241° 
In Graph 3, fractional parts corresponding to the reciprocals of the 
periods (Table 3) were laid off on the vertical axis, and divisions were 
marked on the horizontal axis corresponding to the mean daily tempera- 
tures. Points were then plotted, using the reciprocals of the periods and 
the mean daily temperatures as the coordinates. 
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GrRaPH 3, Larval period. Reciprocals of the periods plotted against mean 
daily temperatures. Larve reared in apples on tree. 
These points do not lie in a straight line, and hence can not be used 
for the purpose of establishing the reciprocal curve accurately. The points 
do not lie in a straight line because in making the mean daily averages 
temperatures were used which are not effective or which retard develop- 
ment. The lower points are less affected by this cause than the other 
points because they represent temperatures that are intermediate between 
the zero of development and the degree of the maximum rate of develop- 
ment. A straight line determined by the two lowest points crosses the 
temperature axis at 52+ degrees, a line determined by the three lowest 
points crosses the axis at 47+. All points between 47 and 52 were tried 
out as to which best fulfilled the condition as the zero of development and 
50 was selected as the one which did so most nearly. 
7. The daily day-degrees above 50 degrees were computed and the 
results were entered in column 6 of Table 3. The figures in this column 
multiplied by the number of days in the periods gave the total accumula- 
tions of day-degrees above 50 degrees, shown in column 9 of Table 3. 
An examination of these results as well as the position of the upper points 
_ in Graph 3 leads us to conclude that the gradual increase in the accumu- 
E lations and the deviation to the right of the points from the line at the 
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