CONTENTS. 



Patfe 



Introduction 1 



I List of the Marine Alga? 5 



II Life-conditions of the Marine Algal Vegetation 25 



1. The Nature of the coast 25 



2. The Ocean 27 



A. The Movements of the Ocean 27 



B. The Temperature of the Water 32 



C. The Salinity 40 



3. The Air 42 



A. The Temperature 42 



B. The Humidity 44 



C. Precipitation, Amount of Cloud, Foggy days, Wet days 44 



D. Winds ' 46 



4. The Light 47 



III The Horizontal Distribution of the Species and the Components of the 



Algal Flora 48 



The Components of the Algal Flora 58 



A. The Arctic Group 58 



B. The Subarctic Group 59 



C. The Boreal-Arctic Group 60 



D. The Cold-Boreal Group 61 



E. The Warm-Boreal Group 62 



Floristic Boundaries 66 



IV Comparison with neighbouring Floral Districts 68 



V The Vertical Distribution of the Species 80 



A. Upper Littoral Zone 85 



B. The lower Littoral Zone and the Belt below down to a depth of 

 about 10 metres 88 



C. The Sublittoral Species ... 91 



Lower Limits of Growth . 92 



