LichenIreland :: Nephroma laevigatum © Mike Simms

What are lichens?

Lichens are a compound organism in which a fungus (called the mycobiont) lives together in symbiosis with an alga and/or cyanobacteria (called the photobiont, because it photosynthesises). Together each combination forms a stable identifiable entity, with both organisms benefitting from the association.

The algal and/or cyanobacterial cells are protected from drying out by the enveloping fungi, which also provides attachment to the rock, wood, soil or other substrate.

In return, the fungus receives nutrients from the alga, in the form of sugar made by photosynthesis.

Cladonia polydactyla © Robert Thompson Lobaria virens © Robert Thompson Limestone lichens © Mike Simms Candelariella medians © Mike Simms