THE NORTH AMERICAN SPECIES OF PENNISETUM. 



223 



Desfontaines. The specimen in the Sloane Herbarium from which the cited 

 figure was drawn is Imperata caudata. 31 



DESCRIPTION. 



Plants perennial, in loose clumps, sometimes of 30 or more culms; culms usually 1 

 to 2 meters tall, slender to robust, subcompressed, ascending or suberect from the 

 more or less geniculate, sometimes rooting lower nodes, bearing one to several flower- 

 ing branches from the lower and middle nodes, scabrous below the panicle, other- 

 wise glabrous; sheaths loose, from glabrous to rather densely papillose-hirsute, usu- 

 ally sparsely hirsute along the margin toward the summit, and otherwise glabrous; 

 ligule membranaceous-ciliate, 2 to 3 mm. long; blades mostly rather firm, ascend- 

 ing or spreading, 10 to 40 cm. long, 4 to 18 mm. wide, tapering toward the base 

 (or the reduced upper blades widest at base), acuminate into a long, slender, 

 very scabrous tip, from scabrous on both surfaces (or rarely glabrous beneath) to 

 rather densely papillose-hirsute on both 

 surfaces, more commonly scabrous be- 

 neath and sparsely papillose - hirsute 

 above, always stiffly hairy back of the lig- 

 ule ; panicles terminating the primary culm 

 and branches, occasionally one or two ax- 

 illary panicles borne in the upper sheaths, 

 10 to 25 cm. long, 8 to 10 mm. thick, 

 excluding the elongate bristles, rather 

 dense, usually somewhat nodding, from 

 pale yellow to dusky purple or brown, the 

 axis slender, scabrous; fascicles sessile, at 

 first ascending, spreading or often reflexed 

 in age; bristles unequal, the outer delicate, 

 scabrous only, most of them shorter than the 

 spikelet, the inner densely silky-plumose 

 below, the hairs directed inward, those of 

 the erect lower part of adjoining bristles 

 matted and beautifully crimped, the bris- 

 tles spreading above; spikelets solitary, 

 sessile, 3.2 to 4 mm. long, 0.8 to 1 mm. 

 wide, the glumes and sterile lemma very 

 thin; first glume usually minute, often 

 obsolete ; second glume exceeding the ster- 

 ile lemma and the fruit, 5-nerved, abruptly 

 acuminate, ciliolate, sometimes obscurely 

 erose or lobed; sterile lemma 5-nerved, 

 ciliolate, minutely 3-lobed at the truncate 

 apex, the palea sometimes and, less often, a staminate flower developed; fruit indu- 

 rate, smooth and shining, 2 to 3 mm. long, 0.8 to 1 mm. wide, the narrowed apex of 

 both lemma and palea stiffly ciliate-f ringed. 



In this species the pubescence of the foliage is exceedingly variable, but the floral 

 characters are unusually constant. 



Fig. 68.—Pennisetum setosum. From Amer. Or. 

 Nat. Herb. 611, Trinidad. 



37 See Hitchcock, Contr. U. S. Nat. Herb. 12 : 133. 1908. It is pertinent in this 

 connection to quote Merrill's observation (Interpretation of Rumphius's Herbarium 

 Amboinense, p. 27. 1917): "It is not at all certain that in quoting illustrations of 

 various species as synonyms Linnaeus and his contemporaries and immediate suc- 

 cessors intended them as exact synonyms; it would seem, in many cases at least, that 

 the citation of illustrations as synonyms was intended to convey to other botanists 

 some conception of what the species was like, and not necessarily to indicate that it 

 was an exact equivalent of the species under which it was cited." 



