Sieve elements are conducting elements of phloem. They are segregated into the less specialized sieve cells and more specialized sieve tubes. Sieve cells are commonly long and slender and they are tapering at their ends. In the tissue they overlap each other and the sieve area are usually numerous on these ends. The sieve tubes are formed by end to end fusion of cells called sieve cells. The sieve tubes are enucleate because the nucleus of sieve cells degenerate during maturation. Two adjoining end walls of neighbouring sieve cells form a sieve plate.