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Glossary of Lichen Terms
Aggregate thallus
of leprose lichens whose granules are scattered or clumped but not arranged in a single even layer resembling a foliose lichen
all the tissues in the rim of a lecanorine apothecium, generally a cortex, algal layer and medulla
Anamorphic fungi
artificial grouping of asexually reproducing fungi (via conidia) including both Basidiomycetes and Ascomycetes
Apothecium, pl. apothecia
a disk or cup-like fungal reproductive structure where the hymenium is directly exposed to the environment
a thallus composed of areoles, or lichen surface appearing composed of areoles
small, tile-like patch of thallus, discrete from others or crowded
Ascoma, pl. ascomata
spore-producing structure of an ascomycete fungus, e.g., apothecium, perithecium, or other, containing asci
any fungus in the phylum Ascomycota, with spores produced in asci; most lichens are ascomycetes
Ascus, pl. asci
the sac in which spores are produced in ascomycete fungi
any fungus in the phylum Basidiomycota, in which spores are produced on specialized club-like cells called basidia; only a few lichens or lichen-like compound organisms are basidiomycetes
Blastidium, pl. blastidia
a granular asexual reproductive structure produced in a budding process from the margin of a lichen thallus
referring to all or part of a lichen thallus composed of a mat of fungal hyphae, or made up of a mat of filamentous algae associated with fungal hyphae
C or Cl
chlorine bleach, used in spot tests to detect secondary metabolites (e.g., gyrophoric acid, olivetoric acid)
a cup-shaped or hemispherical apothecium formed at the tip of a stalk in some lichens
referring to tissue that is black, opaque and brittle, e.g., the exciple in some apothecia
Cephalodium, pl. cephalodia
a gall-like structure on the surface or within certain green-algal lichens, containing cyanobacteria, used as a source of nitrogen by some lichens
used in lichenology to refer to secondary metabolites that are created by some lichens for various purposes, & differences among which are used to distinguish species; detected via color, spot tests, UV tests, or thin-layer chromatography
Conidium, pl. conidia
asexual spores produced within specialized structures, e.g., pycnidia, hyphophores
the hardened, protective outer layers of a lichen thallus or apothecium, made up of gelatinized fungal hyphae or occasionally cells of a basidiomycete yeast
composed of or including a cortex
of lichens that favor bark as a substrate
having a wavy or fluted edge
any lichen entirely adhering to or slightly within its substrate and without a lower cortex
Cyanobacterium, pl. cyanobacteria
bacteria capable of photosynthesis, sometimes used as photobionts in a lichen symbiosis, or occasionally as a source of nitrogenous nutrients (since they can fix atmospheric nitrogen) when contained in cephalodia
Cyphella, pl. cyphellae
a specialized opening in the lower cortex exposing tissues within, characteristic of lichens in genus Sticta
Diahypha, pl. diahyphae
specialized conidia, often filaments of multiple cells, produced on or within hyphophores, especially in Gyalideopsis and other members of family Gomphillaceae
any asexual reproductive fragment of a lichen, e.g., soredia, isidia, schizidia, lobule, etc.
intercellular substance between cells or lumina in some spores (e.g., Pyrenula)
entirely without soredia
a layer of tissue in the apothecium surrounding the hymenium and hypothecium
any lichen with a leafy structure, often with a definite upper and lower surface and stratified interior
any lichen with a shrubby structure, lacking a definite upper or lower surface, and usually with algae beneath every surface
packet of algal cells surrounded by a fungal layer
with a gelatinous halo surrounding each spore
growing on liverworts
of spores or sections of apothecia, when they are clear, colorless or free of pigment
the spore-producing layer within an ascoma, with asci and specialized fungal filaments (e.g., paraphyses)
Hypha, pl. hyphae
cell of a fungus, usually filamentous (sometimes spherical or cuboidal)
a group of fungi often referred to as Fungi imperfecti, Deuteromycota, or anamorphic fungi; hyphomycetes lack closed fruit bodies, & are often referred to as molds
a fertile stalked structure produced by some lichen crusts in Gomphillaceae, often expanded into a blade, fan or umbrella-shape near the top, bearing a bundle of thread-shaped diahyphae
layer of fungal tissue beneath the hymenium, sometimes pigmented, often merging with and difficult to distinguish from the exciple
containing fine granules or oil droplets, e.g., in the hymenium, resulting in a granular cloudiness in the tissue
of a lichen thallus that produces isidia
Isidium, pl. isidia
a specialized asexual reproductive structure projecting from the surface or margin of a lichen, fingerlike (branched or not) or small and knobby
K or KOH
potassium hydroxide, used in spot tests to detect secondary metabolites (e.g., atranorin, norstictic acid)
spot test combination, testing first with K and then with C, used to test for secondary metabolites (e.g., usnic acid, protocetraric acid)
Labium, pl. labia
the lip-like sides of lirellae in some script crusts
on the upper surface of a lichen thallus
on the sides of a lichen thallus, e.g., along the sides of a foliose lichen’s lobes
