Communications. S9o 



of the atmosphere. The funpjus is first recognized by the potato 

 leaves turning brown, owing to the absorbing threads of the "rot" 

 "within the tissue. Soon certain threads come to the surface, pass 

 through the breathing pores, divide into several branches, and 

 bear the conidial spores on the tips. In this condition the leaves 

 look as if covered with a fine frost. The spores thus produced 

 germinate at once, and in this waj the disease is rapidly spread 

 to other plants throughout the field. The fungus soon passes 

 down the stem to the growing tubers, and they in turn give up 

 their substance to this parasite, and then become rotten. As the 

 rot does not make its appearance until the hot and moist days of 

 July, the earlier varieties stand a greater chance of escaping it 

 than the later. In all cases where the disease is gradual in its 

 appearance, and the tubers are nearly mature, they should be dug 

 at once. If the fungus has reached the tubers they will rot to 

 some extent ; but when placed in a dry cellar the rotting is con- 

 siderably retarded. In raising potatoes, select a well drained or 

 naturally dry soil; plant early varieties and plant them early. 

 Always plant the soundest and most mature tubers. Gather the 

 crop as early as possible and burn all tops at once, thus destroy- 

 ing the spores which might otherwise carry the pest over the 

 winter season. "When every condition is the most favorable for 

 its development the rot will take its most violent form, and the 

 crop will fail as it has so often done in the past. 



The potato rot has long been known to the South American 

 Indians dwelling in the regions of the Andes, showing that this 

 plague is not of recent origin, and also that the land which gave 

 us the wild potato has likewise produced its most destructive 

 parasite, which has followed it across the seas. There is no object 

 in nature concerning which men have given more curious and 

 conflicting theories than the plant in question, and today the list 

 is long of those who fail to recognize in it a member of the vege- 

 table kingdom. But when the plant can be cultivated, the spores 

 sown on sound potatoes, and the vegetable watched through its 

 whole existence, culminating in the rot, it is time to believe that 

 it is as much a plant as the one upon which it grows. 



Another species of this same genus, Peronosjjora^ is the Ameri- 



