ASCOMYCETES EUASCI PERISPORIALES 



269 



parasitic fungi, like the powdery mildew of the grape (Uncinula spiralis), 

 mildew of lilac (Microsphaera Alni), mildew of sunflower (Erysiphe Cichor- 

 acearum}, mildew of cherry (Podosphaera tridactyla). 



Erysiphe. (Hedw.) 



Perithecium containing several asci, appendages with simple threads, sim- 

 ilar to and frequently interwoven with the mycelium. A small genus of 20 

 species of wide distribution. 



Erysiphe communis. (Wallr.) 



Amphigenous, mycelium abundant, persistent, or sometimes evanescent; 

 perithecia variable in size and reticulate, appendages variable in length, often 

 long; asci 4-8 or more, ascospores 4-8. 



Distribution. Found on a large variety of different hosts but common on 

 plants of the order of Leguminosae, especially the forage plants like the pea 

 (Vicia saliva}, bean, clover and other members of the clovers. 



Fig. 91. Powdery Mildews. 1-3. Sphaerotheca Castagnei on Hop. 1. Part of leaf 

 of hop with perithecia shown in the form of dots. 2. Perithecia with tortuous appendages 

 (ap) x 175. 3. Ascus with spores within the ascospores x 380. 4. Powdery Mildew on 

 Cherry (Podosphaera tridactyla), conidiophore bearing conidia (c). 5-7. Microthyriunr 

 microscopicum. 5. On leaf. 6. Perithecium, greatly magnified. 7. Ascus and ascospores. 

 1 after Wettstein. 2-4 after Tulasne. 5 after Lindau. 6-7 after Winter. 



