1911-12.] botanical society of edinburgh 81 



The Plant Association-. 



The three most prominent and well-marked associations 

 in this formation are the following: 1. The association 

 of Ammophila curenaria; 2. the association of Saliz 

 rep< ns] 3. the association of Pti ris aquUina. 



1. The association of Am/mophUa <ir<n<ir'm. — This as- 

 sociation is characteristic of the "shifting" dunes, with 

 the Marram grass as the dominant species. This species 

 occupies the first seaward line of sand hills, the Agnropy- 

 retum junc&i (sea couch-gra-s association) of the Somerset 

 and Lancashire dunes bring practically absent in this area. 

 It is worthy of notice that Elymus arena/rius, which in 

 Norfolk gives rise to low dunes, is entirely absent from 

 this coast. The higher inland dunes, many of them over 

 fifty feet in height, bear on their crests the characteristic 

 tufts of Marram grass. It descends on the leeward slopes 

 and colonises the sandy hollows, and in many of the latter 

 its rhizomic habit of growth is particularly obvious. As 

 a " sand-binder " it is pre-eminent, and it is interesting to 

 note that in the Charters of K.ntig of 1330 special 

 provision was made for its protection and preservation. 

 Ammophila also occurs in abundance on some of the 

 • rixed " dune-. 



2. The Salix r< [•< ns association. — Salix repena occur- on 

 the "shifting" dunes as a -sand-binder," producing a well- 

 marked association. In the sandy dune valleys it forms 

 a carpet of low-growing scrub, but in the more exposed 

 stations it collect- around it the blown sand and give- rise 

 to ''hummocks'' and small dunes. In the damp hollows 

 it forms a fringe round the marshy ground and the de- 

 pendent species vary accordingly. Salix represents the 

 second stage in succession on the dunes, as Ammophila 

 represents the first. In the more open stations of this 

 association Marram grass is the subdominant species. Salix 

 repens occurs on the Lancashire dunes, but Moss describes 

 it as a comparativelv rare plant on the Somerset sand 

 hills. 



,3. The Pteris aquil '< i>" association. — The bracken covers 

 acres of the ''fixed" dunes in this area, ami its outlier- 

 blend with the willow of the preceding association. It- 



TRANS. BOT. >OC. EDIX. VOL. XXVI. 6 



