[2] The genus was circumscribed in 1921 by Finnish lichenologist Edvard August Vainio, with Phylloblastia dolichospora assigned as the type species.

The photobiont component is typically chlorococcoid, featuring green algal cells that are angular-rounded and grouped irregularly or in clusters.

While paraphyses (sterile filaments within the ascomata) are absent, periphyses (hair-like structures at the mouth of the perithecia) are usually present.

The asci (spore-bearing cells) have a fissitunicate structure, meaning they have a double wall that splits to release spores.

These spores are oblong to cylindrical in shape, with transverse or muriform (divided in all three dimensions) septation, but without constrictions at the septa, and are colourless.