ecially the case in America, where certain
varieties only will stand the severe climate of Canada. There is one
variety of pear, the Forelle, which both in England and France withstood
frosts that killed the flowers and buds of all other kinds of pears.
Wheat, which is grown over so large a portion of the world, has become
adapted to special climates. Wheat imported from India and sown in good
wheat soil in England produced the most meagre ears; while wheat taken
from France to the West Indian Islands produced either wholly barren
spikes or spikes furnished with two or three miserable seeds, while West
Indian seed by its side yielded an enormous harvest. The orange was very
tender when first introduced into Italy, and continued so as long as it
was propagated by grafts, but when trees were raised from seed many of
these were found to be hardier, and the orange is now perfectly
acclimatised in Italy. Sweet-peas (Lathyrus odoratus) imported from
England to the Calcutta Botanic Gardens produced few blossoms and no
seed; those from France flowered a little better, but still produced no
seed, but plants raised from seed brought from Darjeeling in the
Himalayas, but originally derived from England, flower and seed
profusely in Calcutta.[36]

An observation by Mr. Darwin himself is perhaps even more instructive.
He says: "On 24th May 1864 there was a severe frost in Kent, and two
rows of scarlet runners (Phaseolus multiflorus) in my garden, containing
390 plants of the same age and equally exposed, were all blackened and
killed except about a dozen plants. In an adjoining row of Fulmer's
dwarf bean (Phaseolus vulgaris) one single plant escaped. A still more
severe frost occurred four days afterwards, and of the dozen plants
which had previously escaped only three survived; these were not taller
or more vigorous than the other young plants, but they escaped
completely, with not even the tips of their leaves browned. It was
impossible to behold these three plants, with their blackened, withered,
and dead brethren all around them, and not see at a glance that they
differed widely in their constitutional power of resisting frost."

The preceding sketch of the variation that occurs among domestic animals
and cultivated plants shows how wide it is in range and how great in
amount; and we have good reason to believe that similar variation
extends to all organised beings. In the class of fishes, for example, we
have one kind which ha