CHAPTER XVI 



CONVOLVULACEAE 



IPOMOEA BATATUS 



THE sweet potato is the only representative of the Convolvulaceae 

 that is of major importance as a food plant. Originally a 

 native of tropical America and the West Indies, it is now cultivated 

 in the South Atlantic and Gulf States, South America, Africa, 

 Mediterranean Europe, India, Japan, the Malay Archipelago, 

 Australia, and New Zealand. 



The numerous varieties produced in the United States may be 

 divided into two general groups. In one are the dry, mealy 

 types such as Big Stem Jersey, Yellow Jersey, Early Carolina, and 

 Triumph, which are much favored in the northern markets. The 

 other group consists of those varieties in which the flesh is soft, 

 moist, and sugary when cooked. These are preferred in the 

 southern markets and include Nancy Hall, Georgia, Pumpkin 

 Yam, and Porto Rico. The trade names used are subject to much 

 change, since breeding and selection result in constant fluctuation 

 in the number and names of commercial varieties. 



GENERAL MORPHOLOGY 



The Stem. — For the most part, the sweet potato is a vine-like 

 plant; but, according to Groth Ql), the length of the stem may 

 range from 2. feet in some bunch varieties to xo feet or more in 

 those of the liana type. In the latter, the stem may be strictly 

 twining or may not twine at all. It is purple-green, or a mottled 

 combination of purple, brown, and green ; and varies in diameter 

 from 3^ to more than 34 oi an inch at its largest part. Lenticels 

 are abundant and there may be some degree of pubescence, hairs 

 frequently being present on the young shoots which do not persist 

 on the older stem. In prostrate vines, adventitious roots occur 

 at each node. 



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