Basidiomata: waxy to gelatinous, pale pink, pale brown, reddish brown, grayish brown to almost black, convex, often with a constricted base, often tuberculate when old, sometimes inducing gall formation, 0.1-1.2 mm in diam., sometimes reduced and growing in the hymenium of the host context hyphae: thin-walled, 2-3.5 µm in diam.; clamp connections: sometimes frequent haustorial branches: frequent, tremelloid; mother cell: subspherical to ellipsoid, 2.5-5 µm in diam.; haustorial filament: 0.5 µm in diam., 1-8 µm long hymenium: mostly hyaline, sometimes with dark brown thick-walled hyphae in the outer part with cells 8-15 x 4-9 µm, containing numerous probasidia; probasidial initials: ellipsoid, proliferations occurring through the basal clamp; hyphidia and cystidia: absent basidia: when mature, cylindrical, aseptate, 2455 x 5-7(-9) µm, rarely subspherical, 9-11 µm in diam., with (2-)3-4 epibasidia epibasidia: subulate, 1.5-2.5 µm in diam., 5-9 µm long; sterigmata: refractive at the tip basidiospores: ellipsoid or ovoid to almost limoniform, obliquely attached to sterigmata, refractive at the point of attachment, 7.5-11 x 3.5-6.5 µm Anamorph: lunate conidia, asteroconidia and catenate conidia have been observed; zygoconidia: absent. Hosts: thallus, including cilia, of Heterodermia, Physcia and Physconia, often inducing the formation of galls; in southern California, the species is common on Heterodermia namaquana, but absent on the related H. erinacea (Esslinger and Bratt 1998) World distribution: Europe, Africa, North and South America, and Papua New Guinea; probably cosmopolitan Sonoran distribution: southern California. Notes: Syzygospora physciacearum is relatively common and easily visible by its distinct, often dark-colored galls. It could be mistaken for Tremella christiansenii Diederich, a rare species, known from two European collections on Physcia.