Gyalectidium

Gyalectidium is a genus of lichen-forming fungi in the family Gomphillaceae. Established in 1881 by Swiss lichenologist Johannes Müller Argoviensis, the genus comprises about 50 species of predominantly leaf-dwelling lichens that form small, pale greenish to whitish-grey patches typically only a few millimetres across. Members are characterised by specialised asexual reproductive structures called , which are small scale-like outgrowths that produce propagules containing both fungal and algal partners, and by fruiting bodies that contain single, large, multi-chambered ascospores. The genus has a mainly pantropical to subtropical distribution with highest diversity in the Neotropics, occurring primarily on living leaves in humid tropical forests but also documented from temperate regions including Europe and parts of Australasia.

==Taxonomy== The genus was circumscribed by the Swiss lichenologist Johannes Müller Argoviensis in 1881. In the protologue, he characterised Gyalectidium as a crustose lichen with globose, green (green algae), apothecia with a simple margin that is thalline externally, and paraphyses that are interconnected in a lattice. The spores were described as hyaline and "parenchymatous" (divided into many chambers). He distinguished the genus from Gyalecta by the structure of the paraphyses, and remarked that the species then known were foliicolous and had one-spored asci. He included 3 species: G. xantholeucum, G. dispersum, and G. filicinum; the last of these is now the type species of the genus.