LOCO WEEDS AND OTHER POISONOUS PLANTS 



75 



covered with silky-villous hairs, hence wooly. The bright-purple papili- 

 onaceous flowers are borne in short racemes and are followed by cylindric 

 pods about 2 cm. long. The geographic distribution of this plant partly 

 overlaps that of the first mentioned loco weed. It ranges from South 

 Dakota south to Mexico and through western Nebraska, Kansas, Okla- 

 homa, Texas, nearly the whole of New Mexico, eastern Arizona, Colorado 

 and southwestern Wyoming. It grows on adobe soils in depressions 

 rather than in elevated situations, occurring in patches covering several 



FIG. 31. Stemless loco- weed (Aragallus (Oxytropis) Lamberti) on cattle range of 

 the western plains. (After photograph reproduced as cover illustration of Marsh, C. 

 Dwight: The Loco-weed Disease, Farmers' Bulletin 1054, July, 1919.) 



acres, rather than in continuous stretches of country. It blooms in 

 Colorado about June i, but further south in New Mexico, it flowers as 

 early as April. 



Blue Loco Weed or Rattleweed (Astragalus diphysus = Cystium di- 

 physum). This perennial herb is more western and southwestern in its 

 distribution than the other two loco weeds. It ranges through Colorado, 

 New Mexico, Arizona extreme southern Nevada and southern California, 

 and is the common loco weed, or rattleweed, of New Mexico and Arizona. 



