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.[3] Until about 1850, there were 21 terms for features of the lichen thallus that remain in use today.[3]
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.[4] 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.[4] 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.[5]
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".[6]
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.[7]
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.[9]
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.[8]
-al
A suffix used to indicate a relation to, or having the form and character of something.[20]
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.[24]
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.[25]Compare:
faveolate,
foveolate,
scrobiculate.
amphi-
A prefix used to indicate on both sides, or on all sides.[26]
A morphotype of
corticolousthelotremoid 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.[30]
ampulliform
Bottle-shaped, i.e., with a narrow neck and swollen base.[31]
Also anisotomous.[33] Having branches of unequal length;[34] 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.[33]Contrast:
dichotomous.
annulotremoid
A morphotype of
corticolousthelotremoid 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.[30]
anticlinal
Perpendicular to a surface;[35] used to refer to
hyphal alignment.
apical
Located at the highest point (the apex), the tip, or the end of something.[36]
apiculate
Having a short projection (an apicule) at one end; typically used to describe spore morphology.[37]
apothecium
Plural apothecia. A type of
ascocarp that is open, saucer-shaped or cup-shaped, and in which the
hymenium is exposed at maturity.[38] The term was first used by
Erik Acharius in 1803.[3]
Also araneose, araneous.[40] Having a
cobweb-like form, like that of the irregularly oriented and loosely interwoven
hyphae of the
medullary layer of some lichens.[41]
A shape or structure that is curved or arched like a bow.[43]
ardella
Plural ardelae. A type of
apothecium, typical of lichens in the family
Arthoniaceae, which is small and round. Elongated ardellae are called
lirellae.[44] The term was first used by
William Allport Leighton in 1854, who described an ardella as resembling a "sprinkled spot".[4]
areole
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.[45]
Also ascogenic. Producing or supporting the growth of an
ascus.[47]
ascolichen
A lichen in which the fungal partner (the
mycobiont) is a member of the
Ascomycota. About 98% of lichens are ascolichens.[50]See related:
basidiolichen.
A morphotype of
corticolousthelotremoid 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.[58]
A lichen in which the fungal partner (the
mycobiont) is a member of the
Basidiomycota. About 0.4% of lichens are basidiolichens.[50]See related:
ascolichen.
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.[63]
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.[67]
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.[70]
botryose
Resembling rounded, bead-like structures or clusters resembling grapes.[43]
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.[71]
Also defined: hepaticolous lichen; muscicolous lichen. A lichen that grows on a
moss or
liverwort – i.e. on a
bryophyte.[73] A hepaticolous lichen is found only on liverworts, while a muscicolous lichen is found only on mosses.[74][75]
bullate
Having blister-like or bubble-like swellings on a surface.[76]
Also caespitous, cespitose.[79] Growing in dense clusters or tufts, often used to describe fungi that arise from a common base or grow closely together without fusing.[18]
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.[81]
Having one or more longitudinal grooves or channels.[83]
capitate
Having a well-formed head, usually spherical or hemispherical in shape.[68]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.[84][68]See related:
mazaedium.
carbonized
Also carbonised, carbonaceous. Blackened and brittle tissue resulting from the accumulation of pigments.[85]
cariose
A lichen thallus or structure that is cracked, split, spongy, or otherwise decayed or in a state of disintegration.[43]
cartilaginous
Also 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.[86]
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.[68] These structures are found in most lichens that contain both algal and cyanobacterial
photobionts.[91] The term was first used by
Erik Acharius in 1803.[3]
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.[92]
cetrarioid lichen
An informal
growth form category used for lichens with erect,
foliosethalli, and
apothecia and
pycnidia on the margins of the lobes; characteristic of lichens previously classified in the genus Cetraria (in the broad sense).[93]
chalaroplectenchyma
Plural chalaroplectenchymata. A type of
plectenchyma comprising loosely interwoven
hyphae with holes; found in the
medulla of some lichens.[92]
character
A distinguishing feature that is characteristic for an organism; equivalent to
phenotypic trait.[92]
chasmoendolith
Also chasmoendolithic. A type of organism, typically a lichen or fungus, that lives within cracks and fissures of rocks.[94]See related:
endolith.
checklist
A list of all of the species (sometimes including
subspecies,
varieties and
forms) that occur within a particular region.[95]
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.[96]
A morphotype of
corticolousthelotremoid 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.[30]
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.[100]
CK test
A seldom-used
spot test performed with an application of
C followed immediately by
K.[101]
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.[102]
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.[103]
Having a finely scalloped edge; similar to crenate but with smaller notches.[119]
cruentodiscoid
A morphotype of
corticolousthelotremoid 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.[30]
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.[120]
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.[94]See related:
endolith.
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.[129] The term was first used by
Erik Acharius in 1799.[3]
Having small tooth-like projections or serrations along the edge.[134]
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.[135]
determinate
Having well-defined or clearly marked edges.[136]Contrast:
effuse.
diagnosis
A brief account of a
taxon describing the essential characteristics that distinguish it from its relatives.[137]
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.[138][139]
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.[143]
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.[145] The term was introduced by
Richard P. Korf in 1962.[146]
disk
Also: disc. The curved or flat upper surface of the
hymenium in an
apothecium, often pigmented and surrounded by a margin or rim.[143]
distal
Positioned away from a point of origin or from the center of a body.[147]
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.[148]
Referring to
crustose,
areolate lichens with
marginal areoles that are extended and arranged radially;[154] also defined more generally as "obscurely lobed".[155][156]
A fungus that lives within the
thallus of a lichen without producing any visible symptoms of disease; these fungi are
transmitted horizontally.[165]
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.[166]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.[167]Contrast:
epiphloedal.
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.[168]
epi-
Also ep-. A prefix meaning "upon" or "above".[169][170]
epibryophyllous
Also epibryophytic. Referring to organisms, particularly lichens or fungi, that grow on the surface of mosses (
bryophytes).[169]
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.[171]Compare:
epithecium.
epilithic
Also petricolous, rupicolous, saxicolous. A crustose lichen that grows on the surface of rocks.[166]Contrast:
endolithic.
Also perrumpent. Breaking through a surface.[178] 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.[179]
Plural eucortices or eucortexes. A
cortex made of well-differentiated tissue.[181] 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.[182] The term eucortex was first used by
Gunnar Degelius in 1954.[5]
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.[94]See related:
endolithic.
Plural exsiccata, exsiccatae, exsiccati. A dried and labeled
herbarium specimen, often part of a numbered set.[183]
excipulum
Alsoexciple. Plural excipula. 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.[184]See related:
proper margin,
thallin margin.
A region of the
cortex where the
hyphae are aligned perpendicularly to the main axis of the
thallus.[190] The term was first used by Auguste-Marie Hue in 1906.[5]See related:
palisade cell.
