This glossary provides an overview of terms used in the description of lichens, composite organisms arising from algae or cyanobacteria living symbiotically among filaments of multiple fungus species.
Erik Acharius, known as the "father of lichenology," coined many lichen terms still in use today around the turn of the 18th century. Before that, only a couple of lichen-specific terms had been proposed. Johann Dillenius introduced scyphus in 1742 to describe the cup-shaped structures associated with genus Cladonia, while in 1794 Michel Adanson used lirella for the furrowed fruitbodies of the genus Graphis. Acharius introduced numerous terms to describe lichen structures, including apothecium, cephalodium, cyphellae, podetium, proper margin, soredium, and thallus. In 1825, Friedrich Wallroth published the first of his multi-volume work Naturgeschichte der Flechten ("Natural History of Lichens"), in which he proposed an alternative terminology based largely on roots from the Greek language. His work, presented as an alternative to that of Acharius (of whom he was critical) was not well received, and the only terms he proposed to gain widespread acceptance were epi- and hypophloeodal, hetero- and homoiomerous, and gonidium, the last of which remained in use until the 1960s. Until about 1850, there were 21 terms for features of the lichen thallus that remain in use today. The increasing availability of the optical microscope as an aid to identifying and characterizing lichens led to the creation of new terms to describe structures that were previously too small to be visualized. Contributions were made by Julius von Flotow (e.g. epithecium), Edmond Tulasne (e.g pycnidium), and William Nylander (e.g. pseudocyphella, thecium). Gustav Wilhelm Körber, an early proponent of using spore structure as a character in lichen taxonomy, introduced amphithecium, muriform, and "polari-dyblastae", later anglicized to "polari-bilocular" and then shortened to polarilocular. In the next five decades that followed, many other additions were made to the repertoire of lichen terms, subsequent to the increased understanding of lichen anatomy and physiology made possible by microscopy. For whatever reasons, there were not any new terms (still currently used) introduced from the period 1906 to 1945, when Gustaf Einar Du Rietz proposed replacing epi- and hypothecium with epi- and subhymenium; all four terms remain in use. In some cases, older terminology became obsolete as better understanding of the nature of the fungal–algal relationship led to changes in their terminology. For example, after Gunnar Degelius objected to the use of gonidia for the algal partner, George Scott proposed the use of mycobiont and phycobiont for lichen components, recommendations that were generally accepted by lichenologists. This glossary includes terms defining features of lichens unique to their composite nature, such as the major components the two major components of lichens (mycobiont and photobiont); specialized structures in lichen physiology; descriptors of types of lichens; two- and three-dimensional shapes used to describe spores and other lichen structures; terms of position and shape; prefixes and suffixes commonly used to form lichen terms; terminology used in methods for the chemical identification of lichens; the names of 22 standard insoluble lichen pigments and their associated reference species; and "everyday" words that have a specialized meaning in lichenology. The list also includes a few historical terms that have been supplanted or are now considered obsolete. Familiarity with these terms is helpful for understanding older literature in the field.
A
a- Also an-. A prefix meaning "not having" or "without".
ab- A prefix meaning "positioned away from".
abortive Referring to a developmental process in lichens where certain structures, such as spores or reproductive organs, fail to reach full development or maturity, often resulting in non-viable or malformed structures.
abraded Having a worn or eroded thallus surface.
accessory substance A lichen product that is sometimes present, sometimes not present in a species. In literature, these are usually indicated with a ± symbol, e.g. ±usnic acid.
-aceae A suffix used to indicate the taxonomic rank of family.
-aceous A suffix used to indicate a relation or similarity to something.
acervulate Shaped like a saucer.
acicular Also aciculiform. Needle-shaped; long and slender with a taper at both ends. Typically used to describe spore shape.
acro- Also acr-. A prefix used to indicate that something is positioned on the end or the upper part.
acrogenous Developing on the apex of a structure.
acroton A needle-shaped structure with lateral branches.
actinolichen A lichen-like association between an actinobacterium (Streptomyces) and a green alga (Chlorella xantha).
acuminate Gradually tapering to a point.
ad- A prefix used to indicate positioning at the end or on an extremity.
adglutinated Stuck together.
adnate Having a tight attachment to a surface.
adventive branching Referring to fruticose lichens, a branching pattern that is unusual or abnormal, like that which sometimes occurs after the original branches are damaged in Cladonia.
