A Yellow Lichen

Dry stone walls are a great place to look for lichens.  Usually, I pick one that is on the moor but whilst waiting in Kingussie, I looked at the one by the Duke of Gordon Hotel.

One of the capstones stood out from the rest, as it was the only one with patches of yellow.

The different stone                                  With a ruler marked in cm             Lichen at the top, moss underneath

Looking more closely, there are round orange fruiting bodies (apothecia) which is where the lichen produces spores. I collected one by chipping it off and folding it into a post-it note so I didn't lose it.

A tiny apothecium - about 0.5mm

I also added some  small drops of chemicals. Bleach did not change colour but potassium hydroxide gave an immediate purple colour. When I got home, I sliced that tiny orange apothecium, trying to get a thin slice so the light of my microscope would shine through it.

Here is the slice, and the tiny circles are the spores which are clustered in sacs called asci.  To see the shapes better, you add a few more chemicals  - in this case some fountain pen ink!

Here is a picture of one of the spores showing its odd structure.

A lichen spore - about 12 thousandths of a millimetre long

It is like a dumbbell and that helped with the identification as different lichens have different looking spores.  I think the lichen is called Caloplaca flavovirescens (no common name, I'm afraid).  It is not common round here as it likes a basic (alkaline) rock and most of our rocks are acid.  But that one capstone must be different.