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.[198]
fissurine
Also fissurate. A term used characterize a structure or surface displaying a pattern of narrow, elongated cracks or fissures.[199]
fissurinoid
A morphotype of
corticolousthelotremoid 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.[200]
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.[205][206]
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.[207][208]
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.[216][217]
A morphotype of
corticolousthelotremoid 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.[30]
glaucophaenoid
A morphotype of
corticolousthelotremoid 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.[30]
A now-obsolete, historical term for the algal layer in a lichen.[225]
gonidium
Plural gonidia. A now-obsolete, historical term for a lichen
photobiont.[225] The term was first used by
Friedrich Wallroth in 1825, and supplanted in the 1960s.[3]
gonimium
Plural gonimia. A now-obsolete, historical term for a lichen
cyanobiont.[225]
A term for the general appearance (the
habit) of a lichen.[227]
grumose
Having a
granular or crumbly texture or appearance.[43]
guttulate
Referring to structures containing small oil droplets (guttules); often used to describe spores. More precisely, spores can be described as
uni-,
bi-,
tri-, or
multiguttulate.[228]
Also gyrate. Curved backward and forward; with folds and undulations.[230]
gyrotremoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Gyrotremoid lichens have open apothecia with recurved
lobules, a
disc that is pigmented with concentric rings, and a smooth, more or less shiny thallus; this morphotype occurs in the genus Gyrotrema.[30]
A flattened attachment point formed through direct contact of a lichen
thallus to its
substrate; associated with
foliose and
fruticose lichens that lack other attachment organs, such as Hypogymnia.[231]
halonate
Also defined: halo. Referring to a spore that is surrounded by a transparent outer layer or a gelatinous, translucent sheath. This sheath is readily observed when the spore is
stained with
India ink, as the ink does not penetrate the
mucilage of the sheath, creating a light-transparent halo that is visible against a blackened background.[232][233]
Also heter-. A prefix meaning "other" or "different".[235]
heterocyst
A specialized type of cell found in some
cyanobacteria; heterocysts are thought to be involved in the
fixation of nitrogen by the lichen thallus, as well as in the multiplication of cyanobacteria.[236]
heteromerous
A lichen
thallus that is organized into discrete layers or strata; the term applies to the majority of
foliose,
squamulose, and
crustose lichens.[237]
Also hormocyte. Also defined: hormocystangium, plural hormocystangia. An asexual
propagule, produced in a cup-shaped structure called the
hormocystangium, comprising heavy, gelatinous fungal
hyphae enclosing a few
cyanobiont cells; these structures occur in some
gelatinous lichens in the family
Collemataceae.[242] Both terms, hormocyst and hormocystangium, were introduced by
Gunnar Degelius in 1945.[5] According to one source, hormocyte and hormocytangium (spelled without the "s") are more accurate terms, because the cells (indicated by the ending -cyte) are not sexual propagules (which is implied by the ending -cyst).[243]
Embedded or sunken into the surface; in lichens, often used to describe
perithecia.[253] 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 3/4 beneath the level of the
thallus.[179]
Also defined: inspersion.Also inspers, interspersed. Terms used to describe the presence of minute, scattered
oil droplets or
granules within a tissue, typically observed in
section with a
compound microscope.[256] An inspersion refers to the degree of obstruction caused by the sprinkling of small particles within different sections of a given structure.[257]
A structure that resembles an
isidium, but is formed as an outgrowth of the
medulla rather than the
cortex; associated with
soralia of species in the genus Usnea.[260]
Plural isidia. A
propagule that is an outgrowth of the
thallus; it has a
cortex and contains
photobiont cells.[259] The term was first used in the sense it is used now by Georg Meyer in 1825, and adopted by
Elias Fries in 1831.[3]
isodiametric
Having roughly equal dimensions in all directions, resulting in a roughly spherical or cube-like shape; often used to describe cells that are not elongated or flattened but maintain a uniform size across their width, height, and depth.[261]
Plural jugae. A tiny
carbonized structure made of
hyphal tissue, visible as a black dot, line, or ridge, on or in a
thallus; associated with the genus Verrucaria.[264]
Also LCB. A
histologicalstain commonly used to prepare semi-permanent
slides. With this reagent, fungal
hyphae stain blue, and algal cells stain deep blue to blue-green.[101]
lacunose
Also lacunar, lacunous. A texture that appears pitted or containing gaps or holes, giving it a somewhat rough or uneven appearance.[269]
lageniform
Flask-shaped; with a swollen base tapering to a narrow top.[270]
lamella
Plural lamellae. In the genus Umbilicaria, lamellae are flattened plate- or strap-like structures that project downward from the
thallus undersurface.[271]
Also lecanoroid. An
apothecium in which the
disk is surrounded by a pale thalline margin, which has both algal and fungal cells, as in the genus Lecanora. The term is also used more generally to refer to
crustose lichens of the order
Lecanorales that have rounded apothecia with thick, protruding margins.[274]
lecideine
Also lecideoid. An
apothecium in which the
disk lacks a thalline margin, as in the genus Lecidea. The term is also used more generally to refer to apothecia with a blackened (carbonaeous) ring and a blackish
disk.[275]
leiodisk
Also leiodisc. A
disk of an
apothecia that is smooth and without folds or protrusions.[276] The term was introduced by
George Llano in 1950.[5]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Leprocarpoid lichens have open apothecia with erect lobules and a mealy and more or less
matte thallus; this morphotype occurs in the genus Chapsa.[30]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Leptotremoid lichens have immersed apothecia with small pores, and a rough thallus containing crystals; this morphotype occurs in the genus Leptotrema.[30]
leucodectonoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Leucodectonoid lichens have closed apothecia with tiny pores, and a rough thallus containing crystals; this morphotype occurs in the genus Leucodecton.[30]
The name of a historical
class that contained all of the lichen-forming fungi. This name was used when it was still erroneously believed that these fungi were quite separate from the non lichen-forming fungi; now obsolete.[279]
A lichen that grows on stripped wood (
lignin) – that is, on bare wood rather than bark.[73]
ligulate
Also liguliform, lingulate, lorate. Narrow and flat, with the form of a
strap.[281]
lirella
Plural lirellae.Also hysterothecia, lirelline apothecia. A linear
ascocarp, which may be straight, curved, branched, or
flexuous, with a longitudinal slit; characteristic of lichens in the genus Graphis.[282] The term was first proposed by
Michel Adanson in 1794.[3]
A lichen with a
thallus large enough that its main characteristics can be identified without the use of viewing magnification; generally refers to
foliose,
squamulose, and
fruticose species.[289]
Cuff-shaped; the term is used to describe
soralia that break open to form a central perforation revealing a duct to the
medullary cavity. Maniciform soralia occur in the genera Hypogymnia and Menegazzia.[291]
A morphotype of
corticolousthelotremoid lichens describing a type of apothecium structure resembling
topeliopsidoid apothecia but characterized by a minimized
thallus margin. The distinctive feature of melanotopelioid apothecia is the presence of "teeth" that are black and
carbonized, at least on the external surface.[296]
melanotremoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Melanotremoid lichens have prominent apothecia with wide pores and a black margin; pore filled with broad "stump" (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genera Melanotrema, Ocellularia, Clandestinotrema, and Trinathotrema.[30]
Also microcrystal test. A method used to identify some
lichen products that involves re-
crystallization on a
microscope slide from a range of
solvents and the formation of crystals with characteristic shapes; the crystals are examined microscopically for identification. Although this technique has largely been supplanted by the more reliable and sensitive technique of
thin-layer chromatography, there are certain situations where it is still useful.[298]
microlichen
A small lichen whose physical features cannot be distinguished without the aid of a 10X or greater viewing magnification;[299] it generally refers to
crustose and
foliicolous species.[300] The prefix "micro-" is also used to indicate small versions of particular growth forms, e.g. microfruticose or microfoliose.
Also defined: mycophycobiont. A
symbiosis where an
ascomycete fungus is housed inside multicellular algae; the algae and fungus involved in this association are called mycophycobionts.[309] Contrary to a lichen symbiosis, the fungal partner is the inhabitant, and the algal partner dominates.[310]
myriotremoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Myriotremoid lichens have immersed apothecia with small pores, and a smooth and more or less shiny thallus; this morphotype occurs in the glaucopallensgroup of genus Myriotrema.[30]
Egg-shaped, with the narrower end at the base.[311]
obpyriform
Shaped like an inverted pear.[312]See related:
pyriform.
