Survey of Plant Kingdom 141 



Cuticle 



Epidermis 



Cork cambium 

 Rejin canal. 



Medullary ray !^ 



Cambium 



Stoma /Airspace 



Epidermis 



Resin ducfc 



__ Parenchyma 

 — Phloem 

 -_XyIem 



Cork 



,__Corbcx 



,__Phloem 



, — Xy/em 



;, Xylem 



Resin canal 



—^ndodertnis 

 — MesophyU 



_ SderQnchyma 

 Cuticle 



,-P;th 



Fig. 53. — Pine tree (Pinus sp.). A, One-half of a needle (leaf); B, a stem, 

 both in cross section and somewhat diagrammatically. Note there are two layers 

 of xylem (one for each year of stem growth) and that the outer cells of each 

 xylem represent fall wood, while the inner layers of each xylem represent spring 

 wood. The spring and fall growths of each xylem constitute an annual ring. 

 The sclerenchyma of the leaf is also known as mechanical tissue ; the mesophyll 

 contains chlorophyll and is called photosynthetic tissue. 



