Graphis inustuloides
An easy Graphis to overlook, however, the somewhat serpentine but short lirellae with noticeable thalline margins indicate candidates, but the spores need to be examined to be sure this is not Graphis betulina, which also has thalline margins. Internally the wide ellipsoid muriform spores, are diagnostic and unlike those of any other British Graphis. A widespread but local western species.
Thallus thin, smooth or faintly rimose-cracked, white-grey, ± delimited. Apothecia 0.5–1.2 × 0.1–0.2 mm, ± immersed in the thallus, flat or slightly elevated, branched or not, straight, curved or flexuose; true exciple thin and often inconspicuous, not furrowed, black, not continuing below the hymenium; disc narrow and slit-like or narrowly exposed and ± white-pruinose; hypothecium pale. Ascospores (20–) 25–50 (–60) × (9–) 12–16 (–20) µm, muriform with more than 20 cells, with 7–11 transverse septa. Conidia 6–9 × 2–3 µm. No lichen substances detected by TLC.
Graphis anguina in its original circumscription is a species from tropical South America now referred to as Thalloloma anguinum (Mont.) Trevis. (1853), and the name was misapplied for G. inustuloides by European authors (see Staiger 2002, Lücking & McCune 2012).
In the field, often distinguished from Graphis scripta s. lat. by the white rim of thallus pushed up around the exciple, but G. betulina also shows this character so examination of ascospores is necessary for confirmation. Phaeographis dendritica is K+ red (crystals), KC+ red, Pd+ yellow to orange and has brown, non-muriform ascospores. Occasionally host to Arthonia graphidicola, which is more often found on Graphis scripta s. lat..
On smooth bark of deciduous trees in open or sheltered habitats.
Widespread in Britain and Ireland, but rare in N. Scotland & C. & E. England.
Aptroot, A., Weerakoon, G., Cannon, P., Coppins, B., Sanderson, N. & Simkin, J. (2023). Ostropales: Graphidaceae, including the genera Allographa, Clandestinotrema, Crutarndina, Diploschistes, Fissurina, Graphis, Leucodecton, Phaeographis, Schizotrema, Thelotrema and Topeliopsis. Revisions of British and Irish Lichens 36: 1-23.
Lücking, R. & McCune, B. (2012). Graphis pergracilis new to North America, and a new name for Graphis britannica sensu Staiger auct. Evansia 29: 77-84.
Staiger, B. (2002). Die Flechtenfamilie Graphidaceae. Studien in Richtung einer natürlicheren Gliederung. Bibliotheca lichenologica 85: 1-526.
Text by Neil A Sanderson based on Aptroot et al (2023)