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GALLERY - at bottom of this page They are everywhere to be seen, but so often overlooked or dismissed as ‘part of the background’ but hardly “interesting”. Society members were treated to an education on just how much we have been missing. Keith Palmer, our guest speaker and guide, explained that lichen are actually two plants - a fungus joined together with an alga (“mutualism” - a form of symbiosis in which both parts benefit). If you look very carefully at a cross-section, we learned that you can often see layers of fungus and alga. Lichens (pronounced with a hard “k” by those in the know!) can be found where ever they can gain a purchase - on trees, fences, weathered rocks and gravestones, even rusting metal and plastic bin lids! Harmless - the weathering happened first, so don’t make the mistake of thinking that lichens cause deterioration in the gravestones. Nutrients are delivered by being dissolved in rain, and bird droppings together with photosynthesis. If you feel you must clean a tombstone to read an inscription, do so sparingly. Leave some lichen so it can continue to grow. Breath deeply - Lichens are important because they tell you something about the quality of the air around us - in highly polluted towns (and in Victorian times when coal fired everything), lichens die. The rarest lichens need the kind of pure air you find in such places as Scotland or the Pacific seaboard of Canada! Lynsted was last surveyed in 1989 by Keith Palmer, when he found 25 varieties. Although he believes that a more detailed survey could uncover many more than this. Keith’s talk was supported by a range of slides to help us understand the different types of lichen:
Reproduction - Keith explained that lichen reproduction can be fairly random. Sometimes relying on spores being dislodged as soredia (powdery dust) by rain, slugs, or snails, from fruiting bodies - such as happens with Caloplaca flavescens (orange/golden, radiating lobes, fruiting bodies showing as dots to the naked eye). These fruiting bodies are often deeper in colour than the edge of the lichen, because the lighter edge is where the younger lichen growth is, which is not ready to fruit. Typically, a lichen grows around 1 milimeter per year (although the foliose ones can grow by up to 1 centimetre and year). Identification - Keith told us that some can be identified by taste (bitter - not to be recommended except for identification purposes!). For the most part you have to get down and personal with a magnifying glass and particular chemicals to help identification. Although the Cyphelium has black spots that leave black dust on your fingertips if you touch them. The Graphis scripta has a very distinctive “squiggly” lichen (a bit like handwriting) that forms on trees. Finally, Keith pointed to an Eagles Claw lichen - no prizes for guessing what shape the edges were of this lichen. If you want a good field guide to help with the more than one-hundred lichens on offer, Keith recommended a prolific specialist writer - Frank S. Dobson - “An Illustrated Guide to the British and Irish Species” (published by The Richmond Publishing Company); or the out of print Observer Book of Lichens. Better still, attend a course through the Field Studies Council. So, what did we find in a short guided tour of a few tombstones in Lynsted churchyard? We have produced a Gallery of Images here of the examples we found. |
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