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. 



Fig. 227. 



Willow mildew; Fruit of willow mildew, showing hooked 



bit of mycelium 

 with erect conidio- 



chaS Sf of b ffonidU? ciumV.of two powdery mildews, showing 

 >ni( ? la> escape of asci containing the spores from 



appendages. Genus uncinula. 

 228. 



Fig. 228. 

 Fruit body of an- 

 other mildew with 

 dichotomous _ ap- 



gonidium at left 

 germinating. 



the crushed fruit bodies. 



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- walls of anthe- 



nium (carpogo- ridium and 



nium the larger carpogon ium , 



cell); begin- and fusion of 



ning of fertili- the two nuclei, 

 zation. 

 Figs. 229-231. Fertilization in spha? 



Fig. 231. 



Fertilized egg surrounded 

 by the enveloping threads 

 which grow up around it. 

 theca; one of the powdery mildews. (After 



Harper.) 



an ascus, a 



large majority of the ascomycetes have just 8 spores in an 



