COCKLEBURS AS POISONOUS PLANTS 5 
In this historical sketch a bibliography has been made of those 
publications which were of special significance. The Department 
of Agriculture has received many letters from various sections of 
the country stating conclusively that animals were killed by cockle- 
burs. Most of these statements were with reference to swine, but 
complaints have also been made, especially from Xew Mexico and 
western Texas, of losses of cattle. A number of losses of this kind 
were brought to the attention of the department by Dr. Harry 
Grafke, inspector in charge at Fort Worth, Tex., in the spring of 
1922, in which he felt certain that the deaths were due to cocklebur 
poisoning. 
Some of the Xanthium losses which have been reported in the 
literature and in the correspondence have been rather heavy. 
Pammel, 1920, saj^s that "4 pigs were turned on Xanthium and 
3 died;'' Mayo, 1905, gives an instance in which 33 out of 35 head 
died; one author states that in one section of the country the 
farmers lose 40 per cent of their pigs. 
Dr. Harry Grafke reported in 1922 one loss of 25 cattle out of a 
herd of 150 and another of 20 out of a herd of 58. In the San 
Antonio Express in April, 1922, was reported a loss of 15 registered 
Hereford bulls out of 17. 
Many statements of the same general character as those above have 
been made by correspondents from different sections of the United 
States. 
The foregoing indicates that while many people have been con- 
vinced of the poisonous properties of cocklebur this belief has by 
no means been universal. Others have felt certain that the losses 
occasioned by this plant, if such losses occurred, were due to mechan- 
ical injury. Among those who believed that the plant was poisonous 
there has been a good deal of uncertainty in regard to the part of 
the plant which produced the harm. Most of those, who have 
reported cases of poisoning have stated that it was due to the young 
plant, but some experiments apparently have proved that the plant 
was not poisonous in any stage. Inasmuch as the losses which in 
some localities have been ascribed to Xanthium have been very heavy, 
it was deemed of special importance to determine positively 
whether the plant was poisonous or not and if poisonous what part 
of the plant was injurious, and at what age the plant should be 
avoided, and also, in case the plant proved to be poisonous, to find a 
remedy. The investigations detailed in this bulletin were undertaken 
to answer these questions. 
THE COCKLEBUR PLANT 
The species of Xanthium are widely distributed throughout the 
United States, growing in moist, waste places and along the shores 
of rivers, lakes, and ponds. It has not seemed wise to discuss in this 
bulletin the species relations of the genus, partly because there 
is reason to think that all are equally poisonous and partly because 
there is little doubt that in the literature of the subject there has 
been much confusion in the use of specific names. Because of the 
close relationships and rather wide limits of variation in the plants, 
botanists are by no means agreed as to the specific limitations. 
