AGROSTIDEJE 



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 aUies). 

 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 

 plains and steppes 

 of both hemispheres. 

 The fruit resembles 

 that of Aristida but 

 terminates in a single 



Fig. 35. Aristida longiseta. 

 Spikelet, the floret raised from 

 the glumes, XI- 



