Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Life habit: lichenized Thallus: crustose, sometimes verrucose upper surface: grayish green to silvery or white, continuous or rarely areolate, slightly shiny cortex: cartilaginous corticiform layer of densely arranged parallel hyphae, rarely indistinctly pseudoparenchymatous photobiont: primary one Trebouxia, secondary one absent lower surface: absent Ascomata: apothecial, usually several concentrically arranged on thallus, immersed to erumpent with a zeorine margin disc: greenish to yellowish or brownish gray, round or rarely lobate, plane; thalline margin: usually well-developed, concolorous with the thallus or white; exciple: reduced, hyaline to pale yellow, prosoplectenchymatous hymenium: hyaline, hymenial gel I-, K/I-; paraphyses: rather thin, richly branched and anastomosing; hypothecium: thin, hyaline to pale yellow asci: broadly ovate to saccate, annelasceous, with indistinct tholus and ring-shaped structure protruding down into the lumen, I-, K/I-, 1-spored ascospores: hyaline, richly muriform, ellipsoid to ovoid, 20-50 x 10-30 µm Conidiomata: hyphophoral, sessile on thallus, composed of scale-like structures which might be dissolved into individual setae and which protect the basally produced mass of conidial hyphae (diahyphae) conidia: produced as moniliform chains of cells (diahyphae) branching from a single point, intermingled with small algal cells Secondary metabolites: no substances detected with TLC, but calcium oxalate crystals usually abundant Geography: pantropical, extending into humid subtropical and temperate regions Substrate: mostly on leaves, but also found on bark and rock. Notes: Gyalectidium is one of two usually foliicolous lichen genera found in the Sonoran Desert (the other being Sporopodium). The genus belongs in the family Gomphillaceae, which is well characterized by its hemiangiocarpous apothecia with non-amyloid hymenium and asci, and richly branched and anastomosing paraphyses, and by its peculiar hyphophoral conidiomata. Within this family, Gyalectidium belongs to a group of genera with immersed-erumpent, zeorine apothecia, its closest relative being Calenia. Both indeed have identical apothecial morphology, but Gyalectidium can be readily recognized by its squamiform hyphophores, in which the basally produced diahyphae are protected by a scale-like structure.