The Evolution of Fruits.
9
inquiry as to the morphological nature of ovules, we may
perhaps safely assert that they are originally, normally, and
almost universally developed from the margin of carpellary
leaves. In Cycas such an origin is obvious, for we have a
but slightly modified leaf, some lobes of which only are
transformed into ovules. In the Juniper the three scales at
the base of which the ovules are situated, becoming succulent,
simulate the berry amongst true fruits. In abnormal Prim-
roses the ovules are seen to spring from heel-like, auricular
appendages at the base of the carpellary leaves, and all the
evidence points to the origin of this order from a Caryophyl-
laceous ancestry, from which it differs only in having its
petals united. The originally marginal character of the
placentation of the Caryophyllaceae is clearly seen, e.g., in the
carnations (Dianthus). The structure of those groups in
which the placentation is still simpler, such as the Poly-
gonaceae in which there is a single ovule rising from the base
of the one-chambered ovary, may be best explained as
reduction from the same marginal type.
The original fruit consisting then of a single carpellary
leaf or of several, the ovules in either case being marginal
structures, before tracing the general rules followed by
Nature in the variations of fruits, it is necessary to consider
the objects which fruits have to accomplish. The ultimate
object of the fruit is subsidiary to that of the seed—the
reproduction of the species. The immature seed requires
protection from decay-producing excess of moisture or from
the depredations of birds. The mature seed requires a non-
conducting covering, that it may not be stimulated into
premature germination by the deceptive warmth and moisture
of autumn. Many plants producing offsets and many seeds
necessarily falling near the parent plant, the species becomes
a social one, like the grasses of our temperate regions, in
which case the struggle for existence is more than usually
severe, the relations of each individual to its surroundings—
its hexicology—being similar to those of its neighbours, and
in no way complementary to them. Accordingly dispersion
is advantageous, especially to trees, beneath the shade of