It is Nature herself that has taught us most of these methods, and more particularly that of sowing seed, as it was very soon evident how the seed on falling to the ground revived again in germination. Indeed, there are some trees that are capable of being propagated in no other way, the chesnut[1] and the walnut, for instance; with the sole exception, of course, of such as are employed for coppice wood. By this method, too, as well as the others, some trees are propagated, though from a seed of a different nature, such, for instance, as the vine, the apple, and the pear;[2] the seed being in all these cases in the shape of a pip, and not the fruit itself, as in that of the chesnut and the walnut. The medlar, too, can also be propagated by the agency of seed. All trees, however, that are grown by this method are very slow in coming to maturity,[3] degenerate[4] very rapidly, and must often be renewed by grafting: indeed, the chesnut even sometimes requires to be grafted.