Uncommon Pyrenomycete

[Ditiola]

I went out yesterday to look in Alder Carr for Alder specialists. I found the Ciboria but no other Alder specialist.

I did however collect the uncommon Rosellinia britanica on wet Alnus wood. It has very distinctive large (5-8 microns) apical apparatus at the tip of the ascus. I found that they appear very different depending on the stain used.
Cotton Blue stains the surrounding tissue but not the apparatus, while Melzers Iodine although a brown liquid stains the apparatus bright blue.



Apical apparatus IN KOH



Apical apparatus in Cotton Blue


Apical apparatus in Melzers Iodine



Peter

[Chris Yeates]

hi Peter

what separates this from R. aquila? the macro photo looks very like that, though of course one cannot deduce the spore dimensions

I thought britannica was chiefly an ivy specialist in the UK, which doesn't suggest damp sites . . .

cheers

Chris

[Ditiola]

Hi Chris
R.aquila has appendages at the end of the spores, I examined plenty of spores and none had any appendages, only an inconspicuous gel sheath. From the key in Nordic Macromyces this left R.helvetica, R.britanica, R.mammiformis, R.abscondita and R.nectrioides.

R helvetica was eliminated as there was no hyphal mat present and the spores were to big.

As the stomata were not pointed (they are all papilliate), and not on herbaceous debris I was left with R.britannica and R.mamiformis.

R.mammiformis did not fit as the spores were too wide several I measured were 8.8 microns wide, (up to 8.5 in R.mammiformis) and the apical apparatus was also too big. 5-8 microns. I measured most at between 6 and 8 microns, and in R.mammiformis they are only 2.5-4.5 microns, so this was the deciding factor.

I see from the BMS database that as well as Hedera, R.britannica has also been recorded from Salix x2, Fraxinus, Quercus, Magnoliacae, and unidentified deciduous wood x2. Although the site was mainly Alder there was a few Salix present and I cannot rule out that it was not Salix wood.


Peter