and stumps of trees killed by Dutch Elm Disease, with only a few records from bark.
A lichen that was undoubtedly fairly common on elm bark in Essex is the white-lobed
Diploicia canescens, now found most ofen on limestone walls and gravestones in churchyards.
It is still sometimes seen on what remains of our elm bark, especially in exposed places.
Interestingly, it is on a sample of bark from an old elm felled in Priory Park, Southend-on-Sea
in the 1960s. More common but less conspicuous lichens on elm bark are the dull grey
dark-fruited Buellia punctata, the white crust of Cliostomum griffithii dotted with black pycnidia
and the pale yellow-green powdery sorediate crust of Lecanora expallens. These last three often
grow on decorticate standing trees.
Once the bark has fallen off the exposed wood forms a good lichen substratum. Some logs
become rock hard, covered in a mosaic of crustose lichens. In wayside situations the lichen
flora can resemble that found on concrete with yellow species Caloplaca citrina, Candelariella
aurella and Xanthoria parietina, grey foliose Physcia species and the whitish fruits of Lecanora
dispersa. Another common lichen on hard elm logs is the small-fruited Lecanora saligna which
can cover large areas.
Of the handful of lichen species which are almost restricted to elms in Britain, only two have
been found on elms in Essex in recent years, both by Francis Rose. He found Bacidia incompta
at Danbury in 1973 and the striking orange-fruited Caloplaca luteoalba at Debden Park. The
former has been found recently at Hatfield Forest on Field Maples but the latter has not,
unfortunately, been seen in the last 17 years in Essex, although it is in Suffolk. Other lichens
of interest seen in the county recently on elm include: Bacidia arnoldiana, Caloplaca ulcerosa,
C. virescens, Physconia enteroxantha, Ramalina farinacea, R. fastigiata (not since 1973) and
Rinodina exigua.
Reference
Watson. M. F., Hawksworth, D. L. and Rose, F. (1988) 'Lichens on Elms in the British Isles and the effect
of Dutch Elm Disease on their Status'. Lichenologist 20. (4). 327-352
Fungi
The large number of trees killed by Dutch Elm Disease has given a boost to those fungi that live
on dead elm. This note can unfortunately only be a brief introduction to some of those species,
all of which will presumably become much rarer as the supply of elm wood decreases.
One of the most impressive fungi on elm is Pleurotus cornucopiae, a large, pale, creamy-
brown, funnel-shaped fungus with the gills running right down the stem, almost to the base. It
is an agaric (i.e. of typical 'mushroom' structure, with gills bearing spores) usually growing in
branched masses. Despite being fairly common, illustrations of P. cornucopiae are rather few
and far between, although it is now well shown in Phillips (1981).
Another spectacular sight on elm is Winter Fungus, Flammulina velutipes, an agaric with a
golden-yellow to tan coloured slimy cap and a tough stem which is blackish and velvety at its
base. Unlike most other agarics, it can survive freezing and is a common sight in winter.
A common fungus on elm logs is Auricularia mesenterica, sometimes called Tripe Fungus
from its appearance. It forms tiers of brackets, each bracket being pale and hairy on the upper
surface and purple coloured and rubbery underneath. The closely related and well known Jew's
Ear, A. auricula-judae, known more as a fungus of elder, also grows occasionally on elm.
At the very base of rotting elm stumps and inside hollow elms a massive bracket fungus,
Rigidoporus ulmarius, may sometimes be found. It is a creamy white colour, often discoloured
from being near ground level and from algae growing on its surface. The more common Dryad's
Saddle, Polyporus squamosus, is often seen on elm stumps, another polypore, sometimes
growing to enormous size. The upper surface is a pale golden yellow, flecked with dark brown
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