GRAMTNACEd'!. 439 



34. ARRHENATHERUM. Beauv.Oat Grass. 



(From the Greek appw , male, and uQnp, an awn ; the staminate flower being 

 awned.) 



Spikelets 2-flowered. Lower flower staminate ; the lower 

 palea with a long twisted awn below the middle. Upper flower 

 perfect ; the lower palea with a short straight bristle below the 

 point. Panicle loose. 



A. avenaceum Beauv. Avena elatior Linn. 



Cultivated grounds. Mass. N. Y. and Penn. May, June. ^ . Root creep- 

 ing. Culm 23 feet high, erect. Leaves scabrous on the margin and upper 

 surface. Panicle oblong, at first contracted, finally spreading and somewhat 

 nodding ; the branches short and semiverticillate. Spikelets brownish. Intro- 

 duced from Europe, but naturalized in several places. 



Common Oat-grass. Grass of the Andes. 



35. AVENA. Linn.O&t. 

 (Name of doubtful origin.) 



Spikelets 3 many-flowered ; flowers rather remote, the upper 

 ones often imperfect. Glumes loose and membranaceous, nearly 

 equal. Palese 2 ; the lower one bifid at the summit, with a 

 twisted awn above the base. Panicle compound, loose. 



1. A. Pennsylvania Linn.: panicle attenuated, loose, nodding, the 

 branches somewhat verticillate ; spikelets 2 3-flowered ; flowers smooth, 

 lower one often awnless, upper one on a hairy pedicel : lower palea with a 

 slender awn below the bifid tip, about twice the length of the flower. A. 

 palustris Mich. Trisetum Pennsylvanicum Beauv. T. paluslre Torr. Fl. 



Wet meadows. N. Y. to Flor. June. 'l\..Culm 23 feet high, slender, 

 erect. Leaves flat, narrow, 2 4 inches long. Panicle oblong, yellowish-green, 

 often somewhat one-sided. Pennsylvania Wild Oat. 



2. A. striata Mich. : panicle nearly simple, loose, few-flowered ; spikelets 

 3 5- flowered, somewhat terete, the flowers bearded at the base ; lower 

 palea with a slender nearly straight awn below the tip. Trisetum purpu- 

 rascens Torr. Fl. 



Moist woods. Can. N. Y. and Mass. July. %. Culm 23 feet high, erect, 

 smooth. Leaves narrow-linear. Panicle 4 6 inches long, with a few simple 

 branches. Glumes reddish-purple. Purple Wild Oat. 



36. TRISETUM. Pers. Trisetum. 



(From the Latin, in allusion to the three bristles of the flowers.) 

 Spikelets 2 4-flowered. Glumes membranaceous, keeled, 

 ciwnless. Palese herbaceous ; lower one with 2 long cusps at 

 the summit and a twisted awn on the back ; upper 2-keeled. 

 Caryopsis smooth, with a longitudinal groove. Panicle con- 

 tracted. 



T. molle Kunth: whole plant minutely and softly pubescent; panicle 



