500 



LIFE-HISTORIES 





H/H^^^^ V^/e^Y ^^^) 



Fig. 328. — Powdery-mildew (Erysibe communis. Powdery-mildew Family, 

 Erysihaceoc) . The surface of a leaf upon which the fungus is parasitic, 

 its horizontal hyphoe spreading over the surface and attaching itself 

 bj- sucking organs; and giving rise also to vertical hyphte producing 

 dust-spores (c), and to fruiting bodies such as a, which contain sac- 

 spore-cases such as e. The fruiting bodies h and d and the hyphis from 

 which they arise belong to another fungus (Cinciiinoholus) which is 

 parasitic upon the mildew. Magnified about 450 diameters. (Tu- 

 lasne.) — Powdery-mildews are all too common parasites upon the 

 foliage of flowering plants both cultivated and wild. 



Fig. 329. — Powdery-mildew. Horizontal hyphie (a) from which arise 

 "male" (h) and "female" (c) gametangia; the latter producing sac- 

 spore-cases enclosed within a protective fruit-body {d, e). (Warming.) 



