THE LICHEN FLORA OF THE BASILDON AREA 153
V. muralis Ach.
Frequent on concrete and asbestos-cement; rare on limestone and brick.
51/68, 69.
This species is particularly frequent on man-made calcareous substrates.
V. nigrescens Pers.
Occasional on limestone; scarce on marble. 51/69, 79.
Limestone and marble gravestones, All Saints' Church, Hutton (1972,
PME-B) and similarly at St Mary's Church, Runwell (1974, PME-B);
limestone gravestones, Congregational Church, Billericay (1974, PME-B).
V. Sphinctrina Ach.
Scarce on limestone. 51/69, 79.
Limestone tombs and headstones, St Mary's Church, Runwell (1974,
PME-B); limestone chest-tombs, Congregational Church, Billericay (1974,
PME-B).
V. viridula (Schrad.) Ach. f. viridula
Rare on limestone. 51/69.
Limestone wall of All Saints' Church, Hutton (1974, PME-B).
V. viridula f. tectorum (Massal.) Laund.
Scarce on limestone; rare on marble. 51/69.
Limestone gravestone, Congregational Church, Billericay (1974,
PME-B); marble gravestone and limestone wall of All Saints' Church,
Hutton (1974, PME-B).
Xanthoria aureola (Ach.) Erichs.
Very common on asbestos-cement, concrete and mortar; scarce on
limestone. 51/68, 69, 78, 79.
This species and X. parietina are important members of the two unions
of the Xanthorion federation in this area, namely the Caloplacetum
heppianae and the Physcietum caesiae.
X. parietina (L.) Th. Fr.
Very common on asbestos-cement, concrete and mortar; scarce on
limestone. 15/68, 69, 78.
When young or poorly developed, this species is difficult to separate
from X. aureloa, with which it often grows.
Acknowledgements
I am grateful to Mr S. J. & Mrs I. M. Harding for collecting specimens
for me and Dr M. R. D. Seaward for reading the manuscript. Thanks are
also due to Basildon Urban District Council for making certain un-
published information available to me.