Summary According to earlier work, the lipidic suberin layers of cork cell walls are finely laminated: surface-parallel lamellae of suberin alternate with tilms of wax. This lamellar fine structure, which is easily seen in sections after staining with OsO 4 , can be made visible also with permanganate as a contrasting agent. Lipophilic OsO 4 penetrates readily into suberin layers. On the other hand, MnO 4 - ions infiltrate only slowly in an anisotropic fashion, in that MnO 4 - penetration in directions parallel to the wall surface is about 20 times faster than in perpendicular direction. As the diffusion coefficient of permanganate ions in the extremely hydrophobic wax films is only about 1 % of that in the semihydrophilic suberin lamellae, the anisotropic penetration of suberin layers is a consequence of their laminated fine structure. The excellent isolating properties of suberized cell walls (and cuticles, too) can easily be understood on the basis of these results. Some consequences are briefly discussed.