MOORLAND ASSOCIATIONS 255 



E. angustifolium, and, in places, Empetrum nigrum. 

 Rubus Chamcemorus and Vaccinium Myrtillus are abun- 

 dant. Occasional plants are : Erica Tetralix, Calluna 

 vulgar is, Drosera rotundifolia, Narthecium, Lycopodium 

 Selago, Selaginella selaginoides, Car ex canescens, and Scir- 

 pus ccespitosus. Sphagnum is quite subordinate. On the 

 drier edges Calluna and Erica Tetralix become more 

 common, and on the slopes the moor often passes over 

 a heather-moor. 



7. Vaecinium-Moor. 



Associations dominated by Vaccinium Myrtillus (bil- 

 berry) are in most cases essentially alpine (2,000 to 3,000 

 feet), but in Yorkshire the Vaccinium-moor is not deter- 

 mined by altitude alone ; it invariably forms the sky- 

 limit of the moor where it is exposed to all weathers. 

 The peat is much shallower than in the Eriophorum- 

 moor. 



Two types of Vaccinium-moor may be distinguished 

 one a dry form, a climatic variety of the grass-heath or 

 alpine pasture, and the other wetter, a climatic variety 

 of the heather-moor, or Eriophorum-moor. In either 

 case alpine plants are frequent. The dry type occurs on 

 shallow peat liable to drought, and includes a large 

 number of grasses e.g., Festuca ovina, Air a flexuosa, 

 Nardus stricta, etc., and other plants of the grass- 

 heath or alpine pasture. Alpine plants are : Alche- 

 milla alpina, Empetrum nigrum, Phleum alpinum, club- 

 mosses, etc. 



In the climatic variety of the heather-moor, Calluna is 

 abundant, and in that of the Eriophorum-moor, the 

 cotton-grass. Other plants found are : Erica Tetralix, 

 Rubus Chamcemorus, Arctostaphylos Uva-ursi (bearberry) ; 

 Betula nana (dwarf birch), and Azalea procumbens, con- 

 fined to Scottish highlands ; Trientalis europcea and 

 Tofieldia palustris (Scottish asphodel), confined to North 

 Britain. Cornus suecica (dwarf dogwood) is one of the 

 most constant associates of Vaccinium in the alpine zone 

 of North Britain. 



The relation between the various moorland associations, 

 or groups of associations, may be expressed in the follow- 



