GRAMINE^. (GRASS FAMILY.) 641 



50. TRISETUM, Persoon. Trisetum. (PI. 1 2. ) 



Spikclcts 2 -several-flowered, often in a contracted panicle, the lower palet 

 compressed-keeled, of about the same membranaceous texture as the glumes, 

 bearing a bent or flexuous (rarely twisted) awn below the sharply 2-toothed or 

 2-pointed apex (whence the name, from iris, three, and seta, a bristle) : other- 

 wise nearly as in Avena. Ours are pei'ennials. 



1. T. SUbspicatum, Beau v., var. molle. Minutely soft-downy; panicle 

 dense, much contracted, oblong or linear (2' -3' long); glumes about the length/ 

 of the 2-3 smooth flowers ; awn diverging, much exserted. ( Avena mollis,' 

 Michx.) — Mountains and rocky river-banks, N. New England to Wisconsin, 

 and northward. July. — About 1° high: leaves fiat, short. (En.) 



2. T. pft.iu.stre, Ton*. Smooth ; panicle rather long and narrow (5' long), 

 loose, the branches capillary; spikelets flat (3" long); glumes shorter than the 

 two smooth lanceolate flowers, of which the upper is on a slightly hairy joint of 

 the rhachis, and bears a slender spreading or bent awn next the short 2-pointed 

 tip, while the tower one is commonly awnless or only mucronatc-pointed. (Avena 

 palustris, Michx. Aira pallcns, MM.) — Low grounds, Southern New York to 

 Illinois, and southward. June. — Culm slender, 2° -3° high : leaves flat, short. 

 Spikelets yellowish-white, tinged with green. 



51. AIRA, L. Hair-Grass. (PI. 12.) 



Spikelets small, in an open diffuse panicle, of 2 perfect flowers and often with 

 the pedicel or rudiment of a third, all usually shorter than the membranaceous 

 keeled glumes, and hairy at the base ; the upper remotish. Lower palet thin 

 and scarious, 2-cleft or else truncate and mostly denticulate or eroded at the 

 summit, bearing a slender bent or straight awn on its back, commonly near 

 its base. Stamens 3. Styles plumose to the base. Ovary glabrous. Grain 

 oblong. (An ancient Greek name for Darnel.) 



§ 1. DESCHAMPSIA, Beauv. Lower palet delicately 3-5-nervcd, eroded or 

 toothed at the truncate summit ; the awn attached mostly a Utile ahove the base: 

 grain not grooved, free: glumes about equalling the flowers : root perennial. 



1. A. flexudsa, L. (Common Hair-Grass.) Culms slender, nearly 

 naked (l°-2°high) above the small tufts of involute bristle form root-leaves (1'- 

 C long) ; branches of the small spreading panicle capillary; awn longer than the 

 palet, at length bent and twisted. — Dry places : common. June. (Eu.) 



2. A. CSSSpitdsa, L. Culm tufted (2° -4° high); leaves flat, linear; 

 panicle pyramidal or oblong (6' long) ; awn straight, barely cquedling the palet. 

 — Shoi-es of lakes and streams : common northward. June, July. (Eu.) 



§2. AIROPSIS, Desv. Sjrikelets very small, of 2 closely approximate flowers, and 

 with no rudiment of a third: lower palet of firmer texture, obscurely nerved, acutely 

 2-cleft at the apex: ejrain gre>ovcd, aelnate: low annuals, with short and setaceous 

 leaves. 



3. A. rniECOX, L. Culms tufted, 3' -4' high; branches of the small and 

 dense panicle apprcsscd ; awn from below the middle of the flower. (Avena 

 praicox, Beauv.) — Sandy fields, New Jersey to Virginia : rare. (Nat* from Eu.) 



L & M— 47 



