CoT^oKAoo ExpKRnrEXT Station 
66 
COCKLEBUR (Xanthium echinatum) 
Cocklebiir is an annual plant with thick stout stems that branch 
widely. The stem is often marked with dotted brown spots. The 
leaves may be oval in outline, or heart-shaped at the base, and usually 
have 3 main ribs. Stamens and pistils are in different flowers on the 
same plant. Cocklebur is best recognized by the spiny fruit. The 
‘Turs” are densely covered with long prickles. At the tip of the ‘Tur’" 
are usually two stout hooked prickles. 
• 
The. plant is weedy in nature and may be found throughout the 
state at low altitudes. 
Poisoning by cocklebur. —Dr. Panimel in his Manual of Poisonous 
Plants makes the following statement: ‘‘The injury from this plant 
probably comes largely from its mechanical action. Stock will probably 
not eat very much of it, but on account of the hooked awns of the invol¬ 
ucre the animal may have a considerable difficulty in removing them. 
The hairs of the plant cause itching. The plant contains the poisonous 
glucoside xanthostrufuarin which resembles datiscin!' According to 
Chestnut, the young seedlings of three species of cocklebur are pois¬ 
onous for hogs. Dr. Bitting thinks the injurious properties are large¬ 
ly mechanical. 
COLORADO RUBBER PLANT (Hymenoxys floribunda) 
This is an herb (fig. 91) with an aromatic odor. Numerous 
stems arise from a woody base to a height of about i foot. The stems 
at the base are covered with woolly hairs. Each main stem is branched 
near the tip, each smaller branch being terminated by a yellow flower. 
The leaves are divided into several very slender divisions. The plant 
is found in dry soil at an altitude from 4,000 to 10,000 feet. 
Poisoning by rubber plant. —Reports of serious losses in sheep 
from eating the rubber plant have come from Durango, Saguache and 
^Middle Park. The plant is not known to contain anv poison: the in¬ 
jurious effects are probably mechanical. It is thought that death re¬ 
sults from the formation of indigestible masses that obstruct the di¬ 
gestive tract. On the ranges west of Saguache this is considered a 
most dangerous plant for sheep and they are systematically herded 
away from rubber weed patches. 
Acknowledgments 
All the drawings in this bulletin were made by Mr. N. Lee 
Foster, to whom the writers owe acknowledgment. We express our 
thanks to the Wyoming Experiment Station for the use of the plate 
irom which Figure 89 is made. 