ocellularioid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Ocellularioid lichens have prominent apothecia with wide pores; pores with a "finger" (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genus Ocellularia.[30]
-oid
A suffix meaning "like" or "having the form of".[313]
A small pore or opening; in lichens, it is used to refer to the
paraphysis-lined cavity in a
parathecium that ends in a pore, or more generally to any pore from which spores are released from an
ascus-bearing fruit body.[315]
ostropalean
Referring to asci that are
unitunicate with a thickened apex and a narrow canal ending in a pore; associated with species in the order
Ostropales.[316]
Plural palisade plectenchymata. Also palisadoplectenchyma, plural palisadoplectenchymata. A type of
plectenchyma in a
cortex where the
hyphae are arranged perpendicularly to the plane of the
thallus.[319]
pallidostegoboloid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Pallidostegoboloid lichens have prominent apothecia with wide pores; pore filled with irregular structures; pale walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in wrightiigroup of the genus Stegobolus.[30]
papilla
Plural papillae. A small, conically rounded growth.[320]
An organism that lives in close association with a
host species, deriving benefits at the host's expense but not causing immediate harm; an intermediate state between
symbiosis and
parasitism.[267]
An informal
growth form category used for lichens that are mostly
foliose, often closely attached to the substrate, and have
laminalapothecia and
pycnidia; this group of features is characteristic of lichens previously classified in the genus Parmelia (in the broad sense).[93]
Also clypeate, scutiform. Referring to a rounded structure attached on the lower side at a single central point (often on a short stalk), with free edges.[330]
peltidiangium
A basket-like structure in which
peltidia are produced.[331]
Plural periphyses. A short, sterile
hypha that develops from above the ascus and grows down a short distance, typically lining the internal walls of the
ostiole in a
perithecium.[335]
Also defined: exospore, epispore, mesospore, endospore. The colorless and usually gelatinous outermost layer of a spore.[336] This transparent layer determines the spore's shape.[337] The other four layers of a spore, going inward, are the exospore, epispore, mesospore, and endospore.[336]
perithecium
Plural perithecia. A spherical or flask-shaped
ascocarp that is
sessile or partly immersed in the
thallus, with a single opening (
ostiole) and enclosed by a distinct wall; a characteristic of
pyrenolichens.[338] Although it was in 1831 that
Elias Fries first applied the term perithecium to lichen fruit bodies, the word was originally coined by
Christiaan Hendrik Persoon in 1794.[339]
Plural phenocortices, phenocortexes. A structure, similar to a
cortex, containing
hyphal fragments and dead, collapsed algal cells sloughed off from the
algal layer.[341]
photobiont
Also defined: phycobiont, cyanobiont. The photosynthetic component of a lichen. This can be either a
green alga (known as a phycobiont) or a
cyanobacteria (known as a cyanobiont).[342] The term "phycobiont" was proposed by George Scott in 1957.[5]
Plural phyllidia. A small leaf-like or scale-like
propagule that is
corticate and has distinct upper and lower sides (i.e., it is
dorsiventral); it originates from the margins or on the upper surface of
thallus.[346] Phyllidia occur in some species of the
Lecanorales and the
Peltigerales.[347]
Characterised by longitudinal folds forming
pleats, often used to describe closely adjacent, markedly convex thallus
lobes or elongated
areoles that display a "folded" appearance.[355]
plurilocular
Also multilocular. Having many cavities or
locules; used to describe spore structure.[356]
A lichen test performed by shining a
polarized light at a lichen structure in microscopic view; in the genus Hypogymnia, the presence (POL+) or absence (POL−) of POL-sensitive crystals in the
hypothecium is a useful
character to help distinguish species.[357]
polarilocular
Also placodiomorphic,[252]polar-diblastic, polaribilocular, polocellate. A spore divided into two components (locules) separated by a central
septum with a perforation or
isthmus.[358][359] The term was first used by
Wilhelm Körber in 1855 (as "polari-dyblastae") to describe the spores of Rhizocarpon and Umbilicaria. It was
anglicized to "polari-bilocular" by William Mudd in 1861, and finally shortened to polarilocular by the Henri Olivier in 1882.[4]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Praestantoid lichens have large and prominent apothecia with small pores; pores with "finger" (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the praestansgroup of the genus Ocellularia.[30]
Sticking out from the surface of the
thallus.[363] 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 above the level of the
thallus, and have a base that is expanded outwards.[179]
proper margin
Also proper exciple, ectal excipulum, medullary excipulum, proprium. A ring of tissue around the
disk of a
lecanorineapothecium; this tissue, which originates from the
medulla, is not lichenized, and is internal to the
thalline margin (if present).[364] The term "proper margin" was first used by
Erik Acharius in 1803; in 1825
Elias Fries changed the noun and called it "proper exciple".[3]
Plural prosenchymata. A type of
plectenchyma in which the constituent fungal
hyphae are arranged parallel to each other, such that individual hyphae can be clearly distinguished using microscopy.[365]
prosoplectenchyma
Plural prosoplectenchymata. A type of
plectenchyma, common in the
thalluscortex of lichens, in which the constituent fungal
hyphae are aligned in a particular direction.[365]
A fungal layer upon which an algae-containing
thallus may develop, lacking
photobiont; usually white, brown, or black, and found between the
areoles and at the growing margins of
crustose lichens.[366] The term was first used by Georg Meyer in 1825.[3]
prototunicate
A form of
unitunicateascus in which the wall breaks down before maturity (thus releasing its
ascospores), and which lacks differentiated apical structures.[367]
proximal
Positioned close to a point of origin or near the center of a body.[368]
pruina
A powdery, frost-like or flour-like deposit on a surface. In lichens, pruina is often the result of the accumulation of crystalline
hydrates of
calcium oxalate, of
lichen products, or sometimes of the dead or dying cells of the
epinecral layer.[369]
Also pseud-. A prefix meaning "false";[370] used in terminology to denote something is false, or that one structure resembles something else, such as the
pseudocyphella resembling the
cyphella.[368]
Plural pseudocortices, pseudocortexes. A boundary layer of the
thallus containing distinct
hyphae that are not organized into a regular tissue structure;[371] sometimes used to refer to the false
cortex present on the outer layer of
pseudopodetia, such as those found in the lichen Pycnothelia papillaria.[372]
Plural pseudocyphellae. Small openings in the
cortex of a lichen, where the
medulla is exposed to air, and there are no specialized cells surrounding the cavity.[373] The term was first used by
William Nylander in 1858.[4]
Also cataphysis. A
paraphysis-like
hypha that forms in the locule or perithecial cavity before the formation of the
ascus; it grows downward from the top of the cavity to the base of the ascomata.[375]
Also recurvate, reflexed.[390] Curved or bent back; in lichens, these terms are used to describe the tips of
branches or
lobes that are curved up or down, or back onto themselves.[391]
redingerioid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Redingerioid lichens have immersed apothecia with linear slit; slit filled with irregular structures; black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genera Redingeria and Stegobolus.[30]
reimnitzioid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Reimnitzioid lichens have open apothecia with erect
lobules, and a rough thallus containing crystals; this morphotype occurs in the genus Reimnitzia.[30]
A single
hyphal strand on the
thallus underside that serves as an attachment organ.[395]
rhodostromoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Rhodostromoid lichens have large and prominent apothecia with small pores; pore with “finger” (columella); black walls and pigment (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the rhodostromagroup of the genus Ocellularia.[30]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Schizotremoid lichens lack apothecia and have
schizidia, and a smooth, more or less shiny thallus; this morphotype occurs in the genus Stegobolus.[30]
Plural scleroplectenchymata. A type of
plectenchyma comprising thick-walled
hyphae that are stuck closely together; present as a component of the
stereoma tissue supporting the
thallus in the genera Cladonia and Alectoria.[407]
scrobiculate
Having large, shallow depressions that are narrowly separated by rounded ridges.[191]Compare:
faveolate,
foveolate.
