500 



LIFE-HISTORIES 





V. 



>x^^ 



. 328. — Powdery-mildew (Erysibe comrnunis, Powdery-mildew Famib\ 

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

 its horizontal hj'phce spreading over the surface and attaching itself 

 by sucking organs; and giving rise also to vertical hyphce producing 

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

 sporc-cases such as e. The fruiting bodies h and d and the h>'pliie from 

 which they arise belong to another fungus {(Jincinnoholus) which is 

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

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

 foliage of llowermg plants both cultivated and wild. 



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

 "male" {b) and "femalr" (c) gametangia; the latter piodvicing sac- 

 spore-cascs enclosed within a ijrotective fruit-body id, <). (Warming.) 



