104 MR. G. BENTHAM ON GRAMINE®. 
flexuose rhachis of the spikes bordered by a narrow membrane, 
in the flowering glume aud palea vey small and thin, resembling 
lodieules, and a few other minor points. It is being figured for 
the fortheoming part of Hooker's Icones. 
13. Boureroua, Lag. (Hutriana, Tein., Actinochloa, Willd.), 
eomprises about twenty-five American species, northern or 
southern, but chiefly western. As in the four preceding genera, 
the spikes are distant along the main peduncle, and often nume- 
rous, very rarely reduced to oae or two; but they are usually 
short, with the spikelets densely crowded in two rows on one side 
of the rhachis, and the rhachilla always eontinued beyond the 
single hermaphrodite flower, bearing one to three empty glumes 
or awns, or sometimes a male flower. The flowering and upper 
empty glumes usually end in three or five lobes, points, or awns ; 
but they are often exceedingly variable in this respect even in 
the same specimen, and it becomes difficult to make much use 
of them in the arrangement of the species. The following four 
sections, raised by some to the rank of genera, are founded chiefly 
on inflorescence :—(1) Chondrosia or Chondrosium, Desv. Spikes 
usually few, often rather long, with numerous spikelets (more 
than twelve) neatly pectinate, and the terminal empty glume 
usually three-awned ; the species rather numerous, especially in 
Mexico, where they run much one into another. (2) Atheropo- 
gon, Muehl., including Heterostega or Heterosteca, Desv. Spikes 
often numerous, but usually very short with few (rarely above 
twelve) spikelets, crowded but scarcely pectinate, or almost re- 
duced to clusters, the terminal empty glume varying from three- 
awned to entire, or reduced to a single bristle. The species best 
known, B. racemosa, Lag. (Atheropogon apludoides, Muehl., 
Dinebra curtipendula, DC.), was associated by DeCandolle and 
Beauvois with the Dinebra arabica of Jacquin, which, however, 
differs essentially in its several-flowered spikelets. (3) Zria- 
thera, Desv. Spikes still further reduced than in Atheropogon, 
consisting usually of two to four spikelets so narrow and so close 
together as to appear like a single one, and perhaps sometimes 
really only a single one, the upper empty glume reduced to three 
awns, as in several species of the preceding section. There appear 
to be two species, B. aristidoides (Dinebra aristidoides, H. B. K., 
forming the genus Aristidium, Endl.), with two to four spikelets 
to each spike, and B. £riathera, to which I should, with Munro, 
refer both Zriathera, Desv., and Zriena, H. B.K. The spike- 
