The botany of the grape has been the most perplexing problem to deal with in the preparation of this work. The variability of the grape is so great, and the variations are so often toward closely related species, that it is difficult to tell where one species ends and another begins. This, of course, has led to differences in opinions. Then, too, the several monographers have not had the same specimens to work with; men do not have the same powers of discrimination; and the arrangement of botanical groups, based upon the characters of the plants and the theory of descent with adaptive modifications, is not governed by definite rules; hence botanical divisions are arbitrary and differ with the judgments of the botanists who make them. For these reasons we have as many different arrangements of species of grapes as there are men who have worked them over. Since this work is not written from the standpoint of the botanist but of the horticulturist, no effort has been made to revise the botany of the grape. But it has been necessary to select some arrangement of species in order to make such disposition of the cultivated varieties that their characters and relationships can best be shown. In making a choice of the several recent classifications of American grapes, three main considerations have been in mind: First, that the arrangement should separate the species in the genus freely, thus decreasing the size of the groups so that they may be more easily studied. Second, that it should show as clearly as possible the relationships of the various groups and of their development--the evolution of the grape. Third, that it be an arrangement in good standing with botanists and horticulturists. After having examined all American classifications of grapes and all recent European ones, Bailey's classification, as set forth in his monograph of the Vitaceae in _Gray's Synoptical Flora_, in the _Evolution of our Native Fruits_, and in the _Cyclopedia of American Horticulture_, was adopted.