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Small discomycete on Rubus fruticosus
Chris Yeates, 07-04-2015 20:48
Chris YeatesBonsoir tous
I recently collected a small dark fungus on Rubus fruticosus stems which in the field I took to be a superficial globose prenomycete. Only when viewd under the dissecting microscope did I see that it was a discomycete with urceolate apothecia such as one finds in certain Pyrenopeziza species. A squash under the compound microscope came as quite a surprise: here was a crustose ectal excipulum such as one finds in Micropeziza, but the paraphyses were very different from what one expects in that genus, being more like those of a Pyrenopeziza.
Details are:
*  Apothecia numerous, scattered, 220-300µm diameter. Globose to urceolate dark slate grey to black with slight paler mouths.
*  Asci 8-spored; IKI+; I suspect it has croziers, but have yet to confirm that.
*  Ascospores biseriate, clavate 5.5-7.5 x 1.9-2.4µm; with either no contents or with a quite large apical LB and occasionally also with a smaller basal one.
*  Paraphyses parallel-sided, with a few septa towards the base; lacking VB's and barely widening at the apex, if at all.
*  Basal cells forming a more or less distinct circular pad, composed of thick-walled globose cells.
*  Inner excipulum consisting of texture prismatica towards the base, this changing to texture porrecta approaching the apothecial 'mouth' where these cells form rather coarse tufts or teeth.
*  Outer excipulum consisting of dark reddish brown opaque crustose matter.

I hope the attached images will give an idea of what I am trying to convey above.

Despite the fact that Rubus fruticosus has been quite extensively studied and the list of associated species is quite comprehensive I cannot find a genus to fit this - though I may be overlooking something very obvious.

Any suggestions would be more than welcome.

Cordialement
Chris
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Hans-Otto Baral, 07-04-2015 21:13
Hans-Otto Baral
Re : Small discomycete on Rubus fruticosus
Hi Chris

I still believe that you have something like Pyrenopeziza pulveracea/fuscostriata, although the rather large drop in the spore apex reminds me of Spilopodia. That genus seems impossible however. I assume the asci were IKI blue.

Zotto
Chris Yeates, 07-04-2015 21:41
Chris Yeates
Re : Small discomycete on Rubus fruticosus
Thanks for the fast response Zotto
Yes it did remind me of P. pulveracea though that seems to be almost entirely restricted to Filipendula ulmaria in the UK (but also Rosaceae of course). The habitat was very different from where you would expect F. ulmaria, being drier, so perhaps the crust could be environmentally induced. Yes, asci IKI+.
I note a similar confusion here: http://www.ascofrance.com/forum/880/pyrenopeziza-cf-pulveracea-index-20060708-006-perz though I would not describe the excipulum of my fungus as textura globosa - see image here. I am intending to do some springtime collecting on Filipendula soon - so I shall compare with your suggestion.

LG
Chris
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Hans-Otto Baral, 07-04-2015 21:56
Hans-Otto Baral
Re : Small discomycete on Rubus fruticosus
O.k. for pulveracea, but P. nigrostriata is reported from various herbs, see Ellis & Ellis.

I have one sample asl cf. pulveracea on Rubus: HB 8555.

Piotr's sampe is also doubtfuly, yes.