Pixie cup lichen (Cladonia asahinae) water repellence. Lichen are covered in a water-repellent coating. This prevents them from becoming waterlogged, which prevents the diffusion of gases for photosynthesis. Lichens are symbiotic organisms formed of a fungus and a photosynthetic partner that mutually benefit one another. Here, the photosynthetic partner is a scale-like alga (some seen at bottom right). It favours acid soil with lots of moisture, like roadsides and heath-land. It can grow up to 3 centimetres tall. The pixies cups were once collected to treat tuberculosis.