Lichen Hunting Part 1

Having become interested in lichens when we did our Welsh Winter Walking course at Plas-y-Brenin a couple of years ago I have recently started to learn more about them. To such an extent that recently I purchased some proper identification guides:

• Guide to Common Churchyard lichens, a Field Study guide by Frank Dobson
• Lichens, An Illustrated Guide to British and Irish Species, also by Frank Dobson

The two could not be more dissimilar. The first is a fold out laminated guide with lots of pictures. The second is a 500 page key driven guide.

With these two guides to hand I wanted to get to grips with using both of them, so this morning, a beautiful bright autumnal morning, I headed up the hill to St Andrew’s churchyard in old Headington, to see what I could see. This post is a summary of the notes that I made this morning.

Location

St Andrew’s church is located in old Headington, to the north east of Oxford. The gravestones studied are in the North East corner of the churchyard, grid ref SP 5448 0764. Bing Map.

Since it was a Sunday morning, and there was a service going on in the church I decided to focus my attention on a grave in the far North East corner of graveyard, away from the main entrance.

Early Lessons Learnt

I was expecting this to be a real learning experience, and to take away some tips for future lichen hunts. The first lessons came almost as soon as I had arrived at the first gravestone.

1. Next time make sure that I bring the correct lens for the camera. I had planned to use my macro lens to take some close up shots but was stuck with the 28-80mm zoom because I didn’t look closely when I picked up the camera.
2. Next time take some tape or blu tack that will enable me to secure a ruler to the vertical face of a gravestone to show dimensions of the specimens,

 

Specimen 1

The first lichen I examined was on a West facing side of a grave. It was roughly circular with a total diameter of about 28mm. It had an orange / yellow outer ring with a pale inner ring and an orange center. The outer ring was about 3-7mm wide and the inner orange center had a  diameter of about 11mm.

Looking at the FSC guide the photos suggest that this might be Caloplaca flavescens:

• It is yellow / orange
• The thallus has a lobed margin. I had to examine the specimen using my x40 hand lens to confirm this
• It is growing on a basic substrate. The grave looks like it is made from some form of limestone

The guide describes that the fruits looks like jam tarts with black discs (lecanorine apothecia). However, I could not see any fruiting bodies.

Looking at Dobson’s book seemed to confirm that it is a Caloplaca but initially I did not know if it was C. saxicola or C. flavescens. After reading the descriptions I am pretty certain it was C. flavescens.

Specimen 2

The second sample I examined was visible as large grey patches, with the one I was primarily interested in being about 9cm across.

Examination using the x40 lens showed that the thallus was mainly grey with raised white areas and black spots, looking like they were sunken into the surface.

Looking at the FSC guide initial identification was not obvious. It might have been Aspicilia calcorea, although the specimen did not have the fractured surface of A. calcarea. It might have been Caloplaca teicholyta, but then I saw the image for Verrucaria baldensis and that looked much more likely.

It was white / cream / grey. It was crusty. It was on a basic substrate. The black fruits were pot or volcano like.

Looking at Dobson p460 / 461 it looks like it was V. baldensis, although it might have been V. calciseda.

A puzzle

While looking for a third specimen to identify I saw this.

The light coloured specimen to the top and left I identified as V. baldensis. So what is the darker grey specimen to the bottom, with almost no black pits. And what is the grey specimen on the right hand side with lots more black pits?

The boundary between each grey area shows some pink colouring and in some places there seem to be small mounds of material (10.2 – 10.8cm at the bottom of this image).

The black specimen at the bottom of the image above may be Verrucaria nigrescens. The three different grey areas may be due to different V. spp. Perhaps V. pinguicula.

Specimen 3

For the final specimen I moved to another grave, that of John Musgrove who died in 1855 and his wife, who died in 1864. So the grave is probably around 149 years old.

The lichen was green, powdery and cracked. It lifted easily from the stone.

The FSC guide shows an image of Caloplaca citrina and this identification is supported by Dobson, as far as I can tell.