Polarised light micrograph of a covering scale from the underside of the leaf of the a buckthorn (Hippophae rhamnoides). The different colours are result of the polarized lighting .The undersides of the leaves of sea buckthorn plants are completely covered with these parasol-shaped scales to minimise evaporation through the stomata. These xeromorphic plant parts are found on very many plants that live on dry and/or strongly windy sites. Magnification: x200 at a print width of 10 centimetres.