790 Order 156.— GRAMINB^. 



sheaths striate ; pan. oblong, dense, whitish, with a purple tinge ; fls. shorter than 

 the glumes; sterile one with a recurred, included awn. — If Common in wet 

 meadows, N. Eng., to the uplands of Ga. A beautiful grass, very soft with ■ 

 whitish down. Jl. 



26. APRA, L. (Gr. aipa, a deadly weapon ; originally applied to a 

 poisonous grass.) Spikelets 2-flowered, without abortive rudiments ; 

 glumes 2, membranaceous and sbining, subequal ; one of the flowers 

 pedicellate ; palea3 subequal, pilous at base, the lower one lacerate at 

 apex and awned on the back. — Fls. in panicles of a silvery purplish 

 hue. 



§ Glnmes much longer thnn llio pales. Awns long: No. 1 



§ Glumes about as long as the paics. Awns long or short Kos. 2, 3 



1 A. atropurpiirea Wahl. Casspitous, a foot high ; culms very slender ; Ivs. 

 flat ; pan. thin, with spreading branches ; glumes much longer than the flowers ; 

 pales hairy at apex. — High Mts. of N. Eng. and N. T. Aug. 



2 A. flexuosa L. Culm smooth, 1 — 2f high, nearly naked; bis. setaceous, 

 smooth, with striate sheaths and truncate stipules ; pan. loose, spreading, trichoto- 

 mous, with long, flexuous branches ; awns geniculate, twice longer than the pales. 

 — 11 Tales and hUls, U. S. and Brit. Am., common. An erect, elegant grass, 

 growing in tufts. Jn. 



3 A. ceespitosa L. C^spitous, glabrous ; st. 18 — 30' high ; Ivs. narrow-linear, 

 scabrous above, smooth beneath, flat ; panicle pyramidal, capillary, oblong, finally 

 difiuse ; awns straight, aiout as long as the pales, which are longer than the bluish 

 glumes. — U Swamps, N. States and Can. May. (A. aristulata Torr.) 



27. DAKTHO'NIA, DC. (In honor of M. Banthoine, a French botan- 

 ist.) Spikelets 2 — 7-flowered; glumes 2, subequal, longer than the 

 spikelet of flowers, cuspidate ; palese hairy at the base, lower one bi- 

 dentate at the apex, with a twisted awn between the teeth, the upper 

 one obtuse, entire. 



D. spicSta Bcauv. jSi. slender, nearly erect, 12 — 18' high, lower fos. numerous, 

 4 — 6' long, flat, hairy above, cauline Ivs. much shorter, subulate, erect, on very 

 short sheaths; panicle simple, spicate, short, erect; spikelets 3 — 8 or 10, about 7- 

 flowered ; glumes a little longer than the flowers ; lower pcdea hairy, about half as 

 long as its spirally twisted awn. — Pastures and open woods, common. June 

 — Aug. (A vena, L.) 



28. AVE^WA, L. Oat. Spikelet 2 to 5-flowered ; glumes 2, loose 

 and membranous, awnless, often as long as the pales ; pales 2, 'herba- 

 ceous, at length subcoriaceous, the lower one bifid and usually with a 

 twisted or bent awn at the back. — Fls. paniculate. 



§ AEEHENATIIEEUM. Gls. unequal, 2-flowovea, with a rudiment ; lower fl. stnminato.No. 1 



I AIROPSIS. Gls. subequal, 2-floworwl, with no ilidiment, lis. both perfect. Dw.irf. No. 2 



§ AYENA proper. Gls. equal, longer than the 2 fls., and strongly striate. Cultivated . . . .No. 8 



1 A. elatior L. Culm 2 — if, geniculate, smooth ; Ivs. lance-linear, rough on the 

 margin and upper surface ; panicle loose, equal, nodding, branches in pairs or ter- 

 nate ; spikelets 2-flowered ; awn twice as long as the palea ; wpper flower 5 , 

 mostly awnless. — y A tall grass, introduced and naturalized in cultivated 

 grounds. May, June. (Arrhenatherum avenaceum Beauv.) 



2 A. precox Beauv. Csespitous ; culm erect, a few inches high ; Ivs. \ — 1' 

 long, rough ; sheaths deeply striate ; panicle dense, raopmous ; spikelets ovate, 2- 

 flowered, glumes as long as the flowers ; lower palea ^Ith a bent awn from the 

 lower part of the back twice its length.—® N. T. to Virg. Jn. (Aira, L.) 



3 A. sativaL. Common Oat. Culm smooth, 2— 4f high; iv«. linear-lanceolate, 

 veined, rough, with loose, striate sheaths ; slip, lacerate ; pamick loose ; spikelet 

 psdunculate, pendulous, 2-flowered, both flowers perfect, the lower one mostly 

 awned ; paleai somewhat cartilaginous, closely embracing the caryopsis.— (D A 



