Its ascomata, the fruiting bodies of the lichen, are simple or fused, appearing as black, spherical to pyriform structures that emerge from the substratum.

The ostiole, or opening of the ascomata, can be apical to lateral, brown to black, or exhibit a red anthraquinone colour.

[4] The hamathecium, which refers to the filamentous tissue within the ascomata, is colourless and may contain hyaline or red oil droplets that turn green when treated with potassium hydroxide (KOH) solution.

[4] Conidiomata, or structures that produce conidia (asexual spores), are rather rare in the genus Polymeridium.

In terms of secondary chemistry, the thallus occasionally contains lichexanthone, while anthraquinones are rarely present in the ostiole or hamathecium.