Allographa sessilis is a species of crustose lichen-forming fungus in the family Graphidaceae. It is a white, bark-dwelling lichen with wavy, prominently raised, slit-like fruiting bodies that become strongly elevated above the thallus surface with age. The species was described in 2023 from white-sand savanna habitats in the Colombian departments of GuainÃÂa and Vaupés.
Allographa sessilis was described as a new species in 2023 by Robert Lücking, Norida MarÃÂn-Canchala, and Bibiana Moncada. The species epithet sessilis refers to the fruiting bodies, which become prominently raised and sit directly on the thallus surface (strongly ).
The body (thallus) is crust-forming (crustose), reaching up to 3 cm across and about 100âÂÂ150 üm thick. It is white and opaque, with a smooth to uneven surface; no visible border zone () is present, though a thin, irregular black line may appear where the thallus meets neighboring lichens. In cross-section, the thallus has a loose outer skin (, 15âÂÂ25 üm), a diffuse , measuring 30âÂÂ50 üm, and a thick inner tissue (medulla, 50âÂÂ80 üm) containing clusters of calcium oxalate crystals. The algal partner () is from the green algal genus Trentepohlia.
The slit-like fruiting bodies () are wavy () and irregularly branched, at first partly protruding from the thallus () to prominent, but later becoming strongly raised and sitting directly on the surface. They lack a thallus-derived rim () and measure 2âÂÂ5 mm long, 0.2âÂÂ0.4 mm wide, and up to 0.5 mm high; the inner is hidden from view. The lips () are initially smooth-edged but later become distinctly grooved () and black. The outer wall () becomes deeply scalloped () and is completely blackened (, 70âÂÂ150 üm wide). The asci are club-shaped (, 120âÂÂ130 üm long, 30âÂÂ35 üm wide), each containing 4âÂÂ8 colorless ascospores. The ascospores are oblong and divided by both transverse and longitudinal cross-walls (), measuring 70âÂÂ100 à15âÂÂ25 üm; they stain violet-blue with iodine (I+ violet-blue). No secondary metabolites were detected by thin-layer chromatography.
The species is known from several collections in two departments of Colombia (GuainÃÂa and Vaupés). It grows on tree bark (corticolous), largely in white-sand savanna vegetation. The type collection was made at elevation in natural savannas over white sand near InÃÂrida (GuainÃÂa).