14
The Essex Naturalist
Britain and Scandinavia, a marked decline in the luxuriance of the lichen flora,
possibly caused by a general increase in acidity of the rainfall.
Two other Parmelia species are worthy of mention. In May 1994, Peter
Earland-Bennett showed me a moribund ash tree beside the Bl057 north-east of
Lindsell (TL652275), with abundant P. acetabulum, a rare and showy species
which is bright green when wet and has an eastern distribution. Prior to this, I
was only aware of four Essex records of this lichen, all dating from the 1960s and
only one with detailed locality data. In July of the same year, Peter found
another specimen of this species at Clacton (TM193174), on a detached elder
branch. This is encouraging as the lichen must have colonised the branch only a
few years previously, unlike the relict population at Lindsell which is probably
lost by now.
The other noteworthy Parmelia was also found by Peter Earland-Bennett; this
is P. conspersa, a bright yellow-green species characteristic of exposed siliceous
rocks. He found a large and healthy population on an east-facing slate roof at
Wakes Colne (TL881289) in 1995. The only other Essex record is a 10km
square record for TL81 made by Francis Rose in 1973. At Wakes Colne, it was
growing with the inconspicuous crustose species Polysporina simplex, which is
probably not uncommon on slate roofs in the county.
Returning to pollution-sensitive species, an extraordinary recent find has
been Candelaria concolor, a delicate yellow foliose species which I found on ash
in a small wood, Shales More, at Stapleford Tawney (TQ499986), during a
survey in March 1995. C. concolor has not been recorded in Essex since the
1780s when it was collected in Walthamstow. In the same wood I found
Parmelia caperata, P. perlata and P. revoluta as well as 30 other lichens. What
makes these finds interesting is that the southern end of the wood abuts directly
onto the M25 motorway, evidence that traffic fumes do not have an adverse
effect on the lichens which we normally think of as pollution-sensitive.
A very rare crustose lichen with a strongly pronounced eastern distribution in
Britain has been found around Southend. Cyphelium notarisii, recognisable by its
bright green colour, was found in the late 1980s on park benches made from a
tropical hardwood, in the centre of Southend. Over the last five years, it has
been found on a number of similar benches around the town and on the decking
(also made from tropical hardwood) of the pier. A fuller account of this
interesting find is being prepared, hopefully for the British Lichen Society
Bulletin. The same species was found in 1995 at Colne Point, on a huge old elm
log on the upper beach (TM107123), an excellent lichen substratum with 20
species growing on it.
Terricolous lichens, those that grow on the ground, are not doing so well in
the county, for a number of reasons. Good natural sites, such as St Osyth beach
and Shoeburyness, suffer from increasing trampling, while old sand and gravel
pits, which can be superb sites tor Cladonia species, are either being filled in and