29 



PEA FAMILY (PAPILIONACEAE). 



WOOLLY LOCO WEED. 

 Astragalus mollissimus Torr. 



Other names: Loco weed; crazy weed. (Fig. 12.) 



Description and habitat. — A silvery- white, silky-leaved perennial 8 to 12 

 inches high, with an abundance of soft foliage springing oat in a cluster 

 from a short central stem close to the ground. The flowers are pea- 

 shaped and usually purple. The pod is distinctly two- celled. This 

 plant is native to the Great Plains 

 region, extending from western 

 Texas and New Mexico northward 

 to South Dakota and Wyoming, 

 being most abundant in Colorado 

 and in the western part of Ne- 

 braska and Kansas. It grows in 

 the pasture lands of the dry prairie 

 and on rocky liillsides. 



How stock are affected.— Horses, 

 cattle, and sheep are affected by 

 loco, but the principal damage is 

 done to horses. The effect is not 

 acute, but in its slow progress 

 simulates diseases caused by bac- 

 teria, worms, or other parasites or 

 such as are caused in man by the 

 continued use of alcohol, tobacco, 

 or morphine. Two stages are rec- 

 ognized. The first, which may last 

 several months, is a period of hal- 

 lucination or mania accompanied 

 by defective eyesight, during 

 which the animal may perform 

 all sorts of antics. After acquir- 

 ing a taste for the plant it refuses 

 every other kind of food, and the 

 second stage is ushered in., This 

 is a lingering period of emaciation, characterized by sunken eye- 

 balls, lusterless hair, and feeble movements. The animal dies as if 

 from starvation, in periods ranging from a few months to one or two 

 years. 



Damage done. — The damage done to the live-stock business by this 

 weed is immense. As mentioned in the introduction, the State of Col- 

 orado paid out nearly $200,000 in bounties between 1881 and 1885 to 

 check its ravages. 



Poisonous properties. — Chemists and medical men have studied the 



Fig. 12. — Wooly loco weed. {Astragalus mollissi- 

 mus) : a, whole plant ; b, section of pod — both 

 one-third natural size. 



