INFLUENCE OF MARINE PLANTS 231 



more or less slu-ltered inlets ; they are indeed characteristically 

 harbor plants. Therefore it is mainly to this group that we 

 must look for the effect of vegetable life on the conditions of 

 havens. 



The only group of seaweeds which to an)' considerable 

 extent affects the history of our embayed waters belongs to the 

 family of rock weeds — forms which dwell in the section between 

 high and low tide. In the colder waters of high latitudes, espe- 

 cially on the rocky, embayed shores of the fiord zone, plants of 

 these species are often exceedingly abundant. Thus along the 

 cliffs which border the inlets of the Bay of Fundy, the rocky 

 steeps are usually covered from near high tide to the lowest 

 level of the water with a singularly thick and massive coating 

 of those plants. When the tide is out in this region of great 

 rise and fall, this vegetation may form an almost continuous 

 sheet over the surface left bare by the receding waters. The 

 immediate influence of this envelope is to a considerable extent 

 favorable to the ])reservation of the harbors of the districts in 

 which it abounds. The dense and springy nature of the cover- 

 ing somewhat diminishes the efficiency of the blow which the 

 waves strike upon the shore. A yet more important effect is 

 produced by the nonconductive influence of these plants. When 

 in freezing weather the rocks are laid bare, this coating of vege- 

 tation serves in a more or less perfect way and often very 

 efficiently to prevent the frost' s taking eff ect on the rock to 

 which it is attached. Wherever in the fiord zone we find an 

 area of jointed rocks between high and low tide, unprotected by 

 this vegetable mantle, we can always clearly note how the frost 

 has shattered the stone into fragments, which ma\- readily be 

 tossed about and still further broken up by the waves. At some 

 points on the coast of Maine the effect of this absence of sea- 



