Pertusaria  

Description:
Thallus crustose, often thin and inapparent: photobiont green, Chlorococcaceae.
Ascomata apothecia, round, disc either exposedand often pruinise or poriform.
Hymenium colourless, epihymenium usually hyaline, sometime pigmented K+ purple
Hamathecium of very fine, branched and anastomosing paraphyses.
Hypothecium pale- to dark-brown.
Asci cylindrical, 1–8 spored, Pertusaria-type; ascospores colourless, simple, thick walled, often v large (>200 µm).
Conidiomata rarely present;conidia, short rods.
Soralia and Isidia frequent.
Chemistry xanthones, fatty acides, depsides or depsidones present in many species.

Pertusaria is a widespread genus of c. 350 species that occur on various substrates. In its traditional circumscription, the genus had two different types of apothecia; either lecanorine or poriform and it was long suspected that the genus was not monophyletic. Molecular work (see below) has confirmend this suspicion and clarified the systematics of the genus. The species with poriform apothecia have been shown to belong to Pertusaria s str., some species with small spores have been removed to the new genus Gyalectaria I. Schmitt, Kalb & Lumbsch and the species with one spored asci, pruinose lecanorine apothecia and a thallus lacking depsides were initially removed to the resurrected genus Variolaria Pers. However, this name was shown to be illegitimate and the species are now accommodated in the genus Lepra Scop.

Literature: Dibben 1980, Lumbsch et al. 2006, Schmitt & Lumbsch 2004, Schmitt et al. 2006, 2010, 2012.