39 
indrical or nearly so, dense or sometimes interrupted, 3 to 6 inches long,3 to 4 lines 
thick ; leaves narrow, 1 to 3 lines wide: spikelets as in the preceding species, bristles 
usually much shorter.—Texas to Arizona and Mexico, 
10. S. pauciseta Vasey. This species differs from the preceding in the smaller and 
more slender culms, apparently annual, the much looser, shorter, few flowered spikes, 
smaller, shorter leaves, and smaller spikelets, and corresponds better to the figure of 
S. caudata of Pl, 96, Trin.—Texas (No. 2096 C. Wright, Nealley), also Mexico (No. 381 
Pringle). 
** Bristles downwardly barbed. 
11. S.verticillata Beauv. (Gray’s Manual, 6thed., p. 634.) Spike cylindrical, dense, 
2 to 3 inches long, the clusters apparently whorled; bristles short, adhesive.—In culti- 
vated ground, adventitious from Europe. 
CENCHRUS Linn. 
Spikelets as in Panicum, awnless, but inclosed 1 to 5 together in a 
globular and bristly involucre, which becomes coriaceous, and forms a 
hard, rigid, and deciduous bur; the involucres sessile in a terminal 
spike. 
1, C. tribuloides Linn. (Gray’s Manual, 6th ed., p.634.) Annual; culms ascending, 
branching, 6 to 12 inches high; leaves flat ; spike oblong, of 8 to 20 spherical heads; 
involucre more or less downy, armed above with stout, compressed, broadly subu- 
late, erect, or spreading spines; bristles nore, or usually several below the spines, 
spikelets 2- to 3-flowered.—Sandy soil, extensively distributed. 
2 C.echinatus Linn. (Chapm. Fl. 8, States, p. 578.) Culms erect or ascending, 
1 to 2 feet high; leaves flat; spike cylindrical, 4 to 6 inches long, of 20 to 25 roundish 
involucres, downy, spiny above, and with a row of rigid barbed bristles above the 
base; 3- to 5-flowered; involucies purplish.—Field and waste grounds, North Car- 
olina to Mexico, 
3. C. incertus M. A. Curtis, (Chapm. Fl. 8. States Suppl., p. 667.) Smooth, 
strict, nearly simple, erect or ascending, 2 to 3 feet long; leaves linear, folded; the 
lower sheaths longer than the internodes; spikes cylindrical, many- flowered, invo- 
Jucre naked and acute at the base, the 10 or 11 stout spines ciliate; spikelets gemi- 
nate, smooth ; sterile flower triandrons. (C, strictus Chapm.)—Sandy coast Florida to 
North Carolina. Description from Dr. Chapman's Southern Flora. 
4, ©. myosuroides H.B.K. (Chapm. Fl. 8, States, Suppl. p. 667.) (Panicum cen- 
chroides Ell.) Culms 4 to 8 feet high, erect; leaves long, rigid, flat, or becoming con- 
volute toward the point; spikes cylindrical, 3 to 6 inches long, densely many-flow- 
ered; involucre small, 1-flowered, armed with 20 or more slender (not compressed) 
spines, as long as the spikelet.—South Florida, Georgia to Texas and westward, 
PENNISETUM Pers. 
Spikelets with one terminal perfect flower, and a second male or 
neuter one below it, solitary, or two or three together, closely sur- 
rounded by an involucre of usually numerous simple or plumose bris- 
tles which disarticulate from the pedicel with the spikelets. The 
spikelets crowded in a spike-like panicle, or on pedunculated spike- 
like branches. The lower empty glume is small, the second and third 
larger and longer than the perfect flower, the glume of which is thicker 
and more rigid; sterile flower consisting of a membranaceous palet. 
1. P. setosum Rich. (Kth. Enum. Pl. I. p. 161.) Culm 4 feet high; leaves 
linear-acuminate, glabrous; spike cylindrical, dense, 6 to 7 inches long, involu- 
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