THE SEEDLING AND YOUNG PLANT 



- m 



53 



FIG. 12. Transverse section of young stem, showingprimary 

 vascular bundles, &c., highly magnified, a and &, the 

 pith ; c, primary cortex ; i, epidermis ; k, periderm (cork); 

 g, collenchyma. Two complete primary vascular bundles, 

 and parts of two others, are shown, separated by the 

 primary medullary rays, r, spiral vessels (protoxylem) ; 

 ft, bast-fibres (protophloem) ; n, m, cambium, separating 

 the phloem from the xylem; p, wood-parenchyma. 

 Secondary medullary rays are seen in the bundles, as 

 also are pitted vessels of different sizes. (Th. Hartig.) 



