In biology, the term cuticle or cuticula is given to a variety of tough but flexible, non-mineral outer coverings of an organism, or part of an organism, that provide protection. They are non-homologous, differing in their origin, structure and chemical composition.
The cuticles of plants function as permeability barriers for water and water-soluble materials. The cuticle both prevents plant surfaces from becoming wet and helps to prevent plants from drying out. Xerophytic plants such as Cactus have very thick cuticles to help them survive in their arid climates. Plants that live in range of sea's spray also tend to have thicker cuticles, to protect them from the toxic effects of salt.