Just some of the beautiful autumn leaves that are lying on the grass right now.
These remarkable patterns on leaves of the Horse Chestnut tree (Aesculus hippocastanum) result from a combination of the natural changing of the leaf colour in autumn and the effects of infestation by tiny caterpillars of the Horse Chestnut Leaf Miner moth (Cameraria ohridella). This Spanish species has invaded Britain in recent years and is having a very noticeable impact on the appearance of this one type of tree but it does not seem to have an effect on the wood of the tree. I have noticed a decline in the numbers of conkers this year, which might have had something to do with the loss of photosynthetic capability in trees that have been bady affected, but could be attributed to a number of other causes as well.
The tiny caterpillars live in the shallow space between the upper and lower layers of the leaf, and eat away systematically between parallel veins, killing that area of the leaf and leaving narrow bands of dead tissue that cover the leaf in irregular stripes. These can be seen increasingly throughout the summer in infected leaves but in autumn, as the leaves change colour and naturally die back for the winter, the damage caused by the caterpillars becomes more pronounced. It looks almost as if some artist has been having fun decorating the foliage to celebrate Halloween.
When you go out “trick or treating” this Halloween, not everything that glows in the dark will be a spectre, phantom, or ghost – or someone pretending to be one. By an incredible quirk of nature, one of the commonest of British fungi creates natural luminescence (Ramsbottom 1953). The Honey Tuft Fungus (Armillaria mellea) which grows on both living and decaying wood, has a vast hidden network of black fibres called hyphae that somehow or other make the wood glow in the dark.
This common fungus tends to grow most frequently on or near stumps of trees, with clusters of the fruiting bodies that can reach a metre across. The exact form that the Honey Tuft Fungus assumes can be extremely variable. It is the hidden parts of this fungus, the rhizomorph and mycelium, that are responsible for most of the luminous wood in Britain.
Luminous wood has been recognised since the time of Aristotle and Plato; and it may account for such phenomena as the burning bush that was not consumed by fire as seen by Moses in the Bible. Walter Raleigh in Elizabethan times is quoted as saying “Say to the Court it glowes and shines like rotten wood”. In 1667 Robert Boyle studied the luminescence of rotten wood – and that of decaying fish! However, the discovery of the fact that it was actually the infecting fungus in the rotten wood that was causing the luminescence was not established until the late 18th and early 19th centuries by people like Sowerby (1797), B. von Dershau (1822) and J F Heller (1843).
The fungus is known to widely infect wooden support structures in mines, and has been noted creeping across the floors of damp wine cellars. In the First World War soldiers placed small bits of luminous rotten wood on their gun sights and helmets to avoid collisions in the dark. In the Second World War the wood in a London timber yard is recorded as glowing so brightly on moonless nights that men on fire watch covered it with a tarpaulin in case it attracted enemy aircraft.
It makes me wonder whether many ghostly apparitions both indoors and out might be attributable to the hidden fibrous support networks of this common British fungus.
Ramsbottom, J 1953 Mushrooms and Toadstools, New Naturalist Series, Collins, London. Chapter 14 pp 154 -164, Sixth Impression 1972.
This is the second in a series of posts about coral fossils in Carboniferous Limestone at Broughton Bay on the Gower Peninsula. See the earlier post Fossil Coral at Broughton Bay for more details.
These fossils belong to a group of colonial corals of the lithostrotionid type, probably Lithostrotion junceum.
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