8 BULLETIN 1104, U. S. DEPARTMENT OF AGRICULTURE. 
more pronounced than “‘ 
the value of the fruit appreciably or even make it unsalable. The de- 
scriptions on page 5 accompanying Plates. I and. IJ will assist the 
reader in understanding the significance of the terms “ trace,” “ me- 
dium,” and “bad” as used in classifying the intensity of internal 
browning. It will be seen that these three classes grade from one to 
another with no sharp distinctions between successive classes, so that 
they serve only as a rough method of estimation. 
The method of inspecting the fruit and recording the internal 
browning was as follows: Each apple was cut crosswise into ap- 
proximately equal parts and the presence or absence of browning 
was noted. If no browning appeared the apple was recorded as 
sound regardless of any other imperfections that might be present. 
If internal browning was present, a record of its location, whether 
“core” or “tissue,” and the extent, “ trace,” “ medium,” or “ bad,” 
was made. The total number of apples cut from each box was | 
recorded and the records for each box and each tree were kept 
separately. 
For the most part the fruit has been held in commercial cold- 
storage houses. In one of these houses the air circulation system was 
employed, air being cooled in a bunker room and circulated by fans 
through the storage rooms and back to the bunker room again, in 
the other plant each room was cooled by means of brine coils sup- 
ported near the ceiling. In this case there was, of course, very little 
air movement within the storage rooms and no effort at ventilation. 
The concentration of carbon dioxid was sufficient at times to make it | 
impossible to light a match. No direct comparison was made of the 
keeping quality of fruit stored in these two types of storage houses, 
but from general observations there appeared to be no noticeable 
difference. 
RELATION OF INTERNAL BROWNING TO STORAGE CONDITIONS. 
Previous to the year 1910 apples from the Pajaro Valley district 
were stored at temperatures around 32° F., approximating cold- 
storage temperatures used for apples throughout the United States, 
At that time, however, certain observations by Stubenrauch and 
other workers of the Bureau of Plant Industry led to the belief that 
internal browning developed to a much greater extent at temperatures 
near 32° than at 35° to 40° F. Consequently, after the year 1910 
the commercial cold storages at Watsonville and other points in 
California, where the tendency of this fruit to develop internal 
browning in storage was known, raised the temperatures of their 
apple-storage rooms to 35° F. With the 1917-18 storage season, the 
temperature of storage was raised to 36° F. This is the temperature 
medium ” and sufficiently marked to lower: 