-al A suffix used to indicate a relation to, or having the form and character of something.
alectorioid lichen An informal growth form category used for lichens that are fruticose, typically with beard-like thalli that are pendant or clustered; this group of features is characteristic of lichens now classified in the genera Alectoria, Bryoria, Oropogon, Pseudephebe, and Sulcaria.
algal layer Also photobiont layer. The layer of tissue in a heteromerous lichen thallus that contains the photobiont; it is typically located between the upper cortex and the medulla.
alcobiosis Plural alcobioses. A form of symbiosis involving algae and corticioid fungi, primarily occurring on bark and wood surfaces. In this relationship, algae form a layer beneath the fungal basidiomata—structures akin to the photobiont layer in lichens. This association, unlike in lichens, does not render the fungal partner nutritionally dependent on the algae, thus all involved fungal species are capable of surviving without the algal partner. Alcobiosis represents a diverse interaction, seen in various stages of coevolution, involving multiple species across the Agaricomycetes fungal group and three algal species from the class Trebouxiophyceae.
alveolate Used to describe a surface that has a pattern similar to a honeycomb (i.e. with more or less 6-sided hollows), where the surface appears to be composed of small pits or cavities like alveoli. Compare: faveolate, foveolate, scrobiculate.
amphi- A prefix used to indicate on both sides, or on all sides.
amphithecium Plural amphithecia. The thalline margin of a lecanorine apothecium; equivalent to the thalline exciple. The amphithecium usually contains algal cells. The term was coined by Wilhelm Körber in 1855, but languished in obscurity until 1898, when Otto Darbishire used it in a monograph of the genus Roccella.
ampliotremoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus morphology. Ampliotremoid lichens have prominent apothecia with wide pores, black walls (viewed in microscopic section), and a smooth, more or less shiny thallus; this morphotype occurs in the genera Ampliotrema and Ocellularia.
ampulliform Bottle-shaped, i.e., with a narrow neck and swollen base.
amyloid
Turn a purple or blue color upon reaction with Melzer's reagent.
anisotomic Also anisotomous. Having branches of unequal length; if the branching is anisotomic, one branch is typically stouter than the other, forming a main stem while the other appears like a lateral branch, as in the species Alectoria ochroleuca. Contrast: dichotomous.
annulotremoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus morphology. Annulotremoid lichens have prominent apothecia with wide pores, pores with an inner ring, and a smooth, more or less shiny thallus; this morphotype occurs in the genera Myriotrema and Thelotrema.
anticlinal Perpendicular to a surface; used to refer to hyphal alignment.
apical Located at the highest point (the apex), the tip, or the end of something.
apiculate Having a short projection (an apicule) at one end; typically used to describe spore morphology.
apothecium Plural apothecia. A type of ascocarp that is open, saucer-shaped or cup-shaped, and in which the hymenium is exposed at maturity. The term was first used by Erik Acharius in 1803.
appressed Lying flat; flattened down on a surface.
arachnoid Also arachnoidal, araneose, araneous. Having a cobweb-like form, like that of the irregularly oriented and loosely interwoven hyphae of the medullary layer of some lichens.
Arceutina-yellow A pale yellow insoluble lichen pigment, associated with the reference species Bacidia arceutina.
arcuate A shape or structure that is curved or arched like a bow.
ardella Plural ardellae. A type of apothecium, typical of lichens in the family Arthoniaceae, which is small and round. Elongated ardellae are called lirellae. The term was first used by William Allport Leighton in 1854, who described an ardella as resembling a "sprinkled spot".
areole Plural areoles. Also areola with plural areolae. A small area, typically rounded to polygonal or irregular in shape, and often with a distinct texture. In a lichen thallus, the areolae are often separated from the rest of the thallus by fissures or cracks.
areolate Also areolar. The condition of being made of or covered with areolae, such as the areolate lichens.
