Hypobryon validum

Hosts: Frullania teneriffae (type), F. tamarisci (collection here)

Minute ascomata on Frullania tamarisci as black spots (arrowed). I inadvertantly collected this species on a bit of the Frullania infected by the more common Filicupula suboperculata. It is likely impossible or very difficult to observe in the field. Scotland, Sept. 2024
Asci with 8 2-celled ascospores beside the ruptured, thick-walled peridium.

Hypobryon validum Döbbeler. Ascomata 50-80, dark brown / blackish, glabrous. Asci ovate to ellipsoidal, 8-spored initially but fewer ripen ±6. Interascal filaments absent. Ascospores ellipsoidal, (6-)7.5-10(-12) x 3.5-5(5.5), brown, 1-septate. Hyphae brownish, subcuticular or superficial, forming appressoria and haustoria.

Fruitbodies perforate the exposed portions of upper lobes and the perianths.

Only otherwise known from the type collection, which was on hosts inadvertently collected in a packet of Plagiochila in Scotland. It should be looked for along the west coast.

H. poeltii is similar but grows on Porella platyphylla and P. cordaeana. It has never been reported in the British Isles. A link to photographic documentation of a collection: https://dothideomycetes.org/dothideomycetes/dothideomycetes-genera-incertae-sedis/hypobryon/hypobryon-poeltii.html

References

Döbbeler (1983). Hypobryon gen. nov. (Dothideales), eine bemerkenswerte Gattung bryophiler Pyrenomyceten. Nova Hedwigia 37: 1-17.