Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Mycelium: hyaline to pale brown conidiophores: pale brown, branched, straight to flexuose, septate, often constricted at the septa, 15-35 x 2.5-4 µm conidiogenous cells: pale brown, not clearly defined conidia: catenate, pale brown, dry, ellipsoid, usually 1-septate, smooth, rather thin-walled, 5-8 x 4-6 µm. Hosts: in apothecia of Candelariella vitellina (type specimen); reported from a large number of additional hosts; in the Sonoran region, once in the apothecia of Phacopsis oxyspora on Punctelia perreticulata, and once on the thallus of an unidentified, sterile, saxicolous crust World distribution: widespread in the Northern Hemisphere, also reported from Papua New Guinea Sonoran distribution: collected once in Arizona and once in Baja California. Notes: It is likely that Intralichen christiansenii with its current circumscription is heterogeneous, and that some, or perhaps even most of the earlier reports are erroneous and concern similar, yet undescribed taxa. It could be that the species only grows on Candelariella, but further studies are needed to confirm or to reject such a hypothesis. We treat the species here in its traditional broad sense, including specimens from hosts other than Candelariella.