MOOELAND ASSOCIATIONS 253 



Erica Tetralix-Association. — In the wettest parts Erica 

 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 

 ossifragwi.i, Rubus Chamcemorus, Vaccinium Oxycoccus, 

 Myrica Gale (sweet gale), Salix repens. Sphagnum, 

 Molinia ccerulea, and various species of Juncus, Carex, 

 and Eriophorum. Rare plants occurring in this associa- 

 tion are : Erica ciliaris, more common here than on the 

 dry Calluna-heath, and Erica Mackaii and E. mediter- 

 ranea, confined to a few districts in western Ireland 

 (see p. 213). 



In many parts the Erica Tetralix-a,8soc\a,tion 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 ccerulea and Erica 

 Tetralix. Common or frequent plants, in addition to the 

 above marsh-plants, are : Drosera, Pinguicula, Narthe- 

 cium, Juncus species. Eriophorum vaginatum, Carex species, 

 and Sphagnum. Calluna vulgaris occurs, but is not 

 common. 



5. Sphagnum-Bog. 



Sphagnum is a pecuhar moss with a big system of 

 water-storing cells in its leaves, so that the plant holdj 

 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 



