In other varieties the ground color does not change appreciably as 
the fruit becomes mature. With such varieties the ground color 
cannot be used to indicate maturity; neither can it be used for this 
purpose with fruit on trees highly fertilized with nitrogen, as such 
fruit tends to retain the green color even when mature. 
A color chart has been devised for use in determining the change 
in the ground color of apples from green to yellow. This consists of 
four colors from green (No. 1) to ‘yellow (No. 4), closely approxi- 
mating the color stages Gee which apples pass as they mature 
and ripen. A copy of this color chart may be obtained by writing 
the Plant Industry Station, Beltsville, Md. The ground color of 
the fruit is determined by matching the fruit color with one of the 
colors on the chart. This is done by placing the fruit back of the 
chart and fitting the unblushed portion into holes cut in the different 
colors. This should be done in diffused daylight (not in direct sun- 
light). When the color falls between two standard colors it may 
be described by a number; for example a color between No. 3 and 
No. 4 may be designated 3.5 
SOFTENING 
Under certain growing conditions and with some varieties, soften- 
ing of the flesh “of the apple has been used as an indication of 
maturity. Usually the fruit gradually softens as it approaches 
maturity on the tree. The firmness at maturity varies considerably 
from season to season and with growing conditions so that a precise 
degree of firmness at which an apple becomes mature cannot be given. 
However, if the fruit becomes too soft on the tree it may not hold 
up well in storage. The principal value of firmness measurements 
is to indicate when the fruit is becoming too soft or overmature, 
particularly with varieties that soften rapidly i in storage and tend to 
develop mealiness or a mealy break-down. 
The firmness of the flesh of the fruit can be most accurately 
measured by the use of a pressure-test apparatus. Such an appa- 
ratus with methods for its use has been described in previous publi- 
eations (7, 15) and is now available on the market. It measures 
in pounds the pressure required to force a plunger seven-sixteenths 
of an inch in diameter into the apple to a depth of five-sixteenths of 
an inch, the skin being removed prior to making the test. Figure 1 
FigurE 1.—Fruit pressure tester for apples, pears, and peaches, showing method 
of use. (Photograph through courtesy of R. Schneider. ) 
