730 ORDER 156. GR AMINES. 



3 A. gracilis Ell. 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. If 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, tho 

 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. If "Wet pine barrens, 

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



6 A. purpurascens 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, clavate, appressed pedicels ; gls. 4 to 5" long, purplish ; awns 1' 

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

 woods, Northern States. Sept. (A. affinis Ivuuth. A. racernosa Muhl.) 



7 A. strfcta MX. UPRIGHT ARISTIDA. Culm strictly erect, csespitous, 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 pales, spreading, the middle ona 

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



8 A. oligantha MX. Culms erect, sparingly branched, 12 to 20' high; pan. ra- 

 ceme-like, remotely few-flowered; gls. short awned, equaling the palo (f'), which 

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

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



9 A. ttiberculosa 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 paleas involute, the awns 2' long, hispid upwards, twisted 

 together to near the middle, thenco finally horizontally divaricate. If A very sin- 

 gular species, in dry prairies, 111., "VVis. 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- 

 otis' 2 Fls. paniculate. Lvs. very narrow. The long awns are deli- 

 cately hygrometric twisting or untwisting according to the state of the 

 atmosphere. 



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

 Btriate, 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. Virginica Pers.) 



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

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

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

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

 der, at length contorted and 4 6' in length. If Prairies, 111., Mo. When in fruit 

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



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

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



