and pistils or are perfect
flowers the stigmas and pollen ripen at different times.

With some varieties of fruit it is found that the pistils cannot be
fertilized by pollen of the same variety. This is true of most of our
native plums. For example, the pistils of the wild goose plum cannot
be fertilized by pollen of wild goose plums even if it comes from
other trees than the one bearing the pistils. They must have pollen
from another variety of plum.

VALUE OF A KNOWLEDGE OF THE FLOWER

Many times it happens that a farmer or a gardener wants to start a
strawberry bed and buys plants of a variety of berries that have the
reputation of being very productive. He plants them and cultivates
them carefully, and at the proper time they blossom very freely, and
there is promise of a large crop, yet very few berries appear and this
continues to be the case. Not satisfied with them he buys another
variety and plants near them, and after that the old bed becomes very
productive. Now why is this? It happens that the flowers of some
varieties of strawberries have a great many pistils but no stamens,
or very few stamens, and there is not pollen enough to fertilize all
of the blossoms, and when such a variety is planted it is necessary to
plant near it some variety that produces many stamens and therefore
pollen enough to fertilize both varieties in order to be sure of a
crop. Those strawberries which produce flowers with only pistils are
called pistilate varieties, while those with both stamens and pistils
are called perfect varieties (Fig. 78). In planting them there should
be at least one row of a perfect variety to every four or five
pistilate rows.

[Illustration: FIG. 74.
A magnolia flower showing central column of pistils and stamens, the
pistils being above and the stamens below them.]

[Illustration: FIG. 75.--FLOWERS OF SQUASH.
_A_, pistillate flower; _B_, staminate flower. A means of insuring
cross-pollination.]

We have learned that certain varieties of plums cannot be fertilized
by pollen from the same variety, and to make them fruitful some other
variety must be planted among them to produce pollen that will make
them fruitful. This is more or less true of all our fruits. Therefore
it is not best generally to plant one variety of fruit by itself. Not
knowing this some orchardists have planted large blocks of a single
variety of fruit which has been unfruitful till some other varieties
have been planted near t