80 ME. G. BENTHAM ON GBAMINEiE. 



(2) Arthratlwrum, Nees, the awn is dftcidedly articulate ou the 

 glume and much twisted above the articulation below the branches, 

 the flowering glume itself much shorter than the lower empty- 

 glumes, instead of exceeding them as in Ghmtaria. In (3) &ti- 

 pagrostis, Nees, the awn is articulate on the glume, as in Arthm- 

 therum, but scarcely twisted, and above the branches elegantly 

 plumose, the branches also being plumose in some species ; whilst 

 in others, forming Kgari and De Notaris's proposed genus Schis- 

 tachne, the central awn alone is plumose, the lateral branches 

 short and glabrous. All, however, are most conveniently in- 

 cluded in the great genus Aristida. 



2. Stipa, Liun., is almost as numerous and as widely spread 

 as Aristida. It is also strongly characterized, as to the great 

 majority of species, by the narrow, rather hard fruiting glume, 

 carrying off a rather long or obconical internode of the rhachilla 

 (or so-called callus), by the long undivided awn more or less 

 articulate on the glume and usually twisted at the base, and by 

 the presence of three lodicules ; but the exceptions to one or more 

 of these characters are more numerous than in Aristida ; the in- 

 ternode of the rhachilla varies much in length and in shape, the 

 articulation aud twist of the awn gradually disappear in some 

 species, and the third lodicule, though often as large as the others, 

 is sometimes much smaller or even quite obsolete. The genus is 

 also not so clearly divisible into sections as Aristida, although 

 several genera have been proposed for more or less aberrant 

 species. Macrochloa, Kunth, includes 8. tenacissima, Linu., and 

 S. arenaria, "Brot., both from the Mediterranean region, remark- 

 able for their large membranous glumes, the iiowering one shortly 

 bifid at the apex. In Aristella, Bertol., founded on ;8. aristella, 

 Linn., a European aud Mediterranean species, in Streptachne, Br., 

 a single Australian species, and in OrtTiorapMum, Wees, two or 

 perhaps three East-Indian species, the flowering glume is 2-toothed 

 or shortly bifid at the apex, the awn scarcely or not at all articu- 

 late, and the internode of the rhachilla very short, though still 

 perhaps slightly thickened under the flowering glume. The 

 S. aristella, however, is very closely connected with typical Stipa 

 through iS. sibirica. Lam., S. Redowskii, Trin., and S. altaica, 

 Ledeb. Jarava, Euiz and Pav., was founded on S.jarava, Kunth 

 {S. eriostacliys, Cav., 8. papposa, Nees), a widely-spread West- 

 American species, to which the small spikelets in a long narrow 

 dense panicle, with the flowering glumes crowned under the awn 



