Timber: Structure of Trees

 From  the visibility  aspect, the structure of a tree can be divided into two categories 

1. Macro structure 

2. Micro structure 

1. Macro structure:  

         The structure of wood visible to the naked eye or at a small magnification is called macro structure. Figure shows the macro structure of exogenous tree.

Image source: http://4.bp.blogspot.com

(i) Pith:  

     The innermost central portion or core of the tree is called pith  or medulla 

(ii) Heart wood: 

    The inner annual rings surrounding the pith is known as heart wood. It imparts rigidity to tree

(iii). Sap wood:  

      The cuter annual rings between heart wood and cambium  layer is known as sap wood 

(iv) Cambium layer:  

      Thin layer of sap between sap wood and inner bark is known as cambium  layer 

(v) Inner bark:  

        The inner skin or layer covering the cambium  layer is known as inner bark  

(vi) Outer Bark:  

       The outer skin or  cover of the tree is known as outer bark 

(vii) Medullary rays:  

       The thin radial fibres extending from  pith to  cambium  layer are known as medullary rays

2. Micro strructure:  

      The structure of  wood apparent only at great magnifications is called micro structure under micro scope, it becomes evident that the wood consists of living and lead cells of various sizes and shapes.