Mr. Woods 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 

 Aru7id'inacece, 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 Avenacece, and twisted as well as geni- 

 culate. If Deschampsia ccespitosa 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 Arundinacece. 



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 spiculce of Calamagrostis, to those containing also an abortive rudi- 

 ment in Deyeuxia, and thence through A. Plinli, in which they have sometimes 

 only a rudiment, and sometimes a complete second floret (when it becomes 

 the Arundo blflora of the Florentine botanists), and A. mauritanica (which is 

 perhaps the same species, but is desci'ibed as having from one to three florets,) 

 to A. Donax, 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 affbrds 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 Deyeuxia 

 under the name of Arundo, as was done by Mertens and Koch, and to assign 

 to the remaining plants the generic name of Donax. The genera I am willing 

 to acknowledge are : 



1. Arundo. Spiculee 1- or more-flowered, the lowermost perfect. Glumes 



equal, or the outer the largest. These and the palese membranous. Pa- 

 nicle diffiise. Seed hairless. 



2. Ammophila. Spiculse 1-flowered, with an interior rudiment. Glumes nearly 



equal, membrano-scariose. Palese membranous, nerved, with a short, 

 straight, nearly terminal awn. Panicle spike-like ! 

 VOL. xvin. F 



