510 
2. S. imberbis (Poir.) R. & 8S. Culms3 to 6 dm. high: leaves narrow: spike very 
slender, 3 to 6 em. long; bristles 4 to 8, less than twice as long as the spikelets: 
spikelets about 2 mm. long; perfect floret usually purple at the acute apex.—Through- 
out Texas except on the dry mesas. 
++ Spikes compound or nearly simple in No. 7. 
++ Branches short, crowded, densely flowered: perfect floret obscurely rugose or nearly 
smooth. 
3. S. viridis (L.) Beauy. (PIGEON-GRASS. GREEN FOXTAIL.) Culms3 to6dm. high: 
leaves hispid: panicle 4 to 10 em. long; bristles 2 to 5, mostly light green: spike- 
lets 2 to3 mm, long; perfect floret oval or obovate.—Introduced in cultivated land. 
4, S.Italica (L.) Kth. (ITALIAN MILLET.) Culms 1 to1.5 m, high: panicle lem. 
thick or more, 6 to 20 em. long, sometimes interrupted below, often nodding; bristles 
2 to 5 ina cluster, light green or purple: spikelets nearly 3 mm. long; perfect floret 
obovate, oval or spheroidal.—Introduced from Europe and cultivated in all parts of 
the United States; often escaped from cultivation. 
++ ++ Branches more loosely flowered: panicle interrupted: perfect florets rugose. 
5. S. setosa (Swartz.) Beauv. Culms about 1m. high, usually branching: panicle 
1.5 to3dm. long, very narrowly conical, often nodding; lower branches 2 to 4 em. long: 
bristles 1 to3 in each cluster: spikelets 2mm. long.—From the Pecos river westward. 
6. S. caudata (Lam.) R.& S&S. Culms 6 to 10 dm. high, usually branching, often 
pubescent at the nodes: leaves narrow: panicle 8 to 12 cm. long nearly cylindrical; 
lower branches about 1 em. long: bristles Lor2; spikes2 mm. long, broadly obovate. 
—Throughont Texas and extending to Florida and Arizona. 
7. S. pauciseta Vasey. Culins slender, 2 to 4 din. high: leaves flat, lanceolate: 
panicle cylindrical, narrow, loosely flowered, 3 to Sem. long: bristles 1 to3: spike- 
lets nearly 2 mm. long, oblong, in small clusters, on very short branches. (Perhaps 
only a variety of 8S. caudata.)—Texas to Arizona. 
** Bristles barbed downward. 
8. S. verticillata (L.) Beauv. (BrisTLy roxratn.) Culms weak, 5 to 10 dm. high: 
panicle nearly cylindrical, dense, compound with short branches: bristles 1 or 2, 
adhesive: spikelets 2 mm. long; perfect floret finely rugose.—Introduced in culti- 
vated lands. 
19. CENCHRUS L. (Bur Grass.) 
Spikelets as in Panicum, awnless, but inclosed, 1 to 5 together, in a 
globular bristly or spiny involucre, which becomes coriaceous and forms 
a deciduous hard and rigid bur; the involucres sessile in a terminal 
spike: spines minutely barbed backward, causing the burs to stick to 
anything with which they come in contact. 
* Burs hard and spiny, but with few or no bristles except at the base. 
1. C. tribuloides L. (SAND-BuUR.) Culms branched, ascending, 2 to 5 dm. high: 
spike oblong, often interrupted, of 8 to 20 heads, about 51mm. in diameter, more or 
less downy: spines spreading, rigid, broad at the base.—Sandy soil, waste land, 
throughout the United States. A bad weed. 
2. C. echinatus L. (HEDGE-HO0G Grass). Culms 38 to 6 dm. high, branched, 
ascending: spike 8 to 20 em, long, rather closely crowded with 20 to 40 burs 5 to 7 
mm. in diameter, downy: spines mostly erect: bristles usually purple, mostly from 
near the base, erect like the spines.—Waste land. 
* * Burs softer, bristles numerous, 
