X24 GRAMINEAE (GRASS FAMILY) 



those of the culm 4-10 cm. long; panicle loose, 1-2 dm. long, the sleiidei 

 branches in pairs, lax, finally spreading ; glumes often purplisli, b-10 mm, long, 

 acute, about equaling the dark-brown lemma, which is smooth below, scabrovs 

 above and bears a fringe of short hairs at the summit; awn 4-7. o cm. long ; 

 callus acuminate, covered with dense brownish hairs. — Dry woods, Mass. to Fla., 

 w, to Wis. and Tex. May, June. Fig. 82. 



* * Glumes 2 cm. long or more. 



4. S. comata Trin. & Uupr. Culms erect, simple, 2-12 dm, high ; sheaths 

 mostly crowded at the base, the upper often loose and inclosing the base of the 

 panicle; basal blades usually about \ the length of the culm, mostly involute- 

 filiform, those of the culm 0.5-1.5 dm. long, 2—1 mm. wide, 

 flat or involute ; panicle loose, 1-4 dm. long, branches distant, 

 erect or somewhat spreading, naked below ; glumes 2-2.8 cm. 

 long, tapering into a slender fragile awn, much exceeding the 

 sparsely pubescent lemma ; avm 10-24 cm. long, pubescent to 

 the geniculation, scabrous and curved beyond; callus acute. — 

 Dry plains and hills, la., and westw. June, July. 



5. S. spartea Trin. (Porcupine Grass.) Culm rather 

 stout, simple, 0.5-1.2 m. high; sheaths mostly overlapping, 

 blades usually involute, basal ones | the length of the culm, 

 those of the culm 1-3 dm. long ; panicle finally exserted, narrow, 



5. spartt-a x %. |_3 ^^^ long, branches erect, naked below ; glumes 2.8-8.5 cm. 

 Floret and base of ig^ig^^ attenuate, exceeding the brownish lemma, which is ap- 



awn. Glumes. pressed-pubescent below, and nearly or quite glabrous above ; 

 awn 11-20 cm. long, rigid, scabrous, minutely pubescent below ; callus acuminate, 

 very sharp-pointed, densely clothed with silky appressed hairs. — Plains and 

 prairies, Mich, to Mo., and westw. Fig. 83. 



25. ARISTIDA L. Triple-awxed Grass 



Spikelets 1-flowered, in usually narrow panicles ; glumes unequal, narrow, 

 acute or acuminate ; a hard obconical hairy callus below the floret ; lemma 

 somewhat indurated, convolute, including the thin palea and perfect flower, ter- 

 minating in a trifid awn ; grain elongated, tightly included in the lemma. 

 — Tufted annuals or perennials with narrow leaves. (Name from arista, a 

 beard or awn.) 



A nnuals. 

 Awns separate to the base. 

 Lateral awns much shorter than the middle one. 

 Middle awn coiled at base. 



Glumes 7-8 mm long \. A. dichoioma. 



Glumes 12-14 mm. long ..<,...... 2. ^. ba-sii^amea. 



Glumes 15-2(1 mm. long ^. A. ramoni-ssima. 



Middle awn not coiled at base, horizontal . . . . . . 4:. A. gracilis. 



Lateral awns not much shorter than the middle one. 



Glumes 7-9 mm. long ; awns 1.4-2.2 cm. long 5. A. intermedia. 



Glumes 20-30 mm. long; awns 3.5-7 cm. long 6. A.oUgantkn. 



Awns united below in along twisted neck 7. A. tuherculosa. 



Perennials. 



Awns 5-10 cm. long 8. A. ptvrpurea. 



Awns not over 3 cm. long. 



Sheaths glabrous 9. A.purrmrasicevs. 



Sheaths woolly 10. ^. laiiosa. 



1. A. dich6toma Michx. (Poverty Grass.) Culms tufted, wiry, much 

 branched at the base and usually forking at every node, but in depauperate 

 specimens sometimes nearly simple, 1-6 dm. high ; sheaths loose; blades mosily 

 involute ; panicles few-flowered, simple, narrow, the lateral ones often sessile 

 and partially inclosed in the sheaths ; glumes subequal, 7-8 mm. long, cuspidate ; 

 lemmas about 6 mm. long., excluding the awns ; lateral awns reduced to minuH 



