268 



TEXTBOOK OF BOTANY 



STEM 



CORTEX 



PHLOEM 1936 

 1939 

 r940 



CAMBIUM 



XYLEM 1940 

 1939 

 1938 



ROOT 



Fig. 96. Diagram of relative positions of xylem and phloem in a 3-year-old stem 



and root. 



tlie phloem in the vems of these leaves. It is in this youngest cylinder 

 of wood each year that most of the water is pulled up the stem by 

 transpiration. Food translocation occurs mostly in the youngest phloem. 

 Girdling. As the term is used by botanists, girdling consists in com- 

 pletely removing a band of bark and cambium all the way around the 

 stem. If the girdle is made on the trunk of the tree within a few feet of 



