The Descent of Man

in which the sexes are separate, the male flowers
are generally mature before the female. As
first shewn by C.K. Sprengel, many hermaphrodite
plants are dichogamous; that is, their
male and female organs are not ready at the
same time, so that they cannot be self-fertilised.
Now in such flowers, the pollen is in general
matured before the stigma, though there are
exceptional cases in which the female organs
are beforehand.) The cause of this difference
between the males and females in their periods
of arrival and maturity is sufficiently obvious.
Those males which annually first migrated into
any country, or which in the spring were first
ready to breed, or were the most eager, would
leave the largest number of offspring; and these
would tend to inherit similar instincts and
constitutions. It must be borne in mind that it
would have been impossible to change very
materially the time of sexual maturity in the
females, without at the same time interfering
with the period of the production of the