40 MR. G. BENTHAM ON GRAMINEÆ. 
however, as far as I have observed, usually sterile ; and a similar 
character is to be found in some species or varieties of Setaria, 
and very rarely in Panicum itself, next to which the genus appears 
to be best placed. The synonym Joachimia, Ten., given by Kunth, 
was a name intended for it by Tenore, but I believe never actually 
published. Tenore figures the plant as a Beckmannia. 
7. PANICUM, Linn., after deducting Ichnanthus, Oplismenus, 
Setaria, and several smaller genera, remains one of the larger, and 
probably the largest, among tropical Grasses, and is still in many 
respects polymorphous. In habit and inflorescence it may be 
confounded sometimes with Paspalum, sometimes with Arundi- 
nella, or even with some Agrostesm. Generally speaking, it may 
be easily recognized by technical characters ; but the most marked, 
the very small size of the lowest empty glume, is not quite con- 
stant; for in a few species this glume is wholly deficient as in 
Paspalum, whilst in a few others it is of the size of the second 
glume; the hardening also of the fruiting glume and palea is in 
some species very slight. There is nothing, however, sufficiently 
definite or constant in these exceptional species to mark them out 
as intermediate genera; and here, as in so many other cases of 
large genera of Çyperacew and Graminew, we must admit the 
existence of forms which must be placed in one or the other of 
allied genera from considerations of convenience rather than of 
strict character. Taking the genus Panicum within the limits we 
have ascribed to it, nearly 800 supposed speeies have been pub- 
lished : Steudel enumerates 716; Doell has 134 Brazilian ones, 
Fournier 97 Mexican, Nees 44 South-African; I described 54 
Australian ones ; and they are rather numerous in tropical Africa 
and Asia; but a considerable number are repeated in several or 
even in all of these Floras, and a large proportion of Steudel's 
species are mere synonyms or blunders. The total number of 
fairly distinet species can therefore scarcely be estimated at much 
above 250. These have been variously grouped, chiefly according 
to their inflorescence ; and no less than eighteen supposed genera 
have been at different times separated from it, but are now re- 
united, either as being founded on insufficient, uncertain, or even 
mistaken characters, or as being, in our opinion, more conveniently 
regarded as sections than as genera. But, even as sections, their 
limits are often as far from being absolutely definite as are those 
of the whole genus. The following eleven are those which have 
appeared to be the most distinct; but they are all more or less 
