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 Parmelia 

 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 ( Vaccinmm 

 Myrtillus), the cowberry (F. Vitis-idaed), and the hair-grass 

 (Deschampsia jiexuosa), and even a few trees, such as dwarfed 

 examples of birch (Betida pubescens, and B. pubescens var. 

 parvifolia), oak (Quercus sessilijlora), 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 (Empetrum 

 nigrum) and the bearberry {Arctostaphylos Uva-ursi). 



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 Hajrfield 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 " ; Schroter, 1902), then the Vaccinium edge would be 

 a sub-association (" Nebentypus " ; Schroter, op. ait.). 



The following is a list of the characteristic plants of a 

 Vaccinium edge : — 



Dominant 

 Vaccinium Myrtillus 



Locally sub-dominant 

 Calluna vulgaris Vaccinium Vitis-idaea 



