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 Seta f. pSffix 

 minute or obsolete; rudiment slender, cleft nearly ffim^r'e?) 5 ' (Neal 

 to the base, the awns equaling the awn of the 



fertile lemma, the lobes minute, nar- 

 row. 01 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 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. 21 (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.) 



