502 
F. D. HEALD AND R. C. WALTON 
The way in which the ascospore expulsion occurs was pointed out 
by Rankin (i6). According to his observations the asci are set free 
and rise in succession to the ostiole, where the explosion takes place, 
eight spores, or the entire contents of an ascus, being liberated at each 
pulsation. These observations were confirmed by Anderson (3) and 
in connection with the study of the morphology of the ascus, the 
mechanics of the spore discharge was briefly considered. 
The senior author first pointed out the relation of temperature to 
the expulsion of ascospores (9), showing that moisture and the proper 
temperature are essential to the proper activity of the process. This 
relation was again emphasized (10) and the bulletin referred to con- 
tains the first published illustration of a characteristic spore print on 
an object slide. The first data on relation of temperature to asco- 
spore expulsion were obtained from experiments conducted in constant 
temperature rooms, and these were substantiated later by tests 
carried out under field conditions (11). There was no expulsion of 
ascospores from Nov. 26, 1912, until the rain of March 21, 1913, 
although there were 21 warm winter rains during this period with 
maximum temperatures during or immediately following the rain 
of 35-60 degrees Fahr. 
The length of time during which ascospore expulsion occurred 
following various warm rains was given special attention in some 
recent studies on air and wind dissemination of the chestnut blight 
fungus (12). It was found to depend upon the weather conditions 
following the cessation of a rain, and varied from 45 minutes to a 
maximum of 13 hours. 
Our work on the relation of temperature to ascospore expulsion 
has been summarized by the junior author (22). 
Two facts established by the researches of Falck have a very 
important bearing on the dissemination of the spores of Endothia. 
First, he has shown that " Temperatur-stromungen " alone suffice for 
spore dissemination of Claviceps; and for this reason fields protected 
by woods from strong winds and remaining moist longer than free 
lying fields are more infected. Second, he points out the effect of 
evaporation in the production of convection currents. It is certainly 
worthy of note that the ascospores of Endothia are being expelled 
under natural conditions in the field at a time when evaporation from 
the bark is favorable to the creation of convection currents (12). 
For this reason we chose to speak of the "air and wind dissemination" 
