VARIOUS OBSERVATIONS 63 



In order to determine the interval of time between the dis- 

 charge of successive asci from a single perithecium and also whether 

 or not an ascus, just before it bursts, protrudes at the mouth 

 of the perithecial neck, I proceeded as follows. I took a piece of 

 the pileus of a Lactarius which had been kept in a large damp- 

 chamber, placed it on the base of a compressor cell so that the red 

 stroma of the parasite looked upwards, set the lid on the cell, 

 and then pushed the lid downwards until its cover-glass actually 

 touched the surface of the piece of fungus and pressed here and 

 there against some of the more prominent perithecial necks. The 

 cover-glass was so close to the other necks, all of which were 

 directed upwards, that, if an ascus before its discharge had 

 protruded far beyond the mouth of the perithecium to which it 

 belonged, unavoidably it would have touched the cover-glass. It 

 was observed with the microscope that every now and then groups 

 of eight spores, together with a certain amount of cell-sap, suddenly 

 appeared on the under side of the cover-glass just above the mouths 

 of the necks of certain perithecia. These ascus-contents arrived 

 at their destination without my receiving any preliminary warning 

 that they were about to be shot away from the perithecia con- 

 cerned. The mouths of all the perithecia were found to be very 

 small of about the same width as the diameter of an ascus and 

 more or less concealed by short hairs springing from the wall of 

 the upper part of the neck-canal (Fig. 19, D and E). No ascus, 

 even just before the discharge of its spores, ever pushed its way 

 up the neck-canal sufficiently far to show its free end outside the 

 perithecium. 1 Owing to the perithecial wall being opaque, I was 

 unable to observe directly what was happening inside a perithecium 

 during the discharge of the spores ; but, guided by analogy with 

 other Pyrenomycetes, we may suppose it to be as follows. The 



1 Under abnormal conditions, one or more asci are sometimes squeezed out 

 through the mouth of a perithecium. This occurred when I exposed a piece of 

 pileus so that the red stroma dried rapidly at the surface (Fig. 19, K). The con- 

 traction of the stroma caused each perithecial chamber to diminish in volume, 

 the wall of a chamber thus being caused to press upon the closely-packed asci within. 

 When the pressure upon the ascus-mass attained a certain degree, several asci 

 were often quickly passed outwards through the perithecial neck-canal. Such 

 extruded asci were never seen to discharge any spores. 



