588 BULLETIN 347 
Experimental data are not cited. 
The writers performed experiments in order to determine the conditions 
necessary for ejection, rate of ejection, spore content of the air, ability 
of wind-blown spores to produce infection, and the like. 
Ascospores are not peculiarly winter spores, but they may be found 
maturing and ready for ejection at any time of the year. Experiments 
by Heald and Gardner (1913 a), however, indicate that they are not 
ejected during the winter. These experimenters found that after the 
stromata were subjected to low temperatures they did not resume ejection 
of ascospores again for three or four days after being brought into favorable 
temperatures, and that the minimum temperature for spore ejection 
varies from 52° to 60° F. Experiments show that during the summer 
spores are ejected only during and shortly after rains — in fact, just as 
long as the bark remains wet. This may be a half hour or it may be 
more than a day. The same stroma may resume expulsion any number 
of times during the summer. Alternating periods of abundance of moisture 
and desiccation were not found to interfere with the ability to eject spores. 
In case the bark remains wet continuously, it was found that a single 
stroma would continue uninterrupted ejection for twenty-six days. One 
case is reported in Bulletin 9 of the Pennsylvania Chestnut Tree Blight 
Commission, in which bark containing ascospore pustules continued to 
expel ascospores for over six months (in the laboratory). The rate of 
ejection from a single ostiole was determined to be one ejection for each 
two seconds, that is, about four spores a second. . This would be 14,400 
spores an hour from a single perithecium. The maximum height of 
ejection found was twenty-two millimeters. Horizontally, from a stroma 
two centimeters above an agar plate, spores were ejected to a distance 
of eighty-nine millimeters on the plate, the experiment being performed 
under a bell jar. 
The spore content of the air was determined by two methods. The first 
was the usual aspirator method:used in quantitative analysis for bacteria. 
By this method no spores could be found in the air during dry weather, 
but when the air within a few feet of wet cankers was tested there was 
an average of four and three tenths spores per liter. The second method 
was the exposure of sterile agar plates at varying distances from moist 
cankers. When these plates were exposed for a short time close under 
a canker, as many as gooo spores were caught on one plate, but the number 
decreased as the distance between the canker and the plates was increased. 
Spores were easily secured at a distance of fifty-one feet with a moderate 
wind blowing from the diseased bark toward the plates on a level with 
it. No greater distances were tried; but if spores can be so easily caught 
at that distance on a ten-centimeter plate in a moderate wind on a level 
