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Bearded lichen (Cladonia portentisa), coloured scanning electron micrograph (SEM). This species is common on bogs and heathland. The structures shown are fruiting bodies known as podetia. Lichens are organisms formed by the symbiotic association of a fungus and a green alga or cyanobacterium. They are able to produce nutrients through photosynthesis by the algal cells, and also absorb minerals from rainwater or acidic digestion of the substrate. Cladonia lichen are classified as fruticose due to appearance of free standing, erect structures. Magnification: x72 when printed 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/EYE OF SCIENCE/SCIENCE PHOTO LIBRARY)