550 GRAMINE^E. (GRASS FAMILY.) 



15. ARIST1DA, L. TRIPLE-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 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. 



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



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

 ing; spikelets small, mostly crowded and panicled; glumes 1-nerved, '-J long, 

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

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



2. A raniosf ssinm, 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- 

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

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



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

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

 bearing a long and slender spiked raceme or virgate panicle. 



3. A. tfrsicilis, 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 

 '- J' 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. strictsi, 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. purpur&scens, 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. Geyeriana, Steud.)-~- Massachusetts to 

 Michigan, Illinois, and southward ; common. 



w- ++ Culms branching below (1 - 1 high], the branches nak&l above and racemosely 

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



6. A. Oligantha, Michx. Spikelets large, very shcrt-pedicelled ; glumes 

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

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



