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''Physcia caesia'', known colloquially as blue-gray rosette lichen and powder-back lichen, is a species of
foliose A foliose lichen is a lichen with flat, leaf-like , which are generally not firmly bonded to the substrate on which it grows. It is one of the three most common lichen growth forms, growth forms of lichens. It typically has distinct upper and lo ...
lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
ized fungus. First described by
Georg Franz Hoffmann Georg Franz Hoffmann was a German Botany, botanist and lichenology, lichenologist. He was born on 13 January 1760 in Marktbreit, Germany, and died on 17 March 1826 in Moscow, Russia. Professional career After graduating from the University of Er ...
in 1784, it is common across much of
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
,
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
and
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
, and more patchily distributed in
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
,
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
and
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
. There are 2
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
: ''P. c. caesia'' and ''P. c. ventosa'', as well as a number of distinct forms and
varieties Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...
. Molecular studies suggest that the species as currently defined may be
polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
. It is typically pale gray shading to darker gray in the center (though some forms are considerably darker), and grows in a small rosette, usually some across at maturity. It only rarely has
apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...
, instead reproducing most often vegetatively via
soredia Soredia are common reproduction, reproductive structures of lichens. Lichens asexual reproduction, reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungus, fung ...
, which are piled in round blue-gray mounds across the
thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...
's upper surface. It grows most often on rock—principally calcareous, but also
basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...
and
siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant ...
—and also occurs on bone, bark and soil. It is nitrophilic and is particularly common on substrates where birds perch. Capable of growing at a multitude of angles on a variety of surfaces, ''Physcia caesia'' also tolerates a wide range of environmental extremes from the high temperatures of desert locations to the low temperatures of the Antarctic. It grows on both dry stone and that moistened by seepage, and can survive being irregularly submerged for extended periods underwater. Like many lichens that grow on rock, ''Physcia caesia'' is able to extract nutrients from the substrate upon which it grows, as well as from rainwater and atmospheric dust. It is threatened by habitat loss through development, as well as trampling or overgrowth of its location. A number of
lichenicolous This glossary of mycology is a list of definitions of terms and concepts relevant to mycology, the study of fungi. Terms in common with other fields, if repeated here, generally focus on their mycology-specific meaning. Related terms can be found ...
species are known
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
s.


Taxonomy

''Physcia caesia'' was first described by German botanist
Georg Franz Hoffmann Georg Franz Hoffmann was a German Botany, botanist and lichenology, lichenologist. He was born on 13 January 1760 in Marktbreit, Germany, and died on 17 March 1826 in Moscow, Russia. Professional career After graduating from the University of Er ...
in 1784 as ''Lichen caesius''. Other lichenologists assigned it to various other
genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
both before and after it was moved into its current genus by August Emanuel Fürnrohr in 1839. It has two
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
, ''P. c. caesia'' and ''P. c. ventosa'', as well as a number of distinct forms and
varieties Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...
, some of which were thought to be distinct species in the past. Although this species and '' Physcia aipolia'' have been considered a
species pair In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
, some molecular studies suggest that they should instead be considered
conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...
. Other molecular studies suggest that both ''Physcia caesia'' and ''Physcia aipolia'' are
polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
taxa, with various forms more closely related to other species than to each other. The nomenclatural database
MycoBank MycoBank is an online database, documenting new mycological names and combinations, eventually combined with descriptions and illustrations. It is run by the Westerdijk Fungal Biodiversity Institute in Utrecht. Each novelty, after being screene ...
considers the taxon ''Physcia wainioi'', one of its many synonyms, to be a distinct species. The genus name ''
Physcia ''Physcia'' is a genus of lichen-forming fungi in the family Physciaceae. The widely distributed genus contains about 80 species. The genus is cosmopolitan distribution, cosmopolitan, and has been extensively studied in various regions in the p ...
'' means "inflated" or "sausage-like", referring to the form of the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
. The
specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
''caesia'' is a Latin word meaning "blue-gray". ''Physcia caesia'' is known colloquially as ''blue-gray rosette lichen'' and ''powder-back lichen''.


