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

Life habit: bryophilous, lichenicolous, or saprophytic Thallus: lacking Ascomata: perithecioid, ostiolate, immersed or becoming sessile wall: pseudoparenchymatous, mainly 3-8 cell layers thick, upper part sometimes thickened, black or brown, lower part black, brown or pale hamathecium: periphyses: present, sometimes branched; interascal elements: absent at maturity; interascal gel: hemi-amyloid asci: clavate to subcylindrical, wall apically thickened, Verrucaria-type, outer ascus wall layers hemi-amyloid, (16-)24- to more than 100-spored ascospores: pale brown to dark brown or olivaceous brown, 0-3-septate, ovoid, ellipsoid, oblong or bacilliform, rarely almost subglobose, 2.5-15.5 x 1.5-7 µm, obtuse or acicu Conidiomata: pycnidial, immersed, with a dark brown wall conidiogenous cells: hyaline, ampulliform, enteroblastic conidia: hyaline, short bacilliform Secondary metabolites: none detected Geography: world-wide, mainly in temperate to arctic regions Substrate: soil, bryophytes, lichens on wood, bark, non-calciferous or calciferous rocks. Notes: Muellerella mainly comprises lichenicolous taxa, although two bryophilous species on hepatics are known. The generic position of the saprobic species M. nigra Routien and M. macrospora (Servit) Servit should be reconsidered. Three species are known from the Sonoran region: Muellerella lichenicola and M. pygmaea have a wide host range, whereas M. lecanactidis is known only from the type.