Phlyctis argena

Phlyctis argena has a thin crustose thallus that is white, greyish or green-grey in colour. The identification can be confirmed with the spot test application a drop of potassium hydroxide (K-test) to the thallus, which will turn yellow and then red. ==Range==

The species is widespread, including in Africa, Asia, Europe, and North America. ==Habitat==

Phlyctis argena usually grows as a generalist epiphyte on the bark of deciduous trees, especially Salix cinerea 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 air pollution levels ==Etymology==

The etymology of the genus name, Phlyctis, 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==