| → in our gardens which 1859 1860 1861 1866 1869 |
| which in our gardens 1872 |
|
|
number of plants
→in our gardens which
can perfectly well endure our climate, but which never
naturalised, for they cannot compete with our native
nor resist destruction by our native animals. |
|
| When a species, owing to highly favourable circumstances, increases inordinately in numbers in a small tract,
least, this seems generally to occur with our game
and here we have a limiting check independent of the struggle for life. But even some of these so-called epidemics appear to be due to parasitic worms, which have from some cause, possibly in part through facility of diffusion amongst the crowded animals, been
favoured: and here comes in a sort of struggle between the parasite and its prey. |
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| On the other hand, in many cases, a large stock of individuals of the same species, relatively to the numbers of its enemies, is absolutely necessary for its preservation. Thus we can easily raise plenty of corn and rape-seed, &c., in our fields, because the seeds are in great excess compared with the number of birds which feed on them; nor can the birds, though having a superabundance of food at this one season, increase in number proportionally to the supply of seed, as their numbers are checked during
but any one who has tried, knows how troublesome it is to get seed from a few wheat or other such plants in a
I have in this case lost every single seed. This view of the necessity of a large stock of the same species for its 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
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