Catillaria fungoides
Thallus: Not clearly delimited, thin and pale, on which rounded to irregular blackish soralia develop. Soralia sometimes becoming confluent. Soredia globose, farinose, 12-20 µm diam., composed of clusters of algal cells surrounded by short-celled hyphae, the exposed outer hyphae with dark brown pigment which has negative reactions with K and N.
Anamorph: not known.
Teleomorph: Ascomata apothecial and lecideine. The disc is black and plane to slightly convex. Proper margin thin, persistent, slightly paler than the disc. Exciple in section mostly colourless and interspersed with oil droplets, the upper, outer edge with dark capped hyphae. Hypothecium fuscous brown. Hymenium hyaline, interspersed with oil droplets. Asci Catillaria-type. Paraphyses capitate with dark brown caps. Ascospores colourless, 1-septate, 10-12 x 3-3.5 µm, lacking a perispore.
The black soralia on a thin pale thallus combined with dark apothecia containing Catillaria-type asci and 1-septate spores is unique in Britain.
Dark algal crusts are common in similar situations to C. fungoides and can have a similar appearance in the field. The apothecia of C. fungoides are very similar to those of C. nigroclavata but that species lacks soredia.
In GB&I known from only one site (as of February 2015) where it occurs on two trees at a wood-edge in Huntingdonshire.
C. fungoides is found on eutrophicated bark. The British material grows on Fraxinus bark where moderate water run-off from the canopy caused nutrient-rich conditions. Xanthoria parietina is usually present in the same seepage zone. Candelariella reflexa and Phaeophyscia orbicularis are common co-habitants.