AGROSTIDEZ 199 
229. Aristida L—Needle-grass. A large genus, mostly 
tufted perennials of the warmer parts of the world, 
especially abundant in America. They are easily dis- 
tinguished by the narrow terete lemma bearing a pointed 
hairy callus below and a trifid awn above. The 2 lateral 
awns are sometimes shorter than the others or may be 
absent altogether (A. 
scabra (H.B.K.) 
Kunth and its allies). 
The species not only 
have little forage 
value but on the 
contrary are often 
troublesome to 
ranchmen because of 
the sharp fruits which 
penetrate the skin of 
grazing animals. Sev- 
eral low perennial 
species are found in 
the new soil around 
the burrows of prairie 
dogs, hence the name 
dog-town grass. 
230. Stipa L.— 
Spear-grass. A large 
genus of tufted per- 
ennials found on the 
; Fie. 35. Aristida longiseta. 
plains and f steppes Spikelet, the floret raised from 
of both hemispheres. the glumes, X1. 
The fruit resembles 
that of Aristida but 
terminates in a single 
