WOOD. 
10,0 
ieaves of a book. This substance, bv its development, pro- 
ducer new roots, branches, leaves, flowers, and fruits. 
a. It is composed of a kind of net-work, which has been compared to cloth ; the 
elongated fibers representing the warp, and the cellular texture the filling up. As 
the cambium descends between the liber and the wood, and a layer of new liber 
and of new wood are every year formed, the old layer is pushed outward, and at 
length, losing its vital principle, it becomes a lifeless crust. The natives of Ota 
heite manufacture garments from the liber of the paper mulberry. The liber of 
flax is, by a more refined process, converted into fine linen. This part of the bark 
is important to the life of vegetables ; the outer bark may be peeled off without 
injury to them, but the destruction of the liber is generally fatal. The operation 
of girdling trees, which is often practiced in new countries, consists in making, with 
an axe, one or more complete circles through the outer bark and the liber of the 
trunk. Trees seldom survive this operation, especially if it be performed early in 
the spring, before the first flow of the sap from the root toward the extremities. 
h. During the repose of vegetation, that part of the liber most recently organ- 
ized, and which of course retains its vital power, remains inactive between the 
wood and the outer layers of the bark, until the warmth of spring causes the ascent 
of the sap. After promoting the development of buds, and the growth of new 
wood and bark, the liber, like that of the preceding year, hardens and loses ita 
vital energy. 
k i h g hdca 
Fig. 125, at A, represents a young dicotyledonous stem, cut transversely; ihe 
inner circle surrounds the pith ; the wood extends to the bark, which at a appears 
darkly shaded. 
At B, is a section of the same stem magnified ; a his, the bark, h i the wood, 
and i k the pith. 
The divisions of the bark may be seen as follows : a c represents the cuticle, or 
Ihe dry, disorganized part ; aX c d is the cellular integument ; at d b is the cortex 
the extreme part of which, at b, is the liber. 
^ 128. Wood. The wood (lignum) of exogenous stems con 
sists of two parts, alburnum or sap-wood^ and perfect wood. 
The alburnum is so called from albus^ white, on account of tho 
paleness of its color. This is the newly formed wood, and con- 
stitutes the outer part of the woody substance of the plant. It 
IS at first soft and tender, and in this state appears to be active 
a. Liber annually renewed— Girdling— J. What nltiinately becomes of the liber T— 128. Wood 
Alburnwn. 
