102 THE SWEET POTATO. 



Fig. 17. Longitudinal section of old stem of Georgia. 



a. Epidermis. 



b. Hypodermis, 



c. Cortex. 



d. Latex canals. 



e. Endodermis. 



f . * Pericambium. 



g. Phloem. 



h. Vessel with reticulated thickenings, 

 i. Vessel with bordered pits, 

 j . Protoxylem. 

 k. Internal phloem. 

 1. Fundamental tissue. 

 Fig. 18. Crystal cells in longitudinal section of pith of Southern 

 Queen, weak type. 

 (In course of foi'mation) (?). 



a. Crystals. 



b. Protoplasm. 



c. Nucleus. 



d. Nucleolus. 



e. Double crystal. 



f. Crystal, isolated in the corner of a pith cell. 

 Fie. 19. Latex canals in Van Ness Red. 



a. In cortex of tip of stem. 



b. In pith of old stem. 



Fig. 20. Lenticel or proliferation of the epidermis of old stem of 



Georgia. 

 Fig. 21. A tuber of Red Jersey, fascicular type, smooth, with roots 

 coming off in vertical rows near lenticels. Lenticels not 

 conspicuous. 

 Fig. 22. A tuber of Florida, spherical, five-lobed, with roots coming 



off in the sunken areas. Lenticels conspicuous. 

 Fig. 23. A tuber of Up River, cylindrical, smooth, with lenticels 



inconspicuous. 

 Fig. 24. A tuber of Shanghai, with many conspicuous lenticels and 



long and large roots. 

 Fig. 25. a. A tuber of Belmont, with five longitudinal veins. 



Roots deeply sunk between the veins. Lenticels 

 scattered, inconspicuous, 

 b. Diagram of cross-section through tuber, showing 

 the five exterior bundles. 

 Fig. 26. A tuber of Pumpkin, showing anastomosing veins. Lenti- 

 cels conspicuous. 



