MANUAL OF THE GRASSES OF THE UNITED STATES 533 



Section 2. Chondrosium 



Plants annual (see also B. rothrockii) ; densely tufted, spreading. 



Spike 1 9. B. simplex. 



Spikes 2 or more. 



Rachis papillose-pilose 11. B. parryi. 



Rachis not pilose 10. B. barbata. 



Plants perennial. 



Plants decumbent or stoloniferous; culms white-lanate 17. B. eriopoda. 



Plants erect or nearly so; culms tufted, not lanate. 

 Spikes normally 2, sometimes 1 or 3. 



Rachis prolonged beyond the spikelets as a naked point; glumes tuberculate. 



Culms retrorsely hirsute below the nodes 13. B. glandulosa. 



Culms glabrous 14. B. hirsuta. 



Rachis not prolonged; glumes not tuberculate (slightly so in B. gracilis). 



Culms herbaceous, the base not woody 15. B. gracilis. 



Culms woody and perennial at base 16. B. breviseta. 



Spikes normally 4 or more (see also B. gracilis var. stricta). 



Culms 25 to 50 cm. tall; awn 1 to 2 mm. long; glumes scabrous; spikes spreading. 



12. B. ROTHROCKII. 



Culms 10 to 20 cm. tall; awn about 5 mm. long; glumes glabrous; spikes usually 

 appressed 18. B. trifida. 



Section 1. Atherop6gon (Muhl.) Endl. 



Spikes deciduous from the main ax- 

 is; spikelets not pectinately ar- 

 ranged (somewhat so in B. chon- 

 drosioides) . (Atheropogon Muhl. 

 based on A. apludoides Muhl. 

 (Bouteloua curtipendula) .) 

 1. Bouteloua aristidoides (H. B. 



K.) Griseb. Needle grama. (Fig. 



772.) Annual, erect or spreading, 



Figure 772. — Bouteloua aristidoides. Panicle, X 

 spikelet, X 5. (Griffiths 7308, Ariz.) 



Figure 773. — Bouteloua uniflora, X 7. (Type.) 



branching; culms slender, 10 to 30 

 cm. tall; blades small and few, in 

 vigorous plants as much as 15 cm. 

 long; spikes mostly 8 to 14 on a slen- 

 der axis, reflexed, readily falling, the 

 base of the rachis forming a sharp, 

 bearded point; spikelets 2 to 4, nar- 

 row, appressed; rudiment of 3 sca- 

 brous awns about 5 mm. long, ex- 

 ceeding the fertile floret. O (Tri- 

 athera aristidoides Nash.)— Mesas, 

 deserts, and foothills in open ground, 

 Texas to Nevada, southern Cali- 

 fornia, and northern Mexico; Argen- 

 tina. 



