ASCOMYCOTA | LECANOROMYCETES > OSTROPALES > Phlyctidaceae

Genus Phlyctis, meaning 'ashen', from the pale colour of the thallus

Common name: -

Synonym:                     -

Habitat:                          Woodland, wayside trees

Substrata:                      Bark, more rarely on siliceous rocks and walls

Growth form:                 Corticolous (saxicolous)

Thallus:                   Crustose

Apothecia:                     Lecanorine, immersed

BLS identity rating:        Graded 2/5 (spot-testing required)

Thallus variable in both size and texture; either forming compact patches on smaller branches or, when growing on larger surfaces, spreading to 10cm or more across; sometimes smooth and thin with a thin layer of floury soredia, but more often, particularly when well-developed, rough and slightly cracked, with the central area covered with granular soredia; the surface often irregularly eroded in part, often in lines that from a distance resemble browsed mollusc tracks.  

Colour whitish, greenish-white or greyish-white when fresh, becoming rather creamy to pale brownish when older and dry; surrounded by a white, often glossy, prothallus.

Apothecia extremely rare, tiny to 0.5mm dia., irregular, immersed, grey to grey-black with a white pruinose disk.

To avoid possible confusion with similar species, specimens should be spot-tested, C-, K+ yellow, slowly turning blood red (top in photo), K+C brighter red (bottom).

Phlyctis argena is a common and widespread species, primarily occurring on deciduous trees in well-lit wayside or open woodland habitats; unlikely on conifers, but occasionally on shrubs; rarely on shaded rocks and walls, sometimes overgrowing mosses.