18 
Colorado Experiment Station 
Pig-. 15 — An uncultivated orchard taken by milkweed. 
irrigated fields or orchards. These same observations are dupli- 
cated in other sections of the State. 
Wind. — The buoyancy of the seed, due to the lightness of the 
seed itself, and to the parachute of silky hairs, makes it very well 
adapted to dispersal by wind. Everyone is familiar with the ease 
with which milkweed seeds are carried on a light breeze. It is 
not probable that seeds are carried in this manner as far as they 
are carried in large irrigation laterals, but the wind undoubtedly 
serves to cause a great deal of dispersal. The dispersal by water 
is undoubtedly the most effective because it not only carries the 
seed long distances but always places them in a suitable place for 
germination. 
Eailroads.— This agency is important not so much from the 
standpoint of numbers carried as from the fact that it has prob- 
ably been responsible for the establishment of the weed in en- 
tirely new territories. The railroad right-of-way is a very com- 
mon habitat of the milkweed. This does not, of course, argue 
that the railroad is responsible for the carrying of all the seed 
that has been scattered along the right-of-way. Wind might 
just as easily be responsible for the carrying of much seed to 
the embankments or cuts along the railroad but there have been 
a number of cases of occurrence of the weed at railroad switches, 
especially at points where stock are unloaded, that are very con- 
