Building Material

 👉Classification of Tree

(a) Exogenous                               (b) Endogenous

⟶ Conifers (Soft Food) and Deciduous (Hard wood) are the types of Exogenous tree

👉Endogenous Tree 

• Trees grow inwards
• Example: Bamboo, Cane, Palm

👉Exogenous Tree 

• Trees grow outwards
• annual rings are used for predicting age of the tree

👉 Conifers (Evergreen trees)    

• Trees yield softwood
• Distinct annual rings

👉Deciduous or Broad leaf trees    

• Do not show distinct annual rings
• Trees yield hard wood
• Example: Teak, Mahogany, Sheesham, Oak, Sal, Babool

👉 Difference between Softwood and Hardwood 

                                         Softwood                             Hardwood

Colour :                              Lighter                                  Darker

Growth:                              Faster                                    Slower

Weight:                              Lighter                                  Heavier

Density:                             Low                                       High

Annual rings:                     Distinct                                 Indistinct

Strength:                      Strong along the grains               Strong along and across the grains

Conversion:                         Easy                                     Difficult

Fire resistance:                    Poor                                     Moderate             

👉Detailed Cross sectional view of the trunk of an exogenous tree

(a) Pith

• Innermost central portion or core of the tree called Pith or Medulla
• As the plant becomes old, the pith dies up and decays.

(b) Heartwood (Truewood)

• Inner annual rings surrounding the pith consistute the heartwood
• Dark in colour
• It indicates dead portion of tree

(c) Sap Wood (Alburnum or Xylem)

• Outer annual rings between heart wood and cambium layer in the sap wood
• It is usually light in colour and weight. It contains sap

(d) Cambium Layer

• Cambium is very thin layer of tissue between sapwood and inner bark

(e) Inner Bark (Phloem)

• It gives protection to the cambium layer from any injury
• Phloem transports food from leaves to the roots

(f) Outer Bark (Cortex)

• Outermost protective layer
• Consist of cells of wood fibre

(g) Medullary Ray

• Thin radial fibres extending from pith to cambium layer are known as medullary rays
• Function of these rays is to hold the annual rings tightly together