FLOWERING PLANTS AND FERNS OF ARIZONA 483 



35. Astragalus allochrous A. Gray, Amer. Acad. Arts and Sci. Proc. 



13: 366. 1878. 



Phaca allochroa Rydb., Fl. Rocky Mount. 487, 1063. 1917. 



Coconino and Mohave Counties to Graham, Cochise, Santa Cruz, 

 and Pima (doubtless also Yuma) Counties, 1,500 to 7,000 feet, very 

 common on plains and mesas, March to May, type from Wickenburg, 

 Maricopa County (Palmer 588). Southern New Mexico and Arizona. 



One of the most conspicuous species in the State because of the 

 large size of the plant and of the bladdery pods; It causes loco 

 disease in horses. 



36. Astragalus wootoni Sheldon, Minn. Geol. and Nat. Hist. Survey 



Bot. Studies 1: 138. 1894. 



Phaca wootoni Rydb., North Amer. Fl. 24: 350. 1929. 



Equally common in Arizona as A. allochrous and having about the 

 same range, altitude, habitat, and time of flowering. Western Texas 

 to Arizona and northern Mexico. 



Smaller in all its parts than A. allochrous but otherwise very similar 

 and intergrading with it. Definitely known to produce loco disease in 

 horses, cattle, and sheep. 



37. Astragalus subcinereus A. Gray, Amer. Acad. Arts and Sci. Proc. 



13: 366. 1878. 



Phaca subcinerea Rydb., Torrey Bot. Club Bui. 40: 47. 1913. 



Apache County to Coconino County, 5,000 to 7,000 feet, sandy soil, 

 June to August, t}^pe from Mokiak Pass (Palmer in 1877). Southern 

 Utah and northern Arizona. 



38. Astragalus sileranus M. E. Jones, Zoe 2: 242. 1891. 



Phaca silerana Rydb., Torrey Bot. Club Bui. 40: 47. 1913. 



Kaibab Plateau and north rim of Grand Canyon (Coconino County), 

 7,000 to 9,000 feet, openings in coniferous forests, June to August. 

 Southern Utah and northern Arizona. 



When fresh the corolla is yellowish, with a purple-tipped keel. 

 A. cerrusatus Sheldon and Phaca pardalina Rydb. are perhaps not 

 specifically distinct from A. sileranus. 



39. Astragalus triquetrus A. # Gray, Amer. Acad. Arts and Sci. Proc. 



13: 367. 1878. 



Phaca triquetra Rydb., North Amer. Fl. 24: 353. 1929. 



Beaver Dam, Mohave County, 2,000 feet (Peebles and Parker 

 14678), sandy soil, April and May. Extreme southern Nevada and 

 adjacent Arizona. 



*40. Astragalus aridus A. Gray, Amer. Acad. Arts and Sci. Proc. 6: 

 223. 1864. 



Phaca arida Rydb., North Amer. Fl. 24: 354. 1929. 



The only record for occurrence in Arizona of this species, known 

 otherwise only from the deserts of southeastern California and Baja 

 California, is the label of a specimen reading " southwestern Arizona" 

 (Gilman 1145, Pomona College Herbarium). It greatly resembles A. 

 sabulonum, differing chiefly in the appressed (sericeous) pubescence 

 of the herbage and pods. 



