The Botany of Iceland - 01.12.1912, Blaðsíða 108

94
H. JÓNSSON : MARINE ALGAL VEGETATION
The positive results which are obtained with this small dredge are
satisfactory enough w7hen the material is inspected with sufficient
criticism, but it should not be concluded with certainty from a
negative result (that is, when absolutely nothing comes up from the
bottom) that no plants grow7 there. In great depths, also, dredging
is difficult from a small row7ing'-boat. In some places only, in SW.
Iceland and E. Iceland, have I undertaken dredgings in a depth of
about 80 metres, and the result has been negative. In those places
w’here the plummet revealed a clayey bottom, it was certain that
no plants wrere growdng there. Off S. and SW. Iceland I have met
with no vegetation at a greater depth than about 40 metres, but in
Reyðarfjörður in E. Iceland, on the other hand, I have come across
plants at as great a depth as about 60 metres. This might indicate
that the vegetation extends further dowmwards in E. Iceland; but
as the observations are too few, this point must remain undecided
until further investigations are forthcoming.
It was a fairly common occurrence, especially in the fjords of
E. Iceland, to encounter sunken fragments of algæ (often strictly
littoral species) and of mosses in depths of more than 22 metres.
In Seyðisfjörður I came across leaves of Betula and Salix at a depth
of 14—20 metres.
C. H. Ostenfeld (the Ingolf Expedition) found Lithothamnion
laeve in great quantities at a depth of 88 metres off the north coast
of Iceland, and R. Hörring (on board the “Diana,” off E. Iceland)
found Lithothamnion tophiforme at a depth of 70 metres. In depths
of from 60 to about 100 rnetres Hörring found, in addition, frag-
ments of various algæ, amongst which wrere strictly littoral species,
and of mosses w’hich had evidently fallen to the bottom. In order
to draw’ the attention of future investigators to this matter it must
further be mentioned that Hörring brought home in spirits a
young plant of Laminaria saccharina froni a depth of from 81 to
104 metres (Mjóifjörður, 14.5.1898, St. XIII) and on the label was
written “In the trawl were many large Laminariœ which had been
torn aw ay from the bottom.” The Laminaria brought liome appeared
normal, and, if it had fallen to the bottom could only have lain
there for a short time. What is most likely is that the trawd passed
over an uneven bottom, and that the Laminariœ grew at a lesser
depth than that mentioned; or is it possible that the deep-water
form of Laminaria saccharina ranges so far downwards? I leave it
to future investigation to decide this question.