| → genera naturally living in the United 1866 |
| genera of these 1859 1860 |
| endemic genera of the United 1861 |
| genera now living in the United 1869 1872 |
|
| → struggled 1859 1860 1861 1866 1869 |
| in any country struggled 1872 |
|
| → of any country, 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| → in 1859 1860 1861 1866 1869 |
| of structure in 1872 |
|
|
of the native genera and species, far more in new genera than in new species. To give a single instance: in the last edition of Dr. Asa
of the Flora of the Northern United
260 naturalised plants are enumerated, and these belong to 162 genera. We thus see that these naturalised plants are of a highly diversified nature. They differ, moreover, to a large
from the indigenes, for out of the 162
no less than 100 genera are not there indigenous, and thus a large proportional addition is made to the
→genera naturally living in the United
States. |
|
| By considering the nature of the plants or animals which have
→struggled
successfully with the
→of any country,
and have there become naturalised, we
gain some crude idea in what manner some of the natives would have
to be modified, in order to
an advantage over
and we
at least
infer that diversification of structure, amounting to new generic differences, would
profitable to them. |
|
| The advantage of diversification
→in
the inhabitants of the same region is, in fact, the same as that of the physiological division of
in the organs of the same individual body— a subject so well elucidated by Milne Edwards. No physiologist doubts that a stomach
adapted to digest vegetable matter alone, or flesh alone, draws most nutriment from these substances. So in the general economy of any land, the more widely and perfectly the animals and plants are diversified for different habits of life, so will a greater number of individuals be capable of there supporting themselves. A set of animals, with their organisation but little diversified, could hardly compete with a set more perfectly diversified in structure. It may be doubted, for instance, whether the Australian marsupials, which are divided into groups differing but little from each other,
|
