feARK. 140 



their beauty. The fuci, a species of sea weed, and some oth- 

 er plants, appear to be altogether composed of cellular texture. 



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 called 

 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 ; it is here only, 

 that the essential vital functions are carried on ; this integu- 

 ment 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 principle, it becomes a lifeless crust. 

 The natives of Otaheite manufacture garments from the liber 

 of the paper mulberry. The liber of flax is by a mo re refined 

 process converted into fine linen. This part of the bark is im- 

 portant 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 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 organized, and which of course retains its vital pow- 

 er, 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 developement of buds, and the 

 growth of new radicles, the liber hardens and becomes lifeless 

 like that of the preceding year. 



Cortex, or true barkLiberAnnually renewed Girdling What ultimate- 

 ly becomes of the liber? 



13* 



