CHAPTER XIX
THE FLOWER—FERTILIZATION AND POLLINATION
Fertilization.—Seeds result from the union of two elements or parts. One of these elements is a cell-nucleus
of the pollen-grain. The other element
is the cell-nucleus of an egg-cell,
borne in the ovary. The
pollen-grain falls on the stigma
(Fig. 193). It absorbs the juices
exuded by the stigma, and grows
by sending out a tube (Fig. 194).
This tube grows downward through
the style, absorbing food as it goes,
and finally reaches the egg-cell in
the interior of an ovule in the
ovary (Fig. 195), and fertilization,
or union of a nucleus of the pollen and the
nucleus of the egg-cell in the ovule, takes place.
The ovule and embryo within then develops into a seed. The growth of the pollen-tube is
often spoken of as germination of the pollen,
but it is not germination in the sense in which
the word is used when speaking of seeds.
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Fig. 193.—B, Pollen escaping from anther; A, pollen germinating on a stigma. Enlarged.
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Fig. 194.—A Pollen-grain and the Growing Tube.
Better seeds—that is, those that produce stronger and more fruitful plants—often result when the pollen comes from another flower. Fertilization effected between different flowers is cross-fertilization; that resulting from the
