ing from the tassel is the pollen, and the long silky threads of
the ear are the stigmas.

[Illustration: FIG. 34. A TOMATO BLOSSOM]

Now no plant can bear seeds unless the pollen of the stamen falls on the
stigma. Corn cannot therefore form seed unless the dust of the tassel
falls upon the silk. Did you ever notice how poorly the cob is filled on
a single cornstalk standing alone in a field? Do you see why? It is
because when a plant stands alone the wind blows the pollen away from
the tassel, and little or none is received on the stigmas below.

[Illustration: FIG. 35. CUCUMBER BLOSSOMS]

In the corn plant the stamens and pistils are separate; that is, they do
not occur on the same flower, although they are on the same plant. This
is also true of the cucumber (see Fig. 35). In many plants, however,
such as the hemp, hop, sassafras, willow, and others, the staminate
parts are on one plant and the pistillate parts are on another. This is
also true in several other cultivated plants. For example, in some
strawberries the stamens are absent or useless; that is, they bear no
good pollen. In such cases the grower must see to it that near by are
strawberry plants that bear stamens, in order that those plants which do
not bear pollen may become _pollinated_; that is, may have pollen
carried to them. After the stigma has been supplied with pollen, a
single pollen grain sends a threadlike sprout down through the stigma
into the ovary. This process, if successfully completed, is called
_fertilization_.

=EXERCISE=

Examine several flowers and identify the parts named in the last
section. Try in the proper season to find the pollen on the maple,
willow, alder, and pine, and on wheat, cotton, and the
morning-glory.

How fast does the ovary of the apple blossom enlarge? Measure one
and watch it closely from day to day. Can you find any plants that
have their stamens and ovaries on separate individuals?

SECTION XV. POLLINATION

Nature has several interesting ways of bringing about pollination. In
the corn, willow, and pine the pollen is picked up by the wind and
carried away. Much of it is lost, but some reaches the stigmas, or
receptive parts, of other corn, willow, or pine flowers. This is a very
wasteful method, and all plants using it must provide much pollen.

Many plants employ a much better method. They have learned how to make
insects bear their pollen. In plants of th