The hard, thick and dead covering outside the cell membrane of plant cells is called cell wall. It indicates cell boundaries. In 1665, Robert Hooke first observed the cell wall. In 1804, Carl Rudolf & F. Link proved that plant cells have cell walls. Cell wall is a unique feature of plant cells. The cell wall is formed at the beginning of the telophase phase of mitosis cell division. Animal cells, pollen and gametes do not have cell walls.