Mr. Woops on the Genera of European Grasses. 33 
quite as long as those in A. Halleri or A. sylvatica. The size and coarseness 
of the plant common to the tribe forms certainly part of our notion of the 
Arundinacee, but A. tenella seems intermediate both in this circumstance and 
in the hairs which envelop its florets, and it is placed by some botanists in 
the genus Agrostis. On the other hand, some of the many-flowered species 
seem technically to approach to Avena; but the hairs of the latter genus are 
usually stiffer, and not so fine and silky as in Arundo. The awn too, when it 
occurs, is always stronger among the Avenaceæ, and twisted as well as geni- 
culate. If Deschampsia cespitosa be rightly separated from Aira, its size and 
coarse perennial herbage, as well as the hairs at the base of the floret, might 
almost justify us in placing it among the Arundinacee. 
In forming the genera of this tribe, the number of florets in a spicula seems 
hardly to afford a sufficient ground. The difference of habit between the two 
extremes is not great, and the gradation is complete from the strictly single- 
flowered spiculæ of Calamagrostis, to those containing also an abortive rudi- 
ment in Deyeuxia, and thence through A. Plinii, in which they have sometimes 
only a rudiment, and sometimes a complete second floret (when it becomes 
the Arundo biflora of the Florentine botanists), and 4. mauritanica (which is 
perhaps the same species, but is described as having from one to three florets,) 
to 4. Donaz, where the florets vary from two to five. The gradation of habit is 
as complete as that of the number of florets. Phragmites loves a more watery 
situation than the others, and the barren or neutral lower floret affords us a 
good and stable generic character; but if I were to separate the many- 
flowered species, I should be disposed to unite Calamagrostis and Degenia 
under the name of Arundo, as was done by Mertens and Koch, and to assign 
to the remaining plants the generic name of Donar. The genera I am willing 
to acknowledge are : 
1. Arundo. Spiculæ l- or more-flowered, the lowermost perfect. Glumes 
equal, or the outer the largest. These and the paleze membranous. Pa- 
nicle diffuse. Seed hairless. 
2. Ammophila. Spiculæ 1-flowered, with an interior rudiment. Giuse nearly 
equal, membrano-scariose. Paleæ membranous, nerved, with a short, 
straight, nearly terminal awn. Panicle spike-like ! 
VOL. XVIII. r 
