MANUAL OF THE GRASSES OF THE UNITED STATES 449 



16. Aristida barbata Fourn. Havard three-awn. (Fig. 959.) 

 Perennial, forming hemispherical tufts as much as 30 cm in diameter, 



the culms rather stiffly radiating in all 

 directions, 15 to 30 cm long; blades 

 closely involute, mostly less than 10 

 cm long and 0.5 mm thick; panicles 

 about half the length of the entire 

 culm, open, the branches divaricately 

 spreading or somewhat reflexed, 

 mostly 3 to 6 cm long, in pairs or 

 with short basal 

 branchlets, but 

 without long 

 naked base, the 

 branchlets and 

 pedicels impli- 

 cate or flexuous, 

 the whole pan- 

 icle fragile at maturity, breaking away 

 and rolling before the wind ; glumes 

 about equal, 1 cm long; lemma grad- 

 ually narrowed into a straight or 

 twisted scaberulous beak, the entire 



Figure 956.— Distribution of 

 Aristida adscensionis. 



Figure 955. — Aristida adscensionis, X 1. (Earle 

 559, N.Mex.) 



length 8 to 10 mm; awns some- 



what divergent, nearly equal, 15 to 

 20 mm long. 01 (A havardii Vasey.) — Hills and plains, western 

 Texas to Arizona and central Mexico. 



17. Aristida divaricata Humb. and Bonpl. Poverty three-awn. 

 (Fig. 960.) Perennial; culms erect or 

 prostrate-spreading, usually 30 to 60 cm 

 long, sometimes longer; blades flat or 

 usually loosely involute, or the basal 



closely involute, 



mostly less than 3 



mm wide; panicle 



large, diffuse, usu- 

 ally as much as 



half the entire 



length of the culm, 



the branches 

 spreading or reflexed, naked below; 

 glumes nearly equal, 1 cm long; lemma 



1 cm long, narrowed into a twisted beak 



2 to 5 mm long; awns about equal, 10 

 to 15 mm long. 01 — Dry hills and 

 plains, Kansas to southern California, 

 south to Texas and Guatemala (fig. 961). 



18. Aristida hamulosa Henr. (Fig. 

 962.) Resembling A divaricata; lemma 

 somewhat narrowed at summit but not 

 twisted, central awn a little longer than 

 the two lateral ones. 01 — Dry hills 

 and plains, western Texas to southern California, south to Guatemala 

 (fig. 963). In Arizona more common than A divaricata. 



Figure 958.— Distribution of 

 Aristida intermedia. 



Figure 957.— Aristida intermedia, X 1. 

 (Kearney 236, Miss.) 



