2 P. alpinum L. Mountain Herd's Grass. Culm about If high, simple, erect; lvs. shorter than the sheaths, broad and clasping at base, acute at apex, smooth; sheaths inflated; spicate pan., oblong-ovate, very short (4 to 5" long); gls. truncate, mucronate, with a fringed keel; awns as long as the glumes. -Order CLVI Gramineae Grasses Part 6 2488 Alpine regions of the White Mts., N. H. Also native of Arc. Am.

12. ARISTI'DA, L. Beard Grass. Poverty Grass. (Latin arista, an awn; characteristic of the genus.) Panicle contracted or racemous; spikclets 1-flowered, flower stipitate; glumes 2, unequal; pales pedicellate, lower one with 3 awns at the tip, upper one very small, awn-less; ovary stipitate; scales 2, entire; stamens 3; stigma plumous.

§ Awns twisted-confluend below, and jointed to the pale, very long...........................

No. 9

§ Awns distinct below and not jointed to the pale. (*)

* Awns about equal and divaricate, - thrice as long as the flower...........................

Nos. 7, 8

- twice as long as the flower..............................

Nos. 6, 7

- as long as the flower.....................................

Nos. 4, 5

* Awns unequal, the 2 lateral twice shorter (6") and suberect...................................

No. 3

* Awns very unequal, the 2 lateral 4 times shorter (2") and erect..............................

Nos. 1,2

1 A. dichotoma Mx. Caespitous: culm dichotomously branching above; panicle contracted-racemous; gls. 3 to 4" long; lateral awns very short, erect,' the intermediate one nearly as long as the pales (3"), spreading, contorted. -Order CLVI Gramineae Grasses Part 6 2489 A slender grass, in sandy Boils, U. S., common. Culms 8 - 12' high, branching at each joint Lvs. very narrow, with very short, open sheaths, and a very short stipule. Spikelets slender, on clavate peduncles. Aug.

2 A. ramosissima Engelm. Culms diffuse, tufted; rac. loose-flowered, simple, slender; glumes with short awns, 3 or 5-veined; lower pale about as long as the glumes (7 to 9"), lateral awns short (2") erect, middle one spreading, 1' long. -Order CLVI Gramineae Grasses Part 6 2490 Dry places, Ill. (Engelm.)

3 A. gracilis Ell. Culm very slender, a foot or more high; lvs. 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, intermediate one longer (10 to 12"), spreading. -Order CLVI Gramineae Grasses Part 6 2491 Sandy places, Mass. to Ga., W. to Ill. 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; lvs. 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, tomeutous at base; glumes unequal, longer than the pales; awns about equal, spreading, as long as the pale (4 to 6"), the middle rather longest. -Order CLVI Gramineae Grasses Part 6 2492 In poor, sandy soils, S. States. Sept., Oct. (A. lanosa Ell.)

5 A. spiciformis Ell. Culm 1 to 3f high, simple; lvs. 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 longest, villous at the base, all three about as long as the pale. -Order CLVI Gramineae Grasses Part 6 2493 Wet pine barrens, S. Car. to Fla. Sept., Oct.

6 A. purpurascens Poir. Culm erect, simple, filiform, 2 - 3f; lvs. 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 V long, nearly equal, divaricate, twice the length of the glabrous pale. -Order CLVI Gramineae Grasses Part 6 2494 Sandy-woods, Northern States. Sept. (A. affinis Kunth. A. racemosa Muhl.)

7 A. stricta Mx. Upright Aristida. Culm strictly erect, caespitous, branched, 1 - 3f; lvs. 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 one the longest. -Order CLVI Gramineae Grasses Part 6 2495 Penn. to Fla. (Chapman), W. to Mich.

8 A. oligantha Mx. Culms erect, sparingly branched, 12 to 20' high;, pan. raceme-like, remotely few-flowered; gls. short awned, equaling the pale (3/4'), which bears 3 divaricate awns thrice its own length, the middle one some longer; lvs. involute setaceous. -Order CLVI Gramineae Grasses Part 6 2496 Prairies, Ill. to Ark. and Va.

9 A. tuberculosa Nott. Culm erect (declinate at base), 8 - 20', rigid, with small tubercles in the axils of the numerous branches; nodes tumid; lvs. long and narrow-linear; pan. large, loose, simple; spikelets pedicellate; gls. nearly 1' long, linear, awned; upper paleae involute, the awns 2' long, hispid upwards, twisted together to near the middle, thence finally horizontally divaricate. -Order CLVI Gramineae Grasses Part 6 2497 A very singular species, in dry prairies, Ill., Wis. to Ky., Term., also found in N. J.

13. STIPA, L. Weather Grass. (Lat. stipa, a foot-stalk; alluding to the stipitate fruit.) Spikelets 1-flowcred, the flower deciduous, with its thick, bearded, pointed stipe; glumes membranous; pales coriaceous, shorter than the glumes, the lower with a long, twisted or bent awn, jointed at the apex; caryopsis striate; stamens 3; stigma plum-ous. -Order CLVI Gramineae Grasses Part 6 2498 Fls. paniculate. Lvs. very narrow. The long awns are delicately hygrometric twisting or untwisting according to the state of the atmosphere.

1 S. avenacea L. Black Oat Grass. Culm naked above, 2 - 3f; lvs. 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. Virginica Pers.)

2 S. juncea Pursh. Culm 2 - 3f; lvs. convolute filiform, smooth inside, long; pan. loose; gls. loose, filiformly 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, pubescent; paleae obtuse, distinctly articulated to the awn, which is smooth and slender, at length contorted and 4 - 6' in length. -Order CLVI Gramineae Grasses Part 6 2499 : Prairies, Ill., Mo. When in fruit the pungent stipe adheres to everything that comes in its way. Aug.