| → on this intricate subject 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| → enlarge. 1859 1860 1861 1866 1869 |
| enlarge on this subject. 1872 |
|
|
preservation, explains, I believe, some singular facts in
such as that of very rare plants being sometimes extremely
in the few spots where they do
and that of some social plants being social, that
abounding in individuals, even on the extreme
of their range. For in such cases, we may believe, that a plant could exist only where the conditions of its life were so favourable that many could exist together, and thus save
from utter destruction. I should add that the good effects of
intercrossing, and the ill effects of close interbreeding,
come into play in
of these cases; but
→on this intricate subject
I will not here
→enlarge.
|
|
|
| Many cases are on record showing how complex and unexpected are the checks and relations between organic beings, which have to struggle together in the same country. I will give only a single instance, which, though a simple one,
interested me. In Staffordshire, on the estate of a
where I had ample means of investigation, there was a large and extremely barren heath, which had never been touched by the hand of man; but several hundred acres of exactly the same nature had been enclosed twenty-five years previously and planted with Scotch fir. The change in the native vegetation of the planted part of the heath was most remarkable, more than is generally seen in passing from one quite different soil to another: not only the proportional numbers of the heath-plants were wholly changed, but twelve species of plants (not counting grasses and carices) flourished in the plantations, which could not be found on the heath. The effect on the insects must have been still greater, for
|
