Local Histon Lichens

A closer look at the trees and branches, live and otherwise, in my local meadow which I posted about recently, revealed large quantities of lichen. I’d seen it there before but never really paid it sufficient attention so a couple of weekends ago I decided to rectify this shabby state of affairs.

To my highly untrained eye there didn’t seem to be more than 4-5 species but the ones that were there were present in abundance. There are four basic  morphologies of lichens: they are crustose – the flat ones which form very thin layers, foliose – form leaf like structures but where the leaves lie flat and don’t protrude far from the surface of the substrate, fruticose – have longer branched structures and can look like small shrubs and lastly squamulose –  have horizontal, scaly, overlapping lobes and look rather like some fungi I’ve seen growing on dead wood.

A grey/green crustose species and a fruticose species, the yellow one.

Lichens can be extremely sensitive to pollutants, and as a rule of thumb the foliose species are generally more sensitive and are only found in places where the environment is clean and free of fumes and other chemical pollutants. Consequently the species I find in my local patch, being close to a big town, are of the crustose and fruticose varieties. Sensitivity to pollutants can cut both ways though, those susceptible to acid pollution will obviously suffer in a low pH environment, but others which have a high demand for nitrogen can really benefit from pollution by agricultural fertilisers.

The ones I found were all growing on the surface of live deciduous trees and dead branches and the trees in the meadow are predominantly ash and oak. I’m not going to try to identify the different species here because I don’t have the requisite expert knowledge to unambiguously name lichens, but I plan to do some reading and observing and I’ll post again if I find out what they are. Even though I don’t know the species I think their colours and structures render them particularly photogenic.

The ‘thallus‘ (main body) of the yellow lichen above has the leafy structures of a fruticose species surrounding round saucer shaped structures which are called ‘apothecia‘ and are the reproductive machinery of this lichen. Within the apothecia are tiny structures called ‘paraphyses‘ and these surround the ‘asci‘ from which the fungal spores are generated. Masses of this yellow species covered many trees and fallen branches in the meadow.

Another fruticose lichen which has the leafy structures but no reproductive apothecia – I’m assuming it’s another species and not a different stage in the life cycle of the yellow one

The grey/green species here is definitely a different one. It has some erect leafy and spiky parts and it appears to have apothecia which are more cup shaped

The fungal spores produced from the asci are microspcopic and dispersed on the wind and it is a matter of conjecture how they manage to settle on the requisite species of alga to form a new lichen.

Some species can reproduce both the fungal and the algal part simultaneously by growing structures called ‘lobules‘ or ‘isidia‘ which basically consist of outgrowths of the thallus of crustose or foliose lichens which break off and are dispersed by wind and water. Or there are structures calles ‘soredia‘ which are algal cells enmeshed in a bundle of fungal ‘hyphae‘ (threadlike structures of fungal cells) which are similar to the middle part of the body, the ‘medulla‘.

If anyone out there knows the names of these lichens or has any other snippets of lichen related information please leave a comment as I’d be very interested to hear them.

23 responses to “Local Histon Lichens

  1. Nice lichen explanation 🙂
    I believe the spiky one is Physcia adscendens.
    “often in company with P. tenella and Xanthoria species as indicators of nitrogen enrichment.”, so it fits perfectly to your picture.

    • Hello Sophie, thanks for the help with lichen identification. I find them like fungi in that I can make a tentative id but can rarely be entirely certain. It’s good to get some more expert assistance! I’m glad you like the explanation 🙂

  2. Lovely post, fellow lichenophile. I’m now following your post, too (I thought I was already)!

  3. Your photos are lovely, lichens and fungi are favorite of mine, though I know very little about them 🙂

  4. Sorry, I thought I’d forgotten to press ‘post comment’ and did it twice!

  5. Dear Finn, I’ve just awarded you the Very Inspiring Blogger Award:
    I’ve broken the rules a bit but if you would like to accept it and pass it on to other bloggers please see here: http://cauldronsandcupcakes.com/2012/03/13/my-second-blogging-gong-the-very-inspiring-blogger-award/

  6. Dear Finn, I’ve just awarded you the Very Inspiring Blog Award: http://lornastearoomdelights.wordpress.com/2012/03/15/awards-galore/
    I’ve broken the rules a bit but if you would like to accept this and pass it on to other bloggers, please see here: http://cauldronsandcupcakes.com/2012/03/13/my-second-blogging-gong-the-very-inspiring-blogger-award/

    • Hello Lorna,

      Thankyou very much indeed! I will be extremely happy to accept the award from such an esteemed blogger as your good self. I’ll post the requisite acceptance very soon.


  7. What a challenge! Still, I like a challenge. I accept your gauntlet, sir.

  8. Lichen is such a wonderfully complex and fascinating organism isn’t it Finn?! I’ve had many difficulties identifying the ones I’ve photographed but the bottom-most image might be ‘Xanthoria polycarpa’: http://www.britishlichens.co.uk/species/Xanthoria%20polycarpa%202%20small.jpg. The website: http://www.britishlichens.co.uk where I found the image is quite useful.

    • Hello Meanderer, it is amazing stuff. Thankyou for the link, I think you must be right about the Xanthoria, the picture from the BLS looks like the same the species I found.

  9. Beautiful photos…and a nice science lesson, too! Thank you, Finn. 🙂

  10. They’re very beautiful, it’s a little miniature world. ‘Squamulose’ is a marvellous word.

    • It is indeed a world that is ubiquitous and simultaneously much overlooked, and spectacular when you peer closely.

      Squamulose, crustose, fruticose. Splendid words all and sound as thought they could equally well apply to a piece of moist sponge cake!

      • Ooh, I would love to invent three new cakes to fit those names. It would seem obvious to make the fruitcose cake a fruity one, perhaps with strawberries and/or raspberries in it.The crustose could have a sugary crustiness to it and squamulose sounds to me as if it needs to be something really extra special, I’ll need to cogitate upon it…

      • A little cogitation does indeed seem the best approach in such circumstances. I’m looking forward to seeing the resultant recipes published on ‘tearoomdelights‘.

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