SWEET-POTATO 427 



394. Description. The sweet-potato is perennial, but 

 in cultivation it is treated as annual; that is, new propa- 

 gating material is placed in the soil each year. 



The plant has prostrate stems (Fig. 188), many of which, 

 in the latter part of the season, take root at the nodes. 

 The leaves are extremely variable in shape, and these 

 differences constitute one means of classifying varieties. 



The valuable product is botanically an enlarged root. 

 This is an organ for the storage of food, serving to hasten 

 the growth of the young shoots, from which the plant is 

 ordinarily propagated. Man converts this stored material 

 to his own use. 



Some confusion arises from the fact that the same word 

 " root/' when applied to the sweet-potato, may denote 

 three parts: (1) the enlarged or edible root; (2) the slen- 

 der, fibrous roots which absorb the plant-food and mois- 

 ture from the soil, and (3) the potatoes that are too small 

 for market, but which are used for planting. Therefore, 

 in this chapter, the word " potatoes" will be used to 

 designate the large roots, as well as to include the whole 

 plant. 



395. Flowers and seeds. The sweet-potato seldom 

 produces flowers in the American cotton-belt, and still 

 more rarely, if ever, are perfect seed matured in this region. 

 However, seeds are sometimes matured when the season 

 of growth is prolonged by keeping the plants in a green- 

 house. When sweet-potato seeds are planted, they give 

 rise to young plants differing greatly among themselves 

 and most of them unlike their parents. The best of these 

 'seedlings may be propagated in the usual way, and thus 

 give rise to new varieties. 



