INFLUENCE OF CERTAIN CLIMATIC FACTORS 
3 
Previous Work on Rate of Growth 
Anderson (i, p. i6)^ conducted experiments on the growth of 
Endothia parasitica on Castanea dentata at Charter Oak, Pa., during 
the summer of 19 12, and Rankin (9) during the same summer at 
•Napanoch, N. Y. Both these writers give the average growth for 
each month during the summer and Anderson gives it for the entire 
year. The average annual growth^ at Charter Oak, Pa., for the year 
ending June i, 1912, was 15.97 cm. according to Anderson (i, p. 575), 
while Rankin estimates 12 cm. about the average amount of a season's 
growth at Napanoch. 
Rogers and Gravatt (10) made an intensive study of the spread 
of the chestnut bhght over a small area near Bluemont, Va., and give 
6.35 inches (15.87 cm.) as the average annual diameter growth of 
cankers at this point. They found the average growth on Castanea 
pumila near Leesburg, Va., for the year ending August 15, 1914, to be 
6.8 inch (16.08 cm.). There is fairly close agreement among the 
results from Virginia and Pennsylvania even though they were taken 
in different years. The growth in New York is, however, consider- 
ably less. 
Rate of Lateral Growth 
Since Endothia parasitica kills its host by girdling the parts attacked^ 
vertical growth is of no importance so far as its parasitic qualities are 
concerned, consequently in this work the rate of lateral growth alone 
was measured. As careful comparative measurements for various 
periods of the same year have already been given by Anderson (i) 
and Rankin (9), special attention was paid to determining the amount 
of growth for one year at the various points. On this account no cuts 
were made in the cankers until they were one year old. All measure- 
ments made previous to that time were taken from the sunken area 
in the bark. 
Table I gives the annual lateral growth (determined by cutting 
away the bark) of cankers at the various stations for the years en'ding^ 
in May and in August, 191 5, so far as the data are complete. Each 
figure represents an average of all the normal cankers; that is, cankers 
which developed only on one side of the cut were not included. These 
averages are expressed in the nearest centimeter, as that seems to the 
^ Reference is made by number to "Literature cited," p. 31. 
2 All measurements are for lateral growth. 
