96 MESSRS, J. А. WHELDON AND W. б. TRAVIS ON 
Corticole Lichens.—It is the only part of South Lancashire where corticole 
lichens can be said really to exist, and most of the few bark-loving species 
we record as actually growing on trees have been found there. On the 
trunks of some of the old trees near the banks of the Ribble, where doubtless 
they are somewhat sheltered from the effects of smoke-laden winds, a few of 
the commoner corticole species still survive. The following have been noted 
by us in the district :—Parmelia saxatilis, Ach., P. physodes, Ach., Lecanora 
varia, Ach., Parmelia sulcata, Tayl, P. fuliginosa var. letevirens, Nyl., 
Pertusaria amara, Nyl., Platysma glaucum, Nyl., Everiia Prunastri, Ach. 
(once only and poorly developed), Physcia tenella, Nyl., Lecanora subfusca, 
Nyl., L. rugosa, Nyl., L. chlarona, Nyl., Callopisma luciniosum, А. L. Sm., 
Pertusaria communis, DC., P. leioplaca, Schaer., Lecidea parasema, Ach., 
Buellia myriocarpa, Mudd, B. canescens, De Not., В. spheroides, Koerb., 
Biatorina graniformis, А. L. Xm., and Acrocordia gemmata, Koerb. Only the 
first six can be said to be fairly common on trees in that district. Itis 
clear that the conditions, although relatively good, are far from being 
favourable enough to permit the corticole lichen-flora to assume its uormal 
development. 
Calcareous Rocks.—It is to the lichens of the calcareous rocks (mainly 
Carboniferous Limestone) that we turn with more interest. Unfortunately, 
the Carboniferous Limestone is only developed on an insiznificant scale in 
South Laneashire as compared with its grand development in the adjoining 
Craven district of Yorkshire. In our area it forms a number of grassy 
knolls or low hills—some of which have now almost been removed by 
quarrying—extending N.E. from Clitheroe to the county boundary. The 
most prominent of them is Worsaw НШ, a conspicuous isolated eminence, 
situated between the village of Chatburn and Pendle Hill, and attaining an 
elevation of 600 ft. above sea-level. Natural exposures of the limestone rock 
are small and not numerous. Неге and there at exposed places there are 
small outcrops ; but there are no true “scars,” nor is there any development 
of limestone * pavement." Furthermore, the limestone is in places masked 
by glacial clay, and its peculiar edaphic influence thus nullified. It follows 
that the flora of the Carboniferous Limestone as represented in our area, 
although characteristic so far as it goes, is considerably inferior in richness 
and variety to that of other parts of Lancashire and Yorkshire, where the 
Carboniferous Limestone is developed on a grander scale and presents 
greater diversity in its physical features. 
We have already referred to the advantages of the smoke-neutralizing 
action conferred by a calcareous substratum in a smoky district like ours. 
Apart from this, a factor of importance from a floristic point of view is that 
the Carboniferous Limestone has a characteristic lichen-flora of its own, and 
consequently this limestone tract, sinall though it is, has enabled us to include 
in our list numerous species of lichens which do not occur elsewhere in 
