{{Short description|Genus of lichen-forming fungi}} {{Use dmy dates|date=June 2025}} {{Use Oxford spelling|date=June 2025}} {{Automatic taxobox | image = Xylographa parallela-1.jpg | image_caption = A herbarium specimen of the lichen ''Xylographa parallela'' | taxon = Xylographa | authority = (Fr.) Fr. (1836) | type_species = ''Xylographa parallela'' | type_species_authority = (Ach.) Fr. (1849) | subdivision_ranks = Species | subdivisions = | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = *''Spiloma'' {{au|Ach. (1803)}} *''Spilonematopsis'' {{au|Vain. (1909)}} *''Stictis'' subgen. ''Xylographa'' {{au|Fr. (1822)}} *''Xylographomyces'' {{au|Cif. & Tomas. (1953)}} }}
'''''Xylographa''''' is a genus of lichen-forming fungi in the family Xylographaceae.<ref name="CoL_89HQ"/> These lichens are commonly found growing on decaying wood, where they form thin, often nearly invisible crusts. The genus is most readily recognized by its distinctive elongated, slit-like fruiting bodies that follow the grain of the wood.
==Taxonomy==
The genus was originally proposed by Elias Magnus Fries in 1822 as a subgenus of the genus ''Sticta''. He elevated it to distinct generic status in 1836.<ref name="Fries 1821"/><ref name="Species Fungorum synonymy"/>
==Description==
''Xylographa'' produces an inconspicuous crust that lies flush with, or just beneath, the surface of decaying wood. Where visible the thallus is a thin, diffuse film and may carry scattered brown {{lichengloss|goniocysts}}—microscopic granules in which a few spherical green algal cells are wrapped by fungal hyphae. Because the crust is either immersed or extremely thin, it often blends with the substrate and is easiest to detect once its fruit bodies appear. Chemical analyses reveal either the stictic acid complex, unnamed secondary metabolites, or no detectable lichen products.<ref name="Cannon et al. 2021"/>
The lichen's ascomata take the form of narrow {{lichengloss|lirellae}} that emerge partly embedded and mature into elongate, often one-sided slits aligned with the grain of the wood. Individual lirellae range from nearly round to distinctly linear but share a characteristic brown to dark-brown pigmentation and a low, flat {{lichengloss|disc}}. They lack a {{lichengloss|thalline margin}}; instead, a thin {{lichengloss|true exciple}}—pale to mid-brown rather than black—outlines each slit. Under the microscope the hymenium is colourless yet stains blue with iodine, while the {{lichengloss|hypothecium}} beneath remains clear. Delicate paraphyses thread the hymenium; these filaments branch only sparingly, widen gradually toward their brown-tipped apices and sometimes fuse with neighbouring threads. Club- to cylinder-shaped asci each contain eight smooth, single-celled ascospores that are initially colourless and only rarely become grey-brown in very old material. The ascus apex shows a diagnostic light-blue lateral zone surrounding a colourless plug in iodine preparations, matching the ''Trapelia'' structural type. Immersed, brown-black pycnidia frequently accompany the lirellae and release slender, slightly curved conidia. The combination of pale-brown exciple and less intensely pigmented lirellae separates ''Xylographa'' from the look-alike lichen ''Ptychographa'' (which has black, slit-domed discs), as well as from the non-lichenised wood-dwelling fungus ''Agyrium'', whose apothecia are convex and dull orange.<ref name="Cannon et al. 2021"/>
==Species== {{As of|2026|March}}, Species Fungorum (in the Catalogue of Life) accept 21 species of ''Xylographa''.<ref name="CoL_89HQ"/> [[File:Xylographa hians Tuck nmnhbotany 2160886 NMNH-00069554-000001.jpg|thumb|right|upright=1|Herbarium specimen of ''Xylographa hians'']] *''Xylographa bjoerkii'' {{au|T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa carneopallida'' {{au|(Räsänen) T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa constricta'' {{au|T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa crassithallia'' {{au|B.D.Ryan & T.H.Nash (2004)}} *''Xylographa difformis'' {{au|Vain. (1928)}} *''Xylographa erratica'' {{au|T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa hians'' {{au|Tuck. (1888)}} *''Xylographa isidiosa'' {{au|(Elix) Bendiksby & Timdal (2013)}} *''Xylographa lagoi'' {{au|T.Sprib. & Pérez-Ort. