Stereocaulon Post

 Fencepost of the Week #255

 A soggy wooden post with a rather unusual topping: Stereocaulon dactylophyllum, I think.

 

 

Gigha Woodland Lichens

Lichen list from a visit to Southern Gigha on 8th December 2025

in roughly chronological order

-Leim Farm:
Physconia distorta - https://www.inaturalist.org/observations/329966449
Physcia tenella
Physcia adscendens - https://www.inaturalist.org/observations/330941598
Physcia leptalea? - https://www.inaturalist.org/observations/329966986
Ramalina farinacea
Ramalina fraxinea
Ramalina calicaris
Xanthoria parietina

-Into the mature trees:
Parmotrema perlatum
Anisomeridium sp? - https://www.inaturalist.org/observations/330943560
Peltigera hymenina
Normandina pulchella - https://www.inaturalist.org/observations/330941515
Coenogonium luteum - https://www.inaturalist.org/observations/330941517
Punctelia reddenda - https://www.inaturalist.org/observations/329969734
Flavoparmelia caperata
Melanelixia glabratula
Opegrapha vulgata - https://www.inaturalist.org/observations/330941036
Enterographa sp. (probably E. crassa) - https://www.inaturalist.org/observations/329970533
Pyrenula macrospora - https://www.inaturalist.org/observations/329970742
________
-Achamore, by the car park
Lobaria pulmonaria
Sticta limbata - https://www.inaturalist.org/observations/329973340
Parmotrema crinitum - https://www.inaturalist.org/observations/329973435
Usnea with bright red stems - suggestive of U. rubicunda, but it was probably decomposing Usnea cornuta s. lat. - https://www.inaturalist.org/observations/329974367
________
After lunch: 
- on stone wall
Peltigera praetextata
Peltigera membranacia
Lichenomphalia ericetorum - https://www.inaturalist.org/observations/329981229
- in boggy, newly planted woods
Sticta limbata
Sticta fuliginosa s. lat. (probably S. ciliata) - https://www.inaturalist.org/observations/329981661
Parmotrema perlatum
Parmotrema crinitum
Hypotrachyna laevigata
Lobaria pulmonaria
Lobarina scrobiculata
_______
-Shoreline, waiting for ferry
Scytinium gelatinosum 
Polychidium muscicola

Ricasolia virens - Cyanomorph, Chloromorph and Photosymbiodeme

Some lichenised fungi are capable of associating with both cyanobacteria and algae as photosynthetic partners. In some cases the appearance of the lichen changes very dramatically depending on which photobiont is present.

Ricasolia virens - cyanomorph

For example, here is Ricasolia virens - a small, bushy, cushion-forming jelly lichen. A cyanobacterium is the photobiont here.

But... This is also Ricasolia virens - a large, strikingly green, foliose lichen. This one has an alga as the photobiont:

Ricasolia virens - chloromorph

You can call the cyanobacterium containing lichen a cyanomorph and the alga containing lichen a chloromorph. 

Sometimes you will find a lichen with both photobionts on the same thallus - this can be called a photosymbiodeme. Here is a Ricasolia virens photosymbiodeme:

Ricasolia virens - photosymbiodeme

Related phenomena occur with Sticta canariensis and Ricasolia amplissima.

Sticta canariensis - photosymbiodeme

Ricasolia amplissima - photosymbiodeme

A slight complication: the word cephalodium can also be used to describe a lichen with algae and cyanobacteria both present, but it only allows for cases where the cyanobacteria are kept in small, subsidiary structures within or budding off of a primary chloromorphic thallus.

You can read much more about Ricasolia virens and its forms in this 2016 paper: 
The cyanomorph of Ricasolia virens comb. nov. (Lobariaceae, lichenized Ascomycetes)
By
Tønsberg, Blom, Goffinet, Holtan-Hartwig & Lindblom 
https://doi.org/10.5962/p.386096

Minutely Fruticose Jelly Lichens

 Trying to make sense of some superficially minutely fruticose, corticolous jelly lichens in Cowal. 

