PERENNIAL DICOTYL STEM 



25 



Growth of Perennial Dicotyl Stem and its Histology. — A perennial 

 dicotyl stem in the first year does not differ in structure from an annual. 

 By the close of the year a cork cambium (phellogen) has originated be- 



Fig. 19. — Diagram similar to the preceding but representing a later stage and show- 

 ing the tissues formed by the cambium. {From Stevens.) 



side the epidermis. In origin of cork cambium — one of two methods: 

 (a) either the epidermis may divide into an outer layer of ceils that re- 

 mains epidermis and an inner layer of cells that becomes cork cambium, 



