Hosts: Polytrichum formosum
Reported from herbarium specimens collected in Ireland: E Ireland, Co Galway, Connemara, 29 Apr 1998, H. Hertel 39432b along with its parasite Tremella bryonectriae (Döbbeler, 2019). I have found it on randomly collected P. formosum in England and Wales, sometimes in great abundance, with no indication of infections in the field. There are around 4 GBI records in total as of July 2026. The species is likely not uncommon but takes much time and patience to detect.
B. cuneifera may be found on leaves in middle and lower regions of the host and not on healthy upper green leaves. It grows between the leaf lamellae, particularly in basal regions of the leaves but not folded within the sheathing bases. Perithecia are whitish to transparent, making it extremely difficult to observe the fungus even under a dissecting microscope as the orientation of the incident light changes whether they are visible or not. I found that they were best viewed if the host leaves are more or less sideways rather than by examining the dorsal surface head-on as is normal for most fungi on / between lamellae, if light is coming from above. Good infections have bulging, superficial whitish blobs on the leaf surface. These can be confused with colonies of algae on the plant surface, particularly in dead material where these turn white.
B. phyllogena is a related taxon that grows on the surface of the lamellae of middle or lower leaves of the same host. It is larger and brownish in colour. It has also been reported on Polytrichum juniperinum but not reported in the British Isles thus far.
References
- Döbbeler, P. (1978). Moosbewohnende Ascomyceten I. Die pyrenocarpen, den Gametophyten besiedelnden Arten. Mitt. Bot. Staatssamml. München, 14: 1-360.
- Döbbeler, P. (1985). Ascomyceten auf Polytrichaceen. Sydowia, Ann. Mycol. Ser. II., 38: 41-64.
- Döbbeler, P. (2019). Tremella bionectriae sp. nov. – the first hyperbryophilous fungal species. Nova Hedwigia, 109(3-4): 369-378.
Bryophilous fungi 