MOORLAND ASSOCIATIONS 25 
Or 
E. angustifolium, and, in places, Empetrum nigrum. 
Rubus Chamemorus and Vaccinium Myrtillus are abun- 
dant. Occasional plants are: Erica Tetraliz, Calluna 
vulgaris, Drosera rotundifolia, Narthecium, Lycopodium 
Selago, Selaginella selaginoides, Carex canescens, and Scir- 
pus cespitosus. 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. 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, Aira 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: Hrica Tetralix, 
Rubus Chamemorus, Arctostaphylos Uva-ursi (bearberry) ; 
Betula nana (dwarf birch), and Azalea procumbens, con- 
fined to Scottish highlands; Tvrientalis europea 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- 
