fUNGI: SAC FUNGI. 137 



301. Asci and ascospores. — While we are looking at a few of 

 these through the microscope with the low power, we should 



Fig. 164. 



Leaves of willow showing willow mildew. The black dots are the fruit bodies (perithecia) 



seated on the white mycelium. 



press on the cover glass with a needle until we see a few of the 

 perithecia rupture. If this is done carefully we see several 

 small ovate sacs issue, each containing a number of spores, as 

 shown in fig. 166. Such a sac is an ascus, and the spores are 

 ascospores . 



