582 ORDER CXLII. GRAMLNACE.E. 



1. C. echixa'tus, (L.) Stem erect, glabrous, pubescent ; spikes con- 

 sisting of 6 — 10 heads; spikelets approximate; involucre 10-parted, 

 villous. — §. Aug. — Sept. Sandy soils. 1 — 2 feet. 



2. C. tribuloi'des, (L.) Stem erect, compressed, sometimes branched. 

 Leaves scabrous on the upper surface, glabrous beneath ; sheath twice 

 the length of the joints. Glumes unequal, 2-flowered. Palece 2, the 

 exterior valve acute. — 0. July — Oct. Sandy soils. 12 — 15 inches. 



Tribe IV.— STIPA'CE^E. 



Spikelets l-flowered ; inferior palea awned. Ovarium stip- 

 itate. 



Gexus XV.— STI'PA. L. 



Glumes 2, membranaceous, l-flowered. Palece 2, coriaceous, 

 shorter than the glumes ; the lower one with a long terminal 

 awn, the upper one entire. Panicle lax. 



1. S. avena'cea, (Walt.) (S. Virginica, Pers.) Stem erect, terete, 

 glabrous; lower leaves longest, glabrous beneath, scabrous on the up- 

 per surface. Flowers in diffuse panicles. Glumes nearly equal, concave, 

 sometimes awned. Palece stiped, the stipe bearded. Awn spiral. — If. 

 June. Sandy soils. Common. 2 — 3 feet. Feather-grass. 



Gexus XVI. — ARISTIDA. 

 (From arista, a beard or awn.) 



Glumes 2, membranaceous, unequal. Palea? 2, on pedi- 

 cels ; lower one coriaceous, 3-awned, the upper one very small, 

 or wanting. Scales collateral. 



1. A. gra'cilis, (Ell.) Stem erect, slender, glabrous, branching at the 

 base. Leaves linear, with sheaths shorter than the joints. Flowers in 

 long spikes, appressed. Glumes equaling the paleae in length ; the ex- 

 terior palea involute, banded with light and dark spots, 3-awned ; the 

 interior palea minute, or wanting. — U- Sept. — Oct. Common on the 

 sea-coast. 10 — 15 inches. 



2. A. stric'ta, (Mich.) Stem erect, compressed, branching at the. base, 

 lower joints short. Leaves glabrous ; sheaths longer than the joints, 

 with the throat ciliate. Panicle long, erect. Peduncles scabrous. 

 Glumes unequal, with serrulate keels. Paleit with the exterior one 

 hairy at the base. Awtu long, scabrous. — If. July — Aug. Rocky 

 soils. 2 — 3 feet. 



3. A. diciiot'oma, (Mich.) Stem slender, branching, glabrous. Leaves 

 narrow, flat, finely serrulate. Flowers in panieulate racemes. Glumes 

 narrow-lanceolate, with, short awns ; keels serrulate. Palea involute, 

 3-awned, the middle one longest, contorted. — $ . July. Loose soils. 

 12 — 18 inches. 



4. A. lana'ta, (l'oir.) (A. latwsa. Ell.) Stem erect, pubescent at 

 the base'. Lxic-s glabrous beneath, pubescent above, with scabrous 

 margins; sheaths tomentose. Flower* in racemose panicles. Glume* 

 acute, compressed, unequal ; exterior pales 3-awned, involute, the in- 

 terior one very small. — If. Aug. — Sept. Sandy soils. 2 — 1 feet. 



