If all the anthers could have been placed on the same level
in all the plants, then abundant pollen would have adhered to the same part of
the body of the insects which frequented the flowers, and would afterwards have
been deposited without loss on the stigma, if it likewise stood on the same
unvarying level in all the flowers. But as the stamens and pistils are supposed
to have already varied much in length and to be still varying, it might well
happen that they could be reduced much more easily through natural selection
into two sets of different lengths in different individuals, than all to the
same length and level in all the individuals. We know from innumerable
instances, in which the two sexes and the young of the same species differ, that
there is no difficulty in two or more sets of individuals being formed which
inherit different characters. In our particular case the law of compensation or
balancement (which is admitted by many botanists) would tend to cause the pistil
to be reduced in those individuals in which the stamens were greatly developed,
and to be increased in length in those which had their stamens but little
developed.
Now if in our varying species the longer stamens were to be nearly equalised in
length in a considerable body of individuals, with the pistil more or less
reduced; and in another body, the shorter stamens to be similarly equalised,
with the pistil more or less increased in length, cross-fertilisation would be
secured with little loss of pollen; and this change would be so highly
beneficial to the species, that there is no difficulty in believing that it
could be effected through natural selection.
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