Working primarily from the BLS Lichens of Great Britain and Ireland 3 pdfs

 

Row 1 entire organism

Row 2 surface structure (width ~3mm)

Row 3 cross section from near substrate (bottom left) to surface (top right)

Row 4  cells of the cortex (width ~150µm)

Column 1: this is Scytinium lichenoides with well developed isidia, I think. 

Column 2: Scytinium teretiusculum ?

Column 3: Ricasolia virens cyanomorph ?

Column 4: Ricasolia amplissima cephalodium

 

I recently found a paper describing a cyanomorph of Ricasolia virens. Column 3 conforms very closely to the description given here: The cyanomorph of Ricasolia virens comb. nov. (Lobariaceae, lichenized Ascomycetes) DOI: 10.5962/p.386096

Now updated with a specimen of what I think is Scytinium teretiusculum; which I found for the first time in November. 

 Other similar things: 

Polychidium muscicola and Scytinium pulvinatum - I've only found these in saxicolous situations.  

I believe have yet to find Leptogidium dendriscum or a pure cyanomorph of Ricasolia amplissima both of which would fit into this category. Will keep looking.

Mystery Webs

 

You may find substantial, dense webs on fungi in autumn. These look quite like the tent-webs of some moth and sawfly larvae, but differ in occurring later in the year; enclosing a fungus instead of a food-plant; not being full of specks of caterpillar dung; you also rarely see any living (or dead) creatures, eggs or pupae in them.

The cleanness of the webs and the way they are restricted to a particular fungus might make you think you are looking at a grey, fuzzy mould.

To find out what was making these, I took a piece home and kept it in a vivarium. Checking on the vivarium in the middle of the night I spotted a small mealworm-like creature moving through the web, leaving a slime trail behind it. I caught it and put it in an empty enclosure where it soon started fervently weaving by bobbing its head back and forth at an impressive rate, extruding silk from spinnerets on its snout. In the morning, the new enclosure was full of webs, and the larva resting in the middle.

I believe these larvae are fungus gnats of the family Mycetophilidae - a large family of small, rather plain flies with thousands of described species, most of which lay their eggs on fungi. I haven't found much witten about the function of the webs: maintaining a humid atmosphere; excluding other small creatures; catching spores for consumption have all been mooted. The larvae also seem to be able to move smoothly and rapidly through their silk network.

Bog Pimpernel and an Imposter

 

bog pimpernel - Lysimachia tenella

bog pimpernel - Lysimachia tenella

This pretty little wild flower is bog pimpernel - Lysimachia tenella. It grows in marshy places. I found this one growing along side sundew and pale butterwort very near to one of my adder's tongue fern spots in Argyll.

bog pimpernel - Lysimachia tenella

Having found it once last summer, I have been keeping an eye out, to see if is coming up anywhere else. All through this spring, I kept seeing these plants in various places (not just bogs.) It is almost the same but not quite right. I had to wait till this May for one to flower so that I could identify it:

New Zealand willowherb - Epilobium brunnescens

New Zealand willowherb - Epilobium brunnescens. Which first got off the boat from New Zealand in Edinburgh in 1904 and has been spreading across the countryside ever since. Interestingly, the third record for it outside of Edinburgh is from Ardrishaig - not far from here in 1911.

New Zealand willowherb - Epilobium brunnescens

It does very well in the climate of northern and western Britain and colonises wet, bare ground - ditches and forestry tracks are likely spots, but also gardens and river banks.

New Zealand willowherb - Epilobium brunnescens

New Zealand willowherb - Epilobium brunnescens

Big, Blobby Slime Mould

 

 Walking back from the polling station on the day of the general election - 4th July - I came across this large, pale slime mould newly emerging from a mossy, recumbent beech trunk. From the size and colour I assumed it was Brefeldia maxima. 

 

Over the next couple of weeks, I returned to the site to watch the spore mass develop. Through the first 48 hours, it turned a deep black-currant red.