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa opegraphella'' {{au|Nyl. (1857)}}<ref name="Nylander 1858"/> *''Xylographa pallens'' {{au|(Nyl.) Malmgren (1861)}} *''Xylographa parallela'' {{au|(Ach.) Fr. (1849)}} *''Xylographa perminuta'' {{au|(Juss. ex Müll.Arg.) R.W.Rogers (1982)}} *''Xylographa pruinodisca'' {{au|B.D.Ryan & T.H.Nash (2004)}} *''Xylographa rubescens'' {{au|Räsänen (1921)}} *''Xylographa schofieldii'' {{au|T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa soralifera'' {{au|Holien & Tønsberg (2008)}}<ref name="Holien & Tønsberg 2008"/> *''Xylographa stenospora'' {{au|T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa trunciseda'' {{au|(Th.Fr.) Minks ex Redinger (1938)}} *''Xylographa vermicularis'' {{au|T.Sprib. (2014)}}<ref name="Spribille et al. 2014"/> *''Xylographa vitiligo'' {{au|(Ach.) J.R.Laundon (1963)}}<ref name="Laundon 1963"/>
==References== {{Reflist|colwidth=30em|refs=
<ref name="Cannon et al. 2021">{{cite book |last1=Cannon |first1=P. |last2=Fryday |first2=A. |last3=Spribille |first3=T. |last4=Coppins |first4=B. |last5=Vondrák |first5=J. |last6=Sanderson |first6=N. |last7=Simkin |first7=J. |year=2021 |title=Baeomycetales: Xylographaceae, including the genera ''Lambiella'', ''Lithographa'', ''Ptychographa'' and ''Xylographa'' |series=Revisions of British and Irish Lichens |volume=17 |pages=7–8 |url=https://britishlichensociety.org.uk/sites/default/files/Xylographaceae.pdf}}{{Open access}}</ref>
<ref name="CoL_89HQ">{{Catalogue of Life |id=89HQ |title=''Xylographa'' |access-date=15 May 2025}}</ref>
<ref name="Fries 1821">{{cite book |last=Fries |first=Elias Magnus |title=Systema mycologicum : sistens fungorum ordines, genera et species, huc usque cognitas, quas ad normam methodi naturalis determinavit |trans-title=Mycological System: presenting the orders, genera and species of fungi known up to this point, which have been determined according to the standard of the natural method |year=1821 |publisher=Lundae, Ex Officina Berlingiana |page=192 |edition=2nd |doi=10.5962/bhl.title.5378}}</ref>
<ref name="Holien & Tønsberg 2008">{{cite journal |last1=Holien |first1=H. |last2=Tønsberg |first2=T. |year=2008 |title=''Xylographa soralifera'', a new species in the ''X. vitiligo'' complex |journal=Graphis Scripta |volume=20 |issue=2 |pages=58–63}}</ref>
<ref name="Laundon 1963">{{cite journal |last=Laundon |first=J.R. |year=1963 |title=The taxonomy of sterile crustaceous lichens in the British Isles. 2. Corticolous and lignicolous species |journal=The Lichenologist |volume=2 |issue=2 |pages=101–151 |doi=10.1017/S002428296300013X}}</ref>
<ref name="Nylander 1858">{{cite journal |last=Nylander |first=W. |year=1858 |title=Enumération générale de lichens, avec l'indication sommaire de leur distribution géographique |trans-title=General enumeration of lichens, with a summary indication of their geographical distribution |journal=Mémoires de la Société Impériale des Sciences Naturelles de Cherbourg |volume=5 |pages=85–146 [128] |language=la}}</ref>
<ref name="Species Fungorum synonymy">{{cite web |title=''Xylographa'' (Fr.) Fr., Fl. Scan.: 344 (1836) [1835] |url=https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=5844 |website=Index Fungorum |access-date=15 March 2026}}</ref>
<ref name="Spribille et al. 2014">{{cite journal |last1=Spribille |first1=Toby |last2=Resl |first2=Philipp |last3=Ahti |first3=Teuvo |last4=Pérez-Ortega |first4=Sergio |last5=Tønsberg |first5=Tor |last6=Mayrhofer |first6=Helmut |last7=Lumbsch |first7=H. Thorsten |title=Molecular systematics of the wood-inhabiting, lichen-forming genus ''Xylographa'' (Baeomycetales, Ostropomycetidae) with eight new species |journal=Acta Universitet Uppsala Symbolae Botanicae Upsalienses |year=2014 |volume=37 |issue=1 |pages=1–87 |pmid=26953522 |pmc=4747110}}</ref>
}}
{{Taxonbar |from1=Q8045451 |from2=Q61989162 |from3= }}
Category:Baeomycetales Category:Lichen genera Category:Taxa named by Elias Magnus Fries Category:Baeomycetales genera Category:Taxa described in 1822