18 BULLETIN 575, U. S. DEPARTMENT OF AGRICULTURE. 
performed with wild-cherry leaves, many of which have been with- 
out results. Investigations by the department, however, have 
proved beyond question that the leaves of wild cherry are extremely 
poisonous, and there seems to be no doubt that, under certain cir- ¢ 
cumstances, animals may be killed by eating this plant. These 
cases ordinarily occur along drives that are bordered by wild cherry 
and where there is very little else for the animals to eat. 
Sheepmen should by all means avoid, if possible, trails that are 
lined with wild cherry, and.if it is necessary to drive over these trails, 
they should take great care that the animals are well supplied with 
food before commencing the drive. Poisoning from wild cherry is 
due to prussic acid, and death results very quickly. No treatment 
is likely to modify the results. Plate XXIV shows one of the wild 
cherries of the West. 
MILKWEED (ASCLEPIAS). : 
Several of the species of milkweed are said to cause losses of live 
stock, especially of sheep. The poisonous character of the whorled 
milkweed (Asclepias galioides) has been definitely proved. This plant, 
shown in Plate XXV, grows in the dry plains and foothills of Arizona, 
New Mexico, southern Utah, and southwestern Colorado, and has 
become especially abundant in some of the irrigated lands. It is 
very poisonous, and, while not eaten from choice, has caused heavy 
losses of sheep, when, in a hungry condition, they have been confined 
to a milkweed area. It is also poisonous to horses and cattle, but 
the principal losses have been of sheep. 
WOODY ASTER (XYLORRHIZA PARREYI). 
The woody aster, shown in Plate X XVI, occurs in great abundance * 
in certain regions in Wyoming, and has been accused of causing losses 
of sheep in those localities. There appears to be no doubt that the 
plant is poisonous. It is a fibrous plant, however, and is very dis- 
tasteful to sheep under ordinary circumstances, so there is very 
little danger from it, provided the sheep are kept in a region where 
sufficient feed is obtainable. 
COLORADO RUBBER PLANT, OR PINGUE (HYMENOXYS FLORIBUNDA). 
This plant, shown in Plate X XVII, is confined to the northern part 
of New Mexico and the southern part of Colorado and Utah, and in 
certain localities grows in very great abundance. Its aster-like 
flowers are quite conspicuous, and the plant is readily distinguished 
from other similar plants because of the dark golden-yellow color of | 
the flowers. The rubber plant has had a good deal of advertising 
because it contains a certain amount of rubber and has been the 
