GUAMINK^. (GKASS FAMILY.) G41 



50. TRISETUM, Persoon. Trisetum. (PI. 12.) 



Spikclets 2-sevcral-flowcrcd, 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 tris, three, and sda, a bristle) : other- 

 wise nearly as in Avena. Ours are perennials. 



1. T. SUbspic^tum, Beauv., var. moUe. MinuU'lj) sofl-dowmj ; panicle 

 ch'iuie, muck conlrartKl, ob\on<r or linear (2' -3' long); glumes about the length 

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

 Mic/ix.) — Mountains and rocky river-banks, N. New England to Wisconsin, 

 and northward. July. — About 1° high: leaves flat, short. (Eu.) 



2. T. palustre, Torr. Smooth; ^)«n/c/e rather long and narrow (5' long), 

 IcMse, the branches capillary; spikcleta Jiat (3" long) ; glumes shorter than the 

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

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

 tip, while the luioer one is cominonlij aivnless or only mncronate-pointed. (Avena 

 palustris, Michx. Aira pallens, Muhl.) — Low grounds, Southern New York to 

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

 Spikelcts yellowish-white, tinged with green. 



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



Spikclets 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 nicmbraiuiccons 

 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 dtUcalehj 3-5-nervfd, eroded or 

 toothnl at the truncate summit ; the awn at.tachtd mostlij a little uhove the base: 

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



1. A. flexuosa, L. (Commox ILvir-Grass.) Culms slender, nearly 

 naked (l°-2° high) above the small tufts of involute brislle-form rool-leav(S (]'- 

 6' long) ; branches of the small spreading panicle capillary ; au}n longer than the 

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



2. A. CSespitdsa, L. Culm tufted (2° -4° high); leaves flat. Urn or; 

 panicle pyramidal or oblong (6' long); awn straight, harelg eqtialling the jxilit. 

 — Shores of lakes and streams : common northward. June, July. (Eu.) 



§2. AIROPSIS, Desv. Spikelets very small, of 2 closdg approximate flowers, and 

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

 2-clefl at the apex: grain qroovcd, adnate : low annuals, with short and setaceous 

 leaves. 



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

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

 prtecox, BeauB.) — Sandy flelds. New Jersey to Virginia : rare. (Nat. from Eu.) 



L & M— 47 



