TEIPLE AWN GRASSES. 59 



15. Aeistida. Three-aioned Grass. 



Flowers stipitate or on stalks ; glumes -unequal, often 

 bristle-pointed; paleae two, lower tipped with a triple 

 awn, upper smaller, awnless ; ovary smooth, scales two, 

 smooth, entire ; spikelets in simple or panicled racemes 

 or spikes. 



PovEETY Geass (Aristida dichotoma) is known by its 

 tufted stems or culms being much forked or branched, 

 from five to fifteen inches high. Spikelets small, crowded 

 in short, contracted racemes ; side awns minute ; middle 

 no longer than the palea, bent downwards. Common in 

 old, dry, sterile fields, especially at the South, and in 

 Illinois and adjacent states. 



Three- AWNED Geass {Aristida ramosissima). — Stems 

 diffuse ; spiked raceme loosely flowered ; glumes three 

 to five nerved, nearly equalling the flower; the awn 

 bent back, an inch long. Found on dry prairies of 

 Illinois, and in Kentucky. 



Slendee Theee-awned Geass {Aristida gracilis) is 

 also found in old, sandy fields, dry, sterile hill-sides and 

 pine barrens, but is of no value for cultivation. Its 

 stem is slender and erect, lateral awns as long as the 

 palea. Never found except on the poorest soil. 



Downy Teiple Awn {Aristida striata). — Leaves 

 straight, erect, rigid, downy ; lower palea smooth ; awns 

 spreading, the middle one longest; glumes unequal, short, 

 pointed. Perennial. Grows from two to three feet 

 high, in rocky and shaded places, in Michigan, Illinois, 

 Virginia, and southward. Of no value for cultivation. 



Purple Triple Awn {Aristida purpurascens) has 

 rough, but less rigid leaves ; lower palea rough, Avith 

 slender lateral nerves ; middle awn an inch long. Com- 

 mon from Massachusetts to Illinois and southward. 



