Wednesday, 17 December 2014

On an old church wall

There are close on 1900 lichen species known from the UK. Most people are aware that a lichen is formed by a union of a fungus and an alga; the scientific name of a lichen is actually that of the fungal element. Let me emphasise that I am not a lichenologist - nor will I ever develop much expertise in this field. Nevertheless, when I see a tree trunk or stone surface encrusted with these extraordinary organisms I cannot resist having a closer look. 

Such was the situation when I strolled through the churchyard of Byfield's Holy Cross Church recently.

Verrucaria virescens (probably) on the church wall.
Byfield, Northants. 17 December, 2014

Who among us has not been stopped in our tracks by, for example, the tar-like patches of Black Pit Lichen, Verrucaria nigrescens, on a stone surface? Well, ok, I won't pursue that point. But to look at these organisms, clinging to a rock, it almost beggars belief that these are living creatures.

Cladonia chlorophaea on the church wall at
Byfield, Northants. 17  December, 2014

Quite different is the Mealy Pixie-cup Lichen, Cladonia chlorophaea. It doesn't occur on bare stone but grows where a layer of humus has developed. In reality this 'species' is an aggregate of very similar species - certainly not separable by the likes of me.

Acutely aware of my status as a tyro in the world of lichenology I moved on to look at the mosses and liverworts. But sadly my knowledge of these organisms, collectively known as bryophytes, is equally limited. But now and again I like to have a bash at identifying them.

Porella platyphylla on the churchyard wall, Byfield,
Northants.  17 December, 2014

Liverworts are widespread in Britain but I rarely notice them. However, I could scarcely fail to see the glistening curtain of Wall Scalewort, Porella platyphylla, as it clung to the churchyard wall. It requires a shady spot and if it is damp, so much the better - and these are the conditions in which I found it flourishing.

Orthotrichum anomalum clings to the churchyard wall
in Byfield, Northants. 17 December, 2014

Neat cushions of Anomalous Bristle-moss, Orthotrichum anomalum, clung to a drier part of the wall. Very widespread it is unusual among our Orthotrichum species; they are generally found on trees but this species much prefers stonework.

During these winter months one tends to pay more attention to mosses, liverworts and lichens. When I do so I never fail to be fascinated by their habitat requirements, their form and, yes, their beauty. If only there were about forty hours to each day, I might begin to give them the attention they deserve.

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