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| OMIT 1872 |
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| enlarge on this subject. 1872 |
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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.
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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
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