TRIANDRIA. DIGYNIA. 61 



fVequently sheathed by cyir.biform acute or acuminated 

 leaves, in some species so closely as not to admit the ex- 

 pans. on of the spikes; flowers alternate and sessile, with 

 lateral abortive pedicella e florets, sometimes mere bar- 

 ren pedicelLs, arisini^ near iheir base. In the American 

 species, the involucrate \illus is often short, sometimes 

 inconspicuous. 



Species. 1. A. nutans. 2- avenacevm. 3. ciliatnm, El. 

 4. mela7ioca7^pus, bit.. 5. scoparittm. &. macrourum. 7. tenia- 

 riuin 8. virginicum 9. biconie. 10 avgejiteum, El. 11, 

 di^sitifloriim 12. vaginatum, El. 13. tetrastuchyunty El. 

 lA.furcatum. 



In India ttiere are 11 species of this genus, 2 of which, 

 the A. J>tardiis and .Ji. muricatnm, are e\QY\ where culti- 

 vated for their aromatic odour. There are also 3 species 

 in Japan, 5 in the south of Europe, most o*^" wliich aie also 

 indigenous to Barbaiy, 1 species pt-cidiarto that country, 

 and 1 at the Cape of G(jod Hope, 2 in the West India- 

 islands, and now 14 species (numerated in the United 

 States, of wh ch, several are also com lOn to the tropical 

 reg-ions of the American comment. Bxceptin.^ the con- 

 tinent of India, there appears not to exist a single genu- 

 ine species of Andropugouy within the southern liemia- 

 phere. 



§ II. Calices ^flowiredt dispersed. 



89. TRISETUM. Persoon. (Tliree-awiied Oat- 

 grass.) 



Ccdix 2 to 3 flowered, acuminate and cari- 

 nate. Corolla, (outer valve) terminated bv 2 

 sli<»rter, almost tooth like awns (or the apex of 

 tlie glume setareously bifid,) and 1 longer 

 straight dorsal awn. not contorted. 



Species of .^vena of other authors, distinguished chief- 

 ly by a deeply ci ft acvim.nate and carinate dorsal valve, 

 a central straight awn, witii compressed pale coioui'ed 

 spikelfis, and fiosculi which are generally siiooth. 



Species. 1 T pratense, {Arena Jlavescens, L.) The rest 

 of this gen>is is chiefly cunfined to the South ot Europe, 

 Barbary, and tlie Cape of Good Hope. 



90. AIRA. L. (liair-grass.) 



Calix shining, 2 valved, 2-flowered. Corolla 

 awniess, or awned from the base, 2-vaived. 



G 



