i8 
NEIL E. STEVENS 
host where moisture is most abundant, and where evaporation is very 
sHght, if indeed it occurs at all. 
If the biological relations of the fungus are correctly understood 
it is, while growing as a parasite in or near the cambium of its host, 
uninfluenced by any environmental condition except that of temper- 
ature, at least in the territory it now occupies in this country. And 
the influence of temperature itself is restricted to an increase or de- 
crease of the amount of growth rather than any permanent cessation 
of growth such as is brought about by heavy frost in the case of 
green plants. 
AscospoRE Production 
In studying the relation of climatic conditions to reproduction in 
Endothia parasitica attention was concentrated on the production of 
ascospores. The time necessary for the development of pycnidia is 
so short that to determine the factors involved would necessitate an 
intensive study of a few adjacent localities, with much more frequent 
visits than were possible in covering so large an area as was involved in 
the present study. 
Previous observations on the production of ascospores have been 
isolated rather than comparative. Murrill (8, p. 187), in his original 
description of the fungus, stated: "The winter spores [ascospores] 
mature in late autumn . . . and germinate the following spring." 
Anderson and Babcock (2, p. 36) made several hundred inoculations 
on various dates from May 29 to July 12, 1912, and recorded the date of 
appearance of pycnospore horns and perithecia. They conclude that 
(p- 37)* "Ii^ general it may be said that under natural conditions in 
the summer time the spore horns will be developed in from three to 
six weeks, and that the winter or ascospore stage will develop in ten 
weeks or more. The fact that the perithecial stage on all these plots 
appeared in September and October should not be interpreted as 
indicating that the approach of winter had any influence in bringing 
about this stage." 
Rankin (9, p. 249) made inoculations at Napanoch, Ulster Co., 
N. Y., each month during the summer of 1912 commencing with May 
and observed that stromata were not produced on any of the cankers 
until about the second week of September (p. 254), and that they 
appeared as quickly on cankers produced by inoculations of July 4 
as on those made May I. Cankers produced from inoculations made 
at different times from May i to August i showed uniformly mature 
