EXPULSION OF ASCOSPORES 
The importance of the ascus discharge in the dissemination of the 
black rot of the grape is brought out by Reddick (17) who has con- 
firmed the observations of Scribner and Viala, and Wallace (21) has 
made a similar contribution in his study of the life-history of the apple 
scab fungus, Venturia inaequalis. Perhaps the most notable recent 
work is that of Falck (8) on the air infection of ergot, and the dis- 
semination of infectious diseases of plants by means of convection 
currents ("Temperatur-stromungen"). In the course of this work 
Falck points out the effectiveness of convection currents in the dis- 
semination of ascomycetous spores. 
Expulsion of ascospores hy the chestnut blight fungus. — The earlier 
reports on the chestnut blight fungus make no mention of the way 
in which the ascospores are set free from the perithecia. Although 
the first studies appeared in 1906 it was not until the summer of 191 1 
that Rankin (14) observed the forcible expulsion of the ascospores. 
Later (15) the same writer says: "Under moist conditions the asco- 
spores are shot forcibly out in the air where they can be caught up by 
the wind and carried for a considerable distance. The speaker found 
the ascospores being shot from mature pustules during every rainy 
period last summer." Considering the fact that forcible expulsion 
of ascospores by many pyrenomycetous fungi was a fairly well-known 
phenomenon, as has been pointed out in the previous pages, it seems 
strange that this important observation did not come earlier. It was 
this which served as the impetus for investigations along new lines 
on the dissemination of the fungus. 
Additional observations and experiments on the expulsion of the 
ascospores made at the Field Laboratory of the Pennsylvania Chestnut 
Tree Blight Commission during the summer of 1912 are summarized 
by Anderson (i) and presented in detail by Anderson and Babcock 
(2). The most iniportant points brought out by these investigations 
were as follows : 
I. Ascospore expulsion occurs only during and for a short period 
after rains or as long as the bark remains wet. 2. The maximum 
distance to which ascospores were expelled vertically was 22 mm., 
while the maximum horizontal distance was 89 mm. 3. The rate of 
ejection under favorable conditions was an ascus explosion about every 
two seconds or an average of 4.06 spores per second. 4. Bark bearing 
perithecia and kept moistened continued to expel ascospores for 25 
days. 
