Bulletin of the British Museum (Natural History)

130 BRIAN JOHN COPPINS
predominantly lignicolous species with small, black apothecia, but all such species (except M.
misella as discussed above) appear very different when examined microscopically.
Habitat and distribution: M. denigrata is commonly found on the lignum of fallen trunks and
old stumps of broad-leaved and coniferous trees, especially in rather open situations at the edges
of woodlands, woodland glades, and hedgerows, etc. The communities in which it occurs are
difficult to define, but to give some indication the following list of associated species has been
made from collections from fallen decorticate trunks of Pinus in the native pine-woods of
Scotland: Buellia griseovirens, Cladonia coniocraea, C. macilenta, Hypogymnia physodes,
Lecanora expallens, L. symmicta agg., Lecidea aeruginosa, L. icmalea, Micarea peliocarpa,
Mycoblastus sterilis, Parmelia saxatilis, Platismatia glauca, Pseudevernia furfuracea, Xylographa
abietina, and X. vitiligo.
M. denigrata is a very successful primary coloniser of untreated timber-work. It also occurs on
the same substrate whose preservative has lost its effectiveness, or whose painted surface has
flaked off. On such substrata M. denigrata has been found in a wide range of situations, e.g.
gates, fence posts and rails, garden furniture, picnic tables and seats, window frames of
greenhouses, wooden roof tiles (shingles), telegraph poles, and the woodwork of old carts and
farm machinery. When on such worked wood it often forms almost pure stands, and is often
present as a form with few apothecia but numerous pycnidia containing mesoconidia; the
conidia often extruding as white blobs easily visible to the unaided eye or through a x 10 lens.
Lichens associated with M. denigrata on worked wood in the British Isles include Buellia
punctata, Cyphelium inquinans, Hypogymnia physodes, H. tubulosa, Lecanora conizaeoides, L.
Map 7 Micarea denigrata # 1950 onwards O Before 1950