214 THE SCOTTISH BOTANICAL REVIEW 



towards the inner limit of the mobile dunes. It is also abundant 

 on the fixed dunes, as in Norfolk. Euphorbia portlandica is absent 

 from the Somerset sand hills. 



Salix repens Association. 



As already mentioned, this association includes within its limits 

 plants of the mobile dunes, as well as those of the fixed dunes. The 

 following species occur : — 



DOMINANT SPECIES. 



Salix repens, Linn. 



SUBDOMINANT SPECIES. 



Rubiis ccesiiis, Linn. Ammophiia arenaria, Linn. 



FREQUENT SPECIES. 



Viola ericetorum, Schrad. Leontodon [nudicaule), B. & S. 



Viola Curtisii, Forster. Euphorbia Par alias, Linn. 



Erodiufn circutariuni, L'Herit. Iris fatidissima, Linn. 



Rosa spinosissima, Linn. Carex arenaria, Linn. 



Erigeron acre, Linn. Phleum arenariutn, Linn. 

 Cnic2is arvensis, Hoffm. 



Viola Curtisii was recorded from the sand dunes near Aberavon, 

 over sixty years ago. It is not found in Somerset. The damp 

 sandy hollows which occur within the limits of the Salix association 

 possess a characteristic vegetation. These depressions lie at a low 

 level, and during the winter months are frequently submerged. A 

 layer of humus is formed in places, and in conjunction with an 

 increased water content produce a plant society of a definite type. 

 The Salix forms a fringe round the margin of these hollows, which 

 are colonised by the following species : — 



Samolus Valerandi, Linn. Littorella uniflora, Aschers. 



Erigeron canadense, Linn. Helleborine longifolia, R. & B. 



Hydrocotyle vulgaris, Linn. Orchis i?icarnata, Linn. 



Anagallis te?iella, Murr. Juncus effusus, Linn. 



Blacksionia perfoliata, Huds. Equisetum palustre, Linn. 

 Mentha aquatica, var. hirsuta 

 (Huds.). 



The occurrence of these species in the different hollows depends 

 upon the relative amount of moisture present. Practically pure 

 societies of one particular species are not uncommon. 



Kenfig Pool is situated within the limits of the Salix association, 

 and its general features have already been described. On its sandy 

 margin the vegetation met with is mainly that of the damp hollows. 

 A sheltered bay on its landward side is rich in species, and the 



