postelsia 17 



not growing in the Phyllospadix association, is 

 Zostera marina. It is found only in the sheltered 

 coves of the inner San Juan Harbor and in these 

 places it grows from a muddy or sandy bottom, 

 where its blades at high tide reach up through 

 the water somewhat after the fashion of Val- 

 lisneria spiralis. That it occurs to some extent 

 on the Washington side of the straits is shown 

 by the fact that not infrequently it is washed in 

 after heavy winds from that direction. It does 

 not grow in such great masses as Phyllospadix 

 scold eri. 



II. Formations of the beach. 

 The area occupied by the beach formations 

 varies with the varying contour of the shore. In 

 some places the distance between wave-washed 

 rock and forest edge may be only a few meters, 

 with scattered crevice plants established upon 

 the narrow ground. In other places the inter- 

 vening space may be a hundred meters or more 

 wide, made up either of a sloping sand beach, 

 smooth in front but riddled with drift wood 

 towards the back, or formed of tilted strata 

 supporting a crevice flora of varying aspect, which 



