WOOD IN GENERAL 
The cambium is a continua- 
tion of the formative living 
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, such as palms, 
have nocambium. 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 
255 
Fic. 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.) 
