78 THE POTATO 



5. The nature of the skin . The skin may be thick, 

 medium, or thin. Some growers claim that thick- 

 skinned varieties are of better quality than thin-skinned 

 ones, but such correlation does not always exist. 

 Potatoes grown on sandy soils usually have smoother 

 skins than those grown on heavy loams. Some va- 

 rieties develop a netted, or rough, skin as they mature 

 in storage, although such may not be apparent at 

 harvest-time. The rough, or netted, skin in these 

 cases appears to denote maturity, and this may account 

 for the common idea that a rough-skinned potato is of 

 good quality. The size and type of netting (Fig. 20) 

 varies with the variety, and the conditions under 

 which it is grown. 



6. The shape. Most of the recent introductions, 

 exclusive of the Early Rose type, have had a tendency 

 to partake of the flat-round or oval (Fig. 21). These 

 shapes have been sought because such potatoes appear 

 to be of better quality consistent with an economical 

 shape and shallow eyes. The probable explanation is 

 that in a flat-round or thinnish potato there is a greater 

 surface in proportion to the bulk. The greater the 

 surface the larger the percentage of the tuber taken 

 up in the cortical layer and outer medullary layer (Fig. 

 18). These are the starch-bearing areas, and as they 

 are increased the inner medullary layer, or pith, which 

 has little starch, is diminished, thus rendering the 

 potato more uniform. Whatever shape is desired can 

 be be obtained, but a potato should be true to shape. 

 The tendency of a tuber to become pointed or drawn 

 out at the tip or butt end, especially if the variety is 

 a flat-round or round, indicates lack of vigor (Fig. 21). 



