“One absolutely necessary condition must be fulfilled if this operation is to be successful: the transferred part must find on its new nursing-branch nutriment to its taste, that is to say, a sap like its own. This requires that the two plants, the stock and the one that furnishes the graft, should be of the same species or at least belong to closely related species, since likeness of sap and its products can result only from likeness of organization. It would be a mere waste of time to try to engraft the lilac upon the rose, or the rose upon the willow, for there is nothing in common between these three species either in leaves, flowers, or fruit. This difference in structure is invariably accompanied by a marked difference in respect to nutrition. Hence the rose-bud would starve to death on a lilac-branch, and the lilac-bud would meet with the same sad fate on a rose-bush. But lilac can very well be grafted on lilac, rose-bush on rose-bush, vine on vine. And one can even go further than this: a peach-bud will flourish on an apricot-tree, a cherry-bud on a plum-tree, and vice versa; for between the members of each of these pairs there is a close and easily discernible analogy. In short, there must be the closest possible resemblance between the two plants if grafting is to succeed. “The ancients were far from having any clear idea on this absolute need of likeness in organization. They tell us of grafting the holly with the rose to obtain green roses, the walnut tree with the grape to produce enormous grapes as large as walnuts. In our own time has not the project been seriously considered of grafting a vine shoot on to a mulberry tree in order to restore vigor to the grape whose roots an underground grub has attacked? Such graftings and others between plants completely unlike have never been successfully undertaken except in the imagination of those who dreamt them.