From Greek 'leikhen' (tree-moss), from 'leikhein' (to lick) — named for clinging closely to its surface.
A composite organism formed by a symbiotic relationship between a fungus and a photosynthetic partner (usually algae or cyanobacteria), typically forming a crust-like, leaf-like, or branching growth on rocks, trees, and walls.
From Latin 'lichēn,' from Greek 'leichḗn' (λειχήν, tree-moss, lichen; also a skin eruption, a spreading sore), from the verb 'leíchein' (λείχειν, to lick), from PIE *leyǵh- (to lick). The name refers to the organism's appearance of 'licking' or clinging closely to the surface it grows on — lichen hugs rock and bark the way a tongue licks skin. The same PIE root produced Latin 'lingere' (to lick), Old English
Lichens are so hardy they can survive in outer space. In 2005, the European Space Agency exposed two lichen species (Rhizocarpon geographicum and Xanthoria elegans) to the vacuum of space, cosmic radiation, and extreme temperatures aboard the BIOPAN facility for 15 days. Both species survived and