The Botany of Iceland - 01.12.1912, Qupperneq 61

MARINE ALGAL VEGETATION
47
It happens rather frequently that the winds are stormy and,
as an example, the annual percentage of storms for Stykkishólmur
(from V9 1845 to 31/2 1892) may be given: — N. 32, NE. 61, E. 13,
SE. 17, S. 44, SW. 31, W. 26, NW. 11.
The frequency of “calm” is 10 % at Grímsey and in Berufjörður
and the frequency of “wind” is tlierefore 90 % in both places; at
Stykkishólmur the frequency of “calm” is 12 % and that of “wind”
88%; in the Vestmannaeyjar the frequency of “calm” is 22% and
that of “wind” 78 %.
At Thorshavn, in the Færöes, the annual “calm” is 11 % and
the frequency of “wind” 89 %, somewhat the same, therefore, as
at Stykkishólmur and greater than in the Vestmannaeyjar.
4. LIGHT.
The influence of light 011 the distribution of the algal associa-
tions and on their appearance is, as is well-known, exceedingly
great. Without doubt most investigators assume that the main di-
vision of algal vegetation into a green, a brown and a red zone is
due to the quality of the light, but one cannot on that account
consider the intensity of the light to be of no importance. To what
extent the shades of colour in the red algæ are to be regarded as
an adaptation to the intensity of the light or to the quality of the
light, I find rather difíicult to decide.
I agree with Berthold and Oltmanns in thinking that the
Florideœ may be characterized as shade-plants in the same sense
that we speak of shade-vegetation in lava-clefts and in other places
where there is a faint light. By shade-plants I understand plants
which prefer feebly illuminated spots, and do not, as a rule, thrive
in the full light of day. In the tidal region (Part VI) the littoral
Florideœ evidently prefer crevices and grottoes, i. e. feebly illuminated
places, and thus prove themselves to he shade-plants.
I shall not enter more fully into the question of light, as I
have made no experiments in that connection and, moreover, the
subject requires to be reinvestigated (Oltmanns, 54).