Lichens

Lichens are a symbiosis of fungi and unicellular algae.

The fungus provides a protected living space and continous supply with water and mineral nutrients to the algae, the algae provides carbohydrates from photosynthesis in return. Lichens often grow slowly, colonizing very rough and hostile stands. Because they often are sensitive to various air pollutants, the absence or presence of certain lichens gives information about air quality. The figure shows Pseudevernia furfuracea.