LICHENS Lichens are actually two organisms, fungi and a photosynthetic microorganism, living together. Typically, lichens are comprised of cyanobacteria or green algae in a mutualistic relationship with an ascomycete fungus. The algae contribute food from photosynthesis and the fungus contributes anchorage and water retention. The lichen body, called a thallus, can be found on bare rock, soil, hanging from trees, and many harsh living environments. Lichens are generally the first organisms to colonize cleared rock and soil surfaces after volcanic activity...