Mark Powell

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Mark Powell

Mark Powell

@obfuscans3

Lichens. Anyone with a hand lens can make discoveries. Add a microscope and a couple of chemicals and you can help rewrite the books.

lowland England Katılım Mart 2017
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Mark Powell
Mark Powell@obfuscans3·
Twelve years ago, knowing almost nothing about lichens, I stared at this gravestone and something inside me longed to decipher the complicated mosaics. Now I can name almost every lichen on the stone but there are still mysteries.
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Mark Powell
Mark Powell@obfuscans3·
A single Home Counties gravestone: 31 lichen spp. and 2 lichenic. fungi. Calcareous sandstone so a rich mixture of species straddling the acid/basic divide. Superb colony of Bacidia rubella (much more common on gravestones than on trees around here).
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Mark Powell
Mark Powell@obfuscans3·
One English gravestone, ten years experience, ten minutes examination, 23 species of lichen (three of which will require checking microscopically). To many people's surprise, Pyrrhospora quernea is much more common on gravestones than on trees in E. England
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Mark Powell
Mark Powell@obfuscans3·
@crawley_mick in 2000 my parish list stood at 431. Since then I have added about 65, the most recent being Polypogon viridis today. x.com/obfuscans3/sta…
Mark Powell@obfuscans3

I actually counted subspecies as separate (didn't count vars. or formae) but called them 'species' in this table. Most British natives were considered native to the parish but with exceptions e.g. Ransoms and Red Campion which are known to have been introduced to the parish.

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Mark Powell
Mark Powell@obfuscans3·
@crawley_mick Your archive of X posts are proving very useful. I am updating the flora of my parish which I originally surveyed between 1980 and 2000. Your posts have helped me add E. sumatrensis, floribundus, bonariensis, Polycarpon tetraphyllum and Polypogon viridis to my parish list.
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Mick Crawley
Mick Crawley@crawley_mick·
You may be interested in this brief (15 min) talk about London's Plants. The book of the same name will be appearing shortly, and you will be able to buy it from its eponymous web site at a remarkable pre-publication discount. More of that in due course youtube.com/watch?v=rL1e0y…
YouTube video
YouTube
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Earthling
Earthling@TheHumanDilemma·
“Transmitting one's flaws [through procreation] to someone else is a crime. I could never consent to give life to someone who would inherent my ailments.” — Emile M. Cioran
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Mark Powell
Mark Powell@obfuscans3·
This is what life feels like to me.
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Mark Powell
Mark Powell@obfuscans3·
@sim_nature The reaction is in the medulla and is rather weak so the medulla needs exposing, rather than just applying to the cortex. I must sound like a stuck record but in all cases apply strong fresh reagents very sparingly to dry lichens (exposing the medulla if that is relevant).
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Mark Powell
Mark Powell@obfuscans3·
@sim_nature If you are ever keen to prove a thallus is B. saxorum (rather than e.g. B. subdisciformis), do it only in dry conditions, scuff a tiny portion of the thallus near the margin (where the reaction seems strongest) AND use a cocktail stick or end of dry grass stalk to apply tiny drop
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Mark Powell
Mark Powell@obfuscans3·
Fyfield Down is a magical site. Many, but not all, of the specialist sarsen lichens are also present at Avebury where they are in very good condition despite (or perhaps because of) the visitor pressure. Buellia saxorum is abundant at Avebury but not easy to recognise.
Paul Cannon@fgbi_pfc

Made a pilgrimage to Fyfield Downs for #lichenJanuary to view lichens on the Grey Wethers (bit.ly/2FBLjk1), where the big sarsen stones at Avebury and Stonehenge came from. Classic site for Buellia saxorum and the usually coastal Xanthoparmelia loxodes. @BLSlichens

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Mark Powell
Mark Powell@obfuscans3·
@sim_nature @BLSlichens With the use of something like a cocktail stick, a single structure, or a single apothecium can be tested at a time without the potential for confusing results resulting from leaching from one tissue to another, or one species to another.
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Mark Powell
Mark Powell@obfuscans3·
@sim_nature @BLSlichens ...dark discs just Myriolecis with discs that are darkened for some reason? I am a little suspicious about that strong K+ red-purple reaction, wondering if it is leaching from a little lobe of Xanthoria or a Caloplaca apothecium which I can't see.
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Mark Powell
Mark Powell@obfuscans3·
@sim_nature @specanatura @RSPBPagham @apeasbrain @CyanoEvo @BLSlichens Yes, and you could add L. polytropa and P. soredizodes and a few other common species of siliceous rock. Worth looking out for the shingle specialist R. aspersa. x.com/obfuscans3/sta…
Mark Powell@obfuscans3

@duckinwales @LemonStephen @BLSlichens We ought to produce such lists for various habitats. At Orford Ness the dominants on shingle are: Buellia aethalea, Lec. polytropa, Mel. fuli, Rhizo. reduct., Porpid. soredizodes and Rinodina aspersa (the latter being the closest to a shingle specialist). R. aspersa:

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Mark Powell
Mark Powell@obfuscans3·
@sim_nature @specanatura @RSPBPagham @apeasbrain @CyanoEvo @BLSlichens Here is a thread which includes most the issues I have with identifying R. reductum (I had to do an advanced search to retrieve it, as if the search function on X has changed a bit). x.com/obfuscans3/sta…
Mark Powell@obfuscans3

A new colonist has appeared on the pantiles of the outhouse roof. The darker thalli belong to Buellia aethalea (Catillaria atomarioides is also present on the tiles). What are the little colonists with paler thallus? Thread

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Mark Powell
Mark Powell@obfuscans3·
@specanatura @mothgarden @GPFMOTHMAN1 @apeasbrain I can't shed any further light on this so I will simply use this old thread to highlight how difficult it can be to distinguish between structures belonging to the lichen, and lichenicolous fungi, even with microscopy. x.com/obfuscans3/sta…
Mark Powell@obfuscans3

@CelticWildflow1 It is not always easy to tell whether pycnidia, even perithecia, belong to the lichen or are a lichenicolous fungus. Take the example of the perithecia found immersed in the squamules of Normandina pulchella. Originally, for a century considered to belong to the lichen...

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Anthony Speca
Anthony Speca@specanatura·
@mothgarden @GPFMOTHMAN1 @obfuscans3 @apeasbrain Perhaps you have shreds of C foliacea: upturned and incised squamules with green uppers, white lowers. Lack of podetia typical. But that's not completely diagnostic! C foliacea is variable and resembles other species: try chemical tests in my thread above to take your ID further!
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Graham Featherstone
Graham Featherstone@GPFMOTHMAN1·
Amongst yesterdays Cladonia i notice patches of squamules that had no podetia !I brought a small sample home and noticed under my microscope that the squamules had black fruiting bodies at the tips.Any tips on an ID would be great ! @obfuscans3 @specanatura
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Keşfet

@crawley_mick @BLSlichens @specanatura @RSPBPagham @CyanoEvo @mothgarden @GPFMOTHMAN1 @elonmusk