Noun

1. A thick, fairly rigid, layer formed around individual cells of bacteria, Archaea, fungi, plants, and algae (but not animals and other protists which generally have cell membranes without cell walls). The cell wall is external to the cell membrane and serves a structural function helping the cell maintain its shape and protecting the cell from damage.

Quotations

• 1876 — T. H. Huxley, "On the Border Territory between the Animal and the Vegetable Kingdoms", Littell's Living Age vol. 128, no. 1657.

  The name of Chlamydomonas is applied to certain microscopic green bodies, each of which consists of a protoplasmic central substance invested by a structureless sac. The latter contains cellulose, as in ordinary plants; and the chlorophyll which gives the green colour enables the Chlamydomonas to decompose carbonic acid and fix carbon, as they do. Two long cilia protrude through the cell-wall, and effect the rapid locomotion of this "monad," which, in all respects except its mobility, is characteristically a plant.

• 1947 — Arthur J. Eames & Laurence H. MacDaniels, An Introduction to Plant Anatomy, 2nd ed.

  The structural distinctiveness of the cell—in plants especially—is dues in large part to the presence of an outer layer, or coat, the cell wall, which in plants is usually firm, and often hard and thick; in animals, delicate or lacking.

• 1994 — Robert A. Blanchette, "Lignin biodegradation in cell walls of woody plants", pp. 55-65 in O. Petrini & G. B. Ouellette (eds.) Host Wall Alterations by Parasitic Fungi.

  Terrestrial vascular plants contain considerable quantities of lignin, an amorphous phenylpropanoid structural polymer that binds cell wall components and cell walls together providing structural stability to plants.

• 2000 — John L. Howland, The Surprising Archaea: Discovering Another Domain of Life, p. 70

  Think of the cell wall as a wicker basket in which a balloon has been inflated so that it exerts pressure from the inside. Such a basket is very rigid and resistant to mechanical damage.