Platygramme


Platygramme is a genus of lichen-forming fungi in the family Graphidaceae consisting of about 27 species. The genus was circumscribed by Antoine Laurent Apollinaire Fée in 1874. The type species of the genus is P. caesiopruinosa. These bark-dwelling lichens are found in moist, shaded forests across tropical and warm temperate regions worldwide, where they form pale crusts that develop distinctive flattened, plate-like fruiting structures. A combination of several features characterizes Platygramme: the brown ascospores, a spore-producing layer speckled with granules, and elongated fruiting bodies with distinctive plate-like structures formed from hardened tissue.

Description

Platygramme forms a smooth, pale grey-green to yellow-olive crust that sits flush with the bark and lacks a true. Its fruit bodies start as narrow but soon split their thalline cover and expand sideways into plate-like ; viewed from above they look more like flattened shields than slits. A colourless to faintly brown lines the disc, and the exposed surface may carry a thin whitish. The clear hymenium is non-, while the thin-walled, Graphis-type asci usually contain eight hyaline ascospores that become distinctly —divided by a lattice of transverse and longitudinal septa—yet remain iodine-negative. Most species are chemically inert or produce only traces of stictic acid-series depsidones.
The plate-forming discs separate Platygramme from script lichens with permanent slits such as Glyphis and Hemithecium. Unlike Chapsa, whose discs are star-shaped with radiating, Platygramme displays entire, rounded plates; and in contrast to Kalbographa, it lacks vividly coloured anthraquinone pigments and its margins remain pale or only lightly .

Habitat and distribution

The genus is pantropical to warm-temperate in distribution. All known species are bark-dwelling, occupying shaded boles and large branches in moist evergreen forests from lowland Amazonia and West-Central Africa to Southeast Asia and northern Australia. Although tolerant of brief sunflecks, they disappear quickly when canopy cover is removed; their presence therefore signals long-established, relatively undisturbed woodland with high ambient humidity.

Species

, Species Fungorum accepts 27 species of Platygramme.