B A R K 



265 



showing the location of the cambium and the differenl 

 tissues found in the xylem and phloem strands (Pig. 408). 

 It maybe though! best to precede this experimenl with a 

 similar study of two-year-old stem of moonseed, ivy or 

 other vines. 



430. BARK. In mosl woodj plants that pari of the 

 stem which is outside the cambium ring is called bark. 



in;. White pine stem d The outermost layer is hurk 



At firsl it contains the epidermis or outer layer of cells, 

 the phloem ;iih| the cortex lying between the epidermis and 

 the phloem. The gradual growth of the Btem causes the 

 outer dead layers of bark to crack more or less irregularis 

 and finallj to splil off. Examples of this can be seen ou 

 the trunks of anj large trees. Before the tree is man) 

 years old the cortical cells of the bark become much 

 crushed and are lost to view. The epidermis is shed 

 ral her earlj in t lie life of t lie 1 1 



