2 BULLETIN 575, U. S. DEPAETMENT OF AGRICULTUEE. 



necessary to bring the industry of stock production to the highest possible stage of 

 efficiency, and it becomes a civic duty for every owner 'of live stock to produce as 

 much as possible. 



As a factor to aid in the conservation of food, this bulletin has been prepared with a 

 view to assisting in the ready recognition of the plants which are most to be feared, and 

 with brief suggestions, by following which losses can be largely reduced. 



While our knowledge of poisonous plants is still incomplete, if stockmen will make 

 it a point to recognize the plants and instruct their herders, following out the sug- 

 gested methods of treatment and prevention, it will result in a very material and 

 important increase of the meat supply. 



Plates VIII, XIII, XIV, XV, XXI, and XXIV are from paintings by F. A. 

 Walpole, in the collection of the United States National Herbarium. 



J. R. Mohler, 

 Chief of Bureau . 



INTRODUCTION. 



Poisonous plants have been the cause of heavy losses among live 

 stock on the range. Stockmen generally have recognized the fact, 

 but in the past comparatively little has been done to avoid the 

 losses. The first intimation of trouble has ordinarily been the 

 finding of the dead carcasses, and while the men handling the 

 stock have felt reasonably sure that certain plants were responsi- 

 ble, their knowledge of the plants was very meager, and the 

 evidence against any particular plant was frequently insufficient. 

 It was noticed that these losses were more apt to occur in certain 

 seasons than in others, and it was assumed in some cases that the 

 plant was more poisonous at certain stages of growth than at 

 others. Many of the stockmen were entirely uncertain as to what 

 plant caused the damage, and it was common to speak of the source 

 of the trouble as " poison weed," in a general way, without any very 

 definite idea as to what particular weed was responsible for the loss. 

 Moreover, the investigations which have been carried out on the 

 subject of range-poisoning plants have necessarily been somewhat 

 narrow in scope. There is a popular misconception in regard to 

 the quantity of a poisonous plant necessary to produce illness. It 

 seems to be the general belief that any plant possessing poisonous 

 properties must be violently toxic. It is not unusual to hear stories 

 of poisoning of domestic animals by a very few leaves of a poisonous 

 plant. As a matter of fact, most of the stock-poisoning plants in the 

 United States produce illness only when eaten in considerable quantity. 

 This explains why so many experimental tests of animals with 

 poisonous plants have failed, since some of these plants can be eaten 

 with no apparent harm, provided the quantity eaten at any one time 

 is not sufficient to produce toxic effects. 



The problems of plants poisonous to live stock seem to be very 

 largely peculiar to North America. Although similar plants occur in 

 the eastern continents, very little information could be drawn from 

 European sources to aid the American stockman. 



