5i6 
F. D. HEALD AND R. C. WALTON 
A more significant test because of the greater number of specimens 
was started Feb. 13, 191 3, in damp chambers similar to those above. 
It was continued for 17 days with 6 specimens for the experiment 
proper and 6 for the control. At the end of the test it was found 
that while the checks showed a larger number of spots than the 
experiment specimens there was sufficient shooting from the latter to 
prove conclusively that expulsion will take place rather freely when 
the perithecia are in a saturated atmosphere. 
This would point to ascospore expulsion as the result of high 
osmotic pressure from water absorption rather than to a drying 
effect from contact with the air as has been suggested by some writers 
(6). It should be pointed out in this connection that ascospore 
expulsion takes place during a rain under natural conditions, but con- 
tinues for only a short period after the cessation of rain, the time vary- 
ing with the humidity of the atmosphere. 
Expulsion Without Direct Wetting 
Two tests were conducted to determine whether ascospore expul- 
sion could take place without direct application of water to the upper 
surface of the bark. They were as follows : 
Specimens obtained from West Grove, Pa., were arranged on blof 
ting paper in trays in the customary manner. Six were used for the 
experiment proper and six for the control. Water was applied every 
day to the blotting paper beneath the test specimens and care was 
taken not to give an excessive amount or to wet the upper surface 
of the bark, while the control specimens were drenched from above 
in the regular manner. The test was continued for 17 days at the 
end of which time all but one of the experiment specimens had ex- 
pelled spores. Expulsion however was very light but the controls 
also showed but few active perithecia. While positive results were 
obtained they were not as conclusive as might be desired because the 
specimens were of poor quality. Practically all of them became con- 
taminated with bacteria, and the perithecia appeared to be rather 
immature. 
On Feb. 12, 191 3, another test similar to the above was started 
using specimens from Emilie, Pa. Six traps were used for the experi- 
ment and six for the control. Daily records were taken for 16 days 
during which time there was some heavy ejection of spores from the 
