GRAMINE.E. (GRASS FAMILY.) 653 



39. TRISETUM, IVrsoon. (IM. 12.) 



Spikelets 2 -sevoral-ttowered, often in a contracted panicle; the flowering 

 glume conipresseii-keeled, of about the same thin-niemhrunaceous texture as 

 the empty glumes, hearing a bent or Hexuous (rarely twisted) awn at or helow 

 the sharply 2-t(jothed or 2-pointed apex (whence the name, from tris, tiiree, 

 and S(tn^ a bristle) ; otherwise nearly as in A vena. Ours are perennials. 



1. T. subspicatum, lieauv., var. moUe, Gray. (PI. 12, fig. 1, 2.) 

 Minuteli/ soj\-(lijicnij ; imnicle dense, mncli cuntracUd, oblong or linear (2-3' 

 /ong) ; glumes about the length of the 2-3 smooth flowers; awn dorsal, di- 

 verging, much exserted. — Mountains and rocky river-bauks, N. New Eng. to 

 L. Superior, and northward. July. — About 1° higli ; leaves flat, short. (Ku.) 



2. T. pallistre, Torr. Smooth ; panicle rather long and narrow (.5' long), 

 loose, the branches capillar ij ; spikelets JJ at (3" long); lower glumes shorter 

 than the two smooth lanceolate flowers ; the upper flower on a slightly hairy 

 joint of the rhachis, with a slender spreading or bent awn next the short 2- 

 pointed tip, the lower commonly aicnless or only mucronate-pointed. — Low 

 grounds, southern N. Y. to 111., and southward. June. — Culm slender, 2-3° 

 high; leaves flat, short; spikelets yellowish-white, tinged with green. 



40. AVENA, Tourn. Oat. (PI. 12.) 



Spikelets 2 -many -flowered, panicled ; the flowers herbaceo-chartaceous, or 

 becoming harder, of firmer texture than the large and mostly unequal enjpty 

 glumes ; the uppermost flower imperfect ; rhachis and base of the flower often 

 bearded. Flowering glume rounded on the back, mostly 5-11-nerved, bear- 

 ing a long usually bent or twisted awn on the back or between the two acute 

 teeth at the apex, proceeding from the mid-nerve only. Stamens 3. Grain 

 oblong-linear, grooved on one side, usually hairy at least at the top, free, but 

 invested by the palet. (The cla.ssical Latin name.) 



* Spikelets large (1' long) ; annual. 



A. fAtca, L. Eesembling the common oat {A. sativa), the few spikelets 

 in a loose panicle, mostly pendulous; flowering glumes covered with long 

 brownish hairs and bearing a bent awn 1-2' long. — Wise, Minn. (Nat. 

 from Eu.) 



* * Smnlier-floivered perennials. 



1. A. striata, Michx. (PI. 12, fig. 1,2.) Glabrous and smooth through- 

 out, slender (1 -2° high) ; leaves narrow; ligule short, truncate ; panicle sim- 

 ple, loose; spikelets (6" long) ou capillary pedicels, 3-6-flowered, much 

 exceeding the scarious-margined purple acute empty glumes; loiccr glume 1-, 

 upper 3-nerved ; rhachis smooth ; jlowcrs short-bearded at base ; flowering glume 

 7-nerved, much longer than the ciliate-f ringed palet (4" long), mostly shorter 

 than its soon bent or divergent awn, which rises just below the tapering very 

 shari)ly cuspidate 2-cleft tip. — Rocky, shaded hills, N. New Eng., N. Y., and 

 northwestward. June. 



2. A. Smithii, Porter. Taller (2| - 4^° high ) , rather stout ; leaves broadly 

 linear (3 - 6" wide) and taper-pointed, flat, and with the sheaths and culm re- 

 trorsclji scabrous; ligule elongated, acute; panicle larger (6-12' long), the 

 few branches at length spreading; empty glumes slightly purjilish, the lower 

 3-nerved, the upper 5-nerved, scabrous on the nerves ; rhachis minutely hispid , 



