The nectarine is one of the most interesting phenomena in horticulture. It is the classical example of bud- and seed-variation, furnishing more instances of mutation, and these more instructive, than have yet come from any other fruit. Darwin, with the magnificent exhaustiveness which characterized his method, brought together in _Animals and Plants under Domestication_[174] a striking array of facts which leaves nothing to be added as to the manner in which the peach and nectarine are reciprocally reproduced the one from the other. He shows by numerous examples: (1) That nectarines may spring from peach-stones and peaches from nectarine-stones. (2) That peach-trees produce nectarines by bud-variation and nectarine-trees likewise produce peaches, and that either the nectarines or peaches so arising will come true to seed. (3) That either peach or nectarine-trees may produce individual fruits half-nectarine and half-peach. (4) A case is cited of a nectarine tree bearing a half-and-half fruit and subsequently a true peach. [Illustration: KENTUCKY (Nectarine)] [Illustration: SUMMER SNOW (White Flowered)] It must be noted that in all of the variations so far recorded there are no intermediate forms between the two fruits. The peach produced in these bud-variations is a peach and nothing but a peach; the nectarine, a nectarine and nothing but a nectarine. Even in those remarkable phenomena, of which several are recorded, in which the fruits are divided into halves or quarters, one or more segments being peach and one or more nectarine, there can be no mistake as to peach and nectarine in pubescence, color or flavor. The nectarine from the peach, thus becomes as clear-cut a case of discontinuous variation as can be. If we accept the mutation theory of the origin of species--new species arising suddenly at a single step--the nectarine is a species in process of birth. As yet we are entirely ignorant in regard to the conditions under which the peach or the nectarine sports, the one producing the other. It is wholly a natural phenomenon, for no one has been able to cause the peach to produce the hairless form or the nectarine to bring forth a downy fruit. The relations of the two fruits have furnished a fertile field of inquiry for over a century but the problem is one of those mysterious ones in which there are many facts that cannot be fitted into a theory, so that our ignorance is as profound now as ever. There are, however, several theories which, without going into full detail, need to be stated.