XVI. OBSERVATIONS ON THE TIDE POOL VEGE- 

 TATION OF PORT RENFREW. 



S. A. SKINNER. 



During the summer of 1902 I had the privilege of spending a 

 part of the months of July and August at the Minnesota Seaside 

 Station at Port Renfrew, Vancouver Island, B. C. 



The observations upon which this article is based were made 

 during that time, at the suggestion of Professor Conway Mac- 

 Millan, and I am greatly indebted both to Professor MacMillan 

 and to Miss Josephine E. Tilden for many valuable suggestions 

 and for assistance in determining the plants collected. 



The problem studied is of interest not only in the determina- 

 tion of the plants of the various tide pools, but it becomes of 

 some ecological importance as well when the various factors 

 which have an influence on the distribution of the vegetation of 

 the different pools are taken into consideration. 



The following conditions received especial attention in the 

 series of pools studied. 



The rock formation in which the pool occurs. 



Its location, whether high-tide, mid-tide, or low-tide. 



Its distance from the ocean and its elevation. 



Its exposure to wave action ; its position relative to direction 

 of movement of the wave ; the direction of drainage. 



The nature of the pool ; dimensions ; condition of the bottom ; 

 condition and position of the sides. 



A series of eight pools was studied with some degree of care. 

 The water was removed either with buckets or by syphons im- 

 provised from Nereocystis stems, and observations both at high 

 and low tide were made. 



The pools studied were situated on a ridge of rocks which 

 jutted into the sea some sixty feet and was about thirty feet 

 across at its widest point. It was exposed to wave action on 

 the south, west and east. 



The ridge descends gradually to the south by a series of 

 nearly horizontal planes, each plane being from two to four feet 



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