ABC Wednesday - X

X is for Xanthoria

A few weeks ago I was asked, if I knew what the red/orange covering was that had taken over one of the old wild plums, that live between the hedge and the vegetable patch. "Super colour" I said
moving closer. "Not a clue".

Interest peaked I turned to the old www and trawled tree problems, no luck. Then running out of options I came, can't remember how, to lichens. More trawling until I came to one that looked the right colour, lived in a maritime environment (tick) and on trees (tick). I then looked at the name Xanthoria Pareintina. I then went zip-a-dee-do-da and did a little mental jig. One of those difficult letters of the alphabet had just fallen like a ripe plum into my hand.
Lichen are fascinating things. They are not one organism but at least two consisting of a fungi and algae combined. Simon Schwendener was the first to discover the dual nature in 1869. This was a revolutionary idea that was not believed by a lot of scientists at the time.

Is it symbiosis or parasitism? The algae can produce food from sunlight, fungi provide protection and absorb nutrients from the surface. I needed to know more. One of the websites mentioned a book by William Purvis as a good starting point so I headed for Abebooks
and now I own a copy. Lovely pictures and an written in an accessible style. He favours the symbiosis theory as together they can colonise habitats that would be impossible as single entities. Certainly the more attractive option.

(Put me in mind of the Star Trek Deep Space Nine Dax/Trill symbiosis, which made you wonder if you would have one of those trill slimy things latched onto your spine, although you did get to be very clever and have memories of past hosts. OK I'll go with that. What do you mean it isn't real).

The older the woodland the more lichen there are. Colour is the main way to identify lichen and Xantharia contains an orange pigment, parietin, and is yellow/orange. Chemical tests are used to identify and classify. Apparently a drop of caustic potash on Xanthoria changes it to a deep purple red, Here is the adjoining plum tree which also has the grey Physcia lichen
Lichen are all around us and all over the world in every environment, on every type of surface, each a fascinating miniature ecosystem. I'm off to learn more, because as Alexander Pope wrote

A little learning is a dangerous thing,
Drink deep, or taste not the Pierian spring,
These shallow draughts intoxicate the brain
And drinking largely sobers us again

X marks the spot of ABC Wednesday, go there and you will find treasure.