This article was first published in the Newsletter of the London Natural History Society, No. 240 February 2016
An enthusiastic group of 10 convened at the High Beach visitor centre in Epping Forest for a lichen meeting led by John Skinner, the LNHS Lichen recorder and leader of the day’s meeting, who told us a little about the long history of lichen recording at this site. Records for this area stretch back to at least the 19th century, and, following an apparent dip in lichen diversity in the 1970s, Peter James and Linda Davies recorded 41 species in the High Beach area in 2003. One of the day’s aims was to add to this list of observed lichen species.
After the short drive down to Fairmead Bottom, we suited and booted up and set off in the autumn sunshine, striding confidently away from the car park. In true Lichenology fashion, several paces later we stopped to inspect a Blackthorn next to the main path, swathed in lichen. Its branches yielded many species and provided an excellent ‘get-your-eye-in’ exercise. Dull brown lobes of the foliose lichen Melanelixia subaurifera shared branches with the grey Parmelia sulcata, characterised by its white network of vein-like pseudocyphellae, as well as the common yellow Xanthoria parietina, whose success is attributable in no small part to its high tolerance for nitrogen pollution. Also on the Blackthorn were two Physcia species: P. adscendens and P. tenella, with their characteristic eyelash-like marginal cilia; Evernia prunastri, which appears to be fruticose, but as the algal layer is only present in the upper cortex is anatomically foliose (used in the past as a fixative for perfume, a flavouring for bread and wadding for shotguns); and, the Punctelia species P. subrudecta and P. jeckeri, distinguished from each other by the positioning of the soredia (the powdery propagules which contain algal cells and fungal hyphae), which follow the edges of the lobes in P. jeckeri.
A big, imposing oak was our next subject, home to Arthonia radiata, whose irregular black apothecia are fancifully suggested to resemble stylised stars. In my opinion, they look somewhat more like the spots on a giraffe! An interesting specimen of the widespread lichen Lecanora chlarotera displayed what seemed to be apothecia (fruiting bodies that look like little jam tarts) within apothecia (see photo), perhaps a result of mollusc grazing, a hypothesis which sparked admiration for the plucky snails that made the long journey along the branch for a meal. On the way to our own lunch stop, we recorded the bright yellow Caloplaca flavocitrina on an Elder stump, along with the ‘hidden writing’ that gives the genus name Opegrapha, named for the long, lirellate fruiting bodies that resemble careless doodles against the pale thalli of O. ochrocheila and O. viridipruinosa. Just before lunch, John spotted a single thallus of Ramalina fastigiata on a Hawthorn, its apical apothecia reminiscent of a Dr Suess illustration.
After lunch, we resolved to walk more than the few hundred yards we already had to sample more of the bountiful lichen flora of the area. In among a shaded, damp grove of elders by a pond, we found abundant thalli of Hypotrachyna revoluta and H. afrorevoluta coating the branches, even outcompeting the co-occuring moss species. One particular non-lichen treasure we found here was a cluster of sporangia belonging to an unidentified species of the ever enigmatic myxomycetes, or slime moulds. Hundreds of miniscule, grainy, lilac-coloured egg-like structures provided a shock of colour to the shady habitat and reminded us all once again of the electric excitement of an unexpected discovery.
After the longest uninterrupted walk of the meeting (almost the length of a football pitch), John dropped to the ground at an old stone bridge, announcing the find of the black, gelatinous lichen Collema crispum, notable for its photobiont, which is not an alga, like the rest of the lichens we recorded, but a cyanobacterium of the genus Nostoc, whose independent colonies have been known as star jelly (for the belief that they fell from the heavens) and witches’ butter (not to be confused with the fungus Tremella mesenterica, of which more later). One interesting theory about the etymology of the name Nostoc suggests that the 15th century scientist Paracelsus created a portmanteau word from the Old English word ‘Nosthryl’ and the German word ‘Nasenloch’, both of which mean ‘nostril’. Thus, Nostoc was coined, presumably as a reference to the gelatinous green colonies’ resemblance to certain ‘Nosthryl secretions’.
Optimistically searching for fruticose Usnea species in a clearing dotted with oaks, we found instead the bright orange-yellow parasitic fungus Tremella mesenterica, alongside its fungal host, Peniophora quercina; a neat display of the many trophic levels present within a single dead branch. Nearby was a single thallus of Xanthoria polycarpa, a species related to the more common X. parietina and X. elegans, which, remarkably, survived a fortnight in space in a European Space Agency experiment.
A sweet, cidery smell was a portent of the sea of crab apples through which we had to wade to reach a clearing in which John had found a putative Lepraria lobificans, the lack of certainty displaying the difficulty in differentiating this leprose lichen with the related species, L. incana, especially when they do not occur together. Here, we also inspected the inconspicuous foliicolous lichen, Phylloblastia inexpectata, growing on Holly leaves, eventually resulting in the exasperated exclamation from one of our number “It looks like dirt!”
One final trudge through the wood culminated in the discovery of a clearing carpeted in Hornbeam seedlings, amongst which nestled a jewel: the beautiful vivid purple of Laccaria amethystina, the Amethyst Deceiver. Satisfied with a walk that evidently only scratched the surface of this rich site, we headed back to the car park, only to add two more to our list: the minute chocolate granules of Placynthiella icmalea and the pointed green podetia of Cladonia coniocraea. Thanks go to John for leading the meeting and to everyone who attended for a most enjoyable day.
Other lichens seen: