Description from Cannon et al (2021) below.
Like Lepra excludens, but soralia and isidia absent and fertile. Fertile warts numerous, arising from low tubercles, ± elevated, becoming 1.5–2.5 mm diam. Apothecia 1-4 (- 6) per wart, deeply immersed; disc flat, ± veiled, ± black, coarsely white-pruinose, surrounded by an irregular, often smooth and raised thalline exciple, the inner edge somewhat torn; epihymenium with numerous crystals, K–. Asci 1-spored, often aborting. Ascospores 100–300 × 50–100 μm, wall relatively thin (4–5 μm), not striate or zoned. Thallus reactions and chemistry as in P. excludens: medual C–, K+ yellow→blood-red, KC+ yellow-red, Pd+ yellow-orange, UV± pale grey or grey- yellow, (norstictic, ± salazinic, ± unknown fatty acids, ± UV+ yellow xanthone).
Characterised by the fertile warts in which apothecia are immersed with white pruinose discs and by the K+ red thallus. The broad thick-margined rounded apothecia with an irregular ± pruinose opening and veiled disc are also diagnostic; they are usually paler than the thallus. Lepra monogona is possibly the fertile counterpart of L. excludens, but the former taxon has not been sequenced.
On sunny siliceous coastal rocks.
![Key to map date classes](/sites/default/files/default_images/species-maps-key_2.png)
S.W. England, Isles of Scilly, Channel Islands, Wales (Pembrokeshire, Merionethshire), W. Scotland, W. Ireland; rare.
Britain: Notable
Cannon, P., Kukwa, M., Coppins, B., Fletcher, A., Sanderson, N. & Simkin, J. (2021). Pertusariales: Ochrolechiaceae, including the genera Lepra, Ochrolechia and Varicellaria. Revisions of British and Irish Lichens 5: 1-17. Link