270 



MANUAL OF POISONOUS PLANTS 



Fig. 92. Powdery Mildew. Sphaerotheca Castagnei. 1. Oogonium (o) and anther- 

 idium (a). 2. Separation of antheridium cell. 3. Fertilization and formation of addi- 

 tional cells. 5-8. Further development of cells. All greatly magnified. After Harper. 



Fig. 93. Powdery Mildew of Grass (Erysiphe graminis). 

 A. Oidium stage and mycelium m. B. Perithecium with 

 appendages and mycelium tn. C. Perithecium with asci 

 and ascospores. After Frank. 



