Lichen on cinnamon tree trunks (Cinnamomum verum). Lichens are formed from the symbiotic association between a fungus and an alga. The alga is contained within the hyphae (filaments) of the fungus. They are therefore protected from harsh conditions and in particular from dessication. The alga supplies the fungus with nutrients that it makes by photosynthesis. Lichens are usually found growing on stones and the bark of trees. Photographed in Malaysia.