Hammered shield lichen (Parmelia sulcata), coloured scanning electron micrograph (SEM). 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. Parmelia lichen are classified as foliose due to their flat appearance and leaf-like structures. Fine cilia hairs line the edge of the lichen. Magnification: x14 when printed 10 centimetres wide.