The document summarizes the structure of a tree from the macroscopic level. It discusses that a tree consists of a trunk, crown, and roots. It then describes the main macroscopic components of a tree's structure: the pith, heartwood, sapwood, cambium layer, inner bark, outer bark, and medullary rays. The pith is at the center and nourishes the young tree, while the heartwood and sapwood make up the woody tissue, with the heartwood being the inner, non-living portions and the sapwood being the outer, actively growing portions. The cambium layer separates the sapwood from the inner bark and is responsible for growth.

1. TIMBER
STRUCTURE OF A TREE
A tree basically consist of three parts
- trunk
- crown
- roots
BY KIRTHIGA.E

2. From the visibility aspect ,trees are
divided into categories
1.MACROSTRUCTURE
2.MICROSTRUCTURE
 MACROSTRUCTURE:
 The structure of wood visible to the
naked eye or at a small magnification is
called the macrostructure.
 The components present in tree are as
follows:
1.Pith 2.Heart wood 3.Sap wood
4.Cambium layer 5.inner bark 6.Outer
bark 7.medullary rays.

3. PITH:
 The inner central portion central portion of
the tree is called pith or medulla.
 Varies in size and shape for different types
of trees.
 Consist of cellular tissues and nourishes the
plant in its young age.
 When they become old,pith dies up and
decays and the sap is then transmitted by
the woody fibres deposited roundthe pith.

4. HEART WOOD:
 The inner annual ring surrounding the
pith is the heart wood.
 Dark in colour.
 It indicates dead portion of a tree.
 It does not take active part in the growth
of a tree.
 It imparts rigidity to the tree and hence
provides strong and durable.

5. SAP WOOD:
 The outer annual rings between heart
wood and cambium layer is the sap wood.
 Light in colour and weight.
 Indicates growth and contains sap.
 Annual rings of sap wood are less sharply
defined than of heart wood.
 It takes active part in the growth of tree.
And sap moves upward direction.
 Also known as ALBURNUM.

6. CAMBIUM LAYER:
 The thin layer of sap between sap wood
and inner bark is the CAMBIUM LAYER.
 Indicates sap yet not been converted into
sap wood.
 If the bark is removed for any reason,this
layer get exposed and the cells resulting
in the death of tree.

7. INNER BARK:
 The inner skin covering the cambium
layer is known as the inner bark.
 It gives protection to the cambium
layer from any injury.
OUTER BARK:
 The outer skin of the tree is known as
the outer bark and also protective
layer.
 It contains cracks and fissures.
 It consist of cells of wood fibre,known
as cortex.

8. MEDULLARY RAYS:
-Thin radial fibres extending from pith to cambium is the
medullary rays.
-the function of the ray is to hold together the annual ring
of heart wood and sap wood.
-sometimes broken,in some varieties ,they are prominent.
Cross section of an
exogenous tree