they often
advise persons to be cautious in trying in one country the productions of
another. The ancient agricultural writers of China recommend the
preservation and cultivation of the varieties peculiar to each country.
During the classical period, Columella wrote, "Vernaculum pecus peregrino
longe praestantius est."[794]

I am aware that the attempt to acclimatise either animals or plants has
been called a vain chimaera. No doubt the attempt in most cases deserves to
be thus called, if made independently of the production of new varieties
endowed with a different constitution. Habit, however much prolonged,
rarely produces any effect on a plant propagated by buds; it apparently
acts only through successive seminal generations. {314} The laurel, bay,
laurestinus, &c., and the Jerusalem artichoke, which are propagated by
cuttings or tubers, are probably now as tender in England as when first
introduced; and this appears to be the case with the potato, which until
recently was seldom multiplied by seed. With plants propagated by seed, and
with animals, there will be little or no acclimatisation unless the hardier
individuals are either intentionally or unconsciously preserved. The
kidney-bean has often been advanced as an instance of a plant which has not
become hardier since its first introduction into Britain. We hear, however,
on excellent authority,[795] that some very fine seed, imported from
abroad, produced plants "which blossomed most profusely, but were nearly
all but abortive, whilst plants grown alongside from English seed podded
abundantly;" and this apparently shows some degree of acclimatisation in
our English plants. We have also seen that seedlings of the kidney-bean
occasionally appear with a marked power of resisting frost; but no one, as
far as I can hear, has ever separated such hardy seedlings, so as to
prevent accidental crossing, and then gathered their seed, and repeated the
process year after year. It may, however, be objected with truth that
natural selection ought to have had a decided effect on the hardiness of
our kidney-beans; for the tenderest individuals must have been killed
during every severe spring, and the hardier preserved. But it should be
borne in mind that the result of increased hardiness would simply be that
gardeners, who are always anxious for as early a crop as possible, would
sow their seed a few days earlier than formerly. Now, as the period of
sowing depends much on the so