New species of Polymeridium from Brazil expand the range of known morphological variation within the genus

Five new species of the genus Polymeridium are described from Brazil. All exhibit at least one character that was previously unknown in the genus: P. corticatum has a corticate thallus and 2 ascospores per ascus, P. immersum has the ascomata deeply immersed in the bark under the thallus, P. isohypocrellinum has a red, KOH+ green pigment (iso-hypocrellin) in the ostiole, P. julelloides has short and broad muriform (Julella-like) ascospores, and P. paraproponens has ascomata in groups of two to three. Brazil is clearly the centre of diversity of the genus. Iso-hypocrellin is a new substance for the genus.