Arnoldiana-brown A reddish-brown insoluble lichen pigment, associated with the reference species Bacidina arnoldiana.
ascigerous Having asci.
asco- A prefix meaning "ascus".
ascocarp
Also ascoma, plural ascomata. The fruiting body of an ascomycete fungus, containing the asci and ascospores.
ascoconidium Plural ascoconidia. A conidium that is formed directly from an ascospore.
ascogenous Also ascogenic. Producing or supporting the growth of an ascus.
ascogonium Plural ascogonia. The cell or group of cells within an ascocarp from which the asci (spore-producing cells) ultimately develop.
ascolichen A lichen in which the fungal partner (the mycobiont) is a member of the Ascomycota. About 98% of lichens are ascolichens. See related: basidiolichen.
ascospore A sexual, haploid spore produced in an ascus.
ascus
Plural asci. A sexual, fungal spore-bearing structure, typically sac-like.
aseptate Lacking septa.
aspicilioid Referring to lecanorine apothecia that are (at least initially) partially to completely immersed in the thallus.
astomate Also astomous. Lacking an opening, or ostiole.
astrothelioid Referring to a type of ascospore morphology prevalent in the genus Astrothelium; characterized by thick-walled distosepta and diamond-shaped lumina.
-ate A suffix, added to nouns, used to indicate having the appearance or characteristics of that noun.
Atra-brown A matt brown insoluble lichen pigment, associated with the reference species Opegrapha atra.
Atra-red A dark red insoluble lichen pigment, associated with the reference species Tephromela atra.
aulaxinoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus structure. This term refers to a morphotype of lichen where the apothecia are partially embedded and partially protruding, having a dark, hardened thalline margin that forms irregular cracks. This morphotype is uniquely seen in "Thelotrema" dislaceratum, a species with uncertain taxonomic placement.
B
bacillar Also bacilliform, baculate, baculiform. Shaped like a small rod, typically with a length:width ratio of about 3:1.
Bagliettoana-brown A pale to brownish-green insoluble lichen pigment, associated with the reference species Bacidia bagliettoana.
basidiolichen
A lichen in which the fungal partner (the mycobiont) is a member of the Basidiomycota. About 0.4% of lichens are basidiolichens. See related: ascolichen.
bi- A prefix meaning two or twice.
biatorine A type of lecideine apothecium with a soft, light-colored (not carbonized) margin, like those in genus Biatorella.
bifurcate Divided into two parts or branches. See related: dichotomous.
bifusiform Referring to a shape or structure that is elongated and tapers at both ends, with a constriction or narrowing in the middle. See related: fusiform.
biguttulate Containing two oil droplets (guttules).
bilabiate Referring to a type of ascus in which the ectotunica splits at the top and exposes the endotunica by forming an opening with a lip on each side; bilabiate asci occur in the genus Pertusaria.
bipartite lichen A lichen with a two-partner symbiotic association of mycobiont and photobiont. See related: tripartite lichen.
bipolar lichen A lichen that occurs in polar areas of both the Northern and Southern Hemispheres.
biseriate Lined up in two parallel rows.
bitunicate Also defined: endotunica, ectotunica. A type of ascus that has two functional layers, the internal layer, the endotunica, and the external layer, the ectotunica. Bitunicate asci are characteristic of the historical class Loculoascomycetes.
blastidium Plural blastidia. A rounded granule-like propagule containing mycobiont and photobiont, produced from the thallus margin by budding; subsequent blastidia are formed from the tips of the previous ones. The term was introduced by Josef Poelt in 1980.
borderline lichen
A symbiotic interaction where either green algae or cyanobacteria are enveloped by fungal tissue, but without forming the discrete layers that occur in most lichens.
botryose Resembling rounded, bead-like structures or clusters resembling grapes.
branch A lateral growth of the main stem of a thallus in usneoid lichens; various features of a branch are diagnostically valuable in distinguishing species.
branchlet A small branch.
bryophilous lichen
Also defined: hepaticolous lichen; muscicolous lichen. A lichen that grows on a moss or liverwort – i.e. on a bryophyte. A hepaticolous lichen is found only on liverworts, while a muscicolous lichen is found only on mosses.
bullate Having blister-like or bubble-like swellings on a surface.
byssoid Having the texture of cotton; made of loosely intertwined hyphae. See related: arachnoid, floccose.
C
C test A spot test that uses a solution of bleach (sodium hypochlorite) as a reagent to check for the presence of certain lichen products.
