The Botany of Iceland - 01.12.1912, Blaðsíða 77

MARINE ALGAL VEGETATION
63
1. The arctic group Rhodo- phyceæ 7 Phæo- phyceæ 3 Chloro- phyceæ í Cyano- phyceæ » = n species (5.5%)
2. The subarctic group: Subdivision I 8 13 10 » - 31 — (15.5%)
3. The subarctic group: Subdivision II 12 17 20 1 = 50 - (25.0%)
4. Tbe boreal-nrctic group 10 7 7 3 =27 - (13.5%)
5. The cold-boreal group. 31 25 12 1 = 69 - (34.5%)
6. The warm-boreal group 8 2 1 1 = 12 - (6.0%)
76 67 51 6
If we divide the six groups into two parts, A: the first three
groups, and B: the last three1 groups, we obtain the following
figures: —
A, 92 species (46%) and B, 108 species (54%).
The floral district must therefore be determined as boreal, be-
cause more than half of the species belong to the last three groups.
Of these groups the cold-boreal is the most important because its
species form 64 % of the total number of species (108) in all three
groups. This floral district has not, however, a purely boreal cha-
racter, as the subarctic group is rich in species and gives a rather
high percentage (41 %). The floral district, then, is characterized to
a very higli degree by a boreal element, and next by a subarctic
element.
If wre consider only the red and tlie brown algæ, 143 species
in all, the cold-boreal character is a little rnore strongly pronounced
than the subarctic. The íigures are: — Arctic 10 species (7 %), sub-
arctic 50 species (35%), boreal-arctic 17 species (12%), cold-boreal
56 species (39%) and warm-boreal 10 species (7%). The first three
groups have 60 species (42 %), the last three 78 species (58 %).
If we compare the five divisions of the coast with respect to
the number of species in the different groups, we obtain the figures
given in Tables 3, 4.
If, for instance, we select the red and the brown algæ (Table
4) as a basis, then the diflerence which exists in the different parts
of the coast is very evident. In E. Iceland the arctic group contains
the greatest number of species, and this number — if we follow
the divisions of the coast in the order of the tables — decreases
1 The boreal-arctic group is included in the boreal groups, as its species,
though eommon in the arctic district, have a far larger area of distribution out-
side this.