182 VEGETATION OF THE PEAK DISTRICT [cH. 
BILBERRY Moors 
On the precipitous faces of the dry exposed sandstone rocks, 
very few plants occur. A few lichens, especially Parmelha 
saxatilis, occur; and such situations furnish the few remaining 
stations of species of the rock-mosses (Andreaea spp.). Sand 
and peat, however, find a lodgment on the rock-ledges; and 
here a few moorland plants, especially the bilberry (Vaccuniwm 
Myrtillus), the cowberry (V. Vitis-cdaea), and the hair-grass 
(Deschampsia flecuosa), and even a few trees, such as dwarfed 
examples of birch (Betula pubescens, and B. pubescens var. 
parvifolia), oak (Quercus sessiliflora), and mountain-ash (Pyrus 
Aucuparia), find a home. On the screes and boulder-strewn 
slopes at the foot of the cliffs, the bilberry and the cowberry 
are often very abundant, as well as the crowberry (Lmpetrum 
nigrum) and the bearberry (Arctostaphylos Uva-urst). 
Such Vaccinium associations are exceedingly characteristic 
and very largely developed on the rocky slopes surrounding the 
Peak (see figure 20). 
The bilberry also becomes dominant on the high, bleak, and 
wind-swept ridges and peaks of the sandstone hills. Such 
Vaccinium ridges have been described by Smith and Moss 
(1903: 381), and by Smith and Rankin (1903). As regards 
the Peak District, a typical Vaccinium crest is crossed by the 
public footpath going from Hayfield to the Snake inn. There is 
not very much difference in floristic composition between 
Vaccinium crests and Vaccinium edges, but on the former 
the cotton-grass and the cloudberry are often abundant, and 
the stations of the bearberry seem to be confined to the latter. 
If we regard the Vaccinium crest as an association (“ Haup- 
typus”; Schroéter, 1902), then the Vaccinium edge would be 
a sub-association (“ Nebentypus” ; Schroter, op. cit.). 
The following is a list of the characteristic plants of a 
Vaccinium edge :— 
Dominant 
Vaccinium Myrtillus 
Locally sub-dominant 
Calluna vulgaris Vaccinium Vitis-idaea 