Caesiocinerea-brown An insoluble lichen pigment, colored olive to sordid green to black, associated with the reference species Aspicilia caesiocinerea.
caesious A bluish-gray or bluish-green coloration.
caespitose Also caespitous, cespitose. Growing in dense clusters or tufts, often used to describe fungi that arise from a common base or grow closely together without fusing.
calcicolous lichen A lichen that grows on substrates rich in calcium carbonate, such as calcareous or gypseous rocks or soil.
calcifuge A lichen that prefers acidic soils and tends to avoid, or is intolerant of, alkaline conditions often associated with high calcium carbonate content; opposite of calcicole.
campylidium Plural campylidia. A helmet-shaped conidioma. They are found in several genera of tropical foliicolous lichens, such as Badimia, Loflammia, and Sporopodium. The term was introduced by Johannes Müller Argoviensis in 1881.
canaliculate Having one or more longitudinal grooves or channels.
capitate Having a well-formed head, usually spherical or hemispherical in shape. See related: fuscocapitate.
capitulum Plural capitula; also sphaeridium/sphaeridia. A more-or-less spherical or cup-shaped apothecium on the top of a stalk, found in the genera Calicium and Chaenotheca. See related: mazaedium.
carbonized Also carbonised, carbonaceous. Blackened and brittle tissue resulting from the accumulation of pigments.
cariose A lichen thallus or structure that is cracked, split, spongy, or otherwise decayed or in a state of disintegration.
cartilaginous Also (in taxonomic names) cartilagineus. A term used to describe the texture of certain parts of a lichen. Cartilaginous structures have a texture similar to animal cartilage – firm but somewhat pliable, not brittle or soft.
cataphysis See pseudoparaphysis.
catapyrenioid lichen A member of the Verrucariaceae that is squamulose, has simple ascospores (without any septa), and lacks algae in the hymenium; historically classified in the genus Catapyrenium.
catenate Arranged in chains or end-to-end; refers to spore arrangement.
caudate Having a tail or tail-like appendage.
cavernula Plural cavernulae. A small hollow or cavity; used to refer to the holes in the lower cortex of the genus Cavernularia.
central axis Also chondroid axis. The cartilage-like central core in the branches of usneoid lichens, made of longitudinally arranged hyphae. The term "chondroid axis" was first used by William Nylander in 1858.
cephalodium
Plural cephalodia. A small gall-like structure that contains cyanobacteria, found in some lichens. These structures can be located on the lichen's upper or lower surface, or within the thallus itself. These structures are found in most lichens that contain both algal and cyanobacterial photobionts. The term was first used by Erik Acharius in 1803.
cerebriform Having a surface texture that is deeply wrinkled or convoluted in a manner resembling the structure of a brain. The term is used to characterize the appearance of certain lichens with a complex, highly folded thallus.
cetrarioid lichen An informal growth form category used for lichens with erect, foliose thalli, and apothecia and pycnidia on the margins of the lobes; characteristic of lichens previously classified in the genus Cetraria (in the broad sense).
chalaroplectenchyma Plural chalaroplectenchymata. A type of plectenchyma comprising loosely interwoven hyphae with holes; found in the medulla of some lichens.
character A distinguishing feature that is characteristic for an organism; equivalent to phenotypic trait.
chasmoendolith Also chasmoendolithic. A type of organism, typically a lichen or fungus, that lives within cracks and fissures of rocks. See related: endolith.
checklist A list of all of the species (sometimes including subspecies, varieties and forms) that occur within a particular region.
chemosyndrome A set of lichen products produced by a species; this typically includes one or more major compounds and a set of biosynthetically related minor compounds.
chemotype
Chemically differing types of a species with the same morphological characteristics, of no or unknown taxonomic significance.
chlorococcoid A term describing green algae with a coccoid shape.
chlorolichen A lichen containing green algae (Chlorophyta) as its primary photobiont. The term serves as a counterpart to "cyanolichen" (lichens with cyanobacterial photobionts) and is preferred over the historically ambiguous term "phycolichen". It refers to the vast majority of eukaryotic lichen photobionts which belong to the division Chlorophyta.
chondroid axis See central axis.
chroodiscoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus structure. Chroodiscoid lichens have open apothecia with recurved lobules and a smooth and more or less shiny thallus; this morphotype occurs in the genera Acanthotrema and Chapsa.
cilium Plural cilia. Fine, hair-like outgrowths of the thallus or apothecium, common in foliose and fruticose lichens.
ciliate Having cilia.
Cinereorufa-green A green to turquoise insoluble lichen pigment, associated with the reference species Schaereria cinereorufa.
citriform A shape or form that resembles a lemon or citrus fruit. The term is used to describe structures, particularly ascospores or other components of a lichen, that have an elongated, oval shape with tapered ends.
