PROPAGATION OF WILD-DUCK FOODS. 



23 



Running around the body of the tuber are two or three darker lines 

 from which originate fibrous sheaths. A glance at the illustration of 

 the tubers (fig. 21) of this species shows the aptness of the name " wild 

 potato." It should be explained, however, that normally the tubers are 

 more widely separated than is the case with those on this particular 

 specimen, which was grown in a flower-pot. 



DISTRIBUTION. 



In ancient times the Mississippi River emptied into a vast bay 

 which extended at least as far north as the region now known as 



Fig. 21. — Tubers of delta potato. (About two-thirds natural size.) 



southern Illinois. Its actively growing delta (which is still appar- 

 ently in full vigor) made thick deposits of silt over some thousands 

 of square miles of this area while the remainder was being slowly ele- 

 vated. SagittaHa platyphylla is so nearly confined in its distribution 

 to this ancient basin, and is so characteristic of the present delta, that 

 the name delta potato is eminently fitting. The outlying points 

 of the range of the plant as now known are San Antonio, Tex., Lake 

 City, Mo., Chattanooga, Tenn., and Mobile, Ala. (fig. 22). 



