196 



MORPHOLOGY. 



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

 these through the mirrosrnpe with the low power, we should 



Fig. 325- 



Leaves of willtiw showing wilinw mildew. Tlie black dots are the fruit bodies iperitlnecia) 



seated on tlie wliite in\xeliuin, 



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

 perithelia nipturc. If this is done larefully we see se\eral 

 small owate sacs issue, each containint; a number of spores, a.-- 

 shown 111 fig. 227. Such a sac is au cisc/is, and the sjjores are 

 ascus/iores. 