Description

''Physcia caesia'' is a
foliose lichen A foliose lichen is a lichen with flat, leaf-like , which are generally not firmly bonded to the substrate on which it grows. It is one of the three most common growth forms of lichens. It typically has distinct upper and lower surfaces, each o ...
that forms small rosettes, typically measuring across at maturity, though it can reach diameters of up to . The
thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...
is pale gray shading to darker gray in the center, and adheres closely to the
substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...
on which it grows. Its convex lobes are linear, typically measuring in width, though occasionally as wide as . Forms in some areas, including Greenland, can be considerably darker, with a thallus ranging from gray to dark gray; they can also have broader or narrower lobes. The lichen's surface is white-spotted, though this is not always obvious. It has blue-gray
soredia Soredia are common reproduction, reproductive structures of lichens. Lichens asexual reproduction, reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungus, fung ...
, which are piled in round mounds (such aggregations are known as soralia) across the thallus's upper surface. The lower surface is white to brown with short, dark
rhizine In lichens, rhizines are multicellular root-like structures arising mainly from the lower surface. A lichen with rhizines is termed rhizinate, while a lichen lacking rhizines is termed erhizinate. Rhizines serve only to anchor the lichen to their s ...
s. ''Physcia caesia'' only rarely has
apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...
. Where present, these are black discs measuring up to across, with prominent thalline margins (which means the thallus extends up around the edges of the apothecia) and a grayish
pruinescence Pruinescence , or pruinosity, is a "frosted" or dusty-looking coating on top of a surface. It may also be called a pruina (plural: ''pruinae''), from the Latin word for hoarfrost. The adjectival form is pruinose . Entomology In insects, a "bloom ...
. Each
ascus An ascus (; : asci) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some gen ...
contains 8 spores, which are thick-walled and brown, measuring x . Its
photobiont A lichen ( , ) is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualistic relationship.
is the
green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...
'' Trebouxia impressa'', a species associated with many ''Physcia'' lichens. The lichen's
cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...
and
medulla Medulla (Latin for "marrow") or medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ...
react positively with
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...
(K), turning yellow. Cortex and medulla react positively with para-phenylenediamene (Pd) as well, also turning yellow. They produce no reaction with calcium or
sodium hypochlorite Sodium hypochlorite is an alkaline inorganic chemical compound with the formula (also written as NaClO). It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of ...
(
bleach Bleach is the generic name for any chemical product that is used industrially or domestically to remove color from (i.e. to whiten) fabric or fiber (in a process called bleaching) or to disinfect after cleaning. It often refers specifically t ...
– C), nor with KC (potassium hydroxide quickly followed by bleach). Among the substances produced by the lichen are
atranorin Atranorin is a chemical substance produced by some species of lichen. It is a secondary metabolite belonging to a group of compounds known as depsides. Atranorin has analgesic, anti-inflammatory, antibacterial, antifungal, cytotoxic, antioxidant, ...
and
zeorin Zeorin is a triterpene with the molecular formula C30H52O2 which occurs in many lichens A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, al ...
.


Similar species

''Physcia caesia'' was long considered to be a species pair with the very similar ''Physcia aipolia''; the latter is regularly covered with black apothecia, and typically grows epiphytically. ''Physcia caesia'' may also be confused with ''Physcia poncinsii'', but the latter has "crateriform" (hollowed, like a bowl or saucer) rather than rounded soralia, and obviously convex lobes. It may also be confused with ''Physcia dubia'' which, like ''Physcia caesia'', can be quite variable; however, ''P. dubia'' has lip-shaped soralia (which tend to be primarily
apical Apical means "pertaining to an apex". It may refer to: *Apical ancestor, refers to the last common ancestor of an entire group, such as a species (biology) or a clan (anthropology) *Apical (anatomy), an anatomical term of location for features loc ...
), and its thallus does not react with potassium hydroxide.


Distribution and habitat

''Physcia caesia'' is widespread across much of the world, found in
Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
,
boreal Boreal, northern, of the north. Derived from the name of the god of the north wind from Ancient Greek civilisation, Boreas (god), Boreas. It may also refer to: Climatology and geography *Boreal (age), the first climatic phase of the Blytt-Sernand ...
and
temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
vegetation zones. Widely distributed across Europe, it is one of the most common species of ''Physcia'' in Greenland, and is abundant throughout Britain. Though found across much of North America, it is absent from central and southeastern United States, parts of the
Great Basin The Great Basin () is the largest area of contiguous endorheic watersheds, those with no outlets to the ocean, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja Californi ...
, and northern Alaska. In South America, it is found in Argentina, Chile, and Peru; common and widespread in temperate areas, it occurs only rarely and only at elevations above in tropical regions. It occurs patchily across Asia—in India, Bhutan, Nepal and Japan—as well as in East Africa. It is described as "cosmopolitan" in New Zealand, has been reported from a number of sites in southeastern Australia and Tasmania, and also occurs in Antarctica. It is common on calcareous substrates, growing on
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
(including
tufa Tufa is a variety of limestone formed when carbonate minerals precipitation (chemistry), precipitate out of water in ambient temperature, unheated rivers or lakes. hot spring, Geothermally heated hot springs sometimes produce similar (but less ...
) and
concrete Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
. It also grows on
basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...
and
siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant ...
rock, as well as on bone. It is particularly common on rocks where birds perch and
defecate Defecation (or defaecation) follows digestion and is the necessary biological process by which organisms eliminate a solid, semisolid, or liquid waste material known as feces (or faeces) from the digestive tract via the anus or cloaca. The act ...
. It is uncommon on bark; however, in the Colorado
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
, it is one of the predominant lichens on
juniper Junipers are coniferous trees and shrubs in the genus ''Juniperus'' ( ) of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere as far south ...
trees, growing primarily within of the ground on the northern and eastern side of trunks. In
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
, it grows on mosses, soil and gravel, and may be among the species contributing to the formation of a soil crust on the continent. In California, it is found in
montane Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...
and
subalpine Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial f ...
forests ranging from in elevation.


