The Botany of Iceland - 01.12.1912, Side 160

146
H. JÓNSSON
well developed in E. Iceland. At an insignificant depth, where I was
able to see the sea-bottom, tlie individuals were not really closely
placed, but lay on the bottom, some quite flat, and others slightly
obliquely with the hollow surface turned upwards to the light. In
this way the sea-bottom was almost entirely covered by the broad
fronds.
This character might be termed the calm-water character, and
an association-character exactly corresponding with it is found in
Laminaria saccharina and Fucus inflatus.
Laminaria digitata f. cucullata occurs also scattered arnong La-
minaria nigripes v. atrofulva and Alaria Pylaii.
The Laminaria hyperborea-association. It is developed
luxuriantly in S. and SW. Iceland, and occurs also in E. Iceland
and N. Iceland, in those places which I have visited. I can pro-
nounce no opinion upon its general distribution in N. Iceland, as
dredgings have been undertaken there in a few places only; yet I
think that it occurs everywhere there. In E. Iceland, on the other
hand, where I have done a great deal of dredging, I have only
found it at the mouth of Berufjörður. It is very luxuriant in the
Vestmannaeyjar, forming a continuous belt round the inhabited
island.
The association grows on a rocky substratum, from a deptlr
of about 4 metres to about 30 (or 40) metres, and occurs both on
exposed and on slightly exposed coasts; close to the limit of low-
tide and in water-filled depressions in the lowermost part of the
littoral zone small specimens may occur. In shallow water, with
exceptional low-tides, the upper part of the stipe is frequently seen
rising above the surface, raising the lower part of the frond obliquely
above the water. Börgesen (12, p. 755, Fig. 160) has reported and
illustrated this from the Færöes.
In Iceland L. hyperborea does not vary in the same manner
as do L. saccharina and L. digitata, the fact being that it does not
occur in protected places, and on exposed coasts does not extend
so far up as the two species mentioned. Those specimens which
occur close to the limit of low-tide, or in pools in the littoral zone,
are quite as typical as tlre large, deep-water individuals. The asso-
ciation seems to thrive best at a deptli of about 20 to 30 metres,
but on somewhat exposed coasts it also thrives fairly well at lesser
depths, and is then very frequently mixed with the other members
of the community; while at greater depths it is generally pure. As