But the advantage
is on the side of Asclepias after the insect is loaded with it.
It is only a general rule that insects keep to flowers of a
particular species on their honey and pollen gathering
expeditions. If a bee dusted with loose pollen visits flowers of
another species, it will not long retain pollen in sufficient
quantity to effectually fertilize flowers of the original
species. On the other hand, if an insect returns at any time
during the day, or even after a few days, to the species of
Asclepias from which it got a load of pollinia, it may bring with
it all or most of the pollinia which it has carried from the
first plants visited. The firmness with which the pollinia keep
their hold on the insect is one of the best adaptations for
cross-fertilization."
Ants, the worst pilferers of nectar extant, find the hairy stem
of the whorled milkweed, as well as its sticky juice, most
discouraging, if not fatal, obstacles to climbing. How daintily
the goldfinch picks at the milkweed pods and sets adrift the
seeds attached to silky aeronautic fluff!
WILD POTATO-VINE; MAN-OF-THE-EARTH; MECHA-MECK
(Ipomoea pandurata) Morning-glory family
Flowers - Funnel form, wide-spread, 2 to 3 in.
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