AMERICAN 
JOURNAL OF BOTANY 
Vol. II 
November, 1915 
No. 9 
SEASONAL DURATION OF ASCOSPORE EXPULSION OF 
The effect of moisture upon the expulsion of ascospores of the 
chestnut bhght fungus, Endothia parasitica (Murr.) And., was first 
studied by Rankin (i). Later the same writer (2) made the following 
report: "The speaker found the ascospores being shot from mature 
pustules during every rainy period last summer" (191 1). A more 
detailed study of ascospore expulsion was made during the following 
summer by Anderson and Babcock (3). The main conclusion of these 
writers on the moisture relation can best be presented in their own 
words: "We may say then in general that, as long after a rain as the 
surface of the bark remains wet, the spores will continue to shoot." 
That certain temperature conditions must be fulfilled to insure 
spore expulsion was first brought out by laboratory tests reported 
by the senior author (4). Later in a discussion of "The relative 
prevalence of pycnospores and ascospores of the chestnut blight 
fungus during the winter," Heald and Gardner (5) report the results 
of field tests made during the winter of 1912-13, showing that asco- 
spores were not expelled during the warm winter rains. A brief 
statement of the relation of temperature to the expulsion of ascospores 
of Endothia parasitica has been published by Walton (6) and a more 
detailed consideration by Heald and Walton (7) of the temperature 
relation based on laboratory tests in constant temperature rooms 
has substantiated the earlier results. The only previous work bearing 
on the seasonal duration of ascospore expulsion is that of Rankin to 
* During the first part of the period covered by this paper, Mr. M. W. Gardner 
was associated with the writers, and he deserves special mention for careful and 
painstaking work in connection with the records and observations made at West 
Chester. 
ENDOTHIA PARASITICA* 
F. D. Heald and R. A. Studhalter 
[The Journal for October (2: 375-428) was issued 4 Nov 1915.] 
429 