Lacking a stem.[413] 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 3/4 above the level of the
thallus, with a constricted base.[179]
sibling species
Closely related species that are morphologically indistinguishable but can be distinguished by non-morphological traits, such as chemistry or genetic differences. Initially defined as species recognized mainly through cryptic or non-morphological discontinuities, the concept has evolved to specifically refer to
cryptic species that form a
monophyletic group, meaning they share a
common ancestor not shared with any other species. This concept is a subset of the broader terms
species pair and "cryptic species".[414]
sigmoid
Curved upon itself twice, like the letter "S".[415]
simple
Lacking branches or divisions; in lichenology, it is used to describe structures such as
thalli or
rhizines, or
spores without
septa.[416]
Shaped like the sole of a shoe, with a flat, elongated, and slightly curved appearance.[418]
soralium
Plural soralia. A part of the
thallus where the
cortex has cracked or broken down and
soredia are produced. Soralia can be further characterized as diffuse if they are spread out on the upper thallus surface as a continuous layer, or delimited if they are confined to a more restricted area. If soralia originate in tubercules they are tuberculate, while they are fissural if they are created in fissures.[419] The term was proposed by
Johannes Reinke in 1895.[5]
Plural soredia. A powdery to granular reproductive
propagule that is not covered with a well-defined
cortex (in contrast to
isidia, and contains both algal (
photobiont) and fungal (
mycobiont) components.[419] The term was first used by
Erik Acharius in 1803.[3]
Two lichen species that are identical
morphologically, anatomically, and chemically, but can be distinguished by their
sexual versus
asexual reproductive strategies; the fertile taxon is known as the primary species, while the
vegetatively reproducing taxon is known as the secondary species.[362] The use of
molecular methods to analyze putative species pairs has shown that the underlying phylogenetic situation is more complex than had been assumed, and not necessarily correlated with reproductive strategy.[421]See related:
sibling species.
spermogonium
Also spermagone, spermagonium. In lichenology, an obsolete term for
pycnidium.[422]
A small spine; in some
fruticose lichens of the
Lecanoromycetes, it refers to a small cylindrical outgrowth, with a narrow base, in which the
central axis is not connected with the
central axis of the main branch.[423]
spinulose
Also spinulous. Covered with or having small spines (
spinules) or spiny projections.[423]
A lichen species that is extremely similar (or identical) in external morphology, anatomy, chemistry, and spore size to another, but that is placed in a different genus solely based on differences in spore septation and/or spore colour. The term was introduced by Michael Wirth and
Mason Hale in their 1978
monograph about the
Graphidaceae, a family in which sporomorphs are common.[427]
A
spot analysis used to help identify lichens; it is performed by placing a drop of a
reagent on different parts of the lichen and noting any color change associated with application of the reagent. The four most common tests are
C,
K,
KC, and
PD.[429]
Brush-like, with many short, more or less perpendicular lateral branches. In lichenology, used to refer to
rhizine structure.[431]
stegoboloid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Stegoboloid lichens have prominent apothecia with wide pores; pore filled with irregular structures; black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genus Stegobolus.[30]
Plural stromata. A dense mass of
vegetativehyphae that supports spore-bearing structures.[433] In lichens, the stroma is often hard and carbonaceous.[395]
sub-
A prefix meaning "below", "under", "somewhat, or "almost".[434] Also used in front of names of
taxonomic ranks to indicate intermediate categories, e.g.
subspecies or
subgenus.[435]
Also subicule.Plural subicula. A layer of loosely-compacted
mycelia that covers the
substrate and cushions fruiting bodies such as
apothecia and
perithecia.[436] The texture of the subiculum can be described as net-like, wool-like, or crust-like.[434]
Also substratum; plural substrata. The surface or base upon which a lichen grows or is attached. Although the terms substratum and substrate are often used equivalently in lichenology, the latter term has different meanings in
microbiology and in
enzymology.[437]
subulate
Slender and narrowing to a fine point;
awl-shaped.[438]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Tenuitremoid lichens have immersed apothecia with small pores and a black margin; pore with “finger” (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genus Clandestinotrema.[30]
tegulicolous lichen
A lichen that lives on
tiles.[440] In general, these are
calcicolous lichens or lichens that are indifferent as to their substrate.[441]
Describing a cylindrical or rod-like structure that is round in cross-section.[418]
teretiform
Describing a shape that is nearly cylindrical or rod-like, similar to but not exactly
terete; circular in cross-section, gradually tapering towards one end.[443]
Also thalline exciple, excipulum thallinum. A rim of tissue around the
disk of a
lecanorineapothecium; this tissue, external to the inner
proper margin, is made of tissue with a structure similar to that of the
thallus.[445] The term "thalline margin" was first used by
Erik Acharius in 1803; in 1825
Elias Fries changed the noun and called it "thalline exciple".[3]
Plural thalloconidia. A dark brown, smooth to wrinkled
propagule arising directly from a
thallus, particularly the lower
cortex and/or the
rhizines. They are found in some species of Umbilicaria, and similar structures arise from the
prothallus of some species in the genera Protoparmelia, Rhizoplaca, and Sporastatia. Thalloconidia have distinct cell layers in their walls, and comprise between 1 and about 2500 cells.[447][448]
Plural thalli. The body of a lichen,[450] made up of both fungal and algal or cyanobacterial cells.[451] The term was first used by
Erik Acharius in 1803.[3]
A morphological group of lichens within the
Graphidaceae, the largest family of
crustose lichens.[453] Thelotremoid lichens are characterized by immersed-
erumpent, rounded
ascomata, non-branched to slightly branched
paraphyses, mostly
distoseptate ascospores, and mostly a
prosoplectenchymatousexcipulum. Thelotremataceae, a traditional family of lichens, has been included in Graphidaceae, and its species are now informally accepted as thelotremoid lichens.[453]
tholus
Plural tholi.Also dome. The apical, often thickened part of the inner wall in a
bitunicate ascus.[454]
tomentum
Plural tomenta. Also defined: tomentose. A layer of short interwoven or coiled fungal
hyphae with a texture similar to
velvet. In lichens, the tomentum projects from the lower
cortex and serves to help it attach to its
substrate. Structures with this type of hyphae are called tomentose.[455] Tomentose surfaces are found in
foliose genera such as Lobaria, Pseudocyphellaria, and Sticta.[456]
topeliopsidoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus structure. It pertains to lichens where the apothecia are either prominent or
sessile, often hidden between the
substratum, and they open with multiple, typically regular "teeth" that stay relatively curved over the hardly visible
disk. The margins tend to peel off, meaning the overlaying thallus cortex separates from the underlying marginal thallus tissue, but no distinct, clean split between thallus margin and
excipulum is formed. This morphotype is seen in species like Chapsa meridensis and Topeliopsis.[457]
trabecula
Plural trabeculae. In the genus Umbilicaria, they are rib- or strap-shaped structures radiating outward from the
umbilicus that merge towards the mid-zone of the
thallus undersurface.[271]
trentepohlioid
Resembling or belonging to the
green algal genus Trentepohlia; trentepohlioid cells are filamentous (elongated and cylindrical), multicellular, and have a yellow to orange colour.[458]
Also defined: funiculus, umbilicus, umbilical cord. A lichen with a concave, circular, leafy
thallus that is joined to its
substrate only by its central part, called an umbilicus, umbilical cord or funiculus.[461][462]
A type of
ascus with a single functional layer; the rigid internal and external wall layers do not separate during release of the
ascospores. Most
ascomycetes have unitunicate asci.[466]
Deeply cup-shaped or
urn-shaped; in lichens, the term is used to describe some
apothecia with a sunken
hymenium and elevated
parathecium that forms a narrow mouth.[468]
A lichen test performed by shining a long-wavelength
ultraviolet light (350
nm) at a lichen structure to check if it
fluoresces; a positive test (abbreviated as UV+) indicates the presence of certain
lichen products.
Xanthone compounds in the
cortex tend to fluoresce yellow, orange, or red, while
depsides and
depsidones in the
medulla fluoresce blue to white.[470]
A lichen not attached to a
substrate, typically able to be blown around by wind.[471]
vegetative
Also assimilative. Having to do with the growth phase of an organism before reproduction, including spore germination, growth, development and asexual multiplication.[472]
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Rapai, Sean B.; McMullin, Richard Troy; Newmaster, Steven G. (2012). "The importance of macrolichen traits and phylogeny in forest community assemblage along a high elevation gradient in southwestern British Columbia". Forest Ecology and Management. 274: 231–240.
