20 VEGETATION OF BLAKENEY POINT. 



lines. We find these laterals often shew the Suaedas as a broad 

 belt with extensive elongated islands of Festuca rubra, together 

 forming an interrupted zone in which the Suaedas are either 

 absent or small and very occasional. 



The occurrence of F. rubra between the lines of Suaedas on 

 the main bank, though in small amount only, may indicate a 

 similar origin here as relicts from such a zone. Besides Suoeda 

 fruticosa, the other species which are abundant throughout the 

 less barren portions of the bank are Arenaria peploides, Silene 

 maritima, Glaucium luteum, and Rumex trigranulatus (Fig. 

 16) ; of these, the first two are met with throughout the 

 length of the bank, not only in the regions of relatively greater 

 stability, but also in the older and more mobile parts. 



Arenaria peploides probably only tolerates positions in which 

 a considerable amount of sand is present, a condition which 

 obtains along the greater part of the Blakeney bank ; generally 

 speaking, Arenaria approaches nearer the sea than any of the 

 other plants of this formation, not infrequently being found 

 some way down the seaward slope. Silene maritima, like 

 Arenaria peploides, is not by any means uncommon on the 

 neighbouring dunes, and the presence of these two species here 

 shews that they can endure considerable mobility, which is in 

 harmony with their moderate abundance on the older parts 

 where other species are either very rare or entirely absent. 

 These two plants, with their extensive aerial systems and deep 

 roots, can be regarded as the " Psammas of the shingle," and 

 this is especially true of Silene maritima. 



The densest vegetation, as perhaps we should expect, is to be 

 found where the Suaeda bushes are most numerous on the crest. 

 In general, as has been pointed out by Prof. Oliver (loc. cit.), 

 the barren or almost barren stretches are those where, 

 owing to the absence of fringing marshes, the bank is unfed by 

 accumulations of drift. But the amount of vegetation where 

 there are bordering marshes is far from being constant through- 

 out, and in fact corresponds broadly to the extent of surface 

 stability brought about by the groyne action of the Suaeda 



