102 MESSRS, J. А. WHELDON AND М. G. TRAVIS ON 
favour the maintenance of an open plant-association, and the soil has become 
stale and leached of calcareous matter, Cladoniæ are abundant, but as a rule 
they are poorly developed, doubtless owing to the scantiness of humus. 
These include C. alcicornis, Floerke, C. pyaidata, Fr., С. chlorophæa, Floerke, 
C. fimbriata, Fr., C. furcata var. spinosa, Hook., С. squamosa, Hoffm., 
C. pungens, Floerke, C. cæspititia, Floerke, and C. fibula, Nyl., var. radiata, 
also Cetraria aculeata, Fr., Ke. 
In parts of the sandhill tract where “slacks” or dune-pans exist, the lower 
slopes of the larger dunes, and especially the low secondary dunes which rise 
out of the “slacks,” are worth careful examination for lichens in places where 
the surface is clear of larger vegetation. The following have been found in 
such situations on damp decaying mosses, hepatics, &c. :— Bilimbia squamu- 
losa, A. L. Sm., B. sphaeroides, Koerb., Bacidia muscorum, Mudd, var. atriseda 
nov. Collema pulposum, Ach. (very rare), Lecidea uliginosa, Ach., and 
Cladonia sylvatica, Nyl. 
Usually the dune valleys in the wetter parts of the dunes are not adapted 
for lichens, owing to the moist conditions which favour the development of 
marsh-plants and a luxuriant growth of aquatic mosses ; but in some of the 
more recently formed dune valleys, where stretches of moist bare ground 
occur, is the habitat of Arthopyrenia areniseda, A. L. Sm., which was first 
discovered in this tract of dunes, and will be referred to more fully in the 
Systematic List. 
On portions of the sand-dunes on the South Lancashire coast are large 
plantations of pines, as well as some deciduous trees such as birch, alder, 
poplars, &e. ; but owing to the conditions of atmospheric impurity already 
described, corticole lichens are well nigh absent, and Lecanora varia, Ach., is 
the only lichen common on the bark of these trees. It is interesting to find, 
however, that a number of corticole lichens do exist on the sandhills under 
certain conditions. In the dune-hollows Salix repens, Linn., is everywhere 
abundant, and on the dead underground stems of this willow, exposed by 
wind erosion on the sides of the dunes, the following lichens have been 
found :—Lecanora varia, Ach., Parmelia sulcata, Tayl., P. physodes, Ach., 
Bacidia salicicola, nov. spec., Lecanora symmictera, Nyl., L. sarcopsis, Ach., 
Buellia myriocarpa, Mudd, Bacidia Beckhausii, Koerb., Lecanora chlarona, 
Nyl., and Parmelia fuliginosa, Nyl., var. lætevirens, Nyl. Only the four 
species first mentioned are common; the rest are rare. Lecanora albella, 
Ach., Lecidea enteroleuca, Ach., L. fuliginea, Ach., and one or two other 
species, have also occurred very sparingly on old bark and dead wood. 
The foregoing description mentions most of the lichens which are to be 
found on the South Lancashire dunes, and gives some indication of their type 
of habitat. A few additional species, rare and local in their occurrence, are 
given in our Systematic List (Part V.). 
