Pseudopyrenula guianensis

The species belongs to the Pseudopyrenula subgregaria group (the smaller-spored, 3-septate Pseudopyrenula). It is distinguished within that assemblage by two features used by lichenologists for identification: a clear but oil-dotted internal matrix (a hyaline with ) and the presence of the fluorescent compound lichexanthone in the thallus. The type collection was made in 1986 near Saül, French Guiana. ==Description==

The thallus is thin, whitish and (lacking a differentiated outer ). Sexual fruiting bodies (ascomata) are produced singly; they are black, hemispherical, and 0.3–0.5 mm in diameter, each with a tiny pore at the top (an apical ostiole). Inside, the hamathecium is colourless but contains scattered oil droplets (inspersion). The ascospores are colourless, divided by three cross-walls (3-septate), and measure 21–25 × 6–9 μm; they are smooth-walled and show diamond-shaped internal cavities () formed by thickening of the inner spore wall. The thallus is UV-positive yellow under long-wave ultraviolet light, indicating lichexanthone; thin-layer chromatography confirms this compound. ==Habitat and distribution==

Pseudopyrenula guianensis grows on smooth bark of trees in rainforest. It is confirmed from French Guiana and Suriname. ==References==