Collenchyma is a specialized supporting simple permanent tissue of living cells possessing characteristically unevenly distributed thickenings of cellulose, pectin and hemicelluloses on their walls. Schleiden (1839) discovered and coined the term collenchyma. Lamellar collenchyma is characterized by deposition of heavy thickenings in the tangential than in the radial cell walls, eg, stems of Sambuscus and Raphanus.