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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.[3] Until about 1850, there were 21 terms for features of the lichen thallus that remain in use today.[3]
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.[4] 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.[4] 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.[5]
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".[6]
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.[7]
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.[9]
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.[8]
-al
A suffix used to indicate a relation to, or having the form and character of something.[20]
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.[24]
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.[25]Compare:
faveolate,
foveolate,
scrobiculate.
amphi-
A prefix used to indicate on both sides, or on all sides.[26]
A morphotype of
corticolousthelotremoid 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.[30]
ampulliform
Bottle-shaped, i.e., with a narrow neck and swollen base.[31]
Also anisotomous.[33] Having branches of unequal length;[34] 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.[33]Contrast:
dichotomous.
annulotremoid
A morphotype of
corticolousthelotremoid 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.[30]
anticlinal
Perpendicular to a surface;[35] used to refer to
hyphal alignment.
apical
Located at the highest point (the apex), the tip, or the end of something.[36]
apiculate
Having a short projection (an apicule) at one end; typically used to describe spore morphology.[37]
apothecium
Plural apothecia. A type of
ascocarp that is open, saucer-shaped or cup-shaped, and in which the
hymenium is exposed at maturity.[38] The term was first used by
Erik Acharius in 1803.[3]
Also araneose, araneous.[40] Having a
cobweb-like form, like that of the irregularly oriented and loosely interwoven
hyphae of the
medullary layer of some lichens.[41]
A shape or structure that is curved or arched like a bow.[43]
ardella
Plural ardelae. A type of
apothecium, typical of lichens in the family
Arthoniaceae, which is small and round. Elongated ardellae are called
lirellae.[44] The term was first used by
William Allport Leighton in 1854, who described an ardella as resembling a "sprinkled spot".[4]
areole
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.[45]
Also ascogenic. Producing or supporting the growth of an
ascus.[47]
ascolichen
A lichen in which the fungal partner (the
mycobiont) is a member of the
Ascomycota. About 98% of lichens are ascolichens.[50]See related:
basidiolichen.
A morphotype of
corticolousthelotremoid 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.[58]
A lichen in which the fungal partner (the
mycobiont) is a member of the
Basidiomycota. About 0.4% of lichens are basidiolichens.[50]See related:
ascolichen.
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.[63]
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.[67]
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.[70]
botryose
Resembling rounded, bead-like structures or clusters resembling grapes.[43]
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.[71]
Also defined: hepaticolous lichen; muscicolous lichen. A lichen that grows on a
moss or
liverwort – i.e. on a
bryophyte.[73] A hepaticolous lichen is found only on liverworts, while a muscicolous lichen is found only on mosses.[74][75]
bullate
Having blister-like or bubble-like swellings on a surface.[76]
Also caespitous, cespitose.[79] Growing in dense clusters or tufts, often used to describe fungi that arise from a common base or grow closely together without fusing.[18]
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.[81]
Having one or more longitudinal grooves or channels.[83]
capitate
Having a well-formed head, usually spherical or hemispherical in shape.[68]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.[84][68]See related:
mazaedium.
carbonized
Also carbonised, carbonaceous. Blackened and brittle tissue resulting from the accumulation of pigments.[85]
cariose
A lichen thallus or structure that is cracked, split, spongy, or otherwise decayed or in a state of disintegration.[43]
cartilaginous
Also 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.[86]
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.[68] These structures are found in most lichens that contain both algal and cyanobacterial
photobionts.[91] The term was first used by
Erik Acharius in 1803.[3]
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.[92]
cetrarioid lichen
An informal
growth form category used for lichens with erect,
foliosethalli, and
apothecia and
pycnidia on the margins of the lobes; characteristic of lichens previously classified in the genus Cetraria (in the broad sense).[93]
chalaroplectenchyma
Plural chalaroplectenchymata. A type of
plectenchyma comprising loosely interwoven
hyphae with holes; found in the
medulla of some lichens.[92]
character
A distinguishing feature that is characteristic for an organism; equivalent to
phenotypic trait.[92]
chasmoendolith
Also chasmoendolithic. A type of organism, typically a lichen or fungus, that lives within cracks and fissures of rocks.[94]See related:
endolith.
checklist
A list of all of the species (sometimes including
subspecies,
varieties and
forms) that occur within a particular region.[95]
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.[96]
A morphotype of
corticolousthelotremoid 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.[30]
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.[100]
CK test
A seldom-used
spot test performed with an application of
C followed immediately by
K.[101]
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.[102]
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.[103]
Having a finely scalloped edge; similar to crenate but with smaller notches.[119]
cruentodiscoid
A morphotype of
corticolousthelotremoid 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.[30]
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.[120]
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.[94]See related:
endolith.
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.[129] The term was first used by
Erik Acharius in 1799.[3]
Having small tooth-like projections or serrations along the edge.[134]
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.[135]
determinate
Having well-defined or clearly marked edges.[136]Contrast:
effuse.
diagnosis
A brief account of a
taxon describing the essential characteristics that distinguish it from its relatives.[137]
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.[138][139]
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.[143]
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.[145] The term was introduced by
Richard P. Korf in 1962.[146]
disk
Also: disc. The curved or flat upper surface of the
hymenium in an
apothecium, often pigmented and surrounded by a margin or rim.[143]
distal
Positioned away from a point of origin or from the center of a body.[147]
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.[148]
Referring to
crustose,
areolate lichens with
marginal areoles that are extended and arranged radially;[154] also defined more generally as "obscurely lobed".[155][156]
A fungus that lives within the
thallus of a lichen without producing any visible symptoms of disease; these fungi are
transmitted horizontally.[165]
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.[166]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.[167]Contrast:
epiphloedal.
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.[168]
epi-
Also ep-. A prefix meaning "upon" or "above".[169][170]
epibryophyllous
Also epibryophytic. Referring to organisms, particularly lichens or fungi, that grow on the surface of mosses (
bryophytes).[169]
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.[171]Compare:
epithecium.
epilithic
Also petricolous, rupicolous, saxicolous. A crustose lichen that grows on the surface of rocks.[166]Contrast:
endolithic.
Also perrumpent. Breaking through a surface.[178] 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.[179]
Plural eucortices or eucortexes. A
cortex made of well-differentiated tissue.[181] 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.[182] The term eucortex was first used by
Gunnar Degelius in 1954.[5]
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.[94]See related:
endolithic.
Plural exsiccata, exsiccatae, exsiccati. A dried and labeled
herbarium specimen, often part of a numbered set.[183]
excipulum
Alsoexciple. Plural excipula. 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.[184]See related:
proper margin,
thallin margin.
A region of the
cortex where the
hyphae are aligned perpendicularly to the main axis of the
thallus.[190] The term was first used by Auguste-Marie Hue in 1906.[5]See related:
palisade cell.
