264 VEGETABLE 



bon to form woody matter, and return the oxygen, by a pro 

 cess to be described hereafter. 



Liber. This is the inner portion of the bark, next to the 

 wood. It is generally white, and of a fibrous texture, when 

 examined by the naked eye ; but when seen through the mi- 

 croscope, it is found to consist of bundles of fibres running 

 in a waving direction, and touching each other only at 

 certain points, and forming oblong meshes which are filled 

 with cellular tissue. Their structure is represented by c, 

 Fig. 233. 



These longitudinal fibres are returning vessels, situated be- 

 tween the cellular integument above described, and the wood, 

 and are divided into meshes by the medullary rays, which 

 extend from the pith, through the wood into the bark, and 

 then push between these bundles of vessels, to reach the cel- 

 lular integument. 



It is this portion of the bark of certain trees which was 

 anciently used to write upon, and hence the name Liber, which 

 signifies " book." At the present day, the natives of the 

 South Sea Islands beat this substance into sheets, of which 

 they make clothing. The liber of the Lace-bark tree, (Daphne 

 lagetlo,) after being macerated in water, and beaten, forms a 

 beautiful gauze, which might be worn as a becoming article 

 of dress. 



The bark of the Oak, Chestnut, and many other trees, after 

 long exposure to the weather, presents a reticulated appear- 

 ance, caused by the waving directions of the vessels above 

 described. 



The inner bark is renewed every year, in conse- 

 quence of which the old layers are pushed outwards, and in 

 most trees, as in the Oak, Chestnut, and Elm, cracked into 

 longitudinal fissures. In some old trees, the bark thus be- 

 comes several inches in thickness, with wide and deep fis- 

 sures, which still retain more or less of their reticulated struc- 

 ture. In some trees, as the Plane, usually called the Button- 

 bail tree, the old bark splits in various directions, by the 

 force of the growing wood, and is thrown ofF every year. 

 In the Birch, the layers separate transversely, and being 

 tenacious, the old bark year after year hangs suspended to 

 the body of the tree, giving it that well known ragged ap- 

 pearance. 



Du Hamel demonstrated the fact, that trees renew their 

 bark annually, by passing a silver wire through the young 



