580 BULLETIN 347. 
has become completely filled with maturing asci and the perithecium is 
now ready to discharge its spores. : 
Time of development of perithecia.— On cankers produced by inoculation = 
during spring and summer, 
mature perithecia are de 
veloped in early autumn. It 
is evident, however, that this 
isnot the only season at which 
they may be produced, be- 
cause there is no time of the 
year at which they cannot be 
found in abundance, ready to 
eject spores if the proper 
conditions of moisture and 
temperature are supplied. 
Ejection of ascospores 
One of the writers of this 
bulletin (Rankin, 1912 a) dis- 
covered that during rain 
periods the ascospores are 
ejected with some force into 
the air from the. ostioles of 
Fic. Pee one section of preys Salt cogil the perithecia. The asci, 
before the differentiation of the wall and the core : F 
cells, showing at the center the shriveled remains which usually fill the peri- 
of an ascogonial cell and at the top the begin- thecium, are pushed up 
HEROS TH eee through the neck when abun- 
dant free water is added to the stroma. This expulsion of the asci is 
largely due to the swelling pressure of the asci. A dry ascus with its 
spores (Fig. 89, b, page 562) occupies only about one half the space 
occupied by an ascus after water is added (Fig. 89, c and d). 
Prepared sections of perithecia fixed during the process of ejection of 
spores show that the spores remain in the asci almost to the tip of the neck. 
Since the asci themselves are never ejected into the air, it follows that 
they must burst and liberate the spores when they arrive at the surface 
of the film of water. The ejection may be observed with a hand lens. 
The only visible phenomenon is the sudden and regular breaking of the 
film over the ostiole. This gives for the moment the impression of a point 
of light. The entire contents of the ascus are ejected at once into the air. 
Rankin (1914) has drawn the following conclusions as to the process 
of the actual ejection of the spores from the asci: The imbibition of 
water results in the asci being forced out through the ostiole, where, 
