Surely no description of
this commonest of all garden climbers is needed; everyone has an
opportunity to watch how the bees cross-fertilize it.
The vine has a special interest because of Darwin's illuminating
experiments upon it when he planted six self-fertilized seeds and
six seeds fertilized with the pollen brought from flowers on a
different vine, on opposite sides of the same pot. Vines produced
by the former reached an average height of five feet four inches,
whereas the cross-pollenized seed sent its stems up two feet
higher, and produced very many more flowers. If so marked a
benefit from imported pollen may be observed in a single
generation, is it any wonder that ambitious plants employ every
sort of ingenious device to compel insects to bring them pollen
from distant flowers of the same species? How punctually the
MOON-FLOWER (I. grandiflora), next of kin to the morning-glory,
opens its immense, pure white, sweet-scented flowers at night to
attract night-flying moths, because their long tongues, which
only can drain the nectar, may not be withdrawn until they are
dusted with vitalizing powder for export to some waiting sister.
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