MOORLAND ASSOCIATIONS 253 
Erica Tetralix-Association.—In the wettest parts Hrica 
Tetralix is dominant, and forms a distinct association 
within the heather-moor, characterized by the presence 
of a number of bog-plants—e.g., Drosera rotundifolia, 
Pinguicula vulgaris, Andromeda polifolia, Narthecium 
ossifragum, Rubus Chameemorus, Vaccinium Oxycoccus, 
Myrica Gale (sweet gale), Salix repens, Sphagnum, 
Molinia cerulea, and various species of Juncus, Carex, 
and Hriophorum. Rare plants occurring in this associa- 
tion are: Hrica ciliaris, more common here than on the 
dry Calluna-heath, and Hrica Mackawi and FE. mediter- 
ranea, confined to a few districts in western Ireland 
(see p. 213). 
In many parts the Hrica Tetralix-association merges 
gradually into the Sphagnum-bog or Eriophorum-moor. 
4. Myrica-Bog. 
In parts of the wet heather-moor, where water is very 
abundant, and sweeter than elsewhere, Myrica becomes 
dominant. A similar association is met with in low- 
lying districts where drainage is bad, and on the wet 
margins of the highland type of lake. 
This association is intermediate between the wet 
heather-moor and the marsh, many of the plants of the 
latter being present—e.g., Ranunculus Flammula, Viola 
palustris, and Anagallis tenella. 
Very abundant plants are: Molinia cerulea and Erica 
Tetralix. Common or frequent plants, in addition to the 
above marsh-plants, are: Drosera, Pinguicula, Narthe- 
cium, Juncus species, Hriophorum vaginatum, Carex species, 
and Sphagnum. Calluna vulgaris occurs, but is not 
common. 
5. Sphagnum-Bog. 
Sphagnum is a peculiar moss with a big system of 
water-storing cells in its leaves, so that the plant hold, 
water like a sponge. The stem grows continuously at 
the apex ; the lower part dies away, and gradually be- 
comes converted into peat. The stem is clothed with 
living green leaves for about 6 to 8 inches below the 
tip, and as it is choked with water inside, it cannot 
