ANTHERIDIUM 



ASCOGONIUM 



Fig. 250. — Erysiphe polygoni. Sexual reproduction. A, Two hyphae in contact pushing 

 out branches. B, Branches twisting round one another. C, Young perithecium with 

 fused sex organs. D, Perithecium with central cell and binucleated stalk cell. 

 E, Perithecium with maze. F, Perithecium with degenerate central cell and multi- 

 nucleate stalk cell. G, Perithecium with central group of dead cells and wall cells 

 growing to form asci. H, Mature perithecium with two uninucleate asci in centre. 

 {After Allen.) 



259 



