MANUAL OF THE GRASSES OF THE UNITED STATES 



521 



Scribn.) — Gypsum sands and calcareous rocks, western Texas, New 

 Mexico, and northern Mexico. Resembling B. gracilis but with loose, 

 woody base and wiry culms; rachis prolonged and bearing a 

 rudimentary spikelet at the tip. 



16. Bouteloua eriopoda (Torr.) Torr. Black 

 grama. (Fig. 1101.) Perennial; culms tufted, with 

 swollen bases, slender, wiry, 

 widely spreading with arched 

 internodes or stoloniferous, 

 white-lanate, 40 to 60 cm 

 long; blades 1 to 1.5 mm 

 wide, flexuous; spikes 3 to 

 8, commonly 4 or 5, loosely 

 ascending, 2 to 3 cm long; 

 spikelets 12 to 20, not crowded 

 and pectinate, 7 to 10 mm long, narrow; fertile 

 lemma acuminate, with a terminal awn, the lateral 

 minute or obsolete; rudiment slender, cleft nearly 

 to the base, the awns equaling the awn of the 



fertile lemma, the lobes minute, nar- 

 row. % — Mesas, hills, and dry 

 open ground, Texas to southern Utah 

 and northern Mexico (fig. 1102). 



17. Bouteloua trifida Thurb. 

 (Fig. 1103.) Perennial, tufted, 

 leafy at base, rather delicate; culms 

 erect, 10 to 20 cm tall; blades us- 

 ually only 1 to 2 cm long; spikes 



Figure 1099.— Distribution of 

 Bouteloua gracilis. 



Figure 1100.— Bouteloua 

 breiiseta. Panicle, X 

 1: spikelet, X 5. (Neal- 

 lev 669, Tex.; 



Figure 1102.— Distribution of Bouteloua eriopoda. 



3 to 7, 1 to 2 cm long, ascending or 

 appressed; spikelets about 12, pur- 

 plish, 7 to 10 mm long; fertile lemma 

 pubescent toward base, cleft more 

 than half its length, with awns (5 

 mm long) winged toward base and 

 no intermediate lobes; rudiment 

 cleft to the base, the awns similar 

 to those of the fertile lemma, about 

 as long. Qi {B. trinii Griffiths; B. burkii Scribn.) — Mesas, ravines, 

 and rocky hills, Texas to southwestern Utah and Arizona ; California 

 (Death Valley); northern Mexico (fig. 1104). Variable in length 

 of the awns, the type of B. trifida being the longer-awned form. 



Figure 1101.— Bouteloua eriopoda. Plant, X 

 1; spikelet, X 5. (Hitchcock 13357, Tex.) 



