264 IRISH POTATOES 



in the Burbank group. The general market preference now is for 

 the oval-flat, Rural type, and medium in size. 



Depth of and Number of Eyes. This is also important, as 

 deep eyes cause waste in peeling and injure the appearance. Both 

 Green Mountain and Rurals have few eyes, and very shallow, which 

 is one reason for their great popularity as market potatoes. 



Color of skin adds more to appearance than quality. White or 

 cream-white is preferred. For shipping green, the red or pink col- 

 ored potatoes show the effects of bruising less, and are often grown 

 in the South wher^ " green " potatoes are shipped a long distance. 



Structure and Composition. The potato tuber may be di- 

 vided into four principal parts (Fig. 105), namely: 



Skin 2.5 per cent 



Cortical layer 8.5 per cent 



Outer medullary ) g t 



Inner medullary \ 



The cortical layer and the outer medullary are both rich in starch 

 and constitute 80 to 90 per cent of the potato. The inner medul- 

 lary, sometimes called the core, is quite watery, and spreads irregu- 

 larly from the center. 



It is generally considered a mark of poor quality if the inner 

 medullary is large and conspicuous. 



In composition potatoes contain from 75 to 80 per cent of water, 

 from 16 to 20 per cent starch, 2 to 3 per cent of protein and 1 per 

 cent ash and a trace of fat and fiber. The dry matter of potatoes is 

 very similar in composition to the dry matter of wheat. 



In peeling potatoes, from 10 to 30 per cent is removed in the 

 peeling, depending on the size of the potato and depth of the eyes. 

 The loss is least with large, smooth potatoes. 



CLIMATE AND SOILS FOR POTATOES 



Climate. Potatoes require a moist and cool climate. Climate 

 is probably a much greater factor in potato production than soils, 

 as they appear to grow well on any productive soils in a favorable 

 climate. 



It is well known that the cold summer climate of Scotland is 

 almost ideal for potatoes. Crops of 300 to 500 bushels per acre are 



