30 
NEIL E. STEVENS 
At each visit ten or more inoculations were made on healthy chestnut 
trees and notes taken as to the growth of the previous inoculations. 
The average annual lateral growth was found to be least at the 
most northern locality, Concord, N. H., and to increase gradually 
southward. The growth at Charlottesville, Va., was nearly twice as 
great as that at Concord, N. H. 
A similar relation was found among inoculations made on Overlook 
Mountain, the amount of growth at elevations of 600 to 1,000 feet 
being from 20 to 25 percent greater than that at elevations of 2,500 
to 2,900 feet. 
The stations were all located near regular U. S. Weather Bureau 
observation stations and no meteorological observations were taken. 
This necessitated neglecting evaporation entirely, though evaporation 
is probably less important in the case of a parasitic fungus growing 
under the bark of a tree than in the case of most green plants. 
The difference in the amount of growth of Endothia parasitica at 
the various stations seems to bear no relation to the amount or fre- 
quency of rainfall. Amherst, Mass., and Charlottesville, Va. had 
practically the same rainfall, yet the growth at the latter point aver- 
aged nearly eleven cm. greater. On the other hand, stations differing 
widely in rainfall showed practically the same amount of growth. 
The length of frostless season is apparently unimportant, as the 
fungus has no dormant season. Low temperature retards or even 
prevents its growth, but growth is resumed as soon as favorable tem- 
perature returns. Cultures kept at temperatures as low as 1° C. for 
twenty-four hours resumed growth almost immediately when removed 
to room temperature and grew as rapidly as cultures which had never 
been chilled. 
The amount of growth at the various stations is very closely related 
to the duration and intensity of favorable temperatures. 
In tracing the relation between temperature and growth, temper- 
atures were calculated by direct summation as well as by the method 
of temperature "efficiencies" suggested by Livingston and the results 
of the two methods compared. The methods give nearly parallel 
results, though temperature summations agree slightly more closely 
with amount of growth than do temperature efficiencies. 
The time necessary for the development of pycnospores is so short 
that the climatic factors involved could not be traced. 
The fungus in some cases continued to grow parasitically for over 
eighteen months without producing ascospores. 
