''Physcia stellaris'' is a species of

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 ...

. It is pale grey, but darker in the centre, and lacks

isidia An isidium (plural: isidia) is a tiny, wart- or finger-like outgrowth on the thallus surface of certain lichen species. It is one of two principal types of vegetative reproduction, vegetative reproductive structures in lichens, the other being ...

lobule In anatomy, a lobe is a clear anatomical division or extension of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to the mu ...

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 ...

and

pruina 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" ...

.It tests positive K+ yellow upper cortex with a 10%

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 ...

solution. In North America, it is known

colloquially Colloquialism (also called ''colloquial language'', ''colloquial speech'', ''everyday language'', or ''general parlance'') is the linguistic style used for casual and informal communication. It is the most common form of speech in conversation am ...

as the fringed rosette lichen. It can grow as an

epiphyte An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

. In

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

, it has been reported from the trunk of ''

Platanus ''Platanus'' ( ) is a genus consisting of a small number of tree species native to the Northern Hemisphere. They are the sole living members of the family Platanaceae. All mature members of ''Platanus'' are tall, reaching in height. The type ...

'' trees.

Taxonomy

It was initially described as ''Lichen stellaris'' by

Carolus Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1753 before receiving its own genus of ''Physcia'' in 1856 by

William Nylander William Andrew Michael Junior Nylander Altelius (born 1 May 1996) is a Swedish professional ice hockey Forward (ice hockey), forward for the Toronto Maple Leafs of the National Hockey League (NHL). Nylander was selected by the Maple Leafs in t ...

Description

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 ...

of ''Physcia stellaris'' can be described as

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 ...

as it has aspects of leaf-like lichen structures. The size and shape of the thallus is irregular and can grow up to 4 cm in diameter. Lobes are loosely

appressed This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary ...

and are on average only 0.5 mm in size. The upper surface is whitish grey, appearing as almost a cream color. It lacks any form of soredia or isidia on the upper surface. The lower surface is white to brown with simple

rhizines 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 ...

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 ...

are abundant varying in size from 0.5mm-1.5mm and have fruiting bodies shaped like a plate with a ring around them called lecanorine.

Ascocarp 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. Ascoc ...

containing 8 brown, septate ascospores ranging in size from 15-18

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

. Is found as a lichen in all forms. ''Physcia stellaris'' can be differentiated from all other ''Physcia'' species due to lack of soredia, with exception to '' P. aipolia. P. aipolia'' can be differentiated from ''P. stellaris'' due to ''aipolia’s'' broader lobes and apothecia that tend to be pruinose.

Distribution and habitat

This species is commonly found lichenized on bark and rock all across the

temperate zones 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 ...

of North America as well as parts of Europe. Documented findings of this species range from Georgia to the Canadian Northwest Territories. The species is quite common on

deciduous trees In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flo ...

but can also be found less commonly on

conifers Conifers () are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All e ...

Reproduction

''Physcia stellaris'' shows no evident means of asexual reproduction due to its lack of isidia or soredia. This species has abundance of apothecia that allow for sexual reproduction.

References

{{Taxonbar, from=Q292035 stellaris Taxa named by Carl Linnaeus Lichens described in 1753 Lichens of North America Lichen species