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Mark Powell

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.

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.

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.

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Mark Powell

@obfuscans3

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.
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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.

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?

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Mark Powell

@obfuscans3

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.
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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.

The asci are consistently 4-spored which is supposed to be a D. muscorum trait.

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Mark Powell

@obfuscans3

Jan 31

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.

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Mark Powell

@obfuscans3

Jan 31

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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https://twitter.com/obfuscans3/status/1487904835877883906

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.

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Mark Powell

@obfuscans3

Jan 30

West and East facing sides of the limestone gravestone to Mercy Ann Smith, died 1911. The latest stone to be scrutinised in detail. 24 lichen spp. present, over a third of which would have been unrecognised or likely misinterpreted at the start of this century.
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7/24 are members of the Verrucariaceae, a generally poorly understood and misinterpreted family. Caloplaca dichroa was described as new to science in 2006. V. elaeina and V. ochrostoma were lost to the consciousness of most lichenologists until into the present century.

First for a couple of well known and uncontroversial lichens, both Caloplaca (despite appearances). C. flavescens and C. teicholyta.

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