FUNGI: SAC FUNGI. 



197 



415. Number of spores in an ascus. The ascus is the most important 

 character showing the general relationship of the members of the sac fungi. 



Fig. 226. 



Willow mildew; 

 bit of mycelium 

 with erect conidio- 

 phores, bearing 

 chain of gonidia; 

 gonidium at left 

 germinating. 



Fig. 227. 



Fruit of willow mildew, showing hooked 

 appendages. Genus uncinula. 



Figs. 227 228. Perithecia (perithe- 

 cium) of two powdery mildews, showing 

 escape of asci containing the spores from 

 the 'crushed fruit bodies. 



Fig. 228. 

 Fruit body of an- 

 other mildew with 

 dichotomous ap- 

 pendages. Genus 

 microsphsera. 



While many of the powdery mildews have a variable number of spores in 



Fig. 229. Fig. 230. 



Contact of Disappear- 



antheridium ance of contact 



and carpogo- w_alls of anthe- 



nium Ccarpogo- ridiumand , 



nium the larger carpogonixim, *ig. 231. 



cell) ; begin- and fusion of Fertilized egg surrounded 



ning of fertili- the two nuclei. by the enveloping threads 



zation. which grow up around it. 



Figs. 229-231. Fertilization in sphaerotheca; one of the powdery mildews. (After 



Harper.) 



an ascus, a large majority of the ascomycetes have just 8 spores in an 



