STOCK-POISOXIXG PLANTS OF THE KAXGE 27 



mountain regions, the whole corolla may be of a deep violet or pur- 

 ple color. All gradations in color may be found between these ex- 

 tremes. When the plants are in fruit the pods rattle as one hits 

 them in walking, very closely imitating the rattle of a rattlesnake, 

 hence the name rattleweed. 



Plate 15 is a picture of the white loco weed as found in the plains 

 of Colorado. Plate 16 shows a field of the plant in blossom. The 

 latter picture was taken in the Yellowstone Valley of Montana, but 

 it could easily be duplicated in Wyoming or Colorado. 



It is evident that where the plant occurs in these great numbers 

 such a thing as eradication is impossible except by plowing over the 

 whole area. If animals are turned loose in such a region as this 

 they certainly will have an opportunity to obtain an abundance of 

 loco. 



Purple Loco Wked (Astragalus mollissimus) 



Astragalus mollissimus, popularly known as purple loco, woolly 

 loco, and sometimes as Texas loco, is a plant that has been histori- 

 cally known as the true loco. It is probably the first plant which was 

 recognized as a loco dangerous to livestock. It does not grow north 

 of Nebraska, and perhaps is most abundant in the Panhandle of 

 Texas, although it is found in adjoining regions of New Mexico, 

 Colorado. Kansas, and in Nebraska. The leaflets are very hairy and 

 are much broader than those of the white loco. The plant also has a 

 true stem, while the white loco has sometimes been known as the 

 " stemless loco."' 



Plate 17 shows a very small plant of this loco. The flowers are 

 not so conspicuous as in the white loco weed, and the corolla is of a 

 deep-purple color. The pods are shorter, thicker, and of a deep-brown 

 color. Large plants of purple loco may under favorable circum- 

 stances be about a foot in height and perhaps 2 feet in diameter. It 

 does not commonly grow in the great abundance characteristic of 

 the white loco, but there are sometimes fairly extensive fields. Where 

 it grows in connection with the white loco weed the purple loco weed 

 is more inclined to grow in depressions, while the white loco weed 

 is found more abundantly at slightly higher levels. Purple loco 

 weed is particularly destructive to horses; cattle may be poisoned 

 by it. too. although this is rarely the case, perhaps because cattle do 

 not eat it very readily. 



Bute Loco Weed (Astragalus diphysus) 



Plate 18 is a picture of Astragalus diphysus, known as blue loco. 

 These plants differ in their appearance very markedly from the white 

 and purple locoes. The leaflets are small and of a deep-green color, 

 like alfalfa. This is perhaps the most common loco weed of western 

 Xew Mexico and Arizona, and extends westward into Nevada. It 

 appears in January or February and dries up in the summer. It 

 sometimes form- a considerable portion of the vegetation. Figure 

 16. a picture taken in northern Arizona in April, gives an idea of 

 the size of the plant and of the luxuriance of its growth. It is 

 still poisonous after drying, and considerable losses are said to have 

 occurred in Xevada from the dry plant. 



