Dendrographa decolorans

[SylviaD]

Hi,

I need some help with what I thought was Dendrographa decolorans. I've found a large Oak in an arable field, so probably quite a bit of N enrichment, that looked like it was covered on its south side with a sorediate lichen that had a lilac/grey/light brown hue to it. On closer inspection it scratched orange/yellow and tested K negative and C negative (although on really close inspection there was a slight colouring yellow the same colour as if scratched). So far so good, but then I noticed what looked like apothecia. I have attached photos most of the apothecia are heavily pruinose but some were black where the pruinate (?) had rubbed off. As you can see from the photos most are inset into the thallus. Is this likely to be D decolorans but with apothecia, or is it something else? I have taken a sample.

Thank you for your help,

Sylvia

[Neil Sanderson]

Sylvia

The thallus certainly looks like Dendrographa decolorans, but the apothecia are not like the few examples I have seen, which were not as pruinose as that or not pruinose at all, but descriptions do mention pruina. The spores are quite distinctive 3 septate, curved and 30–37 × 4–5 μm, so a cross section should confirm.

Neil

[Neil Sanderson]

Sylvia

I think that these apothecia are developed on a highly sorediate thallus of Dendrographa decolorans on rough bark, while the Dendrographa decolorans apothecia I have seen before where on thalli on smooth bark with discrete soralia; these look rather diffrent to what you have seen. Best to check the spores however.

Neil

[SylviaD]

Neil,

That's really interesting. The thallus was very well developed on rough bark. I have taken a sample so will sort out looking at the spores. It rather threw me seeing apothecia as I understood they are rare.

Thanks for your help,
Sylvia

[peterbisset]

I ascribed something very much like this to Pachnolepia pruinata (C+ red)

[Neil Sanderson]

Peter

I did also think Pachnolepia pruinata when the pictures were put up, but Pachnolepia pruinata is not sorediate as this clears is. Also as you say Pachnolepia pruinata is strongly C+ red, so quite easy to seperate.

Neil

[SylviaD]

Hi Neil,

I've just got a microscope and so was able to do a section of the possible Dendrographa decolorans apothecia. I'm not yet set up for photography so this is a terrible photograph, but it definitely looked like a spore, but am I right in thinking that this is a D decolorans spore - curved and 3-septate. This one was about 35um long. There were a few what I thought were mature asci with long spores curved coiled around each other, but very few loose no matter how much I squashed and mounted in K. I've not tried staining yet and plan to do that.

Thank you
Sylvia

[Neil Sanderson]

Sylvia

Welcome to microscopy! Yes that seems to a Dendrographa decolorans spore. There are some photos here https://afl-lichenologie.fr/Photos_AFL/ ... s_albo.htm

Have fun

Neil