describing the rims of apothecia, in which the rim functions as an extension of the thallus, with a cortex, algal layer and medulla, and is the same color as the thallus
lichen thallus composed entirely of granules, each made up of algal cells surrounded by a sphere of fungal hyphae
fungi that live in or on the thalli of lichens, either as parasites or in some other type of symbiosis
a fungus adapted to life as a lichen, using a photobiont as a food source
of a lichen preferring decorticate wood as a substrate
Lirella, pl. lirellae
specialized apothecia growing in two directions (rather than radially), creating a linear, often branched structure
of a structure in the form of or resembling a lirella
community of corticolous lichens including various species of Lobaria, Ricasolia, Crocodia & cyanolichens, especially those in Sticta and family Pannariaceae; thought to be pollution-intolerant, & indicative of undisturbed or old-growth forests
Lumen, pl. lumina
the membrane-defined space(s) within a spore containing germ cell(s), either entirely filling the spore to cell walls, or with an intercellular substance called endospore between lumina & cell walls
Mazaedium, pl. mazaedia
a dry, powdery mass of spores and disintegrating tissues of the apothecia of some lichens (especially in Caliciales)
inner fungal layers beneath the algal layer of many lichens, chemically distinct from the cortex
of lichens preferring to grow on bryophytes
the fungal partner in the lichen symbiosis
the pore of a lichen ascoma or pycnidium through which spores emerge
P or PD
para-phenylenediamine, a chemical used in spot tests to detect secondary metabolites (e.g., fumarprotocetraric acid, pannarin)
Perithecium, pl. perithecia
ascoma in which the hymenium is entirely enclosed within the exciple, opening to the environment through the ostiole
the photosynthetic organism supplying food and/or other nutrients to the lichen, either an alga or cyanobacterium (if more than one, distinguished as primary or secondary photobionts)
Placodioid thallus
of leprose lichens whose granules are densely arranged in an even layer resembling a foliose lichen
the growing edge of the lichen, containing the primary fungus without photobiont, usually differently colored than the thallus
a dusting or layer of powder or crystals on the surface of a lichen
Pseudocyphella, pl. pseudocyphellae
pit-like pore on the surface of a lichen exposing the medulla
Pseudostroma, pl. pseudostromata
a specialized layer of fungal tissue, often raised above the thallus, in which ascomata are imbedded
any lichen in which the reproductive structures are perithecia
referring to lobe morphology, with margins curling under, not remaining plane or flat
specialized fungal structures attaching some foliose lichens to the substrate
Rhizohypha, pl. rhizohyphae
hyphae that perform the same function as rhizines
of a lichen thallus that is cracked into polygons, sometimes difficult to discern from a crowded areolate thallus
of fungi that obtain nutrients from the breakdown of dead plant tissue
of lichens that prefer to grow on rock
divided by layers or divisions, especially spores divided into multiple cells along their length
resting on the surface, as apothecia that lie flat on the thallus (rather than immersed in it)
Seta, pl. setae
a sterile, rigid, acute-tipped bristle on a crustose lichen
of a lichen that reproduces via soredia
Soredium, pl. soredia
a specialized asexual reproductive granule made up of algal cells surrounded by a layer of fungal hyphae
the reproductive entity of a fungus, either produced sexually within an ascus (sometimes referred to as ascospores) or asexually (conidia)
Spot test
applying a minute amount of a chemical (e.g., KOH, Cl, PD) or sequence of chemicals on a specific lichen tissue to note color changes; used in lichen identification
a scale-like projection of a lichen thallus, determinate in size, either in a thallus partly or entirely composed of squamules (e.g., many Cladonia) or as scaly asexual reproductive structures on some foliose lichens
with squamules; of a lichen whose thallus is composed partly or entirely of squamules, spreading by the creation of more at thallus edges
on a stalk or other distinct stem-like structure
used to describe labia in Graphis, when they are composed of layers of carbonized material, usually visible under a dissecting scope as grooves along the length of tops of labia, but most apparent when wet mounts of cross sections are examined under higher magnification
Synnema, pl. synnemata
a large, erect reproductive structure in some fungi, bearing compact conidiophores that fuse together to form a strand with conidia at the end or on the edges
referring to something at the tip of a lobe or other lichen structure (e.g., a podetium)
typically growing on or over soil
Thallus, pl. thalli
the body of a lichen, presumed to contain all the elements that make up the compound organism, including primary fungus, one or more photobionts, & associated microbiome
in the shape of a turban: puffed out at sides beyond the edges of base
Ultraviolet light, used to test for secondary metabolites (e.g., lichexanthone, divaricatic acid)
of a thallus surface, with slightly to abundantly bumpy
minutely bumpy surface (i.e., smaller bumps than in verrucose)