Is iridescence a material property?
Not directly. Iridescence is a consequence of the arrangement of material (thin layers) rather than its nature. Of course, the material must be at least somewhat transparent to light; the phone book might be made up of thin sheets, but it certainly isn’t iridescent. The composition of the cuticle is quite ordinary9: protein 50% carbohydrate 40% inorganic salts 5% fatty acids <1% The cuticle does not affect rates of photosynthesis or respiration. Why bother having one? Gerwick and Lang suggest it may help prevent desiccation and deter hungry herbivores. 8 In trouser tear tests, the cuticle rips in such a way as to increase the force necessary for propagation of a crack. Apparently the cuticle helps to prevent the thallus from tearing. More details to come.... Why is Iridaea more iridescent when wet than dry? The outer surface of the cuticle is composed of flake-like material. Water smoothes the flakes and allows a more uniform reflection of light rather than random scattering. Why is Ir
