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Wild White Grape. (Ripe, yet not shrivelled.)
Wild Purple Grape. (Near Adams's Pond; was shrivelled.)
The different kinds of grapes above mentioned behave, in many instances, quite remarkably unlike each other in regard to the setion of their juice towards basic acetate of lead. The latter produces in every case a voluminous, colored precipitate; yet these colors seem to result from the presence of several distinctly different pigments in the grapes, peculiar, in all probability, to the wild native varieties from which our cultivated ones have been produced. This re-action may prove of practical use as an aid in tracing the relationship to each other of the different varieties of grapes under cultivation. Dr. G. Engelmann, in his excellent description of the true American grape-vines, incidentally states that some growers consider the Delaware and the Clinton as derived from the same wild variety Riverside grape (Vitis riparia, Mich.): which appears doubtfal, judging from the re-action with basic acetate of lead; for the juice of the Delaware grape gives a cream-colored precipitate ; while that of the Clinton produces a bluish-green colored one, indicating quite different pigments in these varieties. As this peculiarity of the different kinds of grapes may be of interest to some cultivators, I will state some of my results in this direction. The re-actions are all made with ripe grapes, if not otherwise stated.
From light purple and bluish
green to slate-color.
Purple Wild Grape.
From bright sulphur-yellow to
Whether the various tints of the precipitates are due to the combination of the two extremes, dark purple and light sulphuryellow, or to the result of a peculiar physiological process in the different varieties, is a question which only more detailed inquiries can decide.
INFLUENCE OF GIRDLING THE VINES ON THE GROWTH AND
COMPOSITION OF GRAPES. The current statements regarding the effects of girdling grapevines on the quality of the grapes growing on such plants are quite contradictory. To obtain some more definite idea concerning this practice, a series of experiments were planned, and, with the kind assistance of Professor S. T .Maynard, carried out, during the past season. The vines were girdled during the first week of August, — about the time when the berries of the Concord grape had reached the point when the free acid had attained its highest development, and the grape-sugar had begun slowly to increase. Entire vines, as well as large branches, served for the trial. Two incisions, from one-eighth to one-fourth of an inch apart, were made through the bark and the cambium-layer, and the mass between these cuts, down to the wood, carefully removed. A decided difference in the degree of growth of the grapes began soon to be noticeable, and to manifest itself during the entire season, until the grapes on the girdled branches had just reached their ripeness. The tests made at this point with both the grapes of the girdled and of the ungirdiled branches, grown upon the same vine, showed quite a rernarkable difference in the general quality of the entire grape and in their relative degrees of development. In some instances, it can be safely said that the girdled branches were from two to three weeks in advance of the ungirdled ones. A careful comparison of the previously described rate of growth of the Concord grape can serve as a proof of this statement. Some of the subsequently described analytical results do not as decidedly prove the great difference, because the tests were carried out a few days later than they ought to have been, which gave a good chance for the grapes from the ungirdled branches to gain time on the grapes from the girdled branches, which, being ripe, had reached a period of but very slow change in composition. The analytical statements below, concerning the Concord grape, show, also, that a ripe grape does not improve when kept too long on the vine. The sugar decreases apparently, and the acid increases (most likely on account of the formation of some acetic acid); the taste becomes, by degrees, more indifferent. The girdled vines did not show the slightest difference when compared, at the close of the season, with the ungirdled. The place where the bark had been removed was grown over.
The plants which served for the experiments will be watched during the coming season, to learn whether any serious after-influence may show itself. It is also intended to find out what effect girdling will exert on grapes and juice when carried out at other periods of their growth.
RESULTS OF GIRDLING GRAPE-VINES.