154 MINNESOTA BOTANICAL STUDIES. 



8. Polysiphonia sp. 

 Abundant over the bottom. 



9. Cheilosporum planiusculum. 



Covering the mussels on the bottom of the pool. 



10. Corallina vancouveriensis. 



Associated with No. 9. 



SUMMARY. 



A comparison of the preceding results admits of the follow- 

 ing generalizations. 



I. Corallina aculeata inhabits the high-tide pools and occu- 

 pies a zone near the surface of the mid-tide and low-tide pools. 

 Corallina vancouveriensis was not found so abundantly in the 

 series studied but occupies a zone similar to Corallina aculeata. 



The species of Cheilosporum occur abundantly in the mid- 

 tide and low tide pools. 



Cheilosporum planiusculum seems to have somewhat the 

 wider range, extending from the surface to a depth of two and 

 one half feet to three feet. Cheilosporum frondescens and 

 Cheilosporum californicum occur in general from one to four 

 feet below the surface, frequently covering the mussels on the 

 bottom of the pool. 



Amphiroa cretacea and Amphiroa tuberculosa occur in the 

 mid-tide and low-tide pools at some distance from the surface, 

 frequently covering the mussels on the bottom and sides of the 

 pool. 



Phyllospadix occurs in general around the surface of the pool, 

 in some cases extending some distance toward the bottom as 

 convenient footholds offer and occasionally swinging by means 

 of long stout rhizomes over a smooth perpendicular wall to some 

 coveted point below. It seems to choose the more sheltered 

 places where it will be free from the shock of the waves. If in 

 an exposed position the plants found were always much frayed 

 and battered. 



The various surge and surf plants such as Lessoniopsis, Lami- 

 naria, Hedophyllum and Costaria occur in somewhat limited 

 numbers in the low tide pools. Lessoniopsis, true to its nature, 

 choosing the place of greatest exposure. 



The species of Codium were found in the more sheltered 

 parts of the pools, usually where the illumination was weak. 



