WHITE LOCO WEED. 87 



to vary slightly in different parts of the State. In the Judith Basin 

 and in the Sun River country it does not grow plentifully on the level 

 prairie, while in these same regions the foothills are so completely 

 covered with it that they appear as large white tracts when the plant 

 is in full bloom. On the other hand in the range country along the 

 course of the Musselshell River the white loco weed is met with more 

 extensively on the high prairie ranges. Attention has already been 

 called to the fact that as a general rule native ranges are freer from 

 poisonous plants the farther one goes away from the mountains. This 

 statement is also true of the white loco weed, which seldom occurs 

 abundantly on any prairie range in Montana at a distance of 20 miles 

 from the mountains. 



HISTORY AS A POISONOUS PLANT. 



For many years a disease called loco, affecting cattle, horses, and 

 sheep, has been generally known to the stockmen of the western 

 ranges. This disease has most commonly been attributed to the action 

 of certain plants, more rarely to that of alkali. Several species of 

 plants have been suspected of producing the loco condition in animals 

 and have been called loco plants or loco weeds and also crazy weeds 

 from the nature of the disease. Nearly all of the plants which have 

 been considered loco weeds belong to two genera of the pea family, 

 Astragalus and Aragallus. These genera are represented by numer- 

 ous species on the western stock ranges. Most of the species are 

 somewhat restricted in their distribution either to the southern or 

 northern portion of the range country, or grow more abundantly in 

 one region than in another. In Colorado the plant which is most com- 

 monly known as loco weed is Astragalus inolUsswius. In Montana, 

 on the other hand, the plants most generally called loco weeds by the 

 stockmen are species of Aragallus. A number of other plants have 

 occasionally been mistaken for loco weeds, and among these ma}' be 

 mentioned species of Astragalus and lupine. The species which is 

 most concerned in causing the loco disease in Montana is Aragallus 

 spicatus and is closely related to A. larnhertii. 



It is the belief of a number of stockmen that a condition almost, 

 if not quite, the same as the loco disease may be produced in sheep by 

 eating undue quantities of alkali soil. Reference has already been 

 made to the fact that some stockmen do not salt their animals at all, 

 or onh' at long intervals. When animals are not salted regularl}^ they 

 soon discover localities where large quantites of alkali are found in the 

 soil and visit such places frequently for the purpose of eating this alkali 

 soil. A few of the more observant sheep raisers have come to believe 

 that sheep are less apt to become locoed when regularly salted than 

 when they eat large quantities of alkali in consequence of not being 

 supplied with salt. For this fact two explanations have been offered. 



