Description: Thallus inapparent, not lichenized, developing on bark scales of Acer. Perithecia black, matt, embedded in a pseudostroma, emerging from cracks of bark scales, (0.1-)0.14-0.21(-0.26) μm across, smooth, usually confluent and then irregular in shape and c. 1 mm long, half-immersed in bark, not collapsing, with an indistinct to distinct central apical papilla. Exciple continuous, of a textura angularis, composed of an outer dark brown to black, 10-30(-45) μm thick layer of thin-walled isodiametric cells with dark brown walls, forming a pseudostroma surrounding the inner wall, and an inner, 12-20 μm thick subhyaline to pale brown layer of (sub)hyaline to light brown, slightly smaller and sometimes radially compressed cells. Paraphyses hyaline, Asci 8-spored, cylindrical, unitunicate, thin-walled, without a distinct apical apparatus. Ascospores 1-celled, hyaline, fusiform, lunate to falcate- (20-)25-33(-38) x (2-)2.8-3.7(-4.7) μm, thin-walled, smooth, with subacute to narrowly rounded tapering ends, guttulate. Pycnidia black, usually confluent, resembling perithecia. Conidia of two types: a) holoblastic, falcate, hyaline, smooth, with narrowly rounded ends, with few small guttules, 21-27(-32) x 2-2.5(-3) μm, b) enteroblastic, filiform, curved to semi-circular, (19-)23-28(-31) x (0.8-)0.9-1.2(-1.4) μm. Photobiont absent. Spot tests: all negative. Chemistry: without lichen substances.
Note: on bark scales of mature living trees of Acer pseudoplatanus; known from Austria, Czech Republic, France, Germany, Poland, and Switzerland; to be looked for in Italy.
Source: Keissler K. von 1938. Pyrenulaceae, Mycoporaceae, Coniocarpineae. In: Rabenhorst G L: Kryptogamen-Flora von Deutschland, Österreich und der Schweiz. 2nd, IX, Die Flechten, Abt. 1, 2. Gebr. Borntraeger, Leipzig, pp. 1-846.