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.[198]
fissurine
Also fissurate. A term used characterize a structure or surface displaying a pattern of narrow, elongated cracks or fissures.[199]
fissurinoid
A morphotype of
corticolousthelotremoid 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.[200]
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.[205][206]
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.[207][208]
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.[216][217]
A morphotype of
corticolousthelotremoid 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.[30]
glaucophaenoid
A morphotype of
corticolousthelotremoid 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.[30]
A now-obsolete, historical term for the algal layer in a lichen.[225]
gonidium
Plural gonidia. A now-obsolete, historical term for a lichen
photobiont.[225] The term was first used by
Friedrich Wallroth in 1825, and supplanted in the 1960s.[3]
gonimium
Plural gonimia. A now-obsolete, historical term for a lichen
cyanobiont.[225]
A term for the general appearance (the
habit) of a lichen.[227]
grumose
Having a
granular or crumbly texture or appearance.[43]
guttulate
Referring to structures containing small oil droplets (guttules); often used to describe spores. More precisely, spores can be described as
uni-,
bi-,
tri-, or
multiguttulate.[228]
Also gyrate. Curved backward and forward; with folds and undulations.[230]
gyrotremoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Gyrotremoid lichens have open apothecia with recurved
lobules, a
disc that is pigmented with concentric rings, and a smooth, more or less shiny thallus; this morphotype occurs in the genus Gyrotrema.[30]
A flattened attachment point formed through direct contact of a lichen
thallus to its
substrate; associated with
foliose and
fruticose lichens that lack other attachment organs, such as Hypogymnia.[231]
halonate
Also defined: halo. Referring to a spore that is surrounded by a transparent outer layer or a gelatinous, translucent sheath. This sheath is readily observed when the spore is
stained with
India ink, as the ink does not penetrate the
mucilage of the sheath, creating a light-transparent halo that is visible against a blackened background.[232][233]
Also heter-. A prefix meaning "other" or "different".[235]
heterocyst
A specialized type of cell found in some
cyanobacteria; heterocysts are thought to be involved in the
fixation of nitrogen by the lichen thallus, as well as in the multiplication of cyanobacteria.[236]
heteromerous
A lichen
thallus that is organized into discrete layers or strata; the term applies to the majority of
foliose,
squamulose, and
crustose lichens.[237]
Also hormocyte. Also defined: hormocystangium, plural hormocystangia. An asexual
propagule, produced in a cup-shaped structure called the
hormocystangium, comprising heavy, gelatinous fungal
hyphae enclosing a few
cyanobiont cells; these structures occur in some
gelatinous lichens in the family
Collemataceae.[242] Both terms, hormocyst and hormocystangium, were introduced by
Gunnar Degelius in 1945.[5] According to one source, hormocyte and hormocytangium (spelled without the "s") are more accurate terms, because the cells (indicated by the ending -cyte) are not sexual propagules (which is implied by the ending -cyst).[243]
Embedded or sunken into the surface; in lichens, often used to describe
perithecia.[253] 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 3/4 beneath the level of the
thallus.[179]
Also defined: inspersion.Also inspers, interspersed. Terms used to describe the presence of minute, scattered
oil droplets or
granules within a tissue, typically observed in
section with a
compound microscope.[256] An inspersion refers to the degree of obstruction caused by the sprinkling of small particles within different sections of a given structure.[257]
A structure that resembles an
isidium, but is formed as an outgrowth of the
medulla rather than the
cortex; associated with
soralia of species in the genus Usnea.[260]
Plural isidia. A
propagule that is an outgrowth of the
thallus; it has a
cortex and contains
photobiont cells.[259] The term was first used in the sense it is used now by Georg Meyer in 1825, and adopted by
Elias Fries in 1831.[3]
isodiametric
Having roughly equal dimensions in all directions, resulting in a roughly spherical or cube-like shape; often used to describe cells that are not elongated or flattened but maintain a uniform size across their width, height, and depth.[261]
Plural jugae. A tiny
carbonized structure made of
hyphal tissue, visible as a black dot, line, or ridge, on or in a
thallus; associated with the genus Verrucaria.[264]
Also LCB. A
histologicalstain commonly used to prepare semi-permanent
slides. With this reagent, fungal
hyphae stain blue, and algal cells stain deep blue to blue-green.[101]
lacunose
Also lacunar, lacunous. A texture that appears pitted or containing gaps or holes, giving it a somewhat rough or uneven appearance.[269]
lageniform
Flask-shaped; with a swollen base tapering to a narrow top.[270]
lamella
Plural lamellae. In the genus Umbilicaria, lamellae are flattened plate- or strap-like structures that project downward from the
thallus undersurface.[271]
Also lecanoroid. An
apothecium in which the
disk is surrounded by a pale thalline margin, which has both algal and fungal cells, as in the genus Lecanora. The term is also used more generally to refer to
crustose lichens of the order
Lecanorales that have rounded apothecia with thick, protruding margins.[274]
lecideine
Also lecideoid. An
apothecium in which the
disk lacks a thalline margin, as in the genus Lecidea. The term is also used more generally to refer to apothecia with a blackened (carbonaeous) ring and a blackish
disk.[275]
leiodisk
Also leiodisc. A
disk of an
apothecia that is smooth and without folds or protrusions.[276] The term was introduced by
George Llano in 1950.[5]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Leprocarpoid lichens have open apothecia with erect lobules and a mealy and more or less
matte thallus; this morphotype occurs in the genus Chapsa.[30]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Leptotremoid lichens have immersed apothecia with small pores, and a rough thallus containing crystals; this morphotype occurs in the genus Leptotrema.[30]
leucodectonoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Leucodectonoid lichens have closed apothecia with tiny pores, and a rough thallus containing crystals; this morphotype occurs in the genus Leucodecton.[30]
The name of a historical
class that contained all of the lichen-forming fungi. This name was used when it was still erroneously believed that these fungi were quite separate from the non lichen-forming fungi; now obsolete.[279]
A lichen that grows on stripped wood (
lignin) – that is, on bare wood rather than bark.[73]
ligulate
Also liguliform, lingulate, lorate. Narrow and flat, with the form of a
strap.[281]
lirella
Plural lirellae.Also hysterothecia, lirelline apothecia. A linear
ascocarp, which may be straight, curved, branched, or
flexuous, with a longitudinal slit; characteristic of lichens in the genus Graphis.[282] The term was first proposed by
Michel Adanson in 1794.[3]
A lichen with a
thallus large enough that its main characteristics can be identified without the use of viewing magnification; generally refers to
foliose,
squamulose, and
fruticose species.[289]
Cuff-shaped; the term is used to describe
soralia that break open to form a central perforation revealing a duct to the
medullary cavity. Maniciform soralia occur in the genera Hypogymnia and Menegazzia.[291]
A morphotype of
corticolousthelotremoid lichens describing a type of apothecium structure resembling
topeliopsidoid apothecia but characterized by a minimized
thallus margin. The distinctive feature of melanotopelioid apothecia is the presence of "teeth" that are black and
carbonized, at least on the external surface.[296]
melanotremoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Melanotremoid lichens have prominent apothecia with wide pores and a black margin; pore filled with broad "stump" (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genera Melanotrema, Ocellularia, Clandestinotrema, and Trinathotrema.[30]
Also microcrystal test. A method used to identify some
lichen products that involves re-
crystallization on a
microscope slide from a range of
solvents and the formation of crystals with characteristic shapes; the crystals are examined microscopically for identification. Although this technique has largely been supplanted by the more reliable and sensitive technique of
thin-layer chromatography, there are certain situations where it is still useful.[298]
microlichen
A small lichen whose physical features cannot be distinguished without the aid of a 10X or greater viewing magnification;[299] it generally refers to
crustose and
foliicolous species.[300] The prefix "micro-" is also used to indicate small versions of particular growth forms, e.g. microfruticose or microfoliose.
