Mark Powell Profile picture
Jan 31, 2022 7 tweets 3 min read Read on X
Catillaria nigroclavata is familiar to me these days on twigs and branches in my region. Will I learn any more about it if I attempt to make some drawings of it?
At first sighting, C. nigroclavata (in lower part of image) is very similar to Amandinea punctata (above). With careful study differences in appearance of both thallus and apothecia become apparent.
The thallus of A. punctata consists of minute grey warts, its apothecia become somewhat convex with maturity. C. nigroclavata has a thin, scurfy, dark, dull green thallus; the apothecia have narrow margins and discs remain flatter with age.
Before attempting to draw a microscopic section, I hadn't realised that the apothecia contain three pigments, two shades of brown and blackish green.
The brown-capped paraphyses and colourless, 1-septate ascospores are well known Catillaria characters. Perhaps less well known are the distinct 'computer mouse' haustoria, which are also present in the genus Halecania.
The asci are typical of Catillaria after staining with iodine but the ascus tip seems elongated in C. nigroclavata. I ought to take note when I next examine C. chalybeia and see if these elongated ascus tips are particular to nigroclavata or not.
Back in 2015 I had just been studying the distinctive haustoria in C. nigroclavata and this helped me to identify the first British occurrence of C. fungoides as explained in this thread:

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More from @obfuscans3

Jan 8
Lichen mosaics seem like confusing puzzles to beginners. Once you can recognise basic growth forms such as placodioid, they can be broken down into manageable groups. This list is relevant to churchyards across much of lowland England.
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Read 8 tweets
Feb 27, 2023
A thread about the lichenicolous fungus Laetisaria lichenicola, including the surprising way it was added to the British list in 2015 and hints about identifying/recording it. Image
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With experience, L. lichenicola can sometimes be recorded on sight in the field but a certain amount of caution is advised. Image
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Apr 29, 2022
Micarea curvata is a very inconspicuous lichen. I had the privilege of being present when the first English occurrence was found, in the company of Brian Coppins who originally described the species. Image
Although the 'Flora' gives the habitat of Micarea curvata, more detailed guidance would help people to locate colonies of it in lowland churchyards. ImageImage
The specific epithet relates to the curved ascospores. ImageImage
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Apr 29, 2022
I have a lot of anecdotal information about various lichens, along with copious notes from my own observations. This thread is about Lecanora antiqua, described as new to science by Jack Laundon in 2010.
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Can anyone find L. antiqua on relatively modern stonework?
Read 11 tweets
Feb 1, 2022
A few more parmelioids (Parmelia and related genera) from my walk today.
Can you detect the yellowish tinge in this Flavoparmelia caperata (pure grey Hypotrachyna at top right for comparison).
Flavoparmelia caperata in lower half, Hypotrachyna revoluta above. Again the subtle difference in colour which can only be accurately judged when the lichens are dry (they all become greener and rather similar in colour when damp/wet).
Here we have the two British Flavoparmelia species side by side. Similar colour. F. caperata (left) tends to be more robust, soredia coarser, produced in pustular soralia. If in doubt a simple chemical test will distinguish them.
Read 13 tweets
Feb 1, 2022
When dealing with mature specimens, Ramalina farinacea (left) can usually be readily distinguished from Evernia prunastri (right) and learning to separate them is a good exercise for beginners and improvers.
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Evernia has a slightly matt texture (perhaps like fine tissue) whereas Ramalina is more cartilaginous (as if moulded in plastic). The undersides of Evernia branches are usually starkly different (white) to the upper side. In Ramalina underside similar or only slightly paler.
The soralia of Ramalina farinacea are usually neatly oval in shape and restricted to edges of branches. The soralia of Evernia are irregular in shape and are not restricted to edges of branches.
Read 5 tweets

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