The definition of superimposed layers is given and the ecological significance of their main types such as hairs, wax bloom, and dust covers is summarised. The influence of such layers on the spectral properties of leaves is analyzed and compared using published and new data. Comparisions are made for the visible (400 to 750 nm) and the near infrared (750 to 1350 nm) wave lenghts. Wheigthed means of the spectral propcrties for a given distribution of spectral intensity of the global radiation are calculated. Epidermal hairs and wax bloom reduce the amount of absorbed global radiation mainly as the result of a much increased reflectivity in the visible wave range. For the near infrared region of the spectrum only little influence of hairs or wax bloom on the spectral properties of leaves is determinable. The lowered absorption of energy by leaves covered with hairs or wax bloom reduced heat input to the leaves and therefore a smaller rise of the leaf temperature above the air temperature is observed. The light reflected by the hairs or the wax bloom contributes to a better illumination of leaves in the shade of others. This diffuse reflected light may increase photosynthesis at least if the photosynthetic apparatus is not light saturated without this stray light. Dust layers, mainly if they are of a dark colour increase markedly the absorption of global radiation by the combination leaf-dust compared with a clean leaf. The major part of this increase occours for the infrared radiation. A higher energy input to the leaf from the absorbed additional global radiation and a rised leaf temperature are the result.