2 BULLETIN 1041, U. S. DEPARTMENT OF AGRICULTUEE. 



The sweet potato {Ipomoea 'batatas) belongs to the same family bo- 

 tanically as the common morning-glory (Convolvulacese). Although 

 it frequently blossoms and even produces seed in the extrenie south- 

 ern portions of our country, propagation as practiced is not by the 

 use of seed but of slips and vine cuttings which are set in the field. 



In vine and leaf characters considerable differences are observed 

 among the varieties, some forming long trailing vines, while in 

 others the trailing habit is greatly restricted or almost entirely absent. 

 The shape and size of the leaves also differ widely, varying from the 

 small entire heart-shaped leaves, which closely resemble those of the 

 morning-glory, to large, shouldered, and even deeply cleft forms, 

 which bear little resemblance to those of their close relative. Con- 

 siderable variations both in size and shape often may be observed 

 upon the same plant. 



The edible portions of the plant are produced underground as 

 modified and greatly enlarged roots. True tubers, as found in the 

 case of the Irish potato, are never formed. Among varieties these 

 enlarged roots vary greatly in size, shape, color of the skin and of 

 the flesh, in sugar content, and in cooking and table qualities. In 

 contrast to the sweet potatoes usually seen in markets and retail stores 

 the edible roots in certain varieties may attain a length of 18 to 24 

 inches; in shape they vary all the way from long, cylindrical, root- 

 like forms to spindle-shaped and more or less globoid individuals; 

 and while in certain of the varieties the shape is more or less uniform, 

 in others wide differences are observed in the same plant. The size is 

 variable also, and in some instances individual roots may attain a 

 diameter of 4 to 6 inches, weighing from 5 to 6 pounds. The surface 

 may be smooth and regular, veined, or even deeply grooved. 



The color of the skin passes through all gradations from almost 

 white to cream, warm buff, cinnamon buff, and light Corinthian red 

 to dark vinaceous; and the flesh among the different varieties may 

 vary from almost white to carrot red in color. 



When freshly cooked, still further differences are observed. The 

 color of the flesh, which in the raw potato is more or less unevenly 

 distributed, appears more uniformly dispersed in the cooked potato, 

 which may assume cream, buff, empire yellow, orange, or other inter- 

 mediate colors, depending upon the varieties concerned. In some 

 there is a marked tendency to darken on exposure to the air, while in 

 others this is shown to a much less extent. 



The consistency, texture, flavor, and sweetness also show wide vari- 

 ations. These differences among the varieties, together with their 

 difference in behavior in storage, make the selection of suitable 

 varieties for table use, for the manufacture of numerous sweet-potato 

 products, for commercial storage and shipment, and for the produc- 



