PANICEiE. 159 



Culms stout, 90-120 cm. high. Sheaths hispid; ligule a fringe 

 of liairs; blades glahrous, folded, grooved, 30-120 cm. long, 3-4 

 cm. wide, acuminate at both ends. Panicle dense, lanceolate, the 

 a])ex nodding, 30-60 cm. long, the longest rays 2.5-3 cm, long, the 

 branches and pedicels bearing scattered slender bristles 1-2 cm. 

 long. Spikelets elliptical, acute, 3 mm. long, first empty glume 

 ovate, 3-uerved, 1.5 mm. long, second ovate, obtuse or subacute, 

 5-nerved, 2 mm. long, the third ovate-acute, 5-uerved, a little ex- 

 ceeding the acute floret. Floral glume and palea not very firm. 

 Near streams. 



Mexico (San Luis Potosi), Pringle 3921. 



31. (13). Cenchkus L. Sp. PI. 1049 (1753). Linn. Coroll. 

 Gen. 20 (1737). Rarem Adans. Fam. 2:35 (1763). Echisachys 

 Neck. Elem. 3:228 (1790). 



Spikelets with one terminal perfect flower and sometimes a 

 staminate one below it, not awned, single or 2-3 together within 

 an ovoid or globular involucre of numerous bristles, the inner ones 

 usually broad and flattened, connected at the base and ha/dened 

 around the fruit; the involucres sessile or pedicellate in a simple 

 spike or raceme and falling off with the spikelets. Glumes 4, the 

 outer one much smaller or minute, the second and tliird nearly 

 equal or the second shorter; a palea and sometimes 3 stamens in 

 the third floral glume of the perfect floret rather firm, but not so 

 hard as in most species of Panicum. Styles mostly shortly united 

 at the base. Grain enclosed, but not adherent to the glume and 

 palea. 



There are about 12 species of annuals or perennials, widely 

 scattered over the warmer regions of the New and the Old World. 

 Most of them are troublesome weeds on sandy land. 



Cenchrus is perhaps most nearly related to Pennisetum, also re- 

 lated to Chamwraphis and Panicum. 



a. Spike cylindrical, burs containing 1 spikelet which is as 

 long as the spines 1 



a. Spike cylindrical, burs containing 2 spikelets, blades con- 

 duplicate 2 



