66 H. JONSSON 



element in E. Iceland and the boreal element in S. and SW. Iceland 

 are much more sharply defined; and this is natural, as the species 

 assumed to be common are omitted. Even if we consider only the 

 known distribution of the species, in its entirety (see Table 1), the 

 distribution of the here-mentioned 76 species will still be the most 

 essential reason for the floristic difference between the parts of the 

 coast. 



The species assumed to be common are 124 (see above). Of 

 these none are arctic, 25 belong to the subarctic group I, 46 to the 

 subarctic group II, 26 are boreal-arctic, 26 cold-boreal, and one 

 (Phormidium antumale) is warm-boreal. Of the 76 not- common 

 species, 11 are arctic, 6 belong to the subarctic group I, 4 to the 

 subarctic group II, one (Ahnfeltia plicataj is boreal-arctic, 43 are 

 cold-boreal and 11 warm-boreal. If we add together the numbers 

 representing the species of the corresponding groups as regards the 

 124 species assumed to be common and the 76 not-common species 

 (Table 5), and compare with Table 3, we find that the species are 

 more numerous in each district, but that the percentages are almost 

 the same. 



If the groups are divided in two parts, A and B (see above) so 

 that A includes the arctic and subarctic groups, and B the three 

 other groups, the following figures are obtained (see Table 4) : — 



E. Icel, N. lcel. NW. Icel. SW. Icel. S. Icel. 



A 50 (63 %) 47 (54 %) 42 (58 %) 48 (42 °/o) 25 (30 °/o) 



B 30(37%) 40(46%) 31(42%) 67(58%) 59(70%) 



The arctic group is poorly represented in all the districts of 

 the coast (see Table 4) and therefore the figures mentioned above 

 under A apply chiefly to the subarctic group; the floral districts of 

 E. Iceland, N. Iceland and NW. Iceland are thus subarctic. E. Ice- 

 land is subarctic to a greater extent than N. and NW. Iceland. SW. 

 Iceland is a boreal floral district with a very considerable subarctic 

 element, and thus resembles the coasts of Iceland taken as a whole 

 (see above). S. Iceland is a boreal district with a slightly subarctic 

 element. 



Floristic Boundaries. 



The mixed character of the flora in N. and NW. Iceland has 

 been alluded to several times in the foregoing pages, and is clearly 

 seen from the tables given, as, for example, Tables 2 and 5. Here 



tL 



