m the evidence given by Alph. De Candolle,
the culture of maize has extended since the end of the last century
thirty leagues north of its former boundary.[773] On the authority of
the great Linnaeus,[774] I may quote an {308} analogous case, namely,
that in Sweden tobacco raised from home-grown seed ripens its seed a
month sooner and is less liable to miscarry than plants raised from
foreign seed.

With the Vine, differently from the maize, the line of practical
culture has retreated a little southward since the middle ages;[775]
but this seems due to commerce, including that of wine, being now freer
or more easy. Nevertheless the fact of the vine not having spread
northward shows that acclimatisation has made no progress during
several centuries. There is, however, a marked difference in the
constitution of the several varieties,--some being hardy, whilst
others, like the muscat of Alexandria, require a very high temperature
to come to perfection. According to Labat,[776] vines taken from France
to the West Indies succeed with extreme difficulty, whilst those
imported from Madeira, or the Canary Islands, thrive admirably.

Gallesio gives a curious account of the naturalisation of the Orange in
Italy. Daring many centuries the sweet orange was propagated
exclusively by grafts, and so often suffered from frosts that it
required protection. After the severe frost of 1709, and more
especially after that of 1763, so many trees were destroyed that
seedlings from the sweet orange were raised, and, to the surprise of
the inhabitants, their fruit was found to be sweet. The trees thus
raised were larger, more productive, and hardier than the former kinds;
and seedlings are now continually raised. Hence Gallesio concludes that
much more was effected for the naturalisation of the orange in Italy by
the accidental production of new kinds during a period of about sixty
years, than had been effected by grafting old varieties during many
ages.[777] I may add that Risso[778] describes some Portuguese
varieties of the orange as extremely sensitive to cold, and as much
tenderer than certain other varieties.

The peach was known to Theophrastus, 322 B.C.[779] According to the
authorities quoted by Dr. F. Rolle,[780] it was tender when first
introduced into Greece, and even in the island of Rhodes on