In comparing the vines, those of the Old World grape are more compact in habit, make a shorter and stouter annual growth, therefore require less pruning and training. The roots are fleshier, and more fibrous. The species, taken as a whole, is adapted to far more kinds of soil, and to much greater differences in environment, and is more easily propagated from cuttings, than most of the species of American grapes. The cultivated forms of the wild vines of this country have few points of superiority over their relative from the eastern hemisphere, but these few are such as to make them now and probably ever the only grapes possible to cultivate in America in the commercial vineyards east of the Rocky Mountains. Indeed, but for the fortunate discovery that the vine of _Vitis vinifera_ could be grown on the roots of any one of several species of the American grapes, the vineyards of the Old World grape would have been almost wholly destroyed within the last half century because of one of its weaknesses. This destructive agent is the phylloxera,[5] a tiny plant louse working on the leaf and root of the grape, which in a few years wholly destroys the European vine but does comparatively little harm to most of the American vines. Three other pests are much more harmful in the Old World vineyards than to the vines of the New World; these are black-rot (_Guignardia bidwellii_ (Ell.) V. & R.), downy mildew (_Plasmopara viticola_ (B. & C.) Berl. & De Toni), and powdery mildew (_Uncinula necator_ (Schw.) Burr.). The susceptibility of the Old World grape to these parasites debars it from cultivation in eastern America and so effectually that there is but little hope of any pure-bred variety of it ever being grown in this region. American viticulture must, therefore, depend upon the native species for its varieties, though it may be hoped that by combining the good qualities of the foreign grape with those of one or several of the species of this country, or by combining and rearranging the best characters of the native species, we may in time secure varieties equal in all respects to those of the Old World. The comparative resistance of the American species to the phylloxera, the mildews, and black-rot has been due to natural selection in the contest that has been waged for untold ages between host and parasite. The fact that the native species have been able to survive and thrive is a guarantee of the permanence of the resistance thus acquired. We have said that the Old World grape is debarred from cultivation in eastern America. It is worth while considering how thorough the attempts to grow it in this region have been and to give a more exact account of the failures and their causes, for there are yet those who are attempting its culture with the hope that we may sometime grow some offshoot of _Vitis vinifera_ in the region under consideration.