THE NORTH AMERICAN SPECIES OF PENNISETUM. 



213 



Bristles numerous, most of them about twice the length of the spikelet; 



panicle less dense 9. P. complanatum. 



Panicles terminal and axillary, the latter on slender naked peduncles, 1 to 

 several from a sheath. 

 Blades elongate, rarely over 12 mm. wide, tapering into a long setaceous- 

 involute tip; spikelets 6 to 7 mm. long, the bristles mostly shorter. 



11. P. durum. 



Blades 15 to 40 mm. wide, if narrower not elongate, not setaceous-tipped ; 



spikelets 4.5 to 6 mm. long, some of the bristles always longer. 



Steriiu lemma inclosing a well-developed palea and usually a staminate 



flower; panicles loosely flowered: most of the bristles about twice 



the length of the spikelet 14. P. bambusiforme. 



Sterile lemma empty; panicles rather densely flowered; most of the 

 bristles not more than once and a half the length of the spikelets. 

 Panicles dull green; bristles scant, most of them not exceeding the 

 spikelet, the innermost about twice as long. 12. P. distaehyum. 

 Panicles tawny; bristles numerous, most of them exceeding the spike- 

 let, the innermost not conspicuously longer than the others. 



13. P. prolifieum. 

 1. Pennisetum. villosum. R. Br. 



Pennisetum villosum R. Br. in Salt, Voy. Abyss. App. 62. 1814, nom. nud.; in 

 Fres. Mus. Senckenb. Abh. 2: 134. 1837. Described from specimens collected in 

 Abyssinia during the years 1805 to 1810 by Henry Salt. The type has not been 

 examined. 



Pennisetum villosum var. humile Hochst.; A. Rich. Tent. Fl. Abyss. 2: SS7. 1851. 

 "Prope Adoua [Abyssinia] (Schimper)." A specimen of Schimper's no. 316, col- 

 lected at Adoa, Abyssinia, in September, 1837, in the National Herbarium, is a 

 dwarfed plant like Chase's no. 5600 from Santa Barbara, California. 



Cenchrus villosus Kuntze, Rev. Gen. PI. 3 2 : 347. 1898. Based on Pennisetum 

 villosum R. Br. 



DESCRIPTION. 



Plants perennial, rather pale, at length forming dense clumps from a knotted 

 crown; culms ascending, 15 to 50 cm. tall, rarely 1 meter 

 or more tall, commonly branching from the lower nodes, 

 mostly flattened or angled in drying, the uppermost 

 joint villous, at least below the inflorescence, other- 

 wise glabrous; sheaths loose, mostly overlapping, pilose 

 along the scarious margin and at the summit or gla- 

 brous; ligule a ring of fine hairs 1.5 to 2 mm. long; blades 

 ascending or spreading, 3 to 6 mm. wide, mostly elon- 

 gate, the upper often exceeding the inflorescence, but 

 in dwarf plants sometimes only 8 to 10 cm. long, flat 

 or folded, sparsely pilose on the upper surface or gla- 

 brous, the margins and sometimes the under surface sca- 

 brous; panicle grayish tawny, very dense, oval, 3 to 15 

 cm. long, 3 to 5 cm. wide including the bristles; fas- 

 cicles short-peduncled, with a tuft of white hairs at 

 the base of the peduncles; bristles slender, spreading, 

 the longest 4 to 5 cm. long, the inner plumose below, 

 the innermost not differentiated from the others; spike- 

 lets 1 to 4 in a fascicle, sessile, 10 to 12 mm. long, 1.7 to Fig. 63.— Pennisetum villosum. 

 2 mm. wide; glumes unequal, the first about 1 mm. From Eastwood 172, California. 

 long, one-nerved or nerveless, subacute, the second 



about one-third the length of the spikelet, one-nerved, acuminate; sterile lemma 

 slightly shorter than the fertile one, Ipng-acuminate, finely many-nerved, scabrous 



