56 



INTRODUCTION TO THE STUDY OF FUNGI 



is occupied by the Pyrenomycetes, in which the sporidia are 

 developed in asci ; but, so far as we are aware, it is only in the 

 family Perisporiaceae that sexual fertilisation has been sug- 

 gested — i.e. in Hrysiphe and Eurotium, by De Bary and sup- 

 ported by Tulasne. In Erysijphe lamprocarpa the peritheeia are 

 produced where two filaments of the mycelium cross each other 

 (Fig. 33). They swell slightly, and each emits a process resem- 

 bling a branch. That from the lower filament soon becomes 



Fio. 34. — Development of Eurotium repens. After De Bary. 



oval, and is constricted by a septum from the hypha, becoming 

 a distinct cell, which De Bary calls "oocyst." The process 

 from the upper filament adheres closely to this cell, and 

 elongates into a cylindrical tube, which terminates obtusely at 

 the apex of the cell. This also is divided by a septum from 

 the parent hypha near the base, and another towards the 

 apex cuts off a short terminal cell, which is supposed to be the 

 antheridium. After this eight or nine new tubes spring up 

 around the base of the oocyst and closely applied to it, which 

 gradually develop into the wall of the perithecium. In the 



