VEGETATION OF THE SEA-COAST 381 



as clay, sand, and boulders, obscuring the solid rocks be- 

 neath, so along the coast, thick beds of such materials may 

 be found, sometimes forming high, easily-denuded cliffs. 

 Steep rocks offer a jagged resistant line to the tearing action 

 of the waves, and are covered with spray at every high tide. 

 At the other extreme, low ground may pass gradually 

 seawards and deaden the force of the incoming waves. 

 The varied materials of the coast are exposed to the cease- 

 less efforts of the sea and atmospheric weathering, and the 

 products of denudation are spread out in a characteristic 

 manner along the coast, and form a somewhat unstable soil 

 for plants. In some places it is finely pulverized and 

 muddy, in others it is coarser and sandy, and heaped up 

 into banks or dunes ; or the still coarser pebbles and boulders 

 may form banks of shingle. The coast -line thus offers 

 a great variety of surface and soil, and we might expect 

 the influence of these variations to be reflected on the coast- 

 vegetation. But the factor which most powerfully influ- 

 ences plant-life along the coast is the presence of salt water, 

 and the plants exposed to its influence show many peculiari- 

 ties both in colour, form, and structure. 



In consequence of these conditions, which of necessity 

 are confined to a narrow belt around the coast, we find 

 certain types of vegetation which present a strong contrast 

 to the vegetation immediately beyond it. The best -marked 

 plant-formations of the coast are those of the sand-dunes 

 and salt-marshes, the vegetation of which impresses us at 

 once by its peculiar, blue-grey colour. 



Seaweeds. In the sea, or along that part of the coast 

 often covered by sea-water, seaweeds abound. If the 

 coast is rocky, brown seaweeds, like the Bladder-wrack and 

 other species of Fucus and Pelvetia, often form a long belt, 

 the plants being anchored to the rocks or to stones by 

 peculiar holdfasts. Farther seawards are the light, yellow- 

 brown straps of Laminaria ; and in the rock-pools and in 



