1	"Involucral bristles free throughout, more or less filiform, retrorsely scabrous"	2
1	"Involucral bristles flattened into spines and connate below, often forming a cup, usually antrorsely scabridulous or scabrous"	8
2	"Bristles solitary below each spikelet; panicles both terminal and axillary"	"Cenchrus unisetus"
2	"Bristles several below each spikelet, united at the base into an involucre; panicles always terminal on the stems and branches"	3
3	"Ligules membranous"	"Cenchrus stramineum"
3	"Ligules composed of a line of hairs"	4
4	"At least the inner Involucral bristles ciliate to plumose, 16-65 mm long (if a suffritcose desert grass see Pennisetum divisum)"	5
4	"All involucral bristles glabrous or, occasionally, thinly hairy, 4-20 mm long"	6
5	"Panicles densely ovoid to subspherical; plants low, mat-forming and rhizomatous"	"Cenchrus longisetus"
5	"Panicles linear; plants erect, densely tufted, without rhizomes"	"Cenchrus setaceus"
6	"Stems woody, branched throughout their length; spikelets 6.5-8.6 mm long; leaves tightly inrolled, pungent"	"Cenchrus ramosissimus"
6	"Plants tufted, sometimes branched above the base; spikelets 2-6 mm long; leaves flat or inrolled, not pungent"	7
7	"Lower glumes 1/2 the length of the spikelets; upper glumes 2/3-3/4 the length of the spikelets"	"Cenchrus massaicus"
7	"Lower glumes up to 1/4 the length of the spikelets; upper glumes up to 1/2 the length of the spikelets"	"Cenchrus caudatus"
8	"Bristles of the involucres retrorsely barbellate, tenaciously clinging to clothing or fur"	"Cenchrus biflorus"
8	"Bristles of the involucres antrorsely scabridulous, not clinging to clothing or fur"	9
9	"Inner bristles flexuous, filiform above"	10
9	"Inner bristles rigid, flattened, connate for 1/4 -2/3 their length and forming a cup"	12
10	"Inner bristles united only at the base, forming a shallow disk 0.5-1.5 mm in diameter, occasionally connate for up to 0.5 mm above its rim"	"Cenchrus ciliaris"
10	"Inner bristles connate for 1-2.5 mm about the rim of the disk"	11
11	"Plants annuals or short-lived perennials; leaves flat, 2-5 mm wide"	"Cenchrus pennisetiformis"
11	"Plants tufted perennials; leaves inrolled, about 1 mm wide"	"Cenchrus somalensis"
12	"Involucres glabrous; outer bristles commonly suppressed"	"Cenchrus setiger"
12	"Involucres pubescent; outer bristles numerous"	"Cenchrus mitis"