126 MR. G. BENTHAM ON GRAMINEÆ. 
65. Guycerta, Br., if we include Atropis, Rupr., is a genus of 
nearlythirty species spread over the extratropical regions, northern 
or southern, both of the New and the Old World. It is very 
nearly allied both to Poa and Festuca, differing from the former 
in the flowering glumes rounded at the base without any promi- 
nent keel, from Festuca in the broader more obtuse glumes, and 
the grain usually free from the palea, and from both in the skort- 
ness of the nerves of the glumes. The habit is somewhat variable, 
but as much so in each section as in the whole genus. The two 
sections into which it has been divided, often raised to the rank 
of separate genera, are:—1. Hydrochloa, Hartm. (Porroteranthe, 
Steud., Exydra, Endl., Glyceria proper of many botanists), with 
the lodicules connate and truncate or deficient, and the thick grain 
only marked on the inner face with a very narrow lined furrow or 
quite smooth ; and 2. Atropis, Rupr. (Puccinellia, Parlat.), with 
two distinct lodicules and the grain more or less compressed from 
front to back, with a broad furrow or almost flat on the inner 
face. But these characters are not constant. The lodicules in 
the typical Hydrochloa, G. fluitans, Br., though thicker than in 
Atropis, and usually connate, are readily separable and occasion- 
ally spontaneously free ; in G. aquatica, Sm., they are so short as 
to render it difficult to say whether they do or do not cohere, and 
in G. nervata, Trin., and in G. pallida, Trin., I can find no trace 
of them; in Afropis they are usually, but not always, more deve- 
loped and thinner. The shape of the seed and of its furrow seems 
io vary from species to species, in so far as I have been able to 
procure it well ripened. 
66. Festuca, Linn., is one of the genera as to whose limits 
botanists are the least agreed. With the exception of the exclu- 
sion of Cutanda and Brizopyrum, we have followed generally the 
arrangement proposed by Cosson and Durieu, which would include 
between seventy and eighty species (estimated by some at above 
two hundred and thirty), almost cosmopolitan in their geogra- 
phical distribution, but most abundant in the northern temperate 
regions of the Old World, with not many American and very few 
tropical species. They are generally distinguished in the sub- 
tribe by the flowering glumes rounded without any prominent 
keel at least at the base, and acute or awned at the end, and by 
the glabrous grain adhering to the palea. But there are excep- 
tions to each of these characters; and some species run very much 
into Poa, whilst others are scarcely distinct from Bromus. The 
