306 



DISEASES OF FIELD & GARDEN CROPS. [OH. 



remains of old rotten tubers left in the fields from the 

 previous year, and commonly seen on the ground and 

 about dung-heaps and hedge-sides in March and April. 

 A section through a fragment of decayed tuber is shown, 



FIG. 134. 



Section through fragment of diseased tuber of potato, with starch granules 



and oospores of Peronospora infestans, Mont., in situ. 



Enlarged 400 diameters. 



enlarged 400 diameters, at Fig. 134. One large oospore 

 is seen in an intercellular space, another in a cell amongst 

 the granules of damaged starch, and a third within the 



