150 DISEASES OF THE SWEET PEA 



weather the mycelium of the fungus 

 spreads in the tissue throughout the leaf, 

 which soon assumes a sickly yellow-green 

 color, and finally bleaches, shrivels, and 

 dies without showing any or only a small 

 amount of the mold on the surface. In 

 damp cloudy weather infected leaves show 

 yellow patches, which soon become covered 

 on one or both surfaces with a very delicate 

 grayish lilac colored mold. 



The summer spores are produced on the 

 leaves or on any other part of the host. 

 The winter or resting spores are imbedded 

 in the tissue of the host that has been pre- 

 viously killed by the fungus. The resting 

 spores have a very thick smooth brown 

 wall. 



Peronospora vicia also produces a dis- 

 ease on sweet peas. 



