524 THE POTATO 



lulose forms the walls of a network of cells, which 

 in turn form the body of the tuber. These cells 

 vary in shape and size in different sections of the 

 tuber according to the part they play in its life. 

 In the flesh they serve mainly for storage, and in 

 them lie the starch grains. 



"The interior of the tuber is more or less per- 

 meated by water in which are dissolved nearly all 

 the soluble ingredients, including the various soluble 

 carbohydrates. In this connection it is well to 

 recall that the carbohydrates (cellulose, starch, 

 the different kinds of sugars, etc.) are all closely 

 related, and that under the influence of certain 

 acids, heat, or other agency an insoluble form, 

 such as starch, may be changed into a soluble form, 

 or vice versa. 



"Cultural varieties of a given plant often have 

 very different habits, appearance and quality, 

 and it is natural that the amounts and propor- 

 tions of water, carbohydrates, fats, protein and 

 mineral matters which the potato contains should 

 vary with the variety as well as with the character 

 of the soil, the climate, and other conditions under 

 which it grows. Moreover, since the needs of the 

 potato plant vary at different stages of its develop- 

 ment, it will provide for them by varying the 

 ingredients stored in the tubers and elsewhere. 

 Taking into account all these factors, it might 

 seem impossible to make any general statements 

 about the chemical composition of the potato, but 

 it may be said that the variations are in degree 

 rather than in kind, and so many analyses and 

 studies have been made, both in this country and 

 in Europe, that the average or general character- 

 istics of the potato are now well established. The 

 following table shows the composition of raw and 



