This family of lichens is probably best recognized by the distinctive spores: brown, 1-septate, elliptical. In the absence of macroscopic characters, the ontogeny of the spore is of critical importance: when the septum forms; presence of any thickenings in the septum, walls, and/or tip in the various stages of development; presence of bands of pigment around the cells and around the septum; mature spores sometimes swelling around the septum in KOH.
|Buellia||apothecia lecideine, hypothecium gen. dark|
|Rinodina||apothecia lecanorine, hypothecium gen. hyaline|
|Dimlaena||apothecia initially cryptolecanorine, spore walls not thickened|
|Diploicia||apothecia initially immersed, lecideine, spore walls thick|
|Anaptychia||upper cortex K-, prosoplectenchymatous, lower cortex often lacking|
|Heterodermia||upper cortex K+y, prosoplectenchymatous, lower cortex often lacking|
|Physcia||upper cortex K+y, lower cortex present|
|Phaeophyscia||lower cortex paraplectenchyatous|
|Physciella||lower cortex prosoplectenchymatous|
|Hyperphyscia||pycnoconidia, lower cortex rudimentary with few or no rhizines|
|Dirinaria||tropical, v short rhizines (hapters)|
|Pyxine||tropical, occ. lecideine|
Buellia has been split into several genera by various lichenologists, including Diplotomma, Amandinea, Hafellia, Baculifera, Gassicurtia, among others. However there is little agreement on most of these, and some are definitely not well-defined. It looks like at least Diplotomma and Amandinea will be accepted with minor changes, while Haffelia, although apparently well-defined, is more problematic since the type of Buellia s. str. falls within the definition of Haffelia. Expect additional genera to be created from the residue in Buellia s. l. as research continues.