Scribblings on an aspen twig
On 29th May (2015) Don O’Driscoll and Romany Garnett were carrying out, for the John Muir Trust, a bird survey on the north-eastern slopes of Quinag. On a crag not far from Cnoc Airigh na Beinne (NC2230) they came across a solitary aspen. Dead twigs on this tree were covered with what appeared to be black scribblings and Romany brought me a small sample, which David Haines has photographed.
These black markings are the tiny, crowded, linear fruiting bodies or lirellae of a lichen called Opegrapha atra. They belong to a distinctive group of lichens sometimes referred to as ‘Chinese writing’, which are usually found on trees, but also on rock. Seen through a x10 lens, the lirellae appear carbonaceous, with a central slit or furrow (lira is Latin for a furrow), and the scientific name of this species translates as ‘black hidden writing’, from their small size (up to 2 x 0.3 mm). O. atra is the commonest member of the genus, found mainly in coastal parts of the British Isles, usually on the smooth bark of well-lit trees, but occasionally on their twigs, as in this case.