The genus
Julella was introduced by the French naturalist
Jean-Henri Fabre in 1879, working within the then broadly defined Sphaeriaceae. Fabre separated his material by an unusual : the spore sacs (
asci) contain only two spores, rather than the eight (or at least four) common in related fungi. He also emphasised the very large, lattice-like, many-celled () spores and the immersed, black, flask-shaped
fruiting bodies (
perithecia) formed in the bark. Fabre dedicated the name to his son Jules, his collaborator in microscopical work, who had died young. The
type species,
Julella buxi, was described from boxwood (
Buxus sempervirens) on bark and dead wood in southern France (
Avignon,
Orange,
Sérignan). In a 1985 re-examination of Fabre's original material,
Margaret E. Barr treated
Peltosphaeria and
Polyblastiopsis as
congeneric with
Julella and made the
new combinations
Julella vitrispora and
J. lactea (including var.
naegelii). She also noted long-standing uncertainty about the publication date of Fabre's first "Essai" (the volume shows "1878", but internal and bibliographic evidence points to late 1879 or 1880). Barr placed
Julella in the family
Arthopyreniaceae and regarded
Catharinia as a
synonym of
Julella, while cautioning that its status hinges on rediscovery of
type material. She further observed that several names then assigned to
Julella differ in key characters and likely do not belong in the genus. Re-examining the group,
André Aptroot and Pieter van den Boom treated
Julella as a small genus of mostly corticolous, non-lichenised bark saprophytes that has attracted little attention; although roughly a hundred names had been published across
Julella and allied genera such as
Catharinia,
Peltosphaeria and
Polyblastiopsis, they considered only a few species to be well founded and widely distributed. They noted that in fungi with large, muriform spores, measurements vary widely, so species should be delimited using at least two correlated characters rather than spore size alone. Those authors provided a simple key to the corticolous species:
J. lactea has 2 (rarely as many as 6) spores per ascus and larger ascocarps (typically > 0.5 mm), whereas 8-spored species separate by spore size and ascocarp size—
J. vitrispora with spores usually > 21 μm and ascocarps > 0.5 mm, and
J. sericea with shorter spores (generally < 21 μm) and ascocarps up to 0.5 mm. They stressed that
J. lactea and
J. vitrispora differ mainly by the number of spores per ascus and suggested that the taxonomic weight of this difference needs further testing. Applying this framework, Aptroot and van den Boom reduced several names to synonymy. They placed Fabre's
J. buxi in
J. lactea and regarded a suite of names originally described in
Polyblastiopsis (e.g.,
P. dispora,
P. alba and
P. rappii) as
conspecific with
J. lactea or probably so, based on identified material. For
J. vitrispora, they considered
J. sublactea and
Polyblastiopsis subargentea to be synonyms or probable synonyms. They also excluded a number of names from
Julella altogether, assigning them to lichen-forming trypethelialean genera such as
Polymeridium,
Anthracothecium,
Anisomeridium and
Laurera.
Julella is tentatively included in the family
Thelenellaceae by some sources, while other sources include it in the
Trypetheliaceae or as a genus of "unconfirmed affinities". In their 2021 treatment of the Thelenellaceae in the
Revisions of British and Irish Lichens series, Paul Cannon and
Alan Orange suggest that there is "no convincing morphological distinction between" the genera
Chromatochlamys and
Thelenella, and they consider
Thelenella in a broad sense to include
Chromatochlamys. In the "2024 Outline of Fungi and fungus-like taxa", it is classified in the family
Didymosphaeriaceae. ==Description==