FLOWERING PLANTS AND FERNS OF ARIZONA 489 



Mountains {Goodding 1299). Southwestern New Mexico, southern 

 Arizona, and northern Mexico. 



Sheep loco. Plant handsome in flower, sometimes covering the 

 ground with its purplish-pink flowers that change to violet in drying. 

 Easily distinguished from the related A. arizonicus by the less pros- 

 trate stems, glabrous upper surface of the shorter and broader leaflets, 

 and sharply acuminate beak of the keel. Experiments with sheep and 

 cattle have proved this plant to be as toxic as A. diphysus, although 

 it is reported to be eaten readily by deer. 



67. Astragalus hartwegii Benth., PL Hartw. 10. 1839. 



Hamosa hartwegii Rydb., Torrey Bot. Club Bui. 54: 333. 1927. 



Babocomari Creek, Cochise County (Lemmon 2638). Southeastern 

 Arizona and northern Mexico. 



68. Astragalus nuttallianus DC, Prodr. 2: 289. 1825. 



Hamosa nuttcdliana Rvdb., Colo. Agr. Expt. Sta. Bui. 100: 

 204. 1906. 



Almost throughout the State, 100 to 4,000 (rarely 7,000) feet, very 

 common on dry plains, mesas, and slopes, February to May (occasion- 

 ally late summer). Arkansas and Texas to California and northern 

 Mexico. 



Arizona's most common annual species, occurring in 2 almost 

 equally abundant forms, one with smooth pods (Hamosa emoryana 

 Rydb.) and the other with pubescent pods (var. trichocarpus Torr. 

 and Gray, Hamosa austrina Small). In the form with smooth pods, 

 these are occasionally 1-celled (Hamosa imperfecta Rydb.). 



69. Astragalus hypoxylus S. Wats., Amer. Acad. Arts and Sci. Proc. 



18: 192. 1883. 



Hamosa hypoxyla Rydb., Torrey Bot. Club Bui. 54: 336. 



1927. 



Known certainly only from the type collection in the Huachuca 

 Mountains, Cochise County (Lemmon 2656). 



Plant acaulescent, loosely cespitose, the leaflets small, obovate, 

 obtuse, the inflorescence subcapitate. 



70. Astragalus bigelovii A. Gray., PL Wright. 2: 42. 1853. 

 Cochise, Santa Cruz, and Pima Counties, 4,000 to 5,500 feet, dry 



slopes and mesas, April and May. Texas to southern Arizona and 

 northern Mexico. 



Very similar to A. mollissimus Torr., the very toxic purple or woolly 

 loco, and reputed to cause loco disease, but the dried plants have been 

 fed to cattle in large quantity without ill effect. 



71. Astragalus thompsonae S. Wats., Amer. Acad. Arts and Sci. 



Proc. 10: 345. 1875. 



Apache County to Coconino County, 4,700 to 6,800 feet, usually 

 in sandy soil, sometimes with yellow pine, May and June. Colorado, 

 Utah, and northeastern Arizona. 



Very similar to A. bigelovii and often confused with it, but the geo- 

 graphical distribution of the 2 species in Arizona is very different and 

 the pods of A. thompsonae are normally 1-celled at the apex and 2- 

 celled below, whereas in A. bigelovii they are 2-celled throughout. It 

 should be noted, however, that a specimen from Turkey Tanks, Coco- 



