| →
(
i.e.
, those including many species) being
1872 |
| being 1859 1860 1861 1866 |
|
(
i.e.,
those including many species) being
1869 |
|
| → the former will be found to include a 1872 |
| a 1859 1860 1861 1866 1869 |
|
| →
(
i.e.
1869 1872 |
|
(
i
.
e
.
1859 |
|
(
I. e.
1860 1861 |
|
(
i. e.
1866 |
|
|
Species
of
the
Larger
Genera
in
each
Country
vary
more
frequently
than
the
Species
of
the
Smaller
Genera.
|
| If the plants inhabiting a
described in any
be divided into two equal masses, all those in the larger genera
→
(
i.e.
, those including many species) being
placed on one side, and all those in the smaller genera on the other side,
→the former will be found to include a
somewhat larger number of the very common and much diffused or dominant
might have been anticipated; for the mere fact of many species of the same genus inhabiting any country, shows that there is something in the organic or inorganic conditions of that country favourable to the genus; and, consequently, we might have expected to have found in the larger genera, or those including many species, a
proportional number of dominant species. But so many causes tend to obscure this result, that I am surprised that my tables show even a small majority on the side of the larger genera. I will here allude to only two causes of obscurity.
and salt-loving plants
very wide ranges and are much diffused, but this seems to be connected with the nature of the stations inhabited by them, and has little or no relation to the size of the genera to which the species belong. Again, plants low in the scale of organisation are generally much more widely diffused than plants higher in the scale; and here again there is no close relation to the size of the genera. The cause of lowly-organised plants ranging widely will be discussed in our chapter on
|
|
| From looking at species as only strongly-marked and well-defined varieties, I was led to anticipate that the species of the larger genera in each country would oftener present varieties, than the species of the smaller genera; for wherever many closely related species
→
(
i.e.
of the same genus) have been formed, many varieties or incipient species ought, as a general rule, to be now forming. Where many large trees grow, we expect to find saplings. Where many species of a genus have been formed through variation, circumstances have been favourable for variation; and hence we might expect that the circumstances would generally be still favourable to variation. On the other hand, if we look at each species as a special act of creation, there is no apparent reason why more varieties should occur in a group having many species, than in one having few. |
|
| To test the truth of this anticipation I have arranged the plants of twelve countries, and the coleopterous insects of two districts, into two nearly equal masses, the species of the larger genera on one
|
