Cuticle

Cuticle, in the higher plants, is a continuous membrane extending over the whole epidermis, and consisting of a derivative of cellulose (q.v.) known as cutin, which becomes yellow on treatment with chlor-zinc-iodine (Schulze's solution). The cuticle originates from the outer or primary walls of the epidermal cells, the secondary thickening layers next beneath it being partly unaltered cellulose and staining darker, whilst the innermost and youngest layers are all cellulose and stain blue. This cuticle can be separated as a distinct membrane, but does not extend over hairs, and only a little way down into the entrance of the stomata. It often secretes wax, which may exude from it so as to form a glaucous or blue-grey "bloom." In most characters cuticle agrees with cork (q.v.).