Cetraria

Cetraria is a genus of lichen-forming fungi that includes several species of foliose lichens. The best known member is Cetraria islandica, commonly called Iceland moss. These lichens are primarily found in northern temperate and boreal regions of Europe, Asia, and North America, where they grow on rocks, soil, and mossy substrates in cool, humid environments. They are adapted to nutrient-poor substrates and can tolerate dry spells.

The thallus of Cetraria species is leafy and flattened, typically pale green to grayish in color, with lobed margins. Like other lichens, they represent a symbiotic association between a fungal partner (the mycobiont) and a photosynthetic partner (the photobiont), usually green algae. Reproduction occurs through fragmentation or via fungal sexual structures, and some species produce structures that aid in dispersal.

Cetraria lichens play roles in their ecosystems as primary colonizers of bare substrates and as components of lichen communities in boreal and Arctic habitats. They are sensitive to air quality and environmental changes, making them useful indicators of site conditions in some regions.

Uses and cultural significance: Iceland moss has a long history of use as a famine food in northern Europe and as an ingredient in traditional remedies. It has been processed into flour or beverages and used in herbal preparations for various ailments. In modern contexts, interest in Cetraria islandica is largely historical or ecological, with some applications in natural history and education.