Air-cells

Air-cells, or preferably AIR-SPACES, in plants, are cavities containing air in the stems or leaves, which aid greatly in effecting the interchange of gases necessary for the life of the plant. They consist for the most part either of the intercellular spaces, or of cavities formed by rupture, as in grass and umbelliferous stems. In terrestrial plants they communicate with the exterior by means of the Stomata (q.v.). An interchange is thus established between the living cells of the plant and the outer air, and this is helped by movements due to wind, by changes of temperature, and the like. They are especially large and numerous in many Aquatic Plants (q.v.) which are partly or entirely floating—mainly owing their buoyancy to this cause.