Heald- Studh ALTER : Expulsion of Ascospores 127 
months under perfectly dry conditions.” No detailed description 
is given of the tests on which this statement is based. 
Alternate drying and drenching of cankers is, of course, the 
normal condition in the field. Work to be reported later has 
brought out the fact that under these conditions given areas of 
the bark of cankers will continue to expel ascospores through all 
or at least parts of two seasons. 
Method 
Bark showing an abundance of mature perithecial stromata was 
collected at Emilie, Pa., on July 15, 1913. The bark was then 
moistened and tested to make sure that the perithecia were in a 
condition to expel spores.* As soon as any specimens showed ex- 
pulsion of spores, they were allowed to dry. By July 21, 1913, 
all the specimens to be retained had been tested and were thor- 
oughly dry. They were then grouped in packets of six specimens 
each, giving to each lot as near as possible uniform material. 
They were then stored in a closed pasteboard box and retained 
in the laboratory. 
Each of the six pieces of bark in a packet was of sufficient size 
to support an object glass. Tests were made at about monthly 
intervals employing six pieces each time. The method employed 
was that previously described by Heald and Walton.® 
Results 
The results obtained by the different tests can best be presented 
in tabular form (Table I). From this summary it may be noted 
that the perithecia still retained the power to expel spores after 
II months and 18 days of continuous drying. In all probability 
the limit was not reached, as the perithecia seemed to develop as 
strong powers of spore expulsion during the last test as in any of 
the earlier ones. In the majority of cases all of the pieces of 
bark tested showed active ostioles after being subjected to favor- 
able conditions for a sufficient length of time, and there was 
* The material was collected by Mr. R. C. Walton and some of the earlier 
tests were made by him. 
“ Loc. cit. 
