780 ORDER 156. GRAMINEJ3. 



3 A. gracilis Eli, Culm very slender, a foot or more-high ; Ivs. setaceous, scarce 

 1" wide, erect, with short sheaths, pilous at the throat; panicle very slender; 

 spikelets somewhat remote, appressed; lateral awns short (6 to 7"), erect, interme- 

 diate one longer (10 to 12''), spreading, 2 Sandy places, Mass, to Ga., "W. to 111. 

 A grass of little value, as well as the other species of this genus. 



4 A. lanata Poir. Culm erect, 2 to 4f, hairy and branched below ; Ivs. linear, 

 flat, If long, 2 to 3" wide, hairy, especially on the upper surface; sheaths longer 

 than the joints, clothed with a woolly tomentum ; branches of the erect, contracted 

 panicle, tomentous at base ; glumes unequal, longer than the pales ; awns about 

 equal, spreading, as long as the pale (4 to 6"), the middle rather longest. 2 In 

 poor, sandy soils, S. States. Sept, Oct. (A. lanosa Ell.) 



5 A. spiciformis Ell. Culm 1 to 3f high, simple ; Ivs. and sheaths glabrous, the 

 latter shorter than the joints ; panicle dense-flowered, spike-like and cylindrical ; 

 glumes much shorter than the flower, both awned; middle awn of the flower long- 

 est, villous at the base, all three about as long as the pale. U "Wet pine barrens, 

 S. Car. to Fla. Sept., Oct. 



6 A. purpurdscens Poir. Culm erect, simple, filiform, 2 3f; Ivs. very narrow, 

 flat, erect, a foot in length, with short, open sheaths ; panicle long, loosely spicate ; 

 spikelets on short, clavato, appressed pedicels; gls. 4 to 5" long, purplish; awns V 

 long, nearly equal, divaricate, twice the length of the glabrous pale. If Sandy 

 woods, Northern States. Sept. (A. amnis Kunth. A. racemosa Muhl.) 



7 A. stricta MX. UPRIGHT ARISTIDA. Culm strictly erect, csespilous, branched, 

 1 3f; Ivs. straight, erect, pubescent, linear, convolute above; panicle long, 

 loosely racemous; spikelets appressed; gls. (3 to 5" long) unequal, very acute, lower 

 pales hairy at base ; awns twice as long as the pale?, spreading, the middle one 

 the longest. If Penn. to Fla. (Chapman), "W. to Mich. 



8 A. oligantha MX. Culms erect, sparingly branched, 1 2 to 20' high ; pan. ra- 

 ceme-like, remotely few-flowered; gls. short awntd, equaling the pale (!'), which 

 bears 3 divaricate awns thrice its own length, the middle one some longer ; Ivs. 

 involute setaceous. If Prairies, 111. to Ark. and Va. 



9 A. tuberculosa Nutt. Culm erect (declinate at base), 8 20', rigid, with 

 small tubercles in the axils of the numerous branches ; nodes tumid ; Ivs. long and 

 narrow-linear; pan. large, loose, simple; spikelets pedicellate; gls. nearly 1' long, 

 linear, awned; upper paleee involute, the awns 2' long, hispid upwards, twisted 

 together to near the middle, thence finally horizontally divaricate. 2 A very sin- 

 gular species, in dry prairies, 111., Wis. to Ky., Tenn., also found in N. J. 



13. STIPA, L. WEATHER GRASS. (Lat. stipa, a foot-stalk ; allud- 

 ing to the stipitate fruit.) Spikelets 1 -flowered, the flower deciduous, 

 with its thick, bearded, pointed stipe ; glumes membranous ; pales cori- 

 aceous, shorter than the glumes, the lower with a long, twisted or bent 

 awn, jointed at the apex ; caryopsis striate ; stamens 3 ; stigma plum- 

 ous. It Fls. paniculate. Lvs. very narrow. The long awns are deli- 

 cately hygrometic, twisting or untwisting according to the state of the 

 atmosphere. 



1 S. avenacea L. BLACK OAT GRASS. Culm naked above, 2 3f ; Ivs. smooth, 

 striate, setaceous, chiefly radical ; panicle spreading, somewhat 1-sided, 4 6' long, 

 at length diffuse, branches capillary, solitary and in pairs ; glumes nearly equal, 

 mucronate, as long as the dark brown, cylindric fruit; scales 2, lanceolate; awn 

 twisted below, bent above, 2 3' in length. U. S. and Can. (S. Yirginica Pers.) 



2 S. juncea Pursh. Culm 2 3f; Ivs. convolute filiform, smooth inside, long; 

 pan. loose ; gls. loose, filifwmly acuminated to more than twice the length of the fruit; 

 fr. attenuated at base into a stipe, which is a third of its length, stipe acute, pu- 

 bescent ; palese obtuse, distinctly articulated to the awn, which is smooth and slen- 

 der, at length contorted and 4 6' in length. If Prairies, I1L Mo. When in fruit 

 the pungent stipe adheres to everything that comes in its way. Aug. 



14. ORYZOP'SIS, MX-. MOUNTAIN RICE. (Gr. op<a, rice, tyis, ap- 

 pearance.) Spikelets 1 -flowered ; glumes membranous-bordered, veined, 



