12 
Colorado Experiment Station 
infestation is on the Western Slope, particularly in Mesa County. 
On the Eastern Slope the present known distribution is con- 
fined to isolated spots in Las Animas and Huerfano Counties and 
thru the irrigated sections of the Arkansas Valley from Canon 
City to the state line. In all probability there are^ other in- 
festations in the State not shown on the map. It is also very 
probable that there are other regions in addition to those shown 
on the map where losses have occurred. From the facts at pres- 
ent known about the plant there is no reason why it could not 
occur in any of the irrigated sections of the state. 
The milkweed is known to be present in quantities sufficient 
to cause trouble in Utah and New Mexico, and recently a com- 
munication fom an official of the United States Reclamation 
Service states that the milkweed occurs in large quantities on 
the Truckee-Carson Project near Fallon, Nevada, and is sus- 
pected of causing losses of livestock in that region. 
Fig. 8 — Axillary clusters of blossoms of 
whorled milkweed. 
