116 University of California Publications in Agricultural Sciences [Vol.3 



Curves of Tola/ Solids, Sin/ar. Total Acid, Free Acid, and Cream 

 of Tartar. — In order to present the data in a form in which they may 

 be readily studied, graphs have been constructed using time in days 

 as abscissae and the above constituents expressed in grams per 100 c.c. 

 as ordinates. The curves represent the data for 1914, 1915, and 1916. 

 For comparison, curves of the changes in composition of Catawba 

 grapes reported by W. B. Alwood in the United States Department 

 of Agriculture Bulletin 335 have been included. The acid principles 

 have been plotted to a scale five times as great as that used for total 

 solids and sugar in order that the variations in acidity might be more 

 apparent. 



Discussion of Graphs of Total Solids, Sugar, Total Acid, Cream of 

 Tartar, and Free Acid. — (1) Total Solids and Sugar. The data are 

 more complete for 1916 than for 1914 or 1915, and include the period 

 during which the berries are growing to full size as well as the ripen- 

 ing period itself, during which the rapid increase in sugar occurs. 

 The curves for 1916, therefore, are of more interest than those for 

 1914 and 1915. In the case of the Burger variety, total solids and 

 sugar remained constant for approximately forty clays after the tests 

 were started. There was then a slight rise in these components for 

 a period of about ten days. From that point on the rise in total solids 

 and sugar was very rapid and fairly uniform. The behavior of the 

 Cornichon was very similar. 



The Muscat began ripening about ten days earlier than the Burger 

 and Cornichon, and proceeded much more rapidly up to about the 

 ninetieth day after the experiment was started. There was then a 

 slowing up in the increase in total solids and sugar corresponding to 

 the period of over-ripeness. This slower increase in total solids is 

 also evident in the curves for Emperor, Muscat, Sultana, and Tokay 

 for the 1915 season, and would undoubtedly show in all cases if the 

 observations were continued sufficiently. 



The effect of the season upon the rate of ripening is shown by a 

 comparison of the Cornichon and Muscat varieties for 1915 and 1916. 

 All varieties ripened more slowly in 1915 than in 1916, resulting in 

 steeper curves for 1916. However, owing to the fact that sampling 

 was started later in 1914 and 1915 than in 1916, the curves for the 

 former two years show only the changes taking place during the latter 

 half of the ripening period. No very close comparisons therefore can 

 be made of the three years. 



The Catawba reported by Alwood, and for which curves appear 



