6 4 



RESEARCHES ON FUNGI 



asci were elongating and swelling in succession, thus filling the 

 perithecial chamber. The ripest ascus was elongating to about 

 twice its original length and pushing its free spore-carrying end 

 up into the canal of the perithecial neck (Fig. 19, F). At the 

 same time, other asci in the perithecium were elongating also. 

 Almost as soon as the ripest ascus had raised its free end some 

 way up, but not the whole way, into the neck-canal, its end burst 

 and the eight spores, together with some ascus sap, were squirted 

 through the end of the neck-canal like a bullet through the barrel 

 of a rifle. The ascus, after bursting, immediately contracted 

 and sank down in a collapsed condition within the perithecium. 

 Whereupon, the firing position at the mouth of the perithecium 

 was taken up by another ascus which, after elongating and pushing 

 its free end into the neck-canal, discharged its projectile in its 

 turn, only to make way for a third ascus ; and so forth until all 

 the asci had exploded. 



To find out how often a perithecium fires off an ascus, it was 

 only necessary to concentrate one's attention on one particular 

 perithecium and to observe how often a group of eight spores 

 was delivered to the under side of the cover-glass which was just 

 above the perithecial mouth. The following observations were 

 made on three separate perithecia. 



Frequency of Ascus-discharge from a Single Perithecium. 



From these data we can conclude that a very active peri- 

 thecium may discharge its asci at about the rate of one a minute, 

 but that the average rate of discharge under laboratory conditions 

 is about one ascus every minute and twenty seconds. If there 

 were 1,000 perithecia all active together and all liberating spores 



