MANUAL OF THE GRASSES OF THE UNITED STATES 



515 



Figure 1084.— Distribution of 

 Bouteloua curtipendula. 



rudiment with stout pubescent awns about 5 mm long, the long narrow 

 intermediate lobes glabrous; a second similar but smaller rudiment 

 usually developed. % — Rocky hills, southern Arizona and Sonora, 

 Mexico. 



6. 4 A Bouteloua chondrosioides (H.B.K.) Benth. (Fig. 1087.) 

 Perennial, tufted, leafy at base; culms erect, 20 to 50 cm tall; blades 

 2 to 3 mm wide; axis 4 to 6 cm long; spikes 4 to 

 6, rhomboid-oblong, ascending, 1 to 2 cm long, 

 the rachis densely pubescent, the tip 3-cleft; 

 spikelets several, subpectinate; rachis broad, 

 densely pubescent on the margin; glumes and 

 fertile lemma densely pubescent, the lemma 

 3-cleft, the divisions awn-tipped; rudiment cleft 

 nearly to the base, the middle awn broadly 

 winged, the lateral ones slender, all spreading 

 % ; — Mesas and rocky hills, western Texas, southern Arizona, and 

 Mexico. 



7. Bouteloua radicosa (Fourn.) Griffiths. Purfle grama. (Fig. 

 1088.) Perennial, tufted, from a stout rhizomatous base; culms 

 erect, 60 to 80 cm tall; blades 2 to 3 mm wide, 

 sparsely papillose-ciliate on the margin, mostly aggre- 

 gate toward the lower part of the culm, the upper 

 part naked; axis 10 to 15 cm long; spikes mostly 7 

 to 12, oblong, 2 to 3 cm long; spikelets mostly 8 to 

 glumes broader than in other species; fertile 

 lemma indurate down the center, with 3 

 awns, the middle longest, and no inter- 

 mediate lobes; rudiment with 3 awns 5 to 

 8 mm long and no intermediate lobes, 

 usually containing a palea and staminate 

 flower, sometimes a perfect flower, the 

 lower floret being staminate. % — Rocky 

 hills, southern New Mexico to southern 

 California and Mexico. 



8. Bouteloua filiformis (Fourn.) Griffiths. 

 Slender grama. (Fig. 1089.) Resembling 

 B. radicosa; culms erect or geniculate-spread- 

 ing, sparingly branching, the base not 

 rhizomatous; spikes ascending to spreading, 

 mostly about 1.5 cm long, sometimes as 

 much as 2 cm; spikelets mostly 6 to 10, 

 very like those of B. radicosa. % — Rocky 



Figure 1085.— Bouteloua rigidiseta. 

 Panicle, X 1: spikelet, lemma, and 

 florets, X 5. (Grifliths 6370, Tex.) 



hills, Texas to Arizona and Mexico. 



Section 2. Choxdrosium (Desv.) Benth. 



Spikes persistent; spikelets crowded (looser in B. eriopoda), pectinate; 



florets falling from the glumes. (Chondrosium Desv. based on 



C. procumbens Durand {B. simplex).) 



9. Bouteloua simplex Lag. Mat grama. (Fig. 1090.) Annual, 



tufted, prostrate or ascending; foliage scant; blades 2 to 3 cm long, 



about 1.5 mm wide; spike solitary, 1.5 to 2.5 cm long, strongly arcuate 



at maturity; spikelets mostly 20 to 30, about 5 mm long; fertile lemma 