CK test A seldom-used spot test performed with an application of C followed immediately by K.
cladoniiform lichen Also cladoniform lichen, dimorphic lichen. Also defined: primary thallus and secondary thallus. A lichen with a two-fold growth form that includes both a crustose, squamulose, or foliose form and a fruticose form; the thallus differentiates into both horizontal (primary thallus) and vertical (secondary thallus, or podetium) structures. Cladoniiform lichens occur in the families Cladoniaceae and Baeomycetaceae.
clavate Also claviform. A shape resembling a club, broader at one end and tapering towards the other; typically used to refer to ascospores and asci.
clypeate See peltate.
coalescent Also coalesced. Growing together to form one mass.
coccoid Spherical; resembling a coccus.
collar In some Leptogium lichens, a ring at the apex of the apothecium made up of one, occasionally up to three, continuous lamellar folds encircling the disk; these folds may arise from laterally fused lobules and are distinct from separate, true lobules.
colloplectenchyma A type of apothecial tissue made up of slightly rounded cells with somewhat thickened walls, resembling the angular collenchyma of vascular plants; distinguished from paraplectenchyma, which consists of thin-walled, parenchyma-like cells.
columella
A sterile, central column of tissue that extends upward within some lichen fruiting bodies (such as mazaedia or perithecia), typically from the base toward or to the apex.
complanate Flat and smooth.
concolorous Having the same color throughout.
confervoid Appearing loosely filamentous or thread-like.
confluent Joining together, blending into one.
conidiophore A specialized hyphal structure that produces and bears conidia.
conidium
Plural conidia. Also conidiospore. A fungal asexual spore produced by mitosis in specialized structures such as pycnidia and campylidia.
conglutinate Also conglutinated. Stuck or glued together; usually applied to hyphae or paraphyses.
consoredium An aggregation or cluster of incompletely separated soredia. The term was introduced by Tor Tønsberg in 1992.
coralloid Highly branched, similar to a coral in form.
coriacellate With a somewhat leathery (coriaceous) texture.
coriaceous With a leathery texture.
corrugate Wrinkled; with alternate furrows and ridges.
cortex
The lichen's outer layer(s), made up of tightly woven fungal filaments.
corticate Also cortical. Having a cortex.
corticolous lichen
A lichen that grows on bark.
crateriform Shaped like a bowl or a crater; hemispherical and concave.
crenate Having a scalloped or round-toothed edge.
crenulate Having a finely scalloped edge; similar to crenate but with smaller notches.
cruentodiscoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus morphology. Cruentodiscoid lichens have open apothecia with erect lobules and a pigmented disc, and a smooth, more or less shiny thallus; this morphotype occurs in the genus Chapsa.
crustose
A form of growth where the lichen is pressed so tightly against the substrate upon which it grows that it is impossible to remove without destroying either it or part of the substrate. Crustose lichens have a cortex only on their upper surface.
cryptoendolith Also cryptoendolithic. A type of organism, particularly certain lichens and fungi, that live inside rocks or in the microscopic spaces within the mineral grains of rocks. See related: endolith.
cryptolecanorine A lecanorine apothecium that is mostly immersed in the thallus, with an indistinct thalline margin.
cryptothalline Pertaining to a type of lichen thallus that is largely hidden or immersed within the substrate, making it barely visible or entirely concealed. See related: chasmoendolithic, cryptoendolithic, endolithic. Contrast: euthalline.
crystallocumuli Punctiform or elongated agglomerations of oxalate crystals that are dispersed over the thallus; associated with the family Porinaceae. See related: crystallostratum.
crystallostratum A continuous layer of oxalate crystals embedded in the thallus, associated with the family Porinaceae. The term was introduced by Josef Hafellner and Klaus Kalb in 1995. See related: crystallocumuli.
cuculate Hood-shaped.
cupulate Cup-shaped.
cuneate Also cuneiform. Wedge-shaped; with one end thinner than the other.
cyanolichen
A lichen in which the photobiont is a cyanobacteria.
cyphella Plural cyphellae. A sharply defined, rounded, ovate, or shapeless pore in the lower thallus surface (typically the lower cortex), which is lined with a "pseudocortex" made of loosely connected, non-gelatinized hyphae (often with globular cells, formed from the medulla) and bounded by a pale ring; known to occur in the genera Sticta and Oropogon. The term was first used by Erik Acharius in 1799.
