308 



DISEASES OF FIELD & GARDEN CROPS. [CH. 



spores which escape, as at DD, and speedily come to rest 

 and germinate, as at E ; the germinal threads from oospores 

 and zoospores alike, when placed either on the foliage 

 or tubers of potatoes and kept uniformly moist and warm, 



Peronospora infestans, Mont. 



Oospores a year old germinating in summer. 



Enlarged 400 diameters. 



soon give rise to the fungus of the potato disease, and 

 cause discoloured patches of decomposition as the growth 

 proceeds. This condition of the fungus was described 



