Pyrenula chlorospila
A common Pyrenula very similar to P. macrospora, but distinguished in the field by the small, often closely arranged, perithecia which scarcely project from the thallus. The very rare P. nitidella differs in the K+ red inner exciple and the smaller ascospores. Frequently found with P. macrospora on smooth bark in shaded woods in the west and south, but with a more southern in distribution.
Thallus olive-green to pale brown or fawn; pseudocyphellae 40–120 μm diam., white. Perithecia small, 0.2–0.4 mm diam., often rather densely arranged, forming very low projections in the thallus or not forming projections; exciple containing colourless crystals; hymenium not inspersed with droplets, without anthraquinones. Ascospores (25–) 28–32 (–35) × (9–) 11–13 (–14) μm, 3-septate. Thallus C–, K+ yellow, KC–, Pd+ faintly yellow, UV± whitish (unidentified substance).
Distinguished in the field from Pyrenula macrospora by the small, often closely arranged perithecia which scarcely project from the thallus. Most pre-1980 records of P. nitidella, which has a K+ purple hymenium, refer to P. chlorospila, which has a K– hymenium.
On smooth, shaded bark of deciduous trees, often with P. macrospora, with both species widely dominant in shaded humid woods.
Locally abundant. S. & W. Britain and Ireland. Appears more southern than P. macrospora and some records to the north may refer to stunted examples of that species.
Cannon, P., Coppins, B., Aptroot, A., Sanderson, A. & Simkin, J. (2023). Perithecial genera I, including Acrocordia, Alloarthopyrenia, Anisomeridium, Antennulariella, Arthopyrenia, Celothelium, Cyrtidula, Dichoporis, Eopyrenula, Julella, Leptorhaphis, Leptosillia, Lithothelium, Mycomicrothelia, Mycoporum, Naetrocymbe, Pyrenula, Rhaphidicyrtis, Sarcopyrenia, Swinscowia and Tomasellia. Revisions of British and Irish Lichens 37: 1-59.
Text by Neil A Sanderson