VEGETATION OF THE SEA-COAST 387 



rhamnoides), Burnet Rose (Rosa spinosissima) , Brambles 

 (Rubus spp.), Honeysuckle (Lonicera Periclymenum), Elder 

 (Sambucus nigra). Sometimes moorland plants like Ling 

 (Calluna vulgaris) and Heaths (Erica) occur, and may 

 eventually invade the ground to such an extent as to give 

 rise to a typical heath. The association of the shifting 

 dune thus differs from that of the fixed dune, and within 

 each association various societies occur. These societies 

 and associations developed on sand-dunes form the Sand- 

 dune Formation. 



Strand-plants. Along the strand between the line of 

 shifting dunes and high-water mark a few plants occur very 

 sparingly. They are easily overlooked, being almost buried 

 beneath small dunes an inch or two high. These have all 

 the characteristics of salt-marsh plants, e. g. Sea Rocket 

 (Cakile maritima), Sea Kale (Crambe maritima), Sandwort 

 or Sea Purslane (Arenaria pepioides), several species of 

 Orache (A triplex), Goosefoot (Chenop odium), Saltwort (Sal- 

 sola Kali), and Sea Knot-grass (Polygonum Raii). These 

 form an association of strand-plants. 



The strand and a considerable part of the dunes have 

 a scanty vegetation ; much of the ground is bare, and there 

 is no competition among the plants. Associations of this 

 kind are called open associations. On the other hand, in 

 areas completely covered by vegetation the association is 

 said to be closed. Examples of closed associations are 

 pasture, heath, and woodland. 



Shingle Beaches 



Along many miles of the English coast is a fringe of 

 shingle, consisting of water-worn stones carried from the 

 wasting shore, piled up into banks by the alongshore 

 waves and currents, and driven landward by onshore gales 

 during high tides (Fig. 249). If the bank is a low one 



b b 2 



