Bulletin of the British Museum (Natural History)

LICHEN GENUS MICAREA IN EUROPE 145
Map 9 Micarea lignaria var. lignaria # 1950 onwards O Before 1950
plant debris, loose stones, pieces of timber and sack-cloth. Mr V. Giavarini has recently found it
in Dorset, growing on waste heaps of slag clay, in the company of M. leprosula, Baeomyces
roseus, Cladonia arbuscula, C. ciliata, C. furcata, C. portentosa, and Coeldcaulon aculeatum s.
lat. M. lignaria is very rare in the lowlands of south-east England, but has been found there
growing directly on the rock of east or north facing sandstone walls and churchyard memorials,
and also on natural sandstone outcrops of the Sussex Weald.
In upland areas M. lignaria is frequently found on the exposed lignum of fallen trunks
(especially of conifers) and old timberwork, with, for example, Cladonia spp., Hypogymnia
physodes, Micarea peliocarpa, Mycoblastus sterilis, Ochrolechia turneri, Parmelia saxatilis, and
Lecanora polytropa (worked timber) . Occurrences of M. lignaria on the bark of healthy trees
are rather rare, and in Britain are confined to the high rainfall areas of the north and west, where
it has been collected on Alnus, Betula, Fraxinus, Ilex, Quercus, and old Sambucus.
Reports of M. lignaria on mosses on limestone rocks usually result from the misidentification
of Bacidia sabuletorum or Toninia lobulata. However, on a few occasions I have seen M. lignaria
growing on thick bryophyte cushions or mats at high altitudes over limestone in the north
Pennines, and over calcareous mica-schist in the Breadalbane Mountains; in such situations the
pH and calcium content of the substratum is presumably kept low by the leaching effect of the'
high rainfall in those areas.
The altitude range of M. lignaria in Britain is from sea-level to about 1200 m (Ben Lawers),
although it may well occur at higher altitudes in the Ben Nevis group and the Cairngorni
Mountains. Higher altitudes are attained in the mountains of central Europe, from where it has