2 BULLETIN 575, U. S. DEPARTMENT OF AGRICULTURE. 
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. Mounier, 
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-poisonuig plants in the 
United States produce illness only when eaten in considerable quantity. 
This explams 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. 
a 
