# Ptychographa

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{{Short description|Single-species lichen genus}}
{{Use dmy dates|date=June 2025}}
{{Use Oxford spelling|date=June 2025}}
{{Speciesbox
| image = Ptychographa xylographoides.jpg
| image_caption = Botanical illustration of ''Ptychographa xylographoides'' by [J.M. Crombie](/source/James_Mascall_Morrison_Crombie) & Blair, 1874
| parent_authority = [Nyl.](/source/Nyl.) (1874)
| taxon = Ptychographa xylographoides
| authority = Nyl. (1874)
| synonyms_ref = <ref name="Species Fungorum synonymy"/>
| synonyms = *''Leptographa'' {{au|([Th.Fr.](/source/Th.Fr.)) [M.Choisy](/source/M.Choisy) (1950)}}
*''Placographa'' sect. ''Leptographa'' {{au|Th.Fr. (1874)}}
*''Ptychographomyces'' {{au|[Cif.](/source/Cif.) & [Tomas.](/source/Tomas.) (1953)}}
}}

'''''Ptychographa''''' is a fungal [genus](/source/genus) in the family [Xylographaceae](/source/Xylographaceae).<ref name="CoL_CF2BV"/> It is a [monospecific](/source/monospecific) genus, containing the single species '''''Ptychographa xylographoides'''''. This inconspicuous [lichen](/source/lichen) grows as a barely visible coating of dark grains on rotting logs and branches in [undisturbed](/source/disturbance_(ecology)) old forests. The species is most readily identified by its narrow, elongated black fruiting structures that run parallel to the wood grain.

==Taxonomy==

The genus ''Ptychographa'' was established by the Finnish lichenologist [William Nylander](/source/William_Nylander_(botanist)) in 1874 with the description of the [type species](/source/type_species) ''Ptychographa xylographoides''. In his original Latin {{lichengloss|diagnosis}}, Nylander characterized the genus by its white [thallus](/source/thallus) with black, lance-shaped ({{lichengloss|lanceolate}}) apothecia. He described the apothecia as somewhat prominent above the flattened [thallus](/source/thallus), with longitudinally folded epithecium and margins the same colour. The [asci](/source/ascus) were noted to contain eight colourless, simple [ellipsoid](/source/ellipsoid)al spores measuring 11–14&nbsp;[micrometre](/source/micrometre)s (μm) in length and 6–7&nbsp;μm in width, with a slightly coloured epithecium and blackish hypothecium. Nylander also observed a reddish-brown gelatinous [hymenium](/source/hymenium).<ref name="Nylander 1874"/>

Nylander collected the [type specimen](/source/type_(biology)) from Scotland, growing on wood of ''[Sorbus aucuparia](/source/Sorbus_aucuparia)'' (rowan), and noted its occurrence at Creag na Cailleach in [Killin](/source/Killin). He distinguished ''Ptychographa'' from the related genus ''[Xylographa](/source/Xylographa)'' by noting that while both genera share similar apothecial characteristics, ''Ptychographa'' has a distinctive arrangement of hymenia that differs from ''Xylographa'' and ''[Opegrapha](/source/Opegrapha)'', along with all other members of the [Graphidaceae](/source/Graphidaceae). Nylander concluded that the subglomerate conidia were absent in this genus.<ref name="Nylander 1874"/>

==Description==

''Ptychographa xylographoides'' grows as an exceedingly thin crust that is often little more than a dusting of dark-brown grains on decaying wood. Each grain is a {{lichengloss|goniocyst}}—a microscopic packet in which a few [green alga](/source/green_alga)l cells (the {{lichengloss|chlorococcoid}} photobiont) are wrapped by fungal [hypha](/source/hypha)e. These goniocysts measure roughly 20–50&nbsp;[micrometre](/source/micrometre)s (μm) across and are sheathed in a uniform {{lichengloss|cortex}} of angular, brown-walled cells, giving the thallus its subdued {{lichengloss|matt}} appearance. Because the vegetative body is so inconspicuous, the lichen is easiest to spot when it develops its slit-like fruit bodies.<ref name="Cannon et al. 2021"/>

The reproductive structures are narrowly elongate apothecia ({{lichengloss|lirellae}}) that run parallel to the grain of the wood. Each lirella is 0.3–1.4&nbsp;mm long yet only 0.1–0.3&nbsp;mm wide, with a black fissured {{lichengloss|disc}} that may split into two parallel slits—each over a separate spore layer—separated by dark tissue. The rim surrounding the disc (the {{lichengloss|true exciple}}) is unusually thick, entirely black-brown and friable, being composed of tightly cemented [hypha](/source/hypha)e. Internally, a dark-brown {{lichengloss|hypothecium}} merges into the exciple, while the clear [hymenium](/source/hymenium) above it reaches 45–60&nbsp;μm in height and [stains](/source/staining) yellow then blue in iodine–potassium iodide tests. Sparse, mostly unbranched [paraphyses](/source/paraphyses) thread the hymenium, their tips darkened and stuck together to form an {{lichengloss|epithecium}}.<ref name="Cannon et al. 2021"/>

Club-shaped [asci](/source/ascus) contain eight smooth, colourless [ascospore](/source/ascospore)s, 8.5–13 × 4.5–6.5&nbsp;μm, that remain [aseptate](/source/septum) (single-celled) and lack any gelatinous sheath. The ascus apex shows a blue-staining outer coat in iodine, with a non-reactive dome at the very tip—an arrangement characteristic of the ''[Trapelia](/source/Trapelia)'' type. [Asexual](/source/asexual_reproduction) propagation occurs through minute, immersed or superficial [pycnidia](/source/pycnidia) that release rod-shaped [conidia](/source/conidia) about 4–7 × 0.8&nbsp;μm.<ref name="Cannon et al. 2021"/>

==Ecology==

''Ptychographa xylographoides'' species [colonises](/source/colonisation_(biology)) the upper surfaces of fallen [trunks](/source/trunk_(botany)) and large branches in undisturbed, often [ancient woodlands](/source/old-growth_forest), where the damp, slowly rotting timber provides the stable [microhabitat](/source/microhabitat) it requires.<ref name="Cannon et al. 2021"/>

==References==
{{Reflist|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 |page=7 |url=https://britishlichensociety.org.uk/sites/default/files/Xylographaceae.pdf}}{{Open access}}</ref>

<ref name="CoL_CF2BV">{{Catalogue of Life |id=CF2BV |title=''Ptychographa'' |access-date=19 June 2025}}</ref>

<ref name="Nylander 1874">{{cite journal |last=Nylander |first=W. |year=1874 |title=Addenda nova ad lichenographiam europaeam. Contin. XVIII |journal=Flora (Regensburg) |volume=57 |pages=305–318 [315] |language=la |url=https://www.biodiversitylibrary.org/page/62240}}</ref>

<ref name="Species Fungorum synonymy">{{cite web |title=Synonymy: ''Ptychographa'' Nyl., Flora, Regensburg 57: 315 (1874) |url=http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=4542 |publisher=[Species Fungorum](/source/Species_Fungorum) |access-date=19 June 2025}}</ref>

}}

{{Taxonbar|from=Q7257148}}

Category:Baeomycetales
Category:Lichen genera
Category:Baeomycetales genera
Category:Taxa named by William Nylander (botanist)
Category:Taxa described in 1874

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Adapted from the Wikipedia article [Ptychographa](https://en.wikipedia.org/wiki/Ptychographa) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ptychographa?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.