AGRICULTURE AND RURAL ECONOMY. 551 



2. Another portion is devoted to (a) the nutrition of exist- 

 ing protoplasm, and (b) the formation of new protein mate- 

 rial by combining with nitrogenous materials e. </., ammonia 

 and nitric acid. Our knowledge on this point is still very- 

 indefinite, however. 



3. A third portion probably undergoes decomposition to 

 form coloring matters, acids, etc., and by oxidation, or other- 

 wise, to furnish energy for the plant. 



4. The remainder is stored up in seeds, stems, leaves, etc., 

 as carbohydrates, oil, or fat. 



Chemistry of the American Grape. 



Professor Goessman, of the Massachusetts Agricultural 

 College, has been for some time engaged in studies of the 

 chemistry of the American grape, its growth, composition, 

 and the effect of fertilizing materials upon it. The juice of 

 the Concord grape collected on the 17th of June was watery 

 and of a yellowish-green color; it turned purple by heating 

 with a slight excess of ammonia or potassa, showing, as Pro- 

 fessor Goessman says, "that the coloring matter which is char- 

 acteristic of the ripe grape is already, in some concealed form, 

 present at a very early stage of its growth." 



Acids and Sugar in Grapes at Different Periods of Growth. 



From a tabular statement of analyses of grapes at different 

 periods of growth, " it will be noticed 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 at the 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 de- 

 crease of free acid." The loss of free acid from the juice 

 seems to be "due, in part at least, to the circumstance that 

 the acid has partly formed insoluble acid combinations with 

 potassa and with lime." ..." In consideration of these ob- 

 servations, it seems but reasonable to conclude that Liebig's 



