Hypotrachyna aspera

The thallus forms loose, rather ragged rosettes 4–6 cm (1.6–2.4 in) across. Its upper surface is a dull white that may weather to pale grey; individual lobes (laciniae) are very narrow—only 1.0–2.5 mm wide—giving the thallus a finely frilled appearance. These lobes are more or less flat to slightly up-turned, have truncate (squared-off) tips and carry a thin black marginal line that accentuates each division. Pustulae, blister-like swellings that rise from the surface, develop mainly near the lobe edges; they soon burst to release a coarse, grainy powder of soredia (minute balls of algal and fungal cells used for vegetative reproduction). Unlike the closely related species mentioned above, the pustules here lack any K-reactive yellow pigment, remaining whitish even after reagent is applied. Internally, the medulla (the loose cottony layer inside the thallus) is white, reacting K+ (rose) because of alectoronic acid. The lower surface is jet black, shiny and wrinkled toward the centre but becomes chestnut brown near the margin. Attachment to the substrate is achieved by numerous forked rhizines—root-like fibres—0.3–0.8 mm long that are the same colour as the lower cortex. No apothecia (sexual fruit-bodies) were seen, and pycnidia (minute flask-shaped asexual organs) were likewise absent in the type series.

Hypotrachyna aspera was originally described from collections made in the Serra do Caraça massif (Minas Gerais) in south-eastern Brazil. All material was collected between 1,100 and 1,150 m (3,610 and 3,770 ft) on acid siliceous rock bordering the Tanque Grande reservoir—a setting where moist montane forest intergrades with open candeia (Eremanthus erythropappus) woodland. Here the lichen grows in partially shaded, rain-washed situations where fog is frequent and the air remains humid for much of the year. It has subsequently been reported from Argentina, Bolivia, and Guatemala.

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