54 



H. JONSSON 



of the coast. The percentage of each group is of the greatest im- 

 portance, and for the sake of explicitness I have arranged these 

 figures in a tabular form, both those which refer to c and those 

 which refer to c + (c). 



Species common to all the coastal districts, given as 



percentages. 



All the groups 

 collectively 



22 



c + (c) 38 70 82 100 60 



On considering these two series of figures it becomes evident 

 that the figures given for c Hh (c) come nearer to the real facts, 

 while those given for c merely indicate an incomplete knowledge 

 of the coastal distribution of the species. The fact is that, \vhere 

 there is not a greater climatic difference between the different parts 

 of the coast than is the case in Iceland, it may always be expected 

 that, as regards the common species, the highest numbers will fall 

 to the green and to the blue-green algae; and where the hydrographic 

 differences between the different parts of the coast are as pronounced 

 as they are in Iceland, it is natural that the smallest number will fall 

 to the red alga3, and just as naturally the brown algae will in this re- 

 spect be placed almost midway between the red and the green algae. 



Therefore, as regards the floristic difference between the different 

 parts of the coast, particular stress is laid on the remaining 76 

 species. In the following table they are arranged according to their 

 habitats. Under A, those species are given which either occur in E. 

 or N. Iceland only, or are most common there, and thence are dis- 

 tributed southward along the north-west coast as far as SW. Ice- 

 land. Under B are given species which either have been found in 

 S. or SW. Iceland only, or are most common there, and thence have 

 a distribution northward along the north-west coast, many of them 

 having, moreover, an eastward distribution along the north coast. 



Table 2. The Distribution of the 76 species not common to all 



the coastal districts. 



