5S6 BOTANY OF CROP PLANTS 



sympetalous corolla is i to 2 inches wide, funnel-form, and 

 has a five-lobed limb, and plaited tube. The corolla is folded 

 longitudinally and twisted usually to the right in the bud. 

 The stamens are as given under the family description. The 

 two- to four-celled ovary has a thread-like style which bears 

 one or two stigmas. The fruit is a capsule. 



In northern latitudes, the sweet potato rarely blossoms, 

 and never matures seeds. 



Geographical, and Environmental Relations. — The original 

 home of the sweet potato is the West Indies and Central 

 America. Since the sweet potato is of tropical origin it is 

 largely grown in the Southern States, the five leading ones 

 being North Carolina, Georgia, Alabama, Louisiana and 

 Mississippi. Ample sunshine and high temperatures favor 

 its growth. Although a heavy rainfall is desirable during the 

 first part of the growing season, the maturing of the roots 

 proceeds best with rather dry weather. They do best in 

 well-drained, Hght soils. 



Closely Related Species. — The southern, juicy varieties of sweet potatoes 

 are called "yams." They should not be confused, however, with the true 

 yams, or Chinese potatoes of commerce, which belong to the species Dioscorea 

 batatas, in a family (Dioscoreaceae), closely related to lilies. This is a tall 

 climbing plant with simple cordate, shining leaves, small, white flowers, and 

 large tubers. 



Types and Varieties.— Sweet potatoes may be divided 

 into two groups upon the basis of the amount of water and 

 sugar present: (i) Dry sweet potatoes are ones in which the 

 flesh is dry, mealy, and yellow; they are the sorts most de- 

 sired in the Northern States. The Jersey type, which includes 

 spindle-shaped varieties, is probably the best known. (2) 

 " Yams" are sweet potatoes in which the flesh is watery, rich 

 in sugar, soft and gelatinous when cooked. They are the 

 sorts most in demand in the South. Common southern 



