more serious is this effect on the crop. In most years 

 potato plants which are attacked by Late-Blight, die down 

 much earlier than they would normally. 



When a field has been badly attacked by Late-Blight 

 the tubers almost invariably become infected. This either 

 takes place by spores being washed down into the soil 

 and directly infecting tubers near the surface, or by the 

 growth of the fungus down the tissues of the dying stalks 

 into the tubers. Potato tubers infected by this disease 

 can readily be recognised by the purplish discoloration 

 and rather sunken appearance of the skin in diseased 

 parts. These features are caused by the brown colour 

 of the cells immediately under the skin. Living filaments 

 of the fungus infest the discoloured cells, and if such 

 tubers are stored the fungus slowly invades healthy cells, 

 often producing the so-called dry rot of the tuber. In 

 addition to this, the presence of the fungus in the potatoes 

 renders them extremely susceptible to the attacks of 

 secondary rotting fungi and also of bacteria. In some 

 such cases the potato shows the characters of the winter 

 rot disease caused by Fusarium solani. The tuber 

 gradually shrivels and at a late stage small white tufts 

 of that fungus appear over the sunken parts. In other 

 cases the potato becomes changed into a moist, putrid 

 mass infested by bacteria and mites. These diseases are 

 extremely likely to appear in stored tubers that are to 

 any degree infected by Phytophthora. Much, however, 

 can be done to prevent healthy tubers developing these 

 rots by careful attention to the method of storage. It 

 is well known that the favourable conditions for the 

 growth of most fungi are a moist, warm atmosphere 

 and absence of light. If, therefore, the storage clamp is 

 not carefully made, it is possible that very favourable 

 conditions for the growth of fungi will be provided. If 

 the tubers are stored moist, or if they are too closely 

 covered, and if no provision is made for adequate access 

 of air to all parts of the "pie," the temperature will rise 

 and harmful fungi will become rampant. To avoid these 

 dangers then, potatoes should be stored in a dry, well- 

 ventilated shed ; or, failing that, the " pie " or clamp should 

 be in a dry situation and well ventilated. By such pre- 

 cautions the conditions are rendered unfavourable for the 

 growth of rotting organisms; and even though a few of 

 the tubers are diseased the trouble is then unlikely to 



