Mark Powell Profile picture
Jan 31 7 tweets 3 min read
When sectioning fruiting bodies which are immersed in stone, the fine edge of the blade is soon blunted. How do I cut numerous sections of saxicolous material while minimising waste of razor blades?
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There are two basic types, single edged above which are safer and more robust but without the ultra-fine edge that I prefer in the double edged type below.
It is best to snap (or cut) the double edged type in half lengthwise (careful) before use. The disadvantages of this type are rounded ends of the blade (makes picking up sections more difficult) and the fine edge is very easily ruined by slightest touch against hard substratum.
I was surprised when @maxiePut first mentioned cutting razor blades with scissors but I was soon a convert. Here I have snipped off the rounded end, then snipped off a short segment once the end is blunted.
I can keep snipping off short sections of blade, leaving a pristine and pleasantly right angled end. In this way, I can get satisfyingly parsimonious use out of every razor blade, even when working with saxicolous crusts.
Sometimes transferring a fine section to the slide seems more troublesome than actually cutting the section. The right angled end resulting at the cut end of the blade seems particularly good at picking up sections.
If you struggle to cut good thin sections, consider collecting some spare material of something common on bark like Lecidella elaeochroma. With plenty of apothecia to go at, and without the disruption of transferring to slide, you have opportunity for uninterrupted practise.

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More from @obfuscans3

Feb 1
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). Image
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). Image
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. Image
Read 13 tweets
Feb 1
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.
Thread. Image
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. Image
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. Image
Read 5 tweets
Feb 1
Today's gravestone, Joseph Tomlin, d. 1855, oolitic limestone. 'Only' 18 lichens plus one LF, but something a bit different, mossy and with a taxonomic conundrum.
Thread. Image
Four lichens grew upon bryophytes on this stone: Agonimia, Bilimbia, Diploschistes and Lepraria lobificans. The first two in particular are usually found on moss.
The Weddellomyces was parasitic on Caloplaca flavescens. Image
Verrucaria macrostoma f. furfuracea is a curious looking thing, the sort of lichen that would be difficult to key out. Most people get to know it by being shown it, or recognising it from photos. Image
Read 5 tweets
Feb 1
I have been sent a very interesting query from a correspondent who found this lichen on a fragment of ironstone lying on the ground. This thread will illustrate the value of recording what you observe, even if you can't name the lichen. Image
My correspondent assigned a provisional genus - Lecania. I think it belongs in a different genus but it is useful to make an initial hypothesis and then to keep an open mind. Image
Perhaps my correspondent was led astray by a misinterpretation of the spores as being septate. Spores in fresh material are difficult to interpret without 'clearing' and while iodine is a useful stain (used here), it is not harsh enough on its own to clear spores. Image
Read 14 tweets
Jan 31
Today's gravestones, a headstone and a footstone, both limestone, Eliz. Packwood, 1917. A couple of dozen species, one of which a lichenicolous fungus.
Thread: Image
Plus Verrucaria polysticta on the footstone. 10/24 are members of the Verrucariaceae. C. dichroa described as new in 2006. V. obfuscans added to British list in 2015. Image
Three lichens, all common on the headstone, none of which would have been named correctly (or at all) twenty years ago. Caloplaca dichroa and Verrucaria ochrostoma on left side. But what about the ashy grey expanse on the right? Image
Read 15 tweets
Jan 31
We tend to record Diploscistes muscorum when parasitic on Cladonia (as here, from dorsetnature.co.uk/pages-lichen/l…) and D. scruposus when growing directly on rock. There are supposed to be microscopic differences but my observations seem difficult to resolve with the literature.
Thread: Image
Today I came across a colony growing on moss, no Cladonia in sight, on a gravestone. The number of spores per ascus fits muscorum while the septation of the spores fits scruposus! This not the first time I have noticed this problem. Image
The asci are consistently 4-spored which is supposed to be a D. muscorum trait. ImageImage
Read 5 tweets

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