This shows us how little change is produced by mere cultivation, or even by variety of soil and climate, if there is no _selection_ to preserve and accumulate the small variations that are continually occurring.

When, however, a great amount of modification has been effected in one country, change to another country produces a decided effect.

Thus it has been found that some of the numerous varieties of maize produced and cultivated in the United States change considerably, not only in their size and colour, but even in the shape of the seed when grown for a few successive years in Germany.[31] In all our cultivated fruit trees the fruits vary immensely in shape, size, colour, flavour, time of ripening, and other qualities, while the leaves and flowers usually differ so little that they are hardly distinguishable except to a very close observer.
_Variations of Apples and of Melons._ The most remarkable varieties are afforded by the apple and the melon, and some account of these will be given as illustrating the effects of slight variations accumulated by selection.

All our apples are known to have descended from the common crab of our hedges (Pyrus malus), and from this at least a thousand distinct varieties have been produced.
These differ greatly in the size and form of the fruit, in its colour, and in the texture of the skin.

They further differ in the time of ripening, in their flavour, and in their keeping properties; but apple trees also differ in many other ways.