Perithecia

[chriscant]

The Cumbria lichen group visited Penny Rigg Copper Mill at Tilberthwaite near Coniston in the Lake District yesterday.
There's a mixture of habitats with some metal and basic influence including slate and metal-rich waste, ruined buildings (a crushing plant and settling beds).
On old mortar and bryophytes in a crack between blocks in a north-facing high wall of one of the buildings was a green lichen with large two-thirds immersed perithecia.
The thallus was either minutely squamulose or minutely granulose.
I haven't yet looked for papillae.

The perithecia were up to 0.7mm at the widest, with some having a neck upwards; no involucrellum visible; exciple possibly made up of two layers.
No photobiont in the perithecia.
Some of the large shiny prolate spheroid spores had been ejected and were visible using a hand lens.
The perithecia that I've looked at so far were fairly empty.
I'm fairly certain that one ascus just had two spores in; I can't rule out there being some asci with more spores.
The spores were consistently brown muriform with brown cell walls, with dimensions up to 105μm long and 67μm wide, no perispore.
The larger spore proportions were between 2:1 and 3:2. Various smaller spores around in different shapes.

Having looked through the Verrucariaceae key, there are only a few species that have such long spores: Polyblastia helvetica, Atla wheldonii and Agonimia tristicula. Arguably it looks most like Agonimia tristicula but it has features that match Atla wheldonii. Any suggestions?

Thanks, Chris

[Neil Sanderson]

Chris

The persistently brown spores should rule out Agonimia tristicula. As you say it seems to be a something of a match for Atla wheldonii other than not seen intact asci, but I do not know that species. The few pictures do not look similar, however, there are more at https://fungi.myspecies.info/taxonomy/term/8099/media but the Fungi of Great Britain and Ireland website is not working, again.

Looking again the best fit is probably Agonimia tristicula with a rather strongly developed thallus that has become granular (check for the papillae) and the perithecia containing only old brown spores, which would match the fairly empty perithecia.

Neil

[chriscant]

Thanks Neil

I attach some thallus photos at 1000x.
I can't see papillae (that look like what I've seen before).
My perithecia don't look roughened as per other Agonimia tristicula photos and they aren't barrel shaped.

We did have Agonimia tristicula elsewhere that day so it is already recorded.
If anyone has any other suggestions, let me know.

Chris

[Neil Sanderson]

Chris

Yes does not look like an Agonimia cortex.

Agonimia octospora cortex

So I am out of ideas, sorry

Neil

[chriscant]

I asked John Douglass to look at this thread and he suggested that it may be a "triple whammy" ie "Botrylepraria lesdainii growing over Agonimia tristicula but the perithecia may belong to something else within the Polyblastia agg.". That would make sense but it might be difficult to confirm. Within Polyblastia the best match for the perithecia and spores is the Atla wheldonii hidden amongst the other two.