Photos of the habitat:
Photos of Glen Afton Creek Aug 2021 Impatiens Host
Photos of Ascomata, asci and ascospores
Plagiosphaera immersa (Trail) Petrak
AC – 647, 790, 997, 1233, 1951, 2424, 2432 (all on Impatiens capensis except AC 1951 on Chenopodium sp.)
On dead stems, ascomata often in pale bleached area.
AC 647 – spores 50-65×2µm, many oil globules, possibly septate, asci float free like Diaporthaceae, paraphyses large cells and septate; clearly horizontal immersed ascomata with only the ostiole showing at substrate surface (no elongated neck), some blackening on the substrate surface. AC 790 – horizontal ascomata seem to be on white bleached patches (perhaps different from others). AC 997 – spores 65×2-3µm, possibly septate; ascomata swan-like horizontal with neck turned upright; check Plagiosphaera immersa (Trail) Petrak in Ellis & Ellis Microfungi of Land Plants, found on Urtica sp (a host usually in wet habitats like Impatiens sp); also mentioned in Barr Diaporthales. AC 1233 – ascomata immersed and horizontal with ostiole erumpent; spores 50-60×1-2µm, multiseptate but indistinct, many oil globules; spores somewhat parallel in the ascus. AC 2424 – most ostioles flush with substrate one neck raised above substrate. Collection from Winter R (AC 2432) area has several ascomata with necks above substrate.
AC 1951 – ON CHENOPODIUM STEMS ascomata swan-like (horizontal) no prominent beak but neck excentric and usually only ostiole showing, ascomata immersed; asci with two small dots as apical apparatus, asci float free in water; spores hyaline, 40-60×2.5-3.5µ, many oil globules, spores with gentle bend at middle.
The neck length seems to be more variable in Europe (see Ascofrance postings on Urtica) with both elongated and short necks. My collections showed mostly short necks.
Barr, M.E. 1978. Diaporthales in North America … . Mycological Memoir No. 7, 232 pp.
Ellis and Ellis, Microfungi on Land Plants
Mycoportal – Several collections from Europe (on Urtica sp.) but my collections from Ontario (TRTC 48524) and PEI represent the only records from North America.
Ascofrance – One record on Aconitum (France) and another on Urtica (France)