22. Lichen

A lichen is an example of a symbiotic relationship wherein a fungus and a photosynthetic organism, usually green algae or cyanobacteria, coexist and benefit from the other. The fungus receives a food supply from the photosynthesizer which in turn receives the water and nutrients absorbed by the fungus. Three different types of lichen can be seen on the chair above -- crustose, foliose and fruticose. The characteristics of these variations are; flat orange, thin leaf-like white and three-dimensional bristle-like, respectively.