Fig-. H — The fence row is a common place for this plant to be 
found. 
Whorled Milkweed 1 7 
abandoned fields and in orchards only partially clean cultivated. 
(Fig, 15). Where the infestation becomes bad it will make its 
way by the underground rootstocks into solid stands of blue grass 
or into alfalfa fields. 
HOW IT IS SPREAD 
The seed of this species, like all of the milkweeds, is admir- 
ably fitted for wide and easy distribution. 
The agencies, in the probable order of their importance, that 
are responsible for the spreading of the seed are: (1) Water, (2) 
wind, (3) railroads, (4) animals. 
Water. — In every infested area so far observed it has been 
clearly shown that irrigation water plays an important role in 
carrying the milkweed seed. In territories newly infested, the 
patches are always found along the laterals. This was well dem- 
onstrated in the West Paradox Valley. Four years ago sheep were 
lost in the west and upper end of the valley and at the time 
whorled milkweed was suspected by Mr. John Rohwer. He has 
been watching this plant since then, and has noted the gradual 
spread of it over the ranches in the upper end of the valley. Last 
summer the infestation had spread several miles down the valley 
and the lower patches are largely along irrigation laterals or in 
