128 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



12. Column of the awn straight or obscurely twisted; panicle some- 



what open, the branches rather distant, stiffly ascending, 



naked at base 17. A. parishii. 



11. Glumes unequal, the first half as long as the second, or as much as 

 two-thirds as long in A. glauca (13). 



13. Lemma narrowed into a slender beak 5 to 6 mm. long; awns 1.5 



to 2.5 cm. long, widely spreading 11. A. glauca. 



13. Lemma not narrowed above (14). 



14. Panicle branches very slender, more or less flexuous; lemma 

 conspicuously scabrous in lines; awns terete at base. 



12. A. PURPUREA. 



14. Panicle branches stiffly ascending or appressed, or sometimes 



rather lax in A. longiseta, but then the lemma nearly glabrous 



and the awns flattened toward base (15). 



15. Culms rather stout, 30 to 60 cm. high; panicle 15 to 20 cm. 



long, densely flowered; awns 2 cm. long. 



15. A. WRIGHTII. 



15. Culms rather slender, 20 to 30 cm. high; panicle mostly 10 to 



15 cm. long, relatively few-flowered; awns 2 to 8 cm. 



long (16). 



16. Leaves crowded toward the base in a dense cluster; lemma 



scabrous toward the summit, the awns 2 to 5 cm. long; 



panicle rather stiff 13. A. fendleriana. 



16. Leaves not crowded toward the base; lemma glabrous or 

 nearly so, the awns 6 to 8 cm. long; panicle lax. 



14. A. LONGISETA. 



1. Aristida californica Thurb. in S. Wats., Bot. Calif. 2: 289. 1880. 

 Yuma County, common along roadsides, on desert plains and mesas, 



apparently flowering as favorable conditions permit. Southwestern 

 Arizona, southern California, and northern Mexico. 



2. Aristida glabrata (Vasey) Hitchc, Contrib. U. S. Natl. Herbarium 



22: 522. 1924. 



Aristida calijornica var. glabrata Vasey, Calif. Acad. Sci. Proc. 

 ser. 2, 3: 178. 1891. 



Maricopa, Pinal, Pima, and Yuma Counties, dry ground and mesas, 

 common in the foothills of the Santa Rita Mountains, apparently 

 flowering whenever conditions are favorable. Southern Arizona to 

 Baja California. 



3. Aristida orcuttiana Vasey, Torrey Bot. Club Bui. 13: 27. 1886. 

 Navajo, Yavapai, Graham, Cochise, Santa Cruz, and Pima Counties, 



mostly about 5,000 feet, dry rocky hills and canyons, August to Sep- 

 tember. Texas to southern California and northwestern Mexico. 



4. Aristida ternipes Cav., Icon. PL 5: 46. 1799. 



Cochise, Santa Cruz, and Pima Counties, up to 6,000 feet, rocky 

 hills and mesas, August to October. ISiew Mexico and Arizona to 

 northern South America and West Indies. 



The name spidergrass is sometimes applied to this species. The 

 var. minor (Vasey) Hitchc. is a smaller form with less diffuse panicles, 

 the shorter branches usually stiffly spreading. It is more common 

 than the species and occurs in Mohave, Yavapai, Pinal, Cochise, 

 Santa Cruz, and Pima Counties. 



5. Aristida oligantha Michx., Fl. Bor. Amer. 1: 41. 1803. 

 Coconino National Forest, Coconino County (Forest Service 32581), 



the only specimen known from Arizona and possibly introduced. 

 Dry open ground, Massachusetts to South Dakota, south to Florida 

 and Texas, also Oregon to California and Arizona. 



