550 GRAMINEJS. (GRASS FAMILY.) 



15. ARISTIDA, L. TRIPIE-AWNED GRASS. 



Glumes unequal, often bristle-pointed. Lower palea tipped with three awns ; 

 the upper palea much smaller. Otherwise much as in Stipa. Culms branch- 

 ing : leaves narrow, often involute. Spikelets in simple or panic-led racemes 

 or spikes. (Name from arista, a beard or awn.) All grow in sterile, dry- 

 soil, and all ours have the awns naked and persistent, and flower towards the 

 end of summer. 



* Awns separate to the base, not jointed with the palea. 



*- Aims very unequal; the 2 lateral merely short erect bristles, scarcely I or I the 

 length of the horizontal at length recurved middle one: root annual: culms tufted, 

 much branched throughout, low (5'- 18' high) : racemes short and spike-like. 



1. A. <licll6toina, Michx. (POVERTY GRASS.) Culms erect or ascend- 

 ing; spikelcts small, mostly crowded and panieled ; glumes l-nerw-d, 4'-J " on S> 

 exceeding the flower, which bears a middle awn of about its own length. Com- 

 mon in old fields, &c., especially southward. 



2. A. ramoSlSSinm, Engelm. mss. Culms diffuse ; spiked raceme sim- 

 ple and loosely flowered; glumes f |' long, 3 - 5-nerved, about equalling the 

 flower, the soon recurved middle awn I' long. Dry prairies of Illinois (Kngel- 

 mann), and Kentucky (herb. Micltaux). Glumes short-awned ; the lower 4-5- 

 nerved; the inner and longer one 3-nerved, 2-cleft at the tip. Lateral awns of 

 the palea only l" - 2" long. Ligulc truncate, bearded. 



*- *- Awns unequal but similar ; the 2 lateral about half the length of the horizontally 

 bent middle one: root annual: culms branched only towards the base, naked above, 

 bearing a long and slender spiked raceme or virgate panicle. 



3. A. graciliS, Ell. Culms slender, erect (6' -18' high); flower as long 

 as the glumes (2" -3" long) ; lateral awns a.s Ion;/ as the palea, the middle one 

 '-'long. Sand, E. Massachusetts and New Jersey to Illinois, and south- 

 ward. 



*- - *- Awns nearly equal, divergently spreading : root perennial. 



++ Culms simple or nearly so (l-2 high), terminated by a long and strict virgate 



many-flowered spiked panicle from 6' to 18' in length. 



4. A. Stricta, Michx. Leaves soon involute-filiform, rigid, downy or gla- 

 brous ; lower palea smooth, 3" -4" long, the equally spreading awns %' long, or 

 the lateral rather shorter. Virginia and southward. 



5. A. purpurascens, Poir. Leaves glabrous, less rigid ; hirer palea 

 rough or minutely serrulate-hispid on the keel and the slender lateral nerves, 

 4"- 5" long; the divaricate middle awri 1' long, the lateral a little shorter and 

 at first erect. (A. racemosa, Muhl A. Geyeriuna, Stead.) Massachusetts to 

 Michigan, Illinois, and southward; common. 



w- -* Culms branching behiu (1- 1.' high), the Iranchfs naked above and racemotekj 

 or paniculately sm /<//- (4 -12-) jl 



6. A. Olig lllllia, Michx. Spikelets large, very short-pedicelled ; glumes 

 equalling the flower, 8" -10" long, the lower 3 - 5-nerved and 2-elel't at the tip, 

 the upper 1-nerved and more awned at the tip ; awns of the palea l' -3' long, 



