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U.S. Forest Service

Lichens Glossary

Lichenologists use many unique terms to describe the structure and biology of lichens. Although we keep the lichen jargon to a minimum, there are some commonly used terms that you will see when looking at other lichen websites or books, as well as some used here.

apothecia - the most common sexual reproduction structure of the lichen’s fungal partner, it is cup-shaped or disc-shaped and produces spores.

Two pictures of lichen species: Ochrolechia africans and Rhizoplaca chrysoleuca, arrows pointing at their apothecia.

cephalodia - little pockets of cyanobacteria that form on top of a chlorolichen, normally black in color.

Peltigera britannica, an arrow pointing at the black dots on the green lichen that are the cephalodia.

chlorolichen - a lichen that has a green alga for its photobiont.

Two pictures of chlorolichen species: Hypogymnia physodes and Lobaria pulmonaria, text indicating to note the green lichen on the right (Lobaria pulmonaria).

cilia - little hairs on the margin of a lichen; for example, black hairs on the margins of a foliose lichen.

Parmotremia perforatum, an arrow pointing to the black hairs (cilia) on its margins.

cyanolichen - a lichen that has cyanobacteria for its primary photobiont.

Peltigera collina: text indicating to note the dark color due to the cyanobacteria.

hyphae (hypha) - the filamentous strands of fungal cells that make up the thallus of a lichen; they encapsulate the algal cells.

isidia - a vegetative means of propagation for lichens; normally found on the top-side or outer cortex of the lichen; both fungal and algal cells are combined in a column-like structure that can break off and establish elsewhere.

Coccocarpia parmicola, an arrow pointing to columns of fungus and alga (isidia) on its surface.

lichenized - a fungus, alga, or cyanobacterium that is in a lichen partnership.

lobe - a flattened branch, generally found on foliose lichens.

Pictures of Pseudocyphellaria rainierensis, arrows pointing at the lichen's lobe and lobules.

lobule - a vegetative means of propagation for lichens; small lobe-like two-sided propagules that break off and reestablish elsewhere.

macrolichen - a foliose or fruticose lichen; physical features are seen with the naked eye.

Pictures of a macrolichen, Solorina crocea, and a microlichen, Haematomma accolens.

microlichen - a crustose or squamulose lichen; physical features are difficult to see with a naked eye and a microscope is required for identification.

mycobiont - the fungal partner of a lichen.

photobiont - the photosynthetic partner of a lichen.

soredia (soralia) - a vegetative means of propagation for lichens. Both fungus and alga are intertwined into a granule-like mass that occurs on top of the cortex and on the margins. Some lichens have structures called soralia that produce soredia.

Peltigera didactyla, an arrow pointing to white soralia on the cortex of the lichen that are full of soredia.

spore - in lichens, produced by the mycobiont only for sexual reproduction; a tiny uni- or multi-cellular structure that gives rise to another fungus; no photobiont is included within the spore.

microscopic view of Pertusaria tetrathalamia spores.

squamules (squamulose) - small foliose lichen structures that are attached to their substrate by one end, like a shingle; several of these structures will comprise a lichen.

Psora pseudorussellii, an example of a squalmose lichen entirely made of squamules; and a Cladonia polycarpoides, displaying the primary thallus is made of squamules (green with white undersides) and the secondary thallus is fruticose (stalk with brown tip).

symbiosis - a relationship between two or more organisms in which at least one organism benefits from the other.

thallus (thalli) - the vegetative body of the lichen, composed of both fungus and alga.

tomentum (tomentose) - colorless hyphae that look like short fuzz or hairs on the outside of the lichen.

Nephroma resupinatum, an arrow pointing to the white fuzz (tomentum) on the cortex of this cyanolichen.

Additional Lichen Resources…