from 4 to approximately 38 days after petal fall and approximately 65° from 
38 to 70 days after petal fall. Higher and lower temperatures reduced rate of 
growth, Such effects might manifest themselves in date of harvest maturity. 
Poapst, Ward, and Phillips (64) stated that the relationship between 
mean abscission and complete starch disappearance in attached McIntosh fruit 
is related to prevailing seasonal temperature, 
The physiological heat unit method has been used to some advantage. 
Haller and Smith (27) computed heat units from the monthly mean temperatures 
at a number of locations and presented this information for five of the prin- 
cipal varieties of apples: Jonathan, Grimes Golden, Delicious, Golden Deli- 
cious, and Stayman Winesap. They indicate that not much reliance can be placed 
on heat unit summations. : 
Eggert (18) on the other hand demonstrated that a regression calculated 
on the basis of degree day summations from petal fall to 40 days after petal 
fall should give the most reliable prediction of maturity of McIntosh apples. 
Both the physiological heat units method and the daily mean minus a base tem- 
perature of 0° F, (degree days) were used to calculate heat units summation. 
A correlation coefficient of -0.959 was obtained between length of elapsed 
time (in days) from petal fall to harvest and the degree days accumulated at 
40 days after petal fall. 
LaBelle et al. (37) reported that heat unit accumulation and days after 
full bloom were equally effective. Their results would indicate that predic- 
tion of 1958 harvest maturity based on 1957 would have been a compromise between 
these two indices, 
Aside from temperature, rainfall, and soil moisture effect on apple 
maturity, other factors such as elevation may play a part. Haller and Smith 
(27) showed that there was no evidence that elevation had any direct effect on 
the length of time from bloom to maturity. Damast (12) studied the effects of 
mountainous versus lowland areas on maturity and quality of apples. The same 
variety grown in high areas of Palestine was longer in shape, tending to 
become ribbed and ridged; the hypodermis was thicker, higher in dry matter, 
sugar, cellulose, acid and ash but lower in protein content; and rate of 
respiration was lower. He concluded that intensity and quality of light as 
well as temperature seemed to be the primary factors involved in these differ- 
ences. 
Firmness 
Since Magness and Taylor (49) first described their fruit pressure 
tester it has been used by many workers on a number of different fruits. It 
has proven to be a reliable method of measuring maturity of pears and peaches 
but not apples. 
Haller (25) pointed out in his review of pressure testers that they had 
not been found to form a reliable index to maturity of apples except to indi- 
cate when certain varieties were becoming soft and overmature for storage. They 
do, he said, constitute a fairly accurate guide to ripeness of apples during or 
after storage. Schomer and Olsen (69) developed an attachment, the Mechanical 
Thumb, for the Magness-Taylor pressure tester, It was found satisfactory for 
determining the firmness of unpeeled apples, Pressure readings were comparable 
to those obtained with the Magness-Taylor pressure tester. The bruises made at 
contact points were relatively small and inconspicuous, and the fruit need not 
be discarded after testing. 
