124 GRAMINEAE (GRASS FAMILY) 



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

 branches in pairs, lax, finally spreading ; glumes often purplish, 8-10 mm. long, 

 wnte, about equaling the dark-brown lemma, which is smooth below, scabrous 

 above and bears a fringe of short hairs at the summit; awn 4-7.5 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. & Rupr. 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, 2-4 ruin, 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 ; awn 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 f the length of the culm, 

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

 83. S. spartea x %. j_g jjjjj long, branches erect, naked below ; glumes 2.8-3.5 cm. 

 Floret and base of i on g, 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. TBIPLE-AWNED 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.) 



Annuals. 



Awns separate to the base. 

 Lateral awns much shorter than the middle one. 

 Middle awn coiled at base. 



Glumes 7-8 mm long 1. A. dichotoma. 



Glumes 12-14 mm. long 2. A, buirum<a. 



Glumes 15-20 mm. long 8. A. ramo#i>i*ima. 



Middle awn not coiled at base, horizontal 4. .4. gracilU. 



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 8.5-7 cm. long 6. A. oligantha. 



Awns united below in a long twisted neck 7. A. tuberculota. 



Perennials. 



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



Awns not over 8 cm. long. 



Sheaths glabrous 9. A.purpuratctnt. 



Sheaths woolly 10. A. lanota. 



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 mostly 

 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 aicns reduced to minute 



