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BARK. 
3d. Cortex. Immediately under the cellular integument, we 
find the true bark, which in plants that are only one year 
old, consists of one simple layer; but in trunks of older trees, 
it consists of as many layers as the tree has numbered years. 
The cortex is formed of bundles of longitudinal fibres cal- 
led cortical vessels. 
The peculiar virtues or qualities of plants chiefly reside in the 
bark. Here we find the resin of the fir, the astringent principle 
of the oak, and the aromatic oil of the cinnamon. 
The inner cortical layer is called the liber j it is here only, 
that the essential vital functions are carried on ; this integument 
is called liber, from its fine and thin plates, which are thought to 
bear some resemblance to the leaves of a book, which in Latin is 
liber. This substance by its developement produces new roots, 
branches, leaves, flowers and fruits. It is composed of a 
kind of net work, which has been compared to cloth ; the 
elongated fibres representing the warp and the cellular texture 
the filling up. It has been observed that the cambium descends 
between the liber and the wood, and that a layer of new liber is 
every year made from that liquid ; as the new layer is formed 
the old one is pushed outward, and at length losing its vital princi- 
ple it becomes a lifeless crust. The natives of Otaheite manu- 
facture 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 de- 
struction of the liber is generally fatal. The operation of gird- 
ling trees, which is often practised 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 have been performed early in the 
spring, before the first flow of the sap from the root towards the 
extremities. During the repose of vegetation, that part of the 
liber most recently organised, and which of course retains its vi- 
tal power, remains inactive between the wood and the outer lay- 
ers of the bark, until the warmth of spring causes the ascent of 
the sap. After promoting the developement of buds, and the 
growth of new radicles, the liber hardens and becomes lifeless 
like that of the preceeding year. 
WOOD. 
The wood (lignum) consists of two parts, alburnum or sap 
wood, and perfect wood. 
Cortex or true bark — Liber — Annually renewed — Wood of two parts — 
