cell wall: a rigid layer of polysaccharides enclosing the membrane of plant and prokaryotic cells; maintains the shape of the cell and serves as a protective barrier
layer: a relatively thin sheetlike expanse or region lying over or under another
castor-oil plant: large shrub of tropical Africa and Asia having large palmate leaves and spiny capsules containing seeds that are the source of castor oil and ricin; widely naturalized throughout the tropics