Also defined: mycophycobiont. A
symbiosis where an
ascomycete fungus is housed inside multicellular algae; the algae and fungus involved in this association are called mycophycobionts.[309] Contrary to a lichen symbiosis, the fungal partner is the inhabitant, and the algal partner dominates.[310]
myriotremoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Myriotremoid lichens have immersed apothecia with small pores, and a smooth and more or less shiny thallus; this morphotype occurs in the glaucopallensgroup of genus Myriotrema.[30]
Egg-shaped, with the narrower end at the base.[311]
obpyriform
Shaped like an inverted pear.[312]See related:
pyriform.
ocellularioid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Ocellularioid lichens have prominent apothecia with wide pores; pores with a "finger" (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genus Ocellularia.[30]
-oid
A suffix meaning "like" or "having the form of".[313]
A small pore or opening; in lichens, it is used to refer to the
paraphysis-lined cavity in a
parathecium that ends in a pore, or more generally to any pore from which spores are released from an
ascus-bearing fruit body.[315]
ostropalean
Referring to asci that are
unitunicate with a thickened apex and a narrow canal ending in a pore; associated with species in the order
Ostropales.[316]
Plural palisade plectenchymata. Also palisadoplectenchyma, plural palisadoplectenchymata. A type of
plectenchyma in a
cortex where the
hyphae are arranged perpendicularly to the plane of the
thallus.[319]
pallidostegoboloid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Pallidostegoboloid lichens have prominent apothecia with wide pores; pore filled with irregular structures; pale walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in wrightiigroup of the genus Stegobolus.[30]
papilla
Plural papillae. A small, conically rounded growth.[320]
An organism that lives in close association with a
host species, deriving benefits at the host's expense but not causing immediate harm; an intermediate state between
symbiosis and
parasitism.[267]
An informal
growth form category used for lichens that are mostly
foliose, often closely attached to the substrate, and have
laminalapothecia and
pycnidia; this group of features is characteristic of lichens previously classified in the genus Parmelia (in the broad sense).[93]
Also clypeate, scutiform. Referring to a rounded structure attached on the lower side at a single central point (often on a short stalk), with free edges.[330]
peltidiangium
A basket-like structure in which
peltidia are produced.[331]
Plural periphyses. A short, sterile
hypha that develops from above the ascus and grows down a short distance, typically lining the internal walls of the
ostiole in a
perithecium.[335]
Also defined: exospore, epispore, mesospore, endospore. The colorless and usually gelatinous outermost layer of a spore.[336] This transparent layer determines the spore's shape.[337] The other four layers of a spore, going inward, are the exospore, epispore, mesospore, and endospore.[336]
perithecium
Plural perithecia. A spherical or flask-shaped
ascocarp that is
sessile or partly immersed in the
thallus, with a single opening (
ostiole) and enclosed by a distinct wall; a characteristic of
pyrenolichens.[338] Although it was in 1831 that
Elias Fries first applied the term perithecium to lichen fruit bodies, the word was originally coined by
Christiaan Hendrik Persoon in 1794.[339]
Plural phenocortices, phenocortexes. A structure, similar to a
cortex, containing
hyphal fragments and dead, collapsed algal cells sloughed off from the
algal layer.[341]
photobiont
Also defined: phycobiont, cyanobiont. The photosynthetic component of a lichen. This can be either a
green alga (known as a phycobiont) or a
cyanobacteria (known as a cyanobiont).[342] The term "phycobiont" was proposed by George Scott in 1957.[5]
Plural phyllidia. A small leaf-like or scale-like
propagule that is
corticate and has distinct upper and lower sides (i.e., it is
dorsiventral); it originates from the margins or on the upper surface of
thallus.[346] Phyllidia occur in some species of the
Lecanorales and the
Peltigerales.[347]
Characterised by longitudinal folds forming
pleats, often used to describe closely adjacent, markedly convex thallus
lobes or elongated
areoles that display a "folded" appearance.[355]
plurilocular
Also multilocular. Having many cavities or
locules; used to describe spore structure.[356]
A lichen test performed by shining a
polarized light at a lichen structure in microscopic view; in the genus Hypogymnia, the presence (POL+) or absence (POL−) of POL-sensitive crystals in the
hypothecium is a useful
character to help distinguish species.[357]
polarilocular
Also placodiomorphic,[252]polar-diblastic, polaribilocular, polocellate. A spore divided into two components (locules) separated by a central
septum with a perforation or
isthmus.[358][359] The term was first used by
Wilhelm Körber in 1855 (as "polari-dyblastae") to describe the spores of Rhizocarpon and Umbilicaria. It was
anglicized to "polari-bilocular" by William Mudd in 1861, and finally shortened to polarilocular by the Henri Olivier in 1882.[4]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Praestantoid lichens have large and prominent apothecia with small pores; pores with "finger" (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the praestansgroup of the genus Ocellularia.[30]
Sticking out from the surface of the
thallus.[363] 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 above the level of the
thallus, and have a base that is expanded outwards.[179]
proper margin
Also proper exciple, ectal excipulum, medullary excipulum, proprium. A ring of tissue around the
disk of a
lecanorineapothecium; this tissue, which originates from the
medulla, is not lichenized, and is internal to the
thalline margin (if present).[364] The term "proper margin" was first used by
Erik Acharius in 1803; in 1825
Elias Fries changed the noun and called it "proper exciple".[3]
Plural prosenchymata. A type of
plectenchyma in which the constituent fungal
hyphae are arranged parallel to each other, such that individual hyphae can be clearly distinguished using microscopy.[365]
prosoplectenchyma
Plural prosoplectenchymata. A type of
plectenchyma, common in the
thalluscortex of lichens, in which the constituent fungal
hyphae are aligned in a particular direction.[365]
A fungal layer upon which an algae-containing
thallus may develop, lacking
photobiont; usually white, brown, or black, and found between the
areoles and at the growing margins of
crustose lichens.[366] The term was first used by Georg Meyer in 1825.[3]
prototunicate
A form of
unitunicateascus in which the wall breaks down before maturity (thus releasing its
ascospores), and which lacks differentiated apical structures.[367]
proximal
Positioned close to a point of origin or near the center of a body.[368]
pruina
A powdery, frost-like or flour-like deposit on a surface. In lichens, pruina is often the result of the accumulation of crystalline
hydrates of
calcium oxalate, of
lichen products, or sometimes of the dead or dying cells of the
epinecral layer.[369]
Also pseud-. A prefix meaning "false";[370] used in terminology to denote something is false, or that one structure resembles something else, such as the
pseudocyphella resembling the
cyphella.[368]
Plural pseudocortices, pseudocortexes. A boundary layer of the
thallus containing distinct
hyphae that are not organized into a regular tissue structure;[371] sometimes used to refer to the false
cortex present on the outer layer of
pseudopodetia, such as those found in the lichen Pycnothelia papillaria.[372]
Plural pseudocyphellae. Small openings in the
cortex of a lichen, where the
medulla is exposed to air, and there are no specialized cells surrounding the cavity.[373] The term was first used by
William Nylander in 1858.[4]
Also cataphysis. A
paraphysis-like
hypha that forms in the locule or perithecial cavity before the formation of the
ascus; it grows downward from the top of the cavity to the base of the ascomata.[375]
Also recurvate, reflexed.[390] Curved or bent back; in lichens, these terms are used to describe the tips of
branches or
lobes that are curved up or down, or back onto themselves.[391]
redingerioid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Redingerioid lichens have immersed apothecia with linear slit; slit filled with irregular structures; black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genera Redingeria and Stegobolus.[30]
reimnitzioid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Reimnitzioid lichens have open apothecia with erect
lobules, and a rough thallus containing crystals; this morphotype occurs in the genus Reimnitzia.[30]
A single
hyphal strand on the
thallus underside that serves as an attachment organ.[395]
rhodostromoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Rhodostromoid lichens have large and prominent apothecia with small pores; pore with “finger” (columella); black walls and pigment (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the rhodostromagroup of the genus Ocellularia.[30]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Schizotremoid lichens lack apothecia and have
schizidia, and a smooth, more or less shiny thallus; this morphotype occurs in the genus Stegobolus.[30]
Plural scleroplectenchymata. A type of
plectenchyma comprising thick-walled
hyphae that are stuck closely together; present as a component of the
stereoma tissue supporting the
thallus in the genera Cladonia and Alectoria.[407]
scrobiculate
Having large, shallow depressions that are narrowly separated by rounded ridges.[191]Compare:
faveolate,
foveolate.
