The Botany of Iceland - 01.12.1912, Blaðsíða 187

MARINE ALGAL VEGETATION
173
Group 3. Species which carry on vegetative and reproductive
work only during a part of the year.
In referring the Icelandic species to these groups the difflculfy
at once arises, that we lack knowledge regarding the behaviour of
a number of the species during winter. Such species cannot there-
fore be grouped with any certainty at the present time. True, we
may judge with some probability how they behave here during
winter by a comparison of their winter-activities in other places,
provided these are known; but as it has been shown that one and
the sarne species often behaves differently in two distantly situated
places, a satisfactory result could not be arrived at through sucli
a comparison which lias, for that reason, been omitted. I therefore
mention a few species only, which I think I can group with some
certainty.
Group 1. The following species belong to this group: — Hilden-
brandia rosea which fruits all the year round. Rhodymenia palmata;
it miglit appear doubtful whether this species should be classed as
a perennial. Kjellman (36, p. 150) regards it as an annual plant
which forms tetraspores twice, once as a young plant and the
second time just before it dies. It appears to me that the new
slioots which arise early in spring from evidently old fronds, show
that it lives Ihrougli at any rate more than one period of growth.
Pelvetia