ASCOMYCOTA | LECANOROMYCETES > RHIZOCARPALES > Rhiziocarpaceae

Genus Thelotrema, meaning 'perforated nipple' - from the form of the apothecia

Common name:            Barnacle Lichen

Synonym:                    Thelotrema lepadinum var.scutelliforme

Habitat:                         Woodland

Substrata:                     Bark

Growth form:                Corticolous (saxicolous)

Thallus:                  Crustose

Apothecia:                    Lecanorine

BLS identity rating:        Graded 1/5 (identification should be straightforward)

Thallus variable, somewhat dependent on the bark, but usually thickish, smooth to felt-like or slightly wrinkled; creamy white to grey, often with a greenish tinge.

Apothecia sometimes numerous, evenly distributed, volcano-like with a base to around 2mm dia., and a large central open summit to 0.5mm dia.; rim irregular with a white-cream membrane at the crater bottom; the thin proper margin is visible inside the thalline margin, giving the apothecium the appearance of a barnacle.

Thelotrema lepadinum is primarily found on smooth areas of bark on deciduous trees in sheltered locations; more rarely on silicious rocks.

Not to be confused with Pertusaria hymenea or Pertusaria leioplaca where the apothecia have a different structure.