188 AIEA. 



a bent or flexuons (rarely twisted) awn below the 

 sharply 2-toothed or two pointed apex. 



Whence the name, from tris, three, and seta, a 

 bristle. 



Otherwise nearly as in Avena. Ours are perennials. 



Oray. 



1. T. Subspicatum, Beauv. Var. moUe (Downy 

 Persoon). Found on rocky river banks, from New 

 England to Wisconsin, and northward. Flowers in 

 July. About 1 foot high ; leaves flat, short. 



2. T. Palustre (Marsh Oat grass). Low grounds 

 Southern New York to Illinois and northward. 



3. T. Pubescens (the Downy Oat grass). See 

 page 60. 



51. AIRA — Linn. Hair Grass. 



GENERIC CHARACTER. 



Spikelets small in an open diffuse panicle, of 2 per- 

 fect 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 re- 

 motish ; lower palet thin and scarious, 2-cleft or else 

 truncate, and mostly denticular or eroded at the sum- 

 mit, 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. 



