r a single fact on which this
belief is grounded{267}. One of the commonest statements is that plants
do not become acclimatised; and I have even observed that kinds not
raised by seed, but propagated by cuttings, &c., are instanced. A good
instance has, however, been advanced in the case of kidney beans, which
it is believed are now as tender as when first introduced. Even if we
overlook the frequent introduction of seed from warmer countries, let me
observe that as long as the seeds are gathered promiscuously from the
bed, without continual observation and _careful_ selection of those
plants which have stood the climate best during their whole growth, the
experiment of acclimatisation has hardly been begun. Are not all those
plants and animals, of which we have the greatest number of races, the
oldest domesticated? Considering the quite recent progress{268} of
systematic agriculture and horticulture, is it not opposed to every
fact, that we have exhausted the capacity of variation in our cattle and
in our corn,--even if we have done so in some trivial points, as their
fatness or kind of wool? Will any one say, that if horticulture
continues to flourish during the next few centuries, that we shall not
have numerous new kinds of the potato and Dahlia? But take two varieties
of each of these plants, and adapt them to certain fixed conditions and
prevent any cross for 5000 years, and then again vary their conditions;
try many climates and situations; and who{269} will predict the number
and degrees of difference which might arise from these stocks? I repeat
that we know nothing of any limit to the possible amount of variation,
and therefore to the number and differences of the races, which might be
produced by the natural means of selection, so infinitely more efficient
than the agency of man. Races thus produced would probably be very
"true"; and if from having been adapted to different conditions of
existence, they possessed different constitutions, if suddenly removed
to some new station, they would perhaps be sterile and their offspring
would perhaps be infertile. Such races would be undistinguishable from
species. But is there any evidence that the species, which surround us
on all sides, have been thus produced? This is a question which an
examination of the economy of nature we might expect would answer either
in the affirmative or negative{270}.

{267} In the _Origin_ no limit is placed to variation as far as