426 



BULLETIN NO. 



[August. 



ity. We found no potatoes nearly up to this limit, but from general 

 experience we should conclude that potatoes with a starch content 

 above a certain limit would easily fall to pieces, or if the cell walls 

 were strong enough to hold together under such pressure, they must 

 necessarily be coarse and woody. 



PHYSICAL STRUCTURE AND QUALITY 



The writer was led first by Coudon's and Boussard's work to 

 believe that the physical structure held some relation to the table 

 quality. Microscopical examination of the structure of the potato 

 bears out the chemical analyses of the different zones. 



FIG. 6. a. OUTER SECTION OF CORTICAL LAYER, b. INNER SECTION OF CORTICAL. 



LAYER. 



(Figures 6 and 7 from the same tuber.) 



The corticaL layer (figure 6), below the first few layers of 

 cells which are removed with the skin, shows a remarkably larger 

 amount of starch in the cells, than does the internal medullary layer 

 (figure 7). The starch content of the external medullary layer is 

 also greater than that of the internal. The grains of starch in the 

 cortical and external medullary layers besides existing in greater 

 numbers per cell, are generally of larger average size. The paucity 

 of starch in the internal medullary layer causes the cells to be only 

 partially filled with the cooked starch and the cell walls are scarcely 

 ever ruptured. In the cortical layer, on the other hand, the amount 

 of starch is such that in the swelling due to cooking, the cells 

 are filled completely and many of them ruptured, causing the mealy 

 appearance so much desired by tfae consumer. 



