<P> Collenchyma is Greek word where "Collen" means gum and "chyma" means infusion . It is a living tissue of primary body like Parenchyma . Cells are thin - walled but possess thickening of cellulose, water and pectin substances (pectocellulose) at the corners where number of cells join together . This tissue gives a tensile strength to the plant and the cells are compactly arranged and have very little inter-cellular spaces . It occurs chiefly in hypodermis of stems and leaves . It is absent in monocots and in roots. Sometimes it contains chlorophyll which can help them photosynthesis . </P> <P> Collenchymatous tissue acts as a supporting tissue in stems of young plants . It provides mechanical support, elasticity, and tensile strength to the plant body . It helps in manufacturing sugar and storing it as starch . It is present in the margin of leaves and resist tearing effect of the wind . </P> <P> Sclerenchyma is Greek word where "Scleren" means hard and "chyma" means infusion . This tissue consists of thick - walled, dead cells and protoplasm is very less i.e. negligible . These cells have hard and extremely thick secondary walls due to uniform distribution and high secretion of lignin . Lignin deposition is so thick that the cell walls become strong, rigid and impermeable to water which is also known as stone cell or sclereids . This type of tissues are mainly of two divisions: 1) Sclerenchyma fiber and 2) Sclereids . Schlerenchyma cells have a narrow lumen and are long and narrow and unicellular . </P> <P> The entire surface of the plant consists of a single layer of cells called epidermis or surface tissue . The entire surface of the plant has this outer layer of epidermis . Hence it is also called surface tissue . Most of the epidermal cells are relatively flat . The outer and lateral walls of the cell are often thicker than the inner walls . The cells forms a continuous sheet without inter cellular spaces . It protects all parts of the plant . </P>

A tissue is formed of only one type of cell