THE BAKK. 



25 



Section 2.— The Bark. 



45. The bark lies immediately beneath the epidermis. It 

 consists of several layers. In the early state it is entirely cel- 

 lular, and is exactly like the pith with which it is in contact ; 

 but by the production of vessels and woody fiber, they are sepa- 

 rated and become very different in appearance and constitution. 

 The bark consists of two portions, the cellular and vascular, 

 the latter of which is called Hber, and is the inner portion of 

 the bark. The cellular portion is usually divided into two por- 

 tions. The outer portion is called the suberose or coi-ky layer^ 

 or Epiphloeum, Fig. 22 e^. It is composed of cubical or flat- 



Fig. 22. 



jtti* 



« — the pith ; m— medullfiry sheat 

 dad — dotted ducts; c — canibiim; h — liber; ce — mesophloc 

 ura; ep— epiphloeum; e—cpide 



w ID w — woody fiber ; 

 — mesophl 

 mr — medullary rays. 



tened cells,. having no coloring matter within them, but turning 

 brown by age. It is sometimes composed of a single layer of 

 cells, at others it is produced in great quantities, as in the Cork- 

 tree. The form of the cells makes it easy to distinguish it from 

 the subjacent layer. 



The inner cellular layer of the bark is callo'l the mesophlocum, 

 Fig 22 ce. It consists of prismatic cells, usually inclosing the 

 green coloring matter that gives color to the young stem. It 

 lies looser than the suberose layer, and is largely developed in 

 the coniferce. The lactiferous tissue is found beneath this layer. 



46. The epidermis, cellular integument, and liber, may be 



Into how nmny portions is the ocl- 

 lavcr. Wluit is tlie inner cclliihir 



45. Of what does the bark consist? 

 luhir divided ? Describe the suberose layer. Wluit is the inner colliilar 

 laytr called ? Describe ir. — 40. Where may the several parte of the bark be 

 seen ? How often are they formed ? 



