THE SEEDLING AND YOUNG PLANT 53 
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Fi1ac.12.—Transverse section of young stem,showing primary 
vascular bundles, &c., highly magnified. a@ and 3, the 
pith ; c, primary cortex ; 7, epidermis ; h, periderm (cork); 
g, collenchyma. Two complete primary vascular bundles, 
and parts of two others, are shown, separated by the 
primary medullary rays. 7, spiral vessels (protoxylem) ; 
k, bast-fibres (protophloém); », m, cambium, separating 
the phloém from the xylem; p, wood-parenchyma. 
Secondary medullary rays are seen in the bundles, as 
also are pitted vessels of different sizes. (Th. Hartig.) 