Ecology

''Physcia caesia'' tolerates a variety of locations, occurring on vertical, angled and horizontal surfaces, as well as rocky overhangs. It is found on both dry stone and stone moistened by seepage, and can tolerate being irregularly submerged underwater. It survives in hot desert conditions, primarily on the north side of slopes. It also thrives in cold conditions, and is able to
photosynthesize Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metaboli ...
at temperatures as low as . Like many lichens that grow on rocky substrates, ''Physcia caesia'' is able to accumulate a number of necessary nutrients—including nitrogen, phosphorus, potassium and iron—from the substrate upon which it grows, as well as from rainwater and atmospheric dust. Its
hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...
can extend into substrate as much as . It is a nitrophyte and can tolerate higher levels of atmospheric ammonia than can many other species of lichen, because it can survive on substrates with a higher pH. It has been recorded growing on a lead surface (probably a weathered oxide). ''Physcia caesia'' is known to accumulate high concentrations of heavy metals, including
chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...
,
zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...
,
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
and
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
. It is slow-growing, with an increase in size of only per year for a colony observed in one study. In Greenland, it often grows in association with other lichen species tolerant of enriched environments, including ''
Umbilicaria arctica Rock tripe is the common name for various lichens of the genus ''Umbilicaria'' that grow on rocks. They are widely distributed, including on bare rock in Antarctica, and throughout northern parts of North America such as New England and the Rocky ...
'', '' Polycauliona candelaria'', '' Rusavskia elegans'', '' Physcia dubia'', and '' Rhizoplaca melanophthalma''. In Poland, it is part of
bryophyte Bryophytes () are a group of embryophyte, land plants (embryophytes), sometimes treated as a taxonomic Division (taxonomy), division referred to as Bryophyta ''Sensu#Common qualifiers, sensu lato'', that contains three groups of non-vascular pla ...
communities found on
asbestos Asbestos ( ) is a group of naturally occurring, Toxicity, toxic, carcinogenic and fibrous silicate minerals. There are six types, all of which are composed of long and thin fibrous Crystal habit, crystals, each fibre (particulate with length su ...
tile roofs, occurring with '' Syntrichia ruralis'', ''
Orthotrichum anomalum ''Orthotrichum'' is a genus of moss in the family Orthotrichaceae. It is distributed throughout the world. There are about 125 species in the genus. Species include:Grimmia pulvinata ''Grimmia pulvinata'', otherwise known as grey-cushioned grimmia or pulvinate dry rock moss, is a bryophyte moss common in temperate climates worldwide. Characteristics ''Grimmia pulvinata'' grows in a small, cushion-like shape, around 1–2 ...
'', ''
Schistidium apocarpum ''Schistidium'' is a plant genus in the moss family Grimmiaceae. Species ''The Plant List'' and ''Tropicos'' recognise about 150 accepted species: A * '' Schistidium abrupticostatum'' * '' Schistidium absconditum'' * '' Schistidium a ...
'' and others. Foliose lichens such as ''Physcia caesia'' are intermediate in their response to air pollution — less sensitive than
fruticose lichen A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy growth structure. It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteria and one, two or m ...
s, but more sensitive than
crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...
s. ''Physcia caesia'' is found in cities, though at lower frequencies than more pollution-tolerant species. As with most lichens, ''Physcia caesia'' is impacted by habitat loss through development, as well as by the trampling or overgrowth of its location. However, the retention of old stone walls, buildings and bridges can help to support its populations, even in cities. ''Physcia caesia'' is attacked by
lichenicolous This glossary of mycology is a list of definitions of terms and concepts relevant to mycology, the study of fungi. Terms in common with other fields, if repeated here, generally focus on their mycology-specific meaning. Related terms can be found ...
fungi, including '' Polycoccum galligenum'', ''
Polycoccum pulvinatum ''Polycoccum'' is a genus of lichenicolous fungi in the family Polycoccaceae. It has about 60 species. Species As accepted by Species Fungorum; *''Polycoccum acarosporicola'' *''Polycoccum aksoyi'' *''Polycoccum alboatrum'' *''Polycoccum alp ...
'', '' Zwackhiomyces physciicola'' and ''
Bryostigma epiphyscium ''Bryostigma epiphyscium'' is a species of lichenicolous fungus in the order Arthoniales. Formerly classified in the genera ''Arthonia'' and '' Conida'', it was transferred to the genus '' Bryostigma'' in 2020. It is known to infect the lichen ' ...
''.


References


Cited books

* * * * * * * * * * * * * * *


External links

*
''Physcia caesia'' photos on Stephen Sharnoff's lichen website
(photographer for ''Lichens of North America'') {{Taxonbar, from=Q1572772
caesia ''Caesia'' is a genus of herbs in the family Asphodelaceae, subfamily Hemerocallidoideae,Stevens, P.F. (2001 onwards)"Hemerocallidoideae" ''Angiosperm Phylogeny Website''. Retrieved 2016-06-10. native to Australia, New Guinea, Madagascar and Sou ...
Lichen species Lichens described in 1784 Taxa named by Georg Franz Hoffmann