32 Plants and their Ways in South Africa 



time they lose their elasticity and become too small also. Just 

 underneath lie special cells which keep it renewed. Different 

 trees fashion theincork after different patterns. In Blue Gums 

 the renewing cells form long narrow plates, and the old tattered 

 garment is shed in long thin strips. In the oak and pine the 

 pieces are small and narrow but thick, while pieces of cork in 

 the wild olive are thin, small, and rough. Cork does not fall 

 off as fast as it cracks apart, but from a tree you can remove 

 layer after layer that have been formed in successive years. 

 This portion of the stem as far in as the cork is formed is 

 known as the outer bark. So long as the renewing cells, or 

 cork cambium, are not destroyed, cork may be removed 

 without causing the death of the tree, and so from the Cork 

 Oak, bottle cork is removed year after year. 



In this bark a substance called Tannin preserves the 

 wood from decay. Unfortunately for the tree, tannin is ex- 



FiG. 37. — Lenticels on ihe bark of Poplars, 



cellent for preserving leather also, and so the beautiful Protea 

 cynaroides, Linn., Leucospermum conocarpiim, R. Br. (Kreupel 



