68 MR. G. BENTHAM ON GRAMINEZE, 
10. ARTHRAXON, Beauv. (Pleuroplitis, Trin, Batratherum, 
Nees, Zucea, Kunth, Lasiolytrum, Steud., Alectoridia, A. Rich., 
Psilopogon, Hochst.), has also about ten species, chiefly from 
the Indo-Australian region, but extending on the one hand to 
China and Japan, and on the other to tropical Africa. The 
spikes are slender as in Dimeria; but there are three stamens, 
and the lower empty glume is broad but acute, not truncate as in 
Apocopis. 
Rottboelliee, the third group of Andropogone&, is often re- 
garded as a distinet tribe, characterized by the simple spike, 
the spikelets in pairs at each notch or excavation of the rhachis, 
the one sessile, the other pedicellate, and no awn to the flowering- 
glume. There are, however, as in other subtribes, here and 
there exceptions to one or more of these characters. We have 
seven genera. 
11. Erronurvs, Humb. and Bonpl., has about twelve species, 
chiefly South-American or African, with, however, one Austra- 
lian and one from the East-Mediterranean region. They all 
differ little from Rottboellia besides the long silky hairs which 
clothe the spike, thus connecting Rottboellieze with other An- 
dropogonesx. E. hirsuta, Munro (Rottboellia hirsuta, Vahl), has 
been proposed by Boissier as a distinct genus Lasiurus, as having 
the spikelets in threes instead of in twos at each node of the 
rhachis. But that character is by no means constant; in several 
specimens I have found the spikelets in threes oreven in fours 
at the lower nodes; but in others they are in the normal pairs 
from the base of the spike. 
12. RorrPoELLIA, Linn. f.,a tropical or subtropical genus widely 
spread, but chiefly in the Old World, has been either extended to 
nearly the whole subtribe or very variously restricted to a small 
number or to a single species. It seems best characterized by in- 
cluding all those which have the simple terete spike, without the 
hairs of Elionurus or the peculiarities of the four following genera. 
It would contain about eighteen species, amongst which several have 
been proposedas monotypic genera. Cwlorhachis, Brongn.,is R. mu- 
ricata, Retz (R. glandulosa, Trin.); Peltophorus, Desv.,is R.myurus: 
in both of these the lowest or outer glume of the perfect spikelet is 
rigid and bordered on each side at the apex by a membranous wing, 
which, however, is also present, but much less prominent, in Z. 
rugosa, Nutt. Phacelura, Griseb. ( Pholiurus,'Trin. in Spreng. Neue 
Entd. ii. 67, not of the Fundam. Agrost.), is the Oriental R. digi- 
