48 MR. G. BENTHAM ON GRAMINEA. 
hardened and frequently more or less united at the base, the 
inner ones often broad and scale-like. In some specimens, how- 
ever, of C. calyculatus, Cav., and its allies the hardening appears 
so slight as to bring the genus into very close connexion with 
Pennisetum. 
13. PENNISETUM, Pers., the principal genus of the group, would 
now contain about forty species, chiefly African, amongst which 
two or three extend to the Mediterranean region, tropical or central 
Asia, or tropical America, and a very few may be endemic in Asia, 
Australia, or America. It has been at various times proposed to 
separate several genera from it, and two or three of these have been 
pretty generally adopted ; but they pass so gradually one into the 
other, and their chief characters, derived from the hairiness or 
numbers of the involucral bristles, are so little in accord with any 
other characters or habit, that the several following groups can 
scarcely be considered even as definite sections. Pennisetum 
itself has been restricted to those species in which the bristles are 
numerous and some or all of them more or less hairy ; whilst those 
in which the whole of the bristles are perfectly glabrous form the 
genus Gymnotriz, Beauv. But however easy this distinction may 
appear at first sight, it is neither natural nor always definite. In 
a few African species proposed by Figari and De Notaris as their 
genus Eriochete, the whole of the sete are densely woolly-plumose; 
in some of the commoner species numerous outer sete of each 
involucre are glabrous, and as many or more or fewer of the inner 
ones are hairy. In P. flaccidum, Munro, from East India, and 
P. Benthamianum, Steud., from tropical Africa, amongst very 
numerous glabrous ones there are generally only two or three 
hairy ones, or sometimes none at all, thus forming a gradual con- 
nexion with the true species of Gymnotrix, where the sete are 
always quite glabrous; and there is nothing else whatever to 
distinguish the two series even as marked sections. P. lanatum, 
Klotzsch, is a remarkable Himalayan species, in which the 
involueral bristles are few, sometimes reduced to a single long 
rigid branched one, either plumose or glabrous, showing well the 
true nature of the involucre of the genus. Penicillaria, Willd., 
often still retained as a genus, was founded upona plant frequently 
cultivated in the Indo-African regions, which may at first sight 
appear to be abundantly distinct. The long dense cylindrical 
spike or spike-like panicle is often above a foot long and an inch 
in diameter, although in other cultivated specimens not above 
