124 



GBAMINKAE ((JKASS FAMILY) 



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

 branches in pairs, lax, finally spreading : glnmi-s often purplish, S-10 mm. long. 

 acute, about equaling the dark-lron-ii lemmo. vhirh is smooth h</oi>-, scabrous 

 above and bears a fringe of short hairs at the summit; awn 4-7.5 cm. /</(/; 

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

 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 I lie 

 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 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 ; awn 10-24 cm. long, puoesmit 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, 

 1-3 dm. long, branches erect, naked below ; glumes 2.8-3.5 



S. spartea x %. 



Floret and base of i on g^ attenuate, exceeding the brownish lemma, which is ap- 

 lumes. 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-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 



Glumes 12-14 mm. long 



Glumes 15-20 mm. long 



Middle awn not coiled at base, horizontal . 

 Lateral awns not much shorter than the middle one. 

 Glumes T-'.i mm. Ion" 1 ; awns 1.4-2.2 cm. long 

 Glume* 90-80 nun. loag ; awns 8.5-7 cm. long . 

 Awns unitc.l In-low in along twistrd neck 

 Perennlali. 



Awns 5-ln cm. long 



A \\ us not nvi-r :l cm. long. 



Sheaths glabrous 



Sheaths woolly . 



1. A. 



2. A. 



>. A. 



4. .1. 



.1. 



.1. <>li<j<t ntlin. 

 A. tn)>ercnlox,i. 



8. A. 



9. A. 



lo. .1. 



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, l-(5 dm. high ; xhculhs Ions, ; blades mostly 

 involute; panicles I'ew-tlmvered, simple, narrow, the lateral ones often 

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

 nit,, at ti mm. long, excluding the awns : I, it, -nil (//// r< (!>'<! to minute 