...and then dried out and turned chocolate brown.

Brefeldia maxima has a well-formed, continuous skin covering the spore mass (called the cortex) and this slime mould did not, and on examining the spores with a microscope more discrepancies appeared: 

The retuculate spores and net-like capillitium suggest this could be Symphtocarpus amaurochaetoides. My main reservation about that id is that the spore mass was so much larger than it should be - about 40x12cm where the description (in 'The Myxomycetes of Britain and Ireland" by Bruce Ing) suggested 5cm diameter was usual.

You can monitor or contribute to this observation on iNaturalist, here.

 

 

On my last visit to check on the slime mould, a large sphere of spore mass had fallen off the log and landed on the forest floor. A dor beetle had found it, and seemed happily engrossed in rolling it around the leaf litter.

I just caught the tail end of the performance on video: dor beetle exit stage down to the consternation of the mites.

Rutstroemia firma

 

Rutstroemia firma is a brown cup fungus that grows on dead oak wood. It often has a long, dark stem, but can also come up in crowded rosettes.

Fresh Glue Fungus

 

I can find glue fungus - Hymenochaete corrugata - at any time of the year as blackish, cracking lumps of matter sticking hazel tree branches together.

But at the end of July, I came across this: freshly grown glue fungus. Off-white, with a felty texture. 

Rust-gill?

 

One mouldy mushroom on the log. These are from my visit to Kyoto in 2016. Probably one of the rust-gills - Gymnopilus, but I never did get a solid id.

Adder's Tongue Ferns

 Most example images of adder's tongues are taken side on, something like this:

Adder's Tongue - Ophioglossum vulgatum

 

 

But if you are looking for ferns out in the field, what you will be presented with might look more like this:

Adder's Tongue - Ophioglossum vulgatum

More Blobs

Every so often I find a strange blob of something growing in the woods. Trying to identify what they are is often challenging - it's hard to tell if they are fungi or slime moulds or something else entirely (eg. star slime from gutted toads.)

 But this week, with the aid of a slightly more comprehensive field guide, I resolved two of my longest standing mystery blobs:

Tremella steidleri

Blob 1 was an impressive gelatinous lump I found growing on the side of a mossy oak in 2007. Revisiting the site last week, I found a smaller but similar blob. It was right next to some Stereum hirsutum brackets, and looking through Tremella again I found this species which has a distinctive, knotty form, and a distinctive, frosty bloom. The way the ageing fruiting body disintegrates into slime might also be distinctive enough to aid in identifying similar blobs.

Postia ptychogaster - old, weathered specimen

Postia ptychogaster - fresh specimen

Blobs 2 & 3: One from 2010 and one from 2016, I couldn't figure these out until I was looking up a very ordinary bracket fungus from the genus Postia  and saw an illustration of Postia ptychogaster on the same page.

Winter Polypore

Monday Mushroom #112

Winter Polypore - Polyporus brumalis

The winter polypore is one of the most mushroom-shaped of polypores. It quite often looks just like a regular, gilled mushroom until you look underneath and see the pores, or touch it: it's leathery in a way that very few gilled fungi are.

Winter Polypore - Polyporus brumalis

Blackening Russule

Monday Mushroom #99

The blackening russule begins as a stout, creamy white mushroom with a coffee-coloured flush to the depressed center of its cap.

Young blackening russule - Russula nigricans

This mushroom's gills are very distinctive: exceptionally thick and widely spaced. To me, they look rather like sliced almonds and have the same brittle texture.

blackening russule - Russula nigricans - gills.

As they age, they shrivel and turn black...

Mature blackening russule - Russula nigricans

Persisting as cryptic black lumps on the forest floor after the season ends. 

Blackening russule - Russula nigricans - old, detatched fruiting body. This one is still recognisably a mushroom, but will disintegrate into charcoal-like lumps over time.

 Last time, I covered Asterophora lycoperdoides - the powdery piggyback fungus, which grows out of these black lumps.