MOORLAND ASSOCIATIONS 255 



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

 Ruhus Ghamcemorus and Vacciniwm Myrtillus are abun- 

 dant. Occasional plants are : Erica Tetralix, Calluna 

 vulgaris, Drosera rotundifolia, Narthecium, Lycopodium 

 Selago, Selaginella selaginoides, Carex 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 

 into a heather-moor. 



7. Vaccinium-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, Aira flexuosa, 

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

 heath or alpine pasture. Alpine plants are : Alche- 

 milla alpina, Empetrum nigrum, PJUeum 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, 

 Riibus Chamcemorus, Arctostaphylos Uva-ursi (bearberry) ; 

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

 fined to Scottish highlands ; Trientalis europcea and 

 Tofieldia palu^tris (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- 



