THE ANGIOSPERMAE : STEMS 



865 



Periderm 

 Phloem 



Medullary ray 

 Cambium 



Second annual 

 ring 



First annual ring 



Fig. 850. — Tilia vulgaris. Transverse section of a 

 secondarily thickened stem showing Uvo annual 

 rings and early periderm formation. 



Transverse View 



Radial View 



Xylem 

 Vessel 



Medullary 

 Ray 



Tangential View 



Fig. 851. — Diagram showing a three-dimensional view of the 

 secondary xylem in an Angiosperm, illustrating the relation 

 of the medullary rays to the conducting elements. 



