Crusty Lichen

10.30 a.m.: At first sight this crustose lichen looks like nothing more than a pale stain on the sandstone block at the edge of the raised bed behind the pond. I’m using crayons this morning and the nearest match that I can get is mineral green, applied very lightly with a dash of other colours added. Using watercolours I would have got nearer to the grey in my photograph.

The black oval sporangia* are about a millimetre across.

A neighbouring colony of the same lichen is more densely peppered with sporangia and they appear to me to have a slight brownish cast, like coffee grounds.

I find the details easier to take in on my macro photographs than in real life but peering closely I notice a springtail wandering by. The springtail is a hexapod and it is no longer classified as an insect.

When I don’t have time to get out to anywhere wilder these mossy chunks of sandstone give me a macro landscape to explore.

It would be worth carrying out a BioBlitz focussed on these rocks and making an effort to identify the lichens and mosses and the invertebrates sheltering in the crevices.

I struggle to identify most lichens but at least it is easy to classify their various forms into powdery, crusty, slightly leafy and leafy. In the north and west of the British Isles in cleaner air and in a more humid climate, you could also add shrubby and bushy lichens.

The crustose lichens that I’m most familiar with are species of the genus Lecanora but I wonder if this could be an Enterographa or Opegrapha?

* I’ve used the word sporangia for the reproductive bodies on the lichen but there are two forms of reproduction in lichens:

• the release of ascii which are sac-like cells containing spores, so in this case the ascocarp, also known as the apothecium, is the fruit-bearing structure. In species of Lecanora these look like jam tarts.
• there’s also a form of vegetative reproduction in which powdery granules break off the lichen. These are called soredia.