[665] Many similar facts could be given,
and they are remarkable because it might have been thought that
definite chemical compounds would have been little liable to change
either in quality or quantity.

The wood of the American Locust-tree (_Robinia_) when grown in England
is nearly worthless, as is that of the Oak-tree when grown at the Cape
of Good Hope.[666] Hemp and flax, as I hear from Dr. Falconer, flourish
and yield plenty of seed on the plains of India, but their fibres are
brittle {275} and useless. Hemp, on the other hand, fails to produce in
England that resinous matter which is so largely used in India as an
intoxicating drug.

The fruit of the Melon is greatly influenced by slight differences in
culture and climate. Hence it is generally a better plan, according to
Naudin, to improve an old kind than to introduce a new one into any
locality. The seed of the Persian Melon produces near Paris fruit
inferior to the poorest market kinds, but at Bordeaux yields delicious
fruit.[667] Seed is annually brought from Thibet to Kashmir,[668] and
produces fruit weighing from four to ten pounds, but plants raised from
seed saved in Kashmir next year give fruit weighing only from two to
three pounds. It is well known that American varieties of the Apple
produce in their native land magnificent and brightly-coloured fruit,
but in England of poor quality and a dull colour. In Hungary there are
many varieties of the Kidney-bean, remarkable for the beauty of their
seeds, but the Rev. M. J. Berkeley[669] found that their beauty could
hardly ever be preserved in England, and in some cases the colour was
greatly changed. We have seen in the ninth chapter, with respect to
wheat, what a remarkable effect transportal from the North to the South
of France, and reversely, produced on the weight of the grain.

When man can perceive no change in plants or animals which have been
exposed to a new climate or to different treatment, insects can sometimes
perceive a marked change. The same species of cactus has been carried to
India from Canton, Manilla, Mauritius, and from the hot-houses of Kew, and
there is likewise a so-called native kind, formerly introduced from South
America; all these plants are alike in appearance, but the cochineal insect
flourishes only on the native kind, on which it thrives prodigiously.[670]
Humboldt