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ing industrial crops of a superior quality for the purpose they sta: serve, deserves, in my opinion, the serious attention of fruitculturists in particular.
Judging from our past experience in general farm-management, it seems proper to assume that much benefit may be secured to Tuli-culture and horticulture by studying the relations which erist between the composition of the soil and the ash-constituents of the fruits grown upon it. A rational system of manuring the fruit-bearing plants requires · that kind of information for its foundation. It is quite certain that the practice of restoring to the soil, in suitable form and in due time, those constituents which the fruits abstract, cannot but contribute towards large crops by stimulating a vigorous condition of the entire plant. A strong, healthy plant is quite naturally better qualified to overcome interior local disorders, and to resist more successfully external injurious influences, than feeble specimens. Considering the previously expressed views worthy of serious attention, I have, of late, instituted a series of field-experiments with grape-vines, for the porpose of testing the action of certain special fertilizers on their productiveness, as far as quantity and quality of the grapes are concerned, and to ascertain whether a favorable change in their quality is accompanied with a definite alteration in the relative proportion of their mineral or ash constituents. I selected, for Teasons already stated in previous communications, the fruits of s cultivated and of a wild native variety of grape-vine; namely, the Concord GRAPE AND THE Wild PURPLE GRAPE
(Vitis Labrusca, L.). A due appreciation of the expected results rendered it quite advisable to study previously some of the more prominent features n ihe growth of these grapes, without any application of manure. As bat little has been published regarding the chemical composiDon of our native grapes, I propose to describe at a future time some observations made in that connection, which, in my opinion, sre of a more general interest from a scientific as well as a practical stand-point. My particular thanks are due to Professor S. T. Maynard, and to Messrs. E. B. Bragg and W. P. Brooks (graduates of the College, of the class of 1875), for very efficient assistance rendered in the progress of the investigations. Professor Maynard has taken a very active interest in the field-work; and Messrs. Brooks and Bragg have very satisfactorily carried out, under my direction, most of the analytical work.
1 Bee Thirteenth Annual Report of the Massachusetts Agricultural College. p. 60; and also the Massachusetts Ploughman of June 24, 1877.
ON THE GROWTH AND COMPOSITION OF GRAPES. The examination was confined, in the majority of cases, to the berries and the juice of the grapes. The former were tested for the amount of water they lost at 100° C., and the total dry matter they left behind at that temperature. The juice of the grapes, obtained after crushing by means of a hand-press, was examined for its specific gravity, its percentage of grape-sugar, and its free acid. The sugar was determined by Fehling's mode, after the juice had been treated with an equal volume of a solution of basic acetate of lead, of the same concentration as that usually applied for the defecation of the juice of sugar-beet roots. The amount of free acid was determined with a solution of pure carbonate of soda, containing one gramme of calcined soda in one hundred cubic centimeters of the solution, and the test finished by finally raising the temperature to near the boiling-point. The examination · of both berries and juice was repeated in various important stages of the development of the grapes. Ash-analyses bave also been carried out as far as time has thus far permitted ; yet, as only a small number of the analyses of the ashes of the berries have been finished, a more detailed discussion of the results obtained has to be deferred to some future suitable occasion. The relative amount of acid has been reported for the present, only to secure more exact quantitative statements after the nature of the acid has been more thoroughly studied.
Purple Wild Grape. (Near Adams's Pond.)
White Variety of Wild Grape. (Near the purple grape.)
The juice of the Concord grape collected on the 17th of June, as shove stated, was watery, and of a yellowish-green color : it tamed purple by heating, with a slight excess of either ammonia or potassa, showing that the coloring-matter, which is characteristic of the ripe grape, is already, in some concealed form, present at a very early stage of its growth. The wild purple grape, in a similar condition of growth, showed the same property, with the exception that its juice was of a viscid character, and its color of a deeper tint when rendered alkaline. The color peculiar to these grapes makes its first appearance in the stems of the berries, and passes then rapidly on to the outer tissues of the skin. During the season of 1876, this change became first noticeable about the middle of August; and on the 30th of the month the color had already increased to such an extent, that a solution of basic acetate of lead produced a light purple-blue precipitate, similar in color to a freshly precipitated hydrate of chromium oxide. It will be noticed from the above tabular statement, that with the middle of August began a remarkable change in the growth of the grape. The free acid became most prominent in the juice about the first week in August, sank to less than one-half of its quantity towards the close of that month, and amounted, at the beginning of October, to one-fifth only of the largest quantity noticed in August. The sugar began to increase in the juice about the same time, when the free acid had reached its highest amount, and when the chlorophyl began to suffer a transformation of its green color into a purple pigment: its increase was, however, in a much larger ratio than the decrease of the free acid. A test of the entire berry for free seid, made on the 20th of July, but one week before the highest percentage was observed in the juice, showed that all the free acid noticed at that period in the berries was in solution in the juice; while repeated tests made with entire berries, and also with their jaice, after the free acid in the latter had considerably fallen off. proved the presence of a larger amount of free acid in the berries than in the juice, which demonstrated the fact that the smaller anentity of free acid found in the juice of the grapes at a more advanced state of growth is due, in part at least, to the circumstance that the acid has partly formed quite insoluble acid combinations with potassa and with lime, which are largely distributed, in a crystalline form, through the cellular mass, and thereby cause a less acid re-action of the juice. In consideration of these observations, it seems but reasonable to conclude that Liebig's view, which assumes a conversion of the acid of the grapes in the latter stages of their growth into grape-sugar, does not agree with our present information. Dr. Neubauer, in his interesting investigation of German grapes, comes to similar conclusions. He favors, besides, the opinion that a periodical increased access of potassa and lime into the fruit causes the mentioned alterations at the stated stage of development. I shall return to this subject when discussing the relation of the ash-constituents in different stages of growth to the periodical changes in the composition of the fruit. A careful test made with the sap of grape-vines, taken in the month of May, from an incision in the vine made about from four to five feet above the ground, proved the absence of both cane and grape-sugar in that liquid. Comparing the above reported results of the comparative tests carried out with the juice of the wild purple grape and that of its cultivated offspring, it becomes at once noticeable, that, as far as the present investigation has been extended, their main difference, from a chemical stand-point, consists in changes regarding the quantity of sugar, the amount of total soluble matter, and the intensity of color. The acid, it seems, has not been affected. The sugar increases during the last period of ripening but little, and apparently partly from concentration of the juice by loss of moisture. Once removed from the grape-vine, the grapes lose moisture quite rapidly at ordinary temperature, yet at different rates, as may be seen from the following statement:
The aromatic principles become more prominent at the close of the ripening process ; in all probability, in consequence of a reaction of the albuminoids on the grape-sugar. They consist usually of combinations of alcohols with fatty volatile acids (compound ethers).
Ons THE COMPOSITION OF VARIOUS Kinds of CULTIVATED RIPE
GRAPES. The subsequent statements comprise the observations of 1876 sod 1877: the specimens which served for tests — with the exception of the Catawba, the Isabella, the Eumelan, the first-named Hartford Prolific, and the wild varieties — came from the College vineyard, and were as nearly as possible of the same degree of ripeness.