Pyxine pustulata

The lichen has a pale grey, shiny thallus that is tightly attached to its bark substrate; the lower surface is black, with simple (i.e., unbranched), black rhizines that help attach the thallus to its substrate. The lobes comprising the thallus are 0.7–1.2 mm wide, with rounded tips, and are sparsely covered with white spots (maculae). Older parts of lobes develop pustules (pimple or blister-like swellings) that are about 0.1–0.3 mm wide and about 0.2–0.6 mm high; the species epithet refers to these characteristic structures. The cortex of the thallus contains lichexanthone, a lichen product that causes it to fluoresce yellow when lit with a long-wavelength UV light. Pyxine pustulata also contains terpenoid compounds and a pigment, detectable using thin-layer chromatography.^[2]