Lacking a stem.[413] 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 3/4 above the level of the
thallus, with a constricted base.[179]
sibling species
Closely related species that are morphologically indistinguishable but can be distinguished by non-morphological traits, such as chemistry or genetic differences. Initially defined as species recognized mainly through cryptic or non-morphological discontinuities, the concept has evolved to specifically refer to
cryptic species that form a
monophyletic group, meaning they share a
common ancestor not shared with any other species. This concept is a subset of the broader terms
species pair and "cryptic species".[414]
sigmoid
Curved upon itself twice, like the letter "S".[415]
simple
Lacking branches or divisions; in lichenology, it is used to describe structures such as
thalli or
rhizines, or
spores without
septa.[416]
Shaped like the sole of a shoe, with a flat, elongated, and slightly curved appearance.[418]
soralium
Plural soralia. A part of the
thallus where the
cortex has cracked or broken down and
soredia are produced. Soralia can be further characterized as diffuse if they are spread out on the upper thallus surface as a continuous layer, or delimited if they are confined to a more restricted area. If soralia originate in tubercules they are tuberculate, while they are fissural if they are created in fissures.[419] The term was proposed by
Johannes Reinke in 1895.[5]
Plural soredia. A powdery to granular reproductive
propagule that is not covered with a well-defined
cortex (in contrast to
isidia, and contains both algal (
photobiont) and fungal (
mycobiont) components.[419] The term was first used by
Erik Acharius in 1803.[3]
Two lichen species that are identical
morphologically, anatomically, and chemically, but can be distinguished by their
sexual versus
asexual reproductive strategies; the fertile taxon is known as the primary species, while the
vegetatively reproducing taxon is known as the secondary species.[362] The use of
molecular methods to analyze putative species pairs has shown that the underlying phylogenetic situation is more complex than had been assumed, and not necessarily correlated with reproductive strategy.[421]See related:
sibling species.
spermogonium
Also spermagone, spermagonium. In lichenology, an obsolete term for
pycnidium.[422]
A small spine; in some
fruticose lichens of the
Lecanoromycetes, it refers to a small cylindrical outgrowth, with a narrow base, in which the
central axis is not connected with the
central axis of the main branch.[423]
spinulose
Also spinulous. Covered with or having small spines (
spinules) or spiny projections.[423]
A lichen species that is extremely similar (or identical) in external morphology, anatomy, chemistry, and spore size to another, but that is placed in a different genus solely based on differences in spore septation and/or spore colour. The term was introduced by Michael Wirth and
Mason Hale in their 1978
monograph about the
Graphidaceae, a family in which sporomorphs are common.[427]
A
spot analysis used to help identify lichens; it is performed by placing a drop of a
reagent on different parts of the lichen and noting any color change associated with application of the reagent. The four most common tests are
C,
K,
KC, and
PD.[429]
Brush-like, with many short, more or less perpendicular lateral branches. In lichenology, used to refer to
rhizine structure.[431]
stegoboloid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Stegoboloid lichens have prominent apothecia with wide pores; pore filled with irregular structures; black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genus Stegobolus.[30]
Plural stromata. A dense mass of
vegetativehyphae that supports spore-bearing structures.[433] In lichens, the stroma is often hard and carbonaceous.[395]
sub-
A prefix meaning "below", "under", "somewhat, or "almost".[434] Also used in front of names of
taxonomic ranks to indicate intermediate categories, e.g.
subspecies or
subgenus.[435]
Also subicule.Plural subicula. A layer of loosely-compacted
mycelia that covers the
substrate and cushions fruiting bodies such as
apothecia and
perithecia.[436] The texture of the subiculum can be described as net-like, wool-like, or crust-like.[434]
Also substratum; plural substrata. The surface or base upon which a lichen grows or is attached. Although the terms substratum and substrate are often used equivalently in lichenology, the latter term has different meanings in
microbiology and in
enzymology.[437]
subulate
Slender and narrowing to a fine point;
awl-shaped.[438]
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus morphology. Tenuitremoid lichens have immersed apothecia with small pores and a black margin; pore with “finger” (columella); black walls (viewed in microscopic
section); and a smooth, more or less shiny thallus. This morphotype occurs in the genus Clandestinotrema.[30]
tegulicolous lichen
A lichen that lives on
tiles.[440] In general, these are
calcicolous lichens or lichens that are indifferent as to their substrate.[441]
Describing a cylindrical or rod-like structure that is round in cross-section.[418]
teretiform
Describing a shape that is nearly cylindrical or rod-like, similar to but not exactly
terete; circular in cross-section, gradually tapering towards one end.[443]
Also thalline exciple, excipulum thallinum. A rim of tissue around the
disk of a
lecanorineapothecium; this tissue, external to the inner
proper margin, is made of tissue with a structure similar to that of the
thallus.[445] The term "thalline margin" was first used by
Erik Acharius in 1803; in 1825
Elias Fries changed the noun and called it "thalline exciple".[3]
Plural thalloconidia. A dark brown, smooth to wrinkled
propagule arising directly from a
thallus, particularly the lower
cortex and/or the
rhizines. They are found in some species of Umbilicaria, and similar structures arise from the
prothallus of some species in the genera Protoparmelia, Rhizoplaca, and Sporastatia. Thalloconidia have distinct cell layers in their walls, and comprise between 1 and about 2500 cells.[447][448]
Plural thalli. The body of a lichen,[450] made up of both fungal and algal or cyanobacterial cells.[451] The term was first used by
Erik Acharius in 1803.[3]
A morphological group of lichens within the
Graphidaceae, the largest family of
crustose lichens.[453] Thelotremoid lichens are characterized by immersed-
erumpent, rounded
ascomata, non-branched to slightly branched
paraphyses, mostly
distoseptate ascospores, and mostly a
prosoplectenchymatousexcipulum. Thelotremataceae, a traditional family of lichens, has been included in Graphidaceae, and its species are now informally accepted as thelotremoid lichens.[453]
tholus
Plural tholi.Also dome. The apical, often thickened part of the inner wall in a
bitunicate ascus.[454]
tomentum
Plural tomenta. Also defined: tomentose. A layer of short interwoven or coiled fungal
hyphae with a texture similar to
velvet. In lichens, the tomentum projects from the lower
cortex and serves to help it attach to its
substrate. Structures with this type of hyphae are called tomentose.[455] Tomentose surfaces are found in
foliose genera such as Lobaria, Pseudocyphellaria, and Sticta.[456]
topeliopsidoid
A morphotype of
corticolousthelotremoid lichens used to describe characteristics of
apothecial and
thallus structure. It pertains to lichens where the apothecia are either prominent or
sessile, often hidden between the
substratum, and they open with multiple, typically regular "teeth" that stay relatively curved over the hardly visible
disk. The margins tend to peel off, meaning the overlaying thallus cortex separates from the underlying marginal thallus tissue, but no distinct, clean split between thallus margin and
excipulum is formed. This morphotype is seen in species like Chapsa meridensis and Topeliopsis.[457]
trabecula
Plural trabeculae. In the genus Umbilicaria, they are rib- or strap-shaped structures radiating outward from the
umbilicus that merge towards the mid-zone of the
thallus undersurface.[271]
trentepohlioid
Resembling or belonging to the
green algal genus Trentepohlia; trentepohlioid cells are filamentous (elongated and cylindrical), multicellular, and have a yellow to orange colour.[458]
Also defined: funiculus, umbilicus, umbilical cord. A lichen with a concave, circular, leafy
thallus that is joined to its
substrate only by its central part, called an umbilicus, umbilical cord or funiculus.[461][462]
A type of
ascus with a single functional layer; the rigid internal and external wall layers do not separate during release of the
ascospores. Most
ascomycetes have unitunicate asci.[466]
Deeply cup-shaped or
urn-shaped; in lichens, the term is used to describe some
apothecia with a sunken
hymenium and elevated
parathecium that forms a narrow mouth.[468]
A lichen test performed by shining a long-wavelength
ultraviolet light (350
nm) at a lichen structure to check if it
fluoresces; a positive test (abbreviated as UV+) indicates the presence of certain
lichen products.
Xanthone compounds in the
cortex tend to fluoresce yellow, orange, or red, while
depsides and
depsidones in the
medulla fluoresce blue to white.[470]
A lichen not attached to a
substrate, typically able to be blown around by wind.[471]
vegetative
Also assimilative. Having to do with the growth phase of an organism before reproduction, including spore germination, growth, development and asexual multiplication.[472]
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