864 



A TEXTBOOK OF THEORETICAL BOTANY 



Epidermis 

 Cortex 

 Endodermis 

 Medullary ray 



Phloem 

 Metaxylem 

 Protoxylem 

 Medullary ray 

 Pith 



I 

 I 



Fig. 848. — Tropaeolum mojus. Dicotyledon. Transverse 

 section of the stem showing a single ring of primary vascular 

 bundles separating the pith from the cortex. 



^MS^"' 



Cortex 



l_ Pericyclic 

 fibres 



Protophloem 



Metaphloem 

 Cambium 



Medullary ray 

 Metaxylem 



Pith 



Fig. 849. — Helianthus rigidus. Transverse section of a part of 

 a stem in an early stage of secondary thickening showing 

 the primary medullary rays crossed by the interfascicular 

 cambium. 



