| → on this intricate subject 1859 1860 1861 1866 1869 |
| OMIT 1872 |
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| → enlarge. 1859 1860 1861 1866 1869 |
| enlarge on this subject. 1872 |
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| ←Subtitle not present 1859 1860 1861 Complex
Relations
of
all
Animals
and
Plants
to
each
other
in
the
Struggle
for
Existence.
1866 1869 1872 |
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the ill effects of close interbreeding,
come into play in
of these cases; but
→on this intricate subject
I will not here
→enlarge.
→
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| 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 six insectivorous birds were very common in the plantations, which were not to be seen on the heath; and the heath was frequented by two or three distinct insectivorous birds. Here we see how potent has been the effect of the introduction of a single tree, nothing whatever else having been done, with the exception
the land
been enclosed, so that cattle could not enter. But how important an element enclosure is, I plainly saw near Farnham, in Surrey. Here there are extensive heaths, with a few clumps of old Scotch firs on the distant
within the last ten years large spaces have been enclosed, and self-sown firs are now springing up in multitudes, so close together that all cannot live.
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