''Phlyctis argena'' is a species of

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 ...

Description

''Phlyctis argena'' has a thin crustose

thallus Thallus (plural: 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. Many of these organisms wer ...

that is white, greyish or green-grey in colour. The identification can be confirmed with the spot test application a drop of

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 exp ...

(K-test) to the thallus, which will turn yellow and then red.

Range

Widespread, including Africa, Asia, Europa and North America.

Habitat

''Phlyctis argena'' usually grows as a generalist

epiphyte An epiphyte is an organism that grows on the surface of a 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 epiphytes grow are called phoroph ...

on the bark of deciduous trees, especially ''

Salix cinerea ''Salix cinerea'' (common sallow, grey sallow, grey willow, grey-leaved sallow, large grey willow, pussy willow, rusty sallow) is a species of willow native to Europe and western Asia.Meikle, R. D. (1984). ''Willows and Poplars of Great Britain ...

'' and '' Fraxinus excelsior''. It also occasionally grows on stone, such as gravestones.

Ecology

The lichen is a generalist epiphyte of deciduous trees and is acidophilic. Its abundance appears to have increased generally since the 1970s, possibly in responses to changes in pollution levels

Etymology

The etymology of the genus name, ''

Phlyctis ''Phlyctis'' is a genus of lichenized fungi in the order Gyalectales, and the type genus of the family Phlyctidaceae. Members of the genus are commonly called blemished lichens. The genus was circumscribed In geometry, the circumscribed ci ...

'', comes from the obsolete medical term phlyctidium, meaning a large blister. The species epithet, argena, is derived from the latin "argentum", meaning silver.

Taxonomy

The following varieties of ''Phlyctis argena'' have been described: * ''Phlyctis argena'' var. ''argena'' * ''Phlyctis argena'' var. ''gilvoalbicans'' * ''Phlyctis argena'' var. ''erythrosora'' * ''Phlyctis argena'' var. ''nubilosa''

References

Gyalectales Lichen species Lichens of Africa Lichens of Asia Lichens of North America Taxa named by Erik Acharius Lichens described in 1799 Lichens of Europe {{Lecanoromycetes-stub