Suberized lamellae occur in all walls of the cells of the mestome sheath of wheat and oat leaves. These lamellae are perforated by plasmodesmata at all pit fields that they share with living cells. In maize, the walls of the parenchyma sheath ("starch sheath") contain similar suberized lamellae. The significance of these observations for solute and water exchange between the mesophyll and the bundle is discussed.