D dactyloid See digitate.
decorticate Having had a cortex that has been removed or disintegrated. See related: ecorticate.
decumbent Lying flat on a substrate with the edges curled up.
dendritic Irregularly branched, like a tree.
dentate Having a toothlike or serrated edge.
denticulate Having small tooth-like projections or serrations along the edge.
dextrinoid A chemical property referring to a substance's ability to turn reddish-brown in the presence of Melzer's reagent or iodine due to the presence of dextrins. This color reaction is also called hemiamyloid or pseudoamyloid.
determinate Having well-defined or clearly marked edges. Contrast: effuse.
diagnosis A brief account of a taxon describing the essential characteristics that distinguish it from its relatives.
diahypha Plural diahyphae. A type of conidium formed from hyphae that split apically in several branches, with prominent constrictions at the septa, resulting in the appearance of chain links; found in the family Gomphillaceae.
diaspore
A sexual or asexual propagule used for dispersal; in lichens, usually used to refer to isidia and soredia.
dichotomous Branching into two equal parts. See related: bifurcate. Contrast: anisotomic.
diffuse Spread out and scattered without any definite boundary or margin. See related: effuse. Contrast: determinate.
digitate Also dactyloid, dactyliform, digitiform. Having finger-like outgrowths.
dimidiate A structure that is divided into two unequal halves, often appearing as half-circles; in lichenology the term is often applied to the excipulum.
dimorphic lichen See cladoniiform lichen.
discoid Also: disciform. A shape that is flat and circular, resembling a disk. In lichenology, this term often refers to the apothecia of lichens that have a flat, disk-like shape.
discolichen A grouping of ascolichens that produce disk-like apothecia, somewhat analogous to the fungal Discomycetes; the term applies to the majority of lichens.
discothecium Plural discothecia. The fruiting body of certain types of lichens, with cylindrical, bitunicate asci. It is distinguished from a hysterothecium, which is another type of fruiting body, by not opening through a slit but by expanding the asci to weather or push apart the typically thin upper stromatal layer. The term was introduced by Richard P. Korf in 1962.
disk Also: disc. The curved or flat upper surface of the hymenium in an apothecium, often pigmented and surrounded by a margin or rim.
distal Positioned away from a point of origin or from the center of a body.
distoseptum Plural distosepta. A type of septum found in some conidia and ascospores, which is located within but distinct from the outer wall and surrounds the internal lumina. Structures with distosepta are said to be distoseptate.
doliiform Barrel-shaped.
dome See tholus.
E e- A prefix meaning "not having" or "without".
eccentric Also excentric. Displaced from the center.
echinate Covered with spines or bristles.
echinulate Covered with small spines or bristles.
ecorticate Lacking bark, or a cortex.
ectal excipulum See proper exciple.
ecto- A prefix meaning "outside" or "outer".
ectotunica See bitunicate.
effigurate Referring to crustose, areolate lichens with marginal areoles that are extended and arranged radially; also defined more generally as "obscurely lobed".
effuse Spread out and flat; used to describe the thallus of some crustose lichens lacking a well-defined outline. Contrast: determinate.
eguttulate Lacking oil droplets (guttules).
Elachista-brown A fuscous brown insoluble lichen pigment, associated with the reference species Micarea elachista.
ellipsoid
An object appearing approximately elliptical in longitudinal section and circular in cross-section; often used to refer to spore shape.
emarginate Also immarginate. Lacking a well-defined border or edge. When referring to apothecia, it means lacking a thalline exciple, or a raised proper exciple. See related: effuse, marginate.
endo- Also end-, ecto-, ect-. A prefix meaning "inside" or "inner".
endocarpic Also endocarpinoid. Referring to lichens with perithecia that are sunk into the tissues of the thallus, such as seen in the genera Endocarpon and Dermatocarpon.
endolichenic fungus A fungus that lives within the thallus of a lichen without producing any visible symptoms of disease; these fungi are transmitted horizontally.
endolith Also endolithic. A crustose lichen that grows in the interior of rocks (under and around the rock crystals), typically with little or no visible thallus on the outer rock surface. Contrast: epilithic. See related: chasmoendolith, cryptoendolith, euendolith.
endophloeodal Also endophloeodic, endophloeic, endophloic. Refers to crustose lichens whose thalli are more or less immersed in tree bark. Contrast: epiphloedal.
endotunica See bitunicate.
entire Refers to margins or edges of lichen structures (such as apothecia, lobes, or thalli) that are smooth and unbroken, without any notches, teeth, or irregularities.
