degrees of latitude brings you to a new variety with new climatic
adaptations, and the capacity of the plant to accommodate itself to new
conditions of temperature and season seems almost unlimited.

Many persons now living remember that, when the common tomato was first
introduced into Northern New England, it often failed to ripen; but, in
the course of a very few years, it completely adapted itself to the
climate, and now not only matures both its fruit and its seeds with as
much certainty as any cultivated vegetable, but regularly propagates
itself by self-sown seed. Meteorological observations, however, do not
show any amelioration of the summer climate in those States within that
period.

It may be said that these cases--and indeed all cases of a supposed
acclimation consisting in physiological changes--are instances of the
origination of new varieties by natural selection, the hardier maize,
tomato, and other vegetables of the North, being the progeny of seeds of
individuals endowed, exceptionally, with greater power of resisting cold
than belongs in general to the species which produced them. But, so far
as the evidence of change of climate, from a difference in vegetable
growth, is concerned, it is immaterial whether we adopt this view or
maintain the older and more familiar doctrine of a local modification of
character in the plants in question.

Maize and the tomato, if not new to human use, have not been long known
to civilization, and were, very probably, reclaimed and domesticated at
a much more recent period than the plants which form the great staples
of agricultural husbandry in Europe and Asia. Is the great power of
accommodation to climate possessed by them due to this circumstance
There is some reason to suppose that the character of maize has been