Gymnoderma is a genus of lichen-forming fungi in the family Cladoniaceae. Originally established in 1860 by the Finnish lichenologist William Nylander, this small genus is characterised by forming mats of small, yellow-green scales dotted with spherical brown fruiting bodies. The genus is distinguished from related lichens by a unique microscopic feature: its spore-containing structures (asci) turn deep blue when stained with iodine, which is uncommon among members of the Cladoniaceae.

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