally appressed to ascending (lower spreading in <i>Aristida purpurea</i> var. <i>parishii</i>)"	11
11	"Lemma tip, awn base +- 0.1 mm wide at base, awns delicate"	"Aristida purpurea var. nealleyi"
11	"Lemma tip, awn base 0.2--0.3 mm wide, awns +- stiff"	12
12	"Inflorescence generally 3--15 cm; leaf blade generally 4--10 cm"	"Aristida purpurea var. fendleriana"
12	"Inflorescence generally 12--30 cm; leaf blade generally 10--25 cm"	13
13	"Inflorescence dense, +- red when young; lower branches with 10--20 spikelets"	"Aristida purpurea var. parishii"
13	"Inflorescence +- open, tan to brown when young; lower branches with 2--10 spikelets"	"Aristida purpurea var. wrightii"