16 SYLVA AMERICANA. 



the wood. In the older branches and trunks of trees, it consists 

 of as many layers as they are years old. 



The bark contains a great number of woody fibres, running 

 for the most part longitudinally, which give it tenacity, and in 

 which it differs very essentially from the other parts. These 

 woody fibres when separated by maceration, exhibit in general 

 a kind of net-work, and in many instances great regularity and 

 beauty of structure. 



In the bark the peculiar virtues or qualites of particular plants 

 chiefly reside, and more especially in several of its internal 

 layers nearest to the wood. Here we find in appropriate vessels 

 the resin of the fir and juniper, the astringent principle of the 

 oak and willow, on which their tanning property depends, the 

 fine and valuable bitter of the Peruvian bark, and the exquisitively 

 aromatic oil of the cinnamon. The same secretions do indeed, 

 more or less, pervade the wood and other parts of these plants, 

 but usually in a less concentrated form. 



4. The liber, which is the inner layer of the cortex or bark. 

 It consists of lamina, or plates, bound together by a cellular 

 matter, which, when dissolved by maceration in water, detaches 

 these plates or coatings from each other ; when they resemble 

 the leaves of the books of the ancients ; whence arose the name 

 of liber. The liber is softer and more juicy than the cortex. 



It is in this layer only that the essential vital functions are 

 carried on ; after a while it is pushed outward with the cellular 

 integument, by the successive formation of new layers, and with 

 the cellular integument finally becomes a lifeless crust. Grew, 

 Maipighi, Du Harnel and others, supposed that the liber annually 

 changes, by hardening, into the alburnum or young wood, an 

 opinion also maintained by Mirbel, and some of the ablest 

 philologists, but which is founded upon mistaken principles. It 

 is through the liber, however, that the matter in which the new 

 wood is formed, which annually augments the diameter of the 

 trunk and branches, is secreted ; and hence the importance of 

 this portion of the bark. 



As the net work formed by the dividing threads of the meshes 

 is not readily dissolved in water, while the cellular matter which 



