APIUM GRAVEOLENS 



463 



limited, the leaf bases overlap one another in such a way that there 

 is little exposed epidermal surface. Buds occur in the axils of the 



m but. 



'-xy \ 



Fig. 137. Transection of mature stem showing sector of vascular cylinder and medullary- 

 bundles : ca, cambium; col, collenchyma; conj, conjunctive tissue; ep, epidermis; m hu, 

 medullary bundles in various stages of development ; mech, mechanical tissue ; gl, oil gland ; 

 far, parenchyma; ph, phloem; pi, pith; xy, xylem; xy 1, primary xylem; xy x, secondary 

 xylem. 



