206 THE POTATO 



"The accompanying photograph shows the ex- 

 ternal appearance of badly diseased potatoes. 

 The surface of the potato is more or less wrinkled, 

 and dotted with circular or oval pimples somewhat 

 smaller than a pinhead, or with more irregular and 

 larger nodules. The nodules are of grayish or 

 brownish color, more or less depressed in the centre 

 and sometimes surrounded by a slight furrow. In 

 early stages the potato may be full and firm and 

 the pimples so inconspicuous that they may easily 

 be overlooked. When the disease is more advanced 

 the nodules are more prominent, the specimen more 

 or less shriveled and of softer consistency than 

 normal. The easiest way to determine whether a 

 suspected tuber is diseased or not is to cut off 

 slices. If diseased, the cut surface will show sev- 

 eral dry, brownish spots somewhat smaller than 

 the head of a pin and extending from a sixteenth 

 to a quarter of an inch into the flesh. They are 

 usually circular or oblong in shape and consist of a 

 brownish ring enclosing a central, whitish, pulpy 

 core. Beneath the pimples there is a similar brown 

 dry rot-like area which may or may not connect 

 with the interior spots or worm burrows. Some- 

 times the burrows are so numerous and close to- 

 gether as to form an irregular continuous mass like 

 a number of small shot close pressed together. 

 More rarely the burrows may extend deeper into 

 the flesh. 



"Badly diseased potatoes may shrivel up to one 

 half the natural size, are softer and less nutritious 

 than normal and of course are not desirable for 

 human food. The burrows afford entrance for the 

 bacteria of decay, so that infested potatoes will not 

 keep as well as healthy ones. 



"If a portion of the pulpy centre of one of the 



