The plant cell wall provides mechanical support and protection for the plant cell. It is composed principally of the polysaccharide cellulose. Adjacent plant cells are held together by a thin middle lamella composed of pectic substances that acts as glue. The cells are also interconnected by plasmodesmata, which are fine strands of cytoplasm that pass through pores in the cell walls and middle lamella, forming continuous cytoplasmic bridges between plant cells.