Puttea duplex

The thallus is very thin and inconspicuous, forming a pale grey to brownish film over decaying moss on bark. Apothecia (disc-like fruiting bodies) are tiny—typically 0.15–0.2 mm across—pale yellowish-brown and flat, with a margin similar in colour to the disc. Microscopically, the exciple (the apothecial rim) is nearly colourless; the spore-bearing layer has branched, interwoven paraphyses; and the asci are of the Ectolechiaceae type, each usually containing 16–24 spores. The spores (ascospores) are colourless, simple (without cross-walls), broadly ellipsoid and very small, about (2.5–)3–4(–5) × 2–2.3 μm. No asexual fruiting bodies (pycnidia) have been observed, and thin-layer chromatography detected no lichen products. In the field it can be mistaken for a pale-fruited Micarea, but the many-spored asci and very small, simple spores distinguish it.^[3]

Originally described from the British Isles (Scotland, Wales), where it grows on bleached, decaying moss on tree trunks,^[3] the species is now confirmed from Fennoscandia. It was reported from Norway and then newly recorded for Sweden, where it was found on the bark of birch in mature coniferous forest. The Swedish find, occurring directly on bark rather than only over bryophytes, suggests the species' substrate range is broader than first thought. Current distribution therefore includes the UK, Norway and Sweden, and it is plausibly overlooked elsewhere in oceanic to suboceanic woodland.^[4]