On the submicroscopic structure of cuticular cell walls

By dissolving the cutin in hot alcoholic alkali, the cellulose “skeleton” from the cuticular layer of Clivia nobilis leaves has been isolated (fig. 2) and the fibril orientation therein has been determined (fig. 3). The form double refraction of wax-free cuticular membranes of Clivia nobilis indicates the presence of emptied oblong flat pores, tangentially oriented and with their major axis transversal (fig. 9). The wax platelets are mainly tangentially oriented too, but these probably have a preference for slight transverse inclinations (fig. 10). thus producing a corresponding double refraction in surface view. The cuticle sensu stricto, up till now considered isotropic, is birefringent too (fig. 6). After extraction or heat-destruction of true waxes the major part of the cuticular membrane still shows a faint double refraction with a radially oriented major refractive index (fig. 7). This is tentatively ascribed to chemically bound oriented wax molecules, lining the pore space (fig. 11). A similar state of affairs occurs in the cuticular membranes of Gasteria, Yucca, Dasylirion and Aloe.