Ipostelsia 41 



mation according to its composition and after 

 the manner of its subdivisions we have first to 

 deal with 



a Forest of low altitude front- 



ing the sea (sea level to loom) 

 The width of this zone varies with the degree 

 of slope. In those places where the slope is 

 abrupt, conditions that characterize the higher 

 levels are sooner met with than where the rise is 

 gradual. Elevation is apparently of more im- 

 portance than distance from the sea. In shelter- 

 ed places like within San Juan Harbor where 

 wave action is not greatly felt, the forest ap- 

 proaches much nearer to the high tide mark 

 than along the exposed shores. For this reason 

 a great deal of the vegetation characteristic of 

 the rocky beaches is eliminated and one sees fre- 

 quently the branches of large trees reaching out 

 over the water. No one particular species of 

 tree seems to form the forest vanguard. Picca 

 sitchcjisis, Thuja plicata and Tsiiga heterophyUa 

 occur with about equal frequency, although in 

 some places the hemlock and cedar yield to the 

 spruce. When Alniis oregana occurs it is found 



