^90 ORDER 156. GR AMINES. 



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

 the glumes; sterile one with a recurved, included awn. U Common in wet 

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

 whitish down. Jl. 



26. AI V RA, L. (Gr. alpa, a deadly weapon ; originally applied to a 

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

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

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

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

 hue. 



Glumes much longer than the pales. Awns long No. 1 



Glumes about as long as the pales. Awns long or short Nos. 2, 3 



1 A. atropurpxirea "Wahl. Caespitous, a foot high ; culms very slender ; Ivg. 

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

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



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

 smooth, with striato sheaths and truncate stipules ; pan. loose, spreading, trichoto* 

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

 U Vales and hills, U. S. and Brit. Am., common. An erect, elegant grass, 

 growing in tufts. Jn. 



3 A. caespitosa L. Csespitous, glabrous; st. 18 30' high ; Ivs. narrow-linear, 

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

 diffuse ; awns straight, about as long as the pales, which are longer than the bluish, 

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



27. DAWTHO'NIA, DC. (In honor of M. Danthoine, a French botan- 

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

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

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

 one obtuse, entire. 



D. spicata Beauv. St. slender, nearly erect, 12 18' high, tower Ivs. numerous, 

 4 6' long, flat, hairy above, caulinc 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 palea hairy, about half as 

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

 Aug. (Avena, L.) 



28. AVE X NA, 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. 



ARRHENATHERUM. Gls. unequal, 2-flo\vcred, with a rudiment; lower fl. staminate.No. 1 



AIROPSIS. Gls. subequal, 2-flowered, with no rudiment, tls. both perfect. Dwarf. No. 2 



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



1 A. elatior L. Culm 2 4f, 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; upper flower , 

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

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



2 A. preecox Beauv. Casspitous ; culm erect, a few inches high ; Ivs. % 1' 

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

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

 lower part of the back twice its length. (1) K Y. to Virg. Jn. (Aira, L.) 



3 A. sativa L. COMMON OAT. Culm smooth, 2 4f high ; Ivs. linear-lanceolate, 

 veined, rough, with loose, striate sheaths ; stip. lacerate ; panicle loose ; spikelets 

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

 Awned 5 paleoz gomewhat cartilaginous, closely embracing the caryopsis. (D A 