epi- Also ep-. A prefix meaning "upon" or "above".
epibryophyllous Also epibryophytic. Referring to organisms, particularly lichens or fungi, that grow on the surface of mosses (bryophytes).
epicortex A thin layer of polysaccharides that is present on the surface of the cortex in some parmelioid lichens.
epihymenium A thin tissue layer of interwoven hyphae situated directly above the hymenium, which can contain pigments and sometimes plays a role in the coloration of the lichen. Compare: epithecium.
epilithic Also petricolous, rupicolous, saxicolous. A crustose lichen that grows on the surface of rocks. Contrast: endolithic.
epinecral layer A layer of dead hyphae with indistinct lumina found near the cortex and above the algal layer. See related: hyponecral layer.
epiphloedal Also epiphloeodal, epiphloeodic, epiphloic. Growing on the surface of bark. Contrast: endophloeodal.
epipsamma A region of granule-like, often pigmented material, that permeates the upper parts of hymenium but is distinct from the epithecium; associated with the genus Rhizocarpon. The term was coined by Josef Poelt in 1969.
epithecium Plural epithecia. Tissue on the top of an apothecium (above the hymenium) formed from the coalesced tips of projecting paraphyses. The term was first used by Julius von Flotow in 1851.
epruinose Lacking pruina.
erumpent Also perrumpent. Breaking through a surface. A more precise definition has been suggested by Aptroot and Lücking, who propose that the term applies to ascomata and pseudostromata that are more than 1/2 to 3/4 above the level of the thallus.
esorediate Also esorediose. Lacking soredia.
eucortex Plural eucortices or eucortexes. A cortex made of well-differentiated tissue. Another sense of the term, used by Josef Poelt, refers to cortical tissue made entirely of fungal cells originating from a cambium-like tissue layer in or above the algal layer. The term eucortex was first used by Gunnar Degelius in 1954.
euendolith Also euendolithic. A type of organism, often a lichen or microbe, that actively bores into and resides within the mineral matrix of rocks or other hard substrates. See related: endolithic.
euthalline Describing a type of lichen thallus that is clearly visible and well-developed on the surface of the substrate. See related: epilithic. Contrast: cryptothalline.
evanescent Lasting a short time.
excipulum thallinum See thalline margin.
exsiccatum
Plurals: exsiccata (from exsiccatum), exsiccatae (from exsiccata when used as singular for a collection), exsiccati (from exsiccatus). A dried and labeled herbarium specimen, often part of a numbered set.
excipulum Plural excipula. Also exciple (plural exciples). The cup-shaped or ring-shaped layer of tissue supporting the hymenium in an apothecium; this tissue sometimes develops into a distinct margin, as in the lecanorine apothecia. See related: proper margin, thallin margin.
F fabiform Bean-shaped.
facultatively lichenicolous A fungus species that is commonly collected from lichens (i.e., it is lichenicolous) but is also capable of living on non-lichen substrates.
falcate Also falciform, lunate. Thin and curved with pointed ends, like a scythe or sickle.
farinaceous Also farinose. Covered with a mealy powder; the podetia of Cladonia deformis are covered with farinose soredia.
fasciate Also fasciated. Having a ribbon-like or band-like structure, such as the thallus of some fruticose lichens.
fascicle A bundle or cluster; can be used to refer to asci, conidiophores, hyphae, etc.
fasciculate Arranged in bundles or clusters.
fastigiate cortex A region of the cortex where the hyphae are aligned perpendicularly to the main axis of the thallus. The term was first used by Auguste-Marie Hue in 1906. See related: palisade cell.
faveolate Pitted with large, deep depressions that are narrowly separated by sharp ridges. Compare: alveolate, foveolate, scrobiculate.
fenestrate Having perforations or gaps arranged in a regular pattern.
