6 BULLETIN 575, U. S. DEPARTMENT OF AGEICULTTJRE. 



PURPLE LOCO (ASTRAGALUS MOLLISSLMUS). 



This plant, popularly known as "purple loco/' "woolly loco," and 

 sometimes as "Texas loco," is one that Jias been historically known 

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

 as a loco dangerous to live stock. It does not grow north of Nebraska, 

 and perhaps is most abundant in the Panhandle of Texas, although 

 it is found hi adjoining regions of New Mexico, Colorado, Kansas, and 

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

 not as conspicuous as in the white loco, 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 the purple loco is more 

 inclined to grow at the lower levels, while the white loco is found 

 upon the sides of elevations. Purple loco 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. 



ASTRAGALUS DIPHYSUS. 



Plate VI is a picture of Astragalus diphysus, which is a type of a 

 number of loco plants growing in the Southwest. These plants 

 differ in their appearance very markedly from the white and purple 

 locoes, but although only a few feeding experiments have been per- 

 formed, there is every reason to believe that they are fully as destruc- 

 tive as the better known plants. Horses seem more likely to be 

 affected by these plants than cattle, although hi the Southwest there 

 are a great many locoed cattle. Closely allied to the plant illus- 

 trated are a number of species which there is every reason to con- 

 sider as true loco plants and which it is incumbent upon stockmen to 

 prevent stock from eating. 



SYMPTOMS OF LOCO POISONING. 



All the loco plants produce similar effects. These symptoms 

 appear only after a somewhat prolonged feeding upon the plant, and 

 this fact has led to the failure of a great many feeding experiments 

 with loco. Ordinarily the first symptom in a locoed animal is a 

 loss of condition. This is followed by irregularities of gait and weak- 

 ness which in many cases seems almost to amount to paralysis. The 

 animal shows a lack of coordination in its muscular movements, due 

 without doubt to the effect of the plant upon the central nervous 



