1908.] IMPROVEMENT OF THE POTATO. 419 



9. QUALITY 

 HISTORICAL 



In 1897 Coudon and Boussard (18) came to the conclusion on 

 the ground of their tests with thirty-four varieties of potatoes that 

 their culinary value is dependent upon the chemical composition, 

 and that it varies directly as the nitrogen content and inversely 

 as the starch content, that is culinary value = "^1"*!"- Potatoes 

 with a high starch content were disintegrated by boiling, and pota- 

 toes with a high nitrogen content resistant. 



Their analyses were made of four physical divisions of the po- 

 tato as shown in figures. These parts they designated, from out- 

 side to inside, as skin, cortical layer, outer medullary layer and in- 

 ner medullary. 



FIG. 5. ZONES OF THE POTATO. (AFTER COUDON AND BOUSSARD.) 



a. Cortical layer. 



b. External medullary layer. 



c. Internal medullary layer. 



The outer skin is the colored portion and may be completely 

 separated from the part underneath. The cortical or fibre-vascular 

 layer lies next and is easily distinguished by the separating line of 

 vascular bundles. In the interior the inner medullary layer appears 



