THE SEEDLING AND YOUNG PLANT 



69 



ness or breadth of the bundles at different points, such 

 as where other bundles join or leave them. As the 



FIG. 18. Longitudinal radial section of the cortex and 

 phloem of oak. References as in fig. 17. (Luerssen.) 



leaf- trace passes into the venation of the leaf the ends 

 become thinner (fig. 21), and the same is found as it tails 



