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Journal of Agricultural Research voi. xxvii, No. x 
mber in all varieties. From the middle of September until the first 
Dvember the percentage of acid remained practically constant in the 
sr variety group which they analyzed (Winter Paradise, Huntsman, 
and Ben Davis). When the actual 
quantity of acid in grams per apple 
was calculated, however, these au¬ 
thors found that the amount of acid 
per apple increased until August, fell 
off very slightly during September, 
and again increased during October. 
It is probable that the decrease dur¬ 
ing September was due to local sea¬ 
sonal conditions. 
In Figure 4 the changes in acidity 
for Ben Davis, Delicious, and Rome 
Beauty grown at Arlington, Va., dur¬ 
ing the ripening season of 1922 are 
shown graphically. It is apparent 
that from September 14 until mid- 
October there was a constant, though 
rather slight, decrease in the total 
acidity on the basis of percentage 
composition. Unfortunately, data 
on the relative size of the fruit at the 
time different determinations were 
made are not available. The fact, 
however, that there was a marked in¬ 
crease in size, particularly in Rome 
Beauty and Ben Davis, between Sep¬ 
tember 14 and October 18 strongly 
indicates that the actual acidity in 
grams per apple increased rather 
than decreased during this period. 
To summarize, then, the changes 
in acidity occurring while the fruit 
is on the tree, there is a marked de¬ 
crease in percentage of acid in the 
fruit during most of the growing sea¬ 
son, this decrease becoming less pro¬ 
nounced as the fruit approaches ma¬ 
turity on the tree. This decrease in 
acidity does not involve an actual 
disappearance of acid from the fruit, 
as the increase in size of the fruit is 
sufficient to simply dilute the acid al¬ 
ready there. The most accurate con¬ 
ception of the acidity changes in 
apples while on the trees apparently 
is that of high acidity early in the 
m, followed by dilution of the acid as the fruit increases in size, 
consequent lower acid concentration in the mature fruit. 
ie amount of acid which the fruit of any variety may contain will 
widely with the conditions under which the fruit is grown. Con- 
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EPTEMBER OCTOBER 
4 .—Decrease in acidity in apples while re- 
lining attached to tree, Arlington, Va., 1922. 
id as cc. n/io per 10 gm . wet tissue. 
