550 GRAMINEJS. (GKASS FAMILY.) 



15. ABISTIDA, L. Trifle-awned Grass. 



Glumes unequal, often bristle-pointed. Lower palca 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 panicled 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. 

 -t- Awns very unequal; the 2 lateral merely short erect bristles, scarcely \ or \ the 

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

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



1. A. diclldtotlta, Michx. (Poverty Grass.) Culms erect or ascend- 

 ing; spikelets small, mostly crowded and panicled J glumes \-nerved, j^-\ long, 

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

 mon in old fields, &c, especially southward. 



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

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

 flower, the soon recurved middle awn 1' long. — Dry prairies of Illinois (Engel- 

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

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

 the palca only 1^" - 2" long. Ligule 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 as long as the palea, the middle one 

 i'-S'lonir. — Sand, E. Massachusetts and New Jersey to Illinois, and south- 

 ward. 



i- 4- -i- Awns nearly equal, divergently spreading : root perennial. 



■m- Culms simple or nearly so (1° - 2° high) , terminated by a long and strict virgate 



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



4. A. Stl'icta, 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. piirpiirascews, Poir. Leaves glabrous, less rigid ; lower palea 

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

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

 at first erect. (A. racemosa, Muhl. A. Gcyeriana, Stand.) — Massachusetts to 

 Michigan, Illinois, and southward ; common. 



++ ++ Culms branching below (1°- H° high), the branches naked above and racemosely 



or paniculately several- (4 -12-) flowered. 



G. A. o!ig;lHtlsa, Michx. Spikelets large, very short-pedicelled ; glumes 



equalling the flower, 8"- 10" long, the lower 3-5-ncrved and 2-cleft at the tip, 



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



