Читать книгу Manual of American Grape-Growing - U. P. Hedrick - Страница 71

Many viticulturists, in common with orchardists, believe that their plants should be propagated only from parents which have good characters, that is, are vigorous, healthy, productive, and bear fruit of large size, perfect form, good color and good quality. They believe, in short, that varieties can be improved by bud selection. There is, however, but little in either theory or fact to substantiate the belief of those who say that varieties once established can be improved; or, on the other hand, that they degenerate. Present knowledge and experience indicate that heredity is all but complete in varieties propagated from parts of plants. The multitude of grapes in any variety, all from one seed, are morphologically one individual. A few kinds of grapes go back to Christ's time, and these seem to agree almost perfectly with the descriptions of them made by Roman writers 2000 years ago. How, then, can the differences between vines of a variety in every vineyard in the land be explained?

Ample explanation is found in "nurture" to account for the variation in vines without involving a change in "Nature." Soil, sunlight, moisture, insects, disease, plant-food, and the stock in the case of grafted vines, give every vine a distinct environment and hence a distinct individuality of its own. Peculiarities in a vine appear and disappear with the individual. A variety can be changed temporarily by its environment, but remove the incidental forces and it snaps back into its same old self.

Heredity is not quite complete in the grape, however; for, now and then, sports or mutations appear which are permanent and, if sufficiently different, become a strain of the parent variety or possibly a new variety. There are several such sports of the Concord under cultivation. The grape-grower can tell these sports from the modifications brought about by environment only by propagation. If a variation is transmitted unchanged through successive generations of the grape, as occasionally happens, it may be looked on as a new form. "Pedigreed" vines, then, should be subject to a test of several generations in an experimental vineyard before the grape-grower pays the price demanded for the supposed improvement.

Plate IV.—A well-tilled vineyard of Concords.