138 



MORPHOLOG F. 



302. The sac fungi or ascomycetes. The large group of fungi to which 

 this uncinula belongs is known as the sac fungi, or ascomycetes. While 



Fig. 165. 



Willow mildew; bit 

 of mycelium with 

 erect conidiophores, 



Fig- '66. Fig. 167. 



Fruit of willow mildew, showing hooked ap- Fruit body of an- 



pendages. Genus uncinula. o t her m ildew with 



Figs. 166, 167. Perithecia (perithecium) of dichotomousappen- 



bearing chain of two powdery mildews, showing escape of asci dages. Genus 



gonidia ; gonidium at containing the spores from the crushed fruit microsphasra. 

 left germinating. bodies. 



many of the powdery mildews have a variable number of spores in an ascus, 

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



Fig. 168. Fig. 169. 



Contactofan- Disappear- 



theridium and ance of contact 



carpogonium walls of anthe- 



(carpogonium ridium and rig. 170. 



the larger cell); carpogonium, Fertilized egg surrounded by 



the beginning and fusion of the enveloping threads which 



of fertilization. the two nuclei. grow up around it. 

 Figs. 168-170. Fertilization in sphaerotheca ; one of the powdery mildews. (After Harper.) 



some have 4, others 16, and some an indefinite number. The complex struc- 

 ture of the fruit body, as well as the usually definite and limited number of 



