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Family: RutstroemiaceaeGenus: Rutstroemia
A minute (1-4 mm diam.) yellow-brown to brown discomycete growing from a lumpy black crust (Xenotypa aterrima) on Betula (birch) spp., often where the bark appears to have been stripped away.
Anamorph: not known.
Teleomorph: stromata absent. Ascomata apothecia, superficial, scattered, developing from a black crust of Xenotypa aterrima; 1-2 (-4) mm diam., cupulate, externally yellow-brown when very young and maturing to dark brown, with a paler irregular fringe-like margin; striate and finely scurfy, with a short stout stalk. Disc yellowish-brown, drying blackish brown. Outer excipulum to ca 60 µm thick, composed of globose cells 4-5 µm diam., covered with short undulating thin-walled septate hairs 3-4 µm diam. Internal tissues of loosely interwoven hyaline hyphae to ca 4 µm diam. Interascal tissue of simple cylindrical paraphyses ca 2 µm diam., slightly enlarged and pale yllowish brown at the apices. Asci 110-110 x 10-12 µm, clavate, short-stalked, with croziers, the apex rounded with a broad shallow ring staining blue in iodine, 8-spored. Ascospores (18-) 25-33 x 6-8 µm, fusiform, straight or slightly curved, hyaline, aseptate, 1-septate or infrequently 2- to 4-septate, often with several large lipid globules when living.
Link to external images: Ascofrance : Baral's image library.
Map of known distribution in Great Britain and Ireland.
Description based on Ahti et al. (2000) and Dennis (1956). Previously known as Dencoeliopsis johnstonii, but reassigned to Rutstroemia on the basis of DNA evidence (Pärtel et al. 2016).