AGROSTIDEAE 57 



10. Aristida fendleriana sumuI. a small, tew-flowcred 



"needle gra.-.-." rioiii ili.- inoas and loolhili.s at elevations of from 

 about 5500 ieet l<> 700(1 led in tlie middle and northern part of the 

 State. Cppci" Sonoran Zone. 



11. Aristida wrightii Na>ii. A stiff c.arse grass 18 niches 

 high or more --oiiii wliai ic.-cinliling ihc "Arizona needle grass" but 

 the glumes are quite dilTt'i-cnt. It occurs in the -.oufnern part ot 

 the State in llic Soiioran Zones. 



12. Aristida purpurea Nuti. The I'LRrLii xeeule Grass, 



perhaps the commonest throughout the State but often not purple at 

 all. It occui's on the mesas and plains and in the foothills at ele- 

 vations of tnm M.'iUn lecf ti ()50() feet al)ove sea leve'. 



The Porcupine Grasses 1)cl ir<.:;inL, in the geims Stipa 

 are an iiitercstiiii;- and somewhat varied _$^roup and several of 

 them are ni more or less importance. They may be recog- 

 nized by the single beard or awn attached to the indurated 

 single- 'seeded" spikelet. This awn is generally ratlier con- 

 spicuous ])y its length, sometimes long and feathery, but it is 

 always twisted just above the "seed" and bent more or less, 

 in a direction at right angles to the "seed." The seed is tipped 

 at the base willi a vjry sharp ])ointed hairy callous which, taken 

 witli the ]).'ciiliar awn ]ial)i: of twisting and untwisting- as 

 affected 1)y UK^isture, is no doubt in some way coimectcd with 

 the distribution and planting of the seed. 



The Xi:w Mexican Stipa (S. neo-mexicana) has a 

 long pdumose awn about 2 inches long and S. comata is much 

 like it except thai the awn is not feathery. Both these grasses 

 are rather large and moderately coarse perennial bunch 

 grasses producing tufts 6 to 8 inches in diameter, of slender 

 tough leaves, quite earlv in the spring or even in the late 

 winter. Tlic leaves are from 8 inches to a foot long and 

 numerous in the tuft and the panicles when they appear are 

 abo.it two feet high. I'hese grasses occur on the sand hills 

 and i^lain? in the v. rthern part of tiie Sta;e and to some extent 



