Cup lichen (Cladonia sp.). The cup-like stalked structures 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. Lichen are classified according to morphology. Fruticose lichen, which include Cladonia species, are free standing lichen with erect strcutures. Some species of Cladonia lichen are important sources of food for caribou and other wildlife in tundra regions where food is scarce. Lichen reproduce both sexually and asexually.