iven before it its great
congener. One species of charlock will supplant another, and so in
other cases. We can dimly see why the competition should be most severe
between allied forms, which fill nearly the same place in the economy
of nature; but probably in no one case could we precisely say why one
species has been victorious over another in the great battle of life.

A corollary of the highest importance may be deduced from the foregoing
remarks, namely, that the structure of every organic being is related,
in the most essential yet often hidden manner, to that of all other
organic beings, with which it comes into competition for food or
residence, or from which it has to escape, or on which it preys. This
is obvious in the structure of the teeth and talons of the tiger; and in
that of the legs and claws of the parasite which clings to the hair on
the tiger's body. But in the beautifully plumed seed of the dandelion,
and in the flattened and fringed legs of the water-beetle, the relation
seems at first confined to the elements of air and water. Yet the
advantage of plumed seeds no doubt stands in the closest relation to the
land being already thickly clothed by other plants; so that the
seeds may be widely distributed and fall on unoccupied ground. In the
water-beetle, the structure of its legs, so well adapted for diving,
allows it to compete with other aquatic insects, to hunt for its own
prey, and to escape serving as prey to other animals.

The store of nutriment laid up within the seeds of many plants seems at
first sight to have no sort of relation to other plants. But from the
strong growth of young plants produced from such seeds (as peas and
beans), when sown in the midst of long grass, I suspect that the chief
use of the nutriment in the seed is to favour the growth of the young
seedling, whilst struggling with other plants growing vigorously all
around.

Look at a plant in the midst of its range, why does it not double or
quadruple its numbers? We know that it can perfectly well withstand a
little more heat or cold, dampness or dryness, for elsewhere it ranges
into slightly hotter or colder, damper or drier districts. In this case
we can clearly see that if we wished in imagination to give the plant
the power of increasing in number, we should have to give it some
advantage over its competitors, or over the animals which preyed on it.
On the confines of its geographical range, a change of constitution