4 The Sweet Potato 



leaves themselves. Variation is also commoii in the 

 prominence and abundance of leaf-veins. 



Flowers and seed. — Although rarely producing 

 flowers and less frequently maturing perfect seed in the 

 sweet potato producing areas of the United States, occa- 

 sionally a small bell- or morning-glory-shaped bloom, 

 with a purple throat and white margin, may be noticed 

 in commercial fields. Matured seed may be produced 

 if the growing period is prolonged by the use of artificial 

 means. These seeds, however, are unreliable for use in 

 perpetuating varieties as the resulting plants cannot be 

 depended on as coming true to the mother plant. In 

 fact, they may differ widely among themselves. This 

 characteristic enables the production of new varieties by 

 selecting strong and prepotent offspring. 



Tubers. — The sweet potato as known to commerce is 

 an enlarged tuberous root. In nature this root serves 

 as an organ for the storage of food, to be used in nour- 

 ishing the young shoots from which the plant is ordinar- 

 ily propagated, but man has converted this stored mate- 

 rial to his own use. This edible tuber is much prized 

 throughout the warmer parts of Asia and the Americas 

 as well as to considerable extent in other semi-tropical 

 and tropical countries as a staple article of food. The 

 tubers are variable in shape, size and color as well as in 

 food value and chemical constituents. Some are long 

 and cylindrical while others are short, thick and blunt 

 at the ends. (Plate IV.) The skin may be pink, yel- 

 lowish or dull straw color, purple, red or whitish in 

 color. The flesh is variable also in color, quality, 

 moisture and texture. These tubers (unlike the com- 

 mon or Irish potato) do not bear definite eyes; but are 

 formed in underground clusters immediately beneath 



