What is the outermost covering of a plant cell?

The cell wall is a rigid layer that is found outside the cell membrane and surrounds the cell in plant cells. The cell wall contains not only cellulose and protein but other polysaccharides as well. The cell wall provides structural support and protection to the plant cell. 

The plasma membrane is the outermost covering of animal cells, while the outer membrane is a component of bacterial cells. Flagella are hair-like structures that are responsible for movement in some cells, but they are not a part of the outermost covering of plant cells.