WOOD IN CENERAL 



255 



The cambium is a continua- 

 tion of the formative Uving 

 material out of which the 

 whole young shoot is devel- 

 oped. The living part of such 

 a tree as a maple or pine is 

 thus seen to be like a mantle 

 completely covering the older 

 wood and lining the older 

 bark, renewing each, some- 

 what as our skin and nails are 

 renewed. 



Some trees, sucli as palms, 

 have no cambium. The trunk 

 in such cases may be regarded 

 as a sheaf of numerous mixed 

 fibers embedded in pith, and 

 growing upward by additions 

 formed in the terminal mass 

 of living material from which 

 the continually expanding 

 terminal bud is derived. As 

 shown in Fig. 234, a cylindri- 

 cal shaft is the result, instead 

 of the tapering shaft formed 

 by concentric conical layers 

 where a cambium is present. 

 A stem made up of tough 

 strands thus embedded in 

 pith, forms a flexible column 

 often of considerable strength 

 as a whole, and therefore well 

 adapted to resist tropical gales 

 and carry aloft a heavy crown 

 of leaves, flowers, or fruit. At 

 the same time such a stem is 

 economically of some use as 

 a log in rough building, but 

 it does not make serviceable 



Fig. 234. — Diagram of palm stem 

 showing development, for com- 

 parison with that of maple. Cor- 

 responding material is shaded as 

 in the previous figure. Note the 

 absence of a cambium, and the 

 uniform diameter of the stem, 

 which is here surrounded en- 

 tirely by the bases of the leaves. 

 (Original.) 