-fer Also -ferous. A suffix meaning to carry or produce.
fibercle A scar on lichen thalli resulting from the breaking of attached fibrils; associated with the genus Usnea.
fibril A tiny fibre; when referring to the genus Usnea, it means short branches that are perpendicular to the main branches.
fibrillose Covered with silky fibres.
filiform Thread-like; fine and slender.
fimbriate Having hairs or fibres on the margin. See related: arachnoid, fimbrillate.
fimbrillate Delicately fimbriate; bordered with minute fringe.
fissitunicate A form of bitunicate ascus in which the flexible layers of the inner wall (the endotunica) and the more rigid layers of the outer wall (the ectotunica) are physically separated; as a consequence, the inner walls extend past the outer walls before the spores are released.
fissurine Also fissurate. A term used characterize a structure or surface displaying a pattern of narrow, elongated cracks or fissures.
fissurinoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus structure. This morphotype is somewhat similar to the chroodiscoid, but it differentiates by the way the apothecia open through irregular thallus cracks, finally resembling chroodiscoid apothecia. It often has a unique elongated form at maturity and can be seen in species such as Acanthotrema brasilianum and various Chapsa species.
fistular Also fistulose. Tubular and hollow.
flabellate Also flabelliform. Fan-shaped.
flexuous Also flexuose. Bending or curving in alternate directions, like a zigzag.
floccose Having the texture of loose cotton or wool.
foliicolous lichen
Also epiphyllous lichen. A lichen that grows on a plant leaf.
foliole A small leaf-like outgrowth from the thallus of a foliose lichen.
foliose
Leaf-like; a type of lichen thallus comprising numerous small leafy lobes, often extending in a roughly circular pattern from a center of growth, on a lower cortex that is attached to the substrate by rhizines or at a base.
forage lichen Lichens that serve as important food sources for fauna. For example, species from the genera Alectoria, Bryoria, and Cladonia are winter forage lichens for caribou in northern North America.
foveate Having pits or perforations.
foveolate Pitted with small, deep depressions that are widely separated by a more or less even thallus. Compare: faveolate, scrobiculate.
friable
Readily crumbled or pulverized.
fruit wart An informal term for a type of apothecium that has perithecioid (pertusariate or thelotremoid) characteristics.
fruticose
A lichen with a shrub-like or hairy thallus attached to the substrate at a single point.
fruticulose Also fruticulous . A smaller version of a fruticose lichen. See related: microlichen.
fulvous A yellow-brown or tawny color.
funiculus See umbilicate lichen.
funoid Made of fibers or rope-like strands.
furcate Forked.
furfuraceous Covered with small flakes.
fuscocapitate A term used to describe structures, such as hairs or other appendages, that have a dark or dusky-colored rounded tip or head.
fuscous A dark, grayish-brown or grayish-black color.
fusiform
Tapered at both ends, like a spindle.
fuzzy coat The outer gelatinous layer, also known as the g-layer, found on the exterior of an ascus, often exhibiting a gelatinous consistency and staining blue in iodine. Typically present in all asci, the fuzzy coat usually forms a thin layer along the ascus sides but may also appear as an apically thickened cap.
G
gelatinous lichen A rubbery or jelly-like lichen with a cyanobacterial photobiont. See related: homoiomerous.
geniculate Having a knee-like bend; applied to parts of hyphae and conidiophores where a bend forms due to directional changes during growth.
glabrescent Becoming glabrous.
glabrous Lacking hair or bristles; smooth.
glaucescentoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus morphology. Glaucescentoid lichens have open apothecia with erect lobules, and a rough thallus containing crystals; this morphotype occurs in the species Leucodecton glaucescens.
glaucophaenoid A morphotype of corticolous thelotremoid lichens used to describe characteristics of apothecial and thallus morphology. Glaucophaenoid lichens have prominent apothecia with wide pores, pale walls (viewed in microscopic section), and a smooth and more or less shiny thallus; this morphotype occurs in the genus Myriotrema.
gleolichen Also gloeolichen. A homoiomerous lichen with cyanobacterial cells belonging to the genera Chroococcus, Gloeocapsa, or other Chroococcales; these algae have a mucilaginous capsule.
globose Also globoid, globular. Approximately spherical.
glomerule Plural glomerules. Also Latin glomerulus with plural glomeruli. A dense clump or aggregate of cells or spores.
glypholecideous Also glypholecine. Having especially labyrinth-like lirella, as in the genus Glypholecia.
gonidial layer A now-obsolete, historical term for the algal layer in a lichen.
gonidium Plural gonidia. A now-obsolete, historical term for a lichen photobiont. The term was first used by Friedrich Wallroth in 1825, and supplanted in the 1960s.
gonimium Plural gonimia. A now-obsolete, historical term for a lichen cyanobiont.
goniocyst A vegetative propagule found in some tropical foliicolous lichens that consists of photobiont cells wrapped in mycobiont hyphae; it is similar in form to soredia, but it is made in a specia