ROOTS AND TUBERS WE EAT 189 



hardly claim it exclusively as an American plant. 

 It is one of those cosmopolitan "weeds," whose 

 value was independently discovered on both sides 

 of the globe, by hungry, primitive men, who nib- 

 bled any fleshy root that tasted good, and laid it 

 on the fire to soften it by roasting or parching. 

 The next step was to cultivate it. So the size 

 of the tubers has been increased and improved by 

 selection and better tillage, until we have almost 

 one hundred varieties to choose from, and tubers 

 weighing from one to twelve pounds are produced. 



The range of this tropical plant has been ex- 

 pended until any region that has a growing season 

 of four months free from raw winds and frost, 

 can raise the crop. The best soil is a loose, sandy 

 loam, well-drained. Growth must proceed with- 

 out interruption. 



The sweet potato plant is a creeping vine, related 

 to the bindweed, dodder, cypress vine, and morn- 

 ing-glory, as its coiling stems and trumpet-shaped 

 flowers prove. The seeds are borne in dry, two- 

 celled capsules, more familiar to us in the morning- 

 glory and moon-flower. Underground, the sweet 

 potato forms the tubers, which are true roots, not 

 stems, as in the "Irish" potato. No eyes are 

 seen on the sides or ends of the sweet potato, but 

 fibrous roots instead. The grower puts the tubers 



