STEMS AKB THEIE APPENDAGES. 



55 



plants just before and at the time they commence their 

 growth in spring. It is of a mucilaginous nature, and 

 filled with cells that are actiyely assuming their more 

 regular and solidified form, as 

 found in the completed or ma- 

 ture wood. 



Outside and resting upon the 

 cambium layer, or partly im- 

 mersed, as it were, in it, we find 

 the liber, qr inner bark, which 

 in some kinds of trees, like the 

 Beech, is of a granular structure 

 and very brittle, while in others, 

 like the Papaw, Persimmon, and 

 Lindens, it is cloth-like and filled 

 with strong, tough fibres. Sur- 

 rounding the liber we find the 

 older layers of bark partaking 

 somewhat of the character of 

 the liber, but generally quite 

 porous, coarser, and of a more 

 brittle texture. The old bark of 

 trees often breaks up into deep 

 furrows, as on the stems of the 

 Chestnut and Elm, or cleaving 

 off in thin irregular plates, as 

 from the Plane or Buttonwood 

 tree, while in some it peels off in 

 lu the form of annular paper- 

 like rings, as in the Birch and 

 Cherry. This outer bark is 

 merely effete or. dead matter, an Fig. 14.— seedling oak. 

 excrescence of no further use to the tree than to cover 

 and protect the inner bark from the elements. 



The exogens are also called dicotyledonous plants, be-, 

 cause their seeds have two cotyledons, or seed-leaves, as 



