Distribution of Bryophytes in Somerset Woodlands. 91 
In extreme cases these three woodland associations are well 
differentiated, but transitions occur which are difficult to refer to 
any one of the types. The oak-hazel-woods are usually found at 
low elevations on the Triassic and Jurassic marls and clays, the 
oak-woods at higher elevations on the sandstones, whilst the ash- 
woods are especially characteristic of the slopes of the Carbo¬ 
niferous limestone. Dr. Moss, in his “ Geographical Distribution 
of Vegetation in Somerset,” has shown that each of these woodland 
types has its characteristic association of Phanerogams and 
Vascular Cryptogams, and I am in agreement with the general 
results of his careful investigations, the interesting exposition of 
which has earned him the thanks of Somerset botanists. 
Native beech-woods are probably absent; the rings of beech 
trees which are so conspicuous a feature around the woods near 
Minehead, Taunton and Alfred’s Tower have probably been planted. 
At Norton Fitzwarren, near Taunton, there is a small wood which 
almost entirely consists of beech trees, with their characteristic 
lack of undergrowth, but these trees also are probably planted. 
Extensive planting of trees has taken place, so that a large number 
of woods cannot be referred to any of the types ; Dr. Moss refers 
to these as “mixed woods,” an interesting case of which occurs near 
Yatton. 
In all these woods, except where beeches are dominant, the 
lower forms of plant-life are abundant, bryophytes clothing the 
ground with a mantle of various hues, whilst the trees are draped 
with lichens. The commonest species 1 of the latter are Collema 
flaccidum, Calicium hyperellum, Ramalina calicaris, R. fraxinea, 
with its variety ampliata, R. fastigiata, R. fariuacea, R. pollinaria, 
Usnea florida, U. hirta, Evernia prunastri , Parmelia saxatilis with 
its form ftirfuracea, P. caperata, P. physodes, P. pulverulenta, P. 
tenella, Leccinorci subfusca, L. rugosa, Pevtusaria amarx , P. globulifera, 
P. communis, P. Wulfenii, Lecidea canescens, Graphis scripta, Cladonia 
pyxidata, C. pungens, C. niacilenta, C. pityrea, C. squamosa and 
Cladina sylvatica. The lichens seem to be more susceptible than 
the bryophytes to the influence of man, disappearing near the 
towns at a more rapid rate, though Collema chedeum appears to be 
on exception to this rule. 
The commonest and most prominent mosses are pleurocarpous, 
whilst the chief liverworts belong to the Jungermanniaceac. 
The upland ash-woods are characterised by the abundance of 
1 Names according to Crombie’s Monograph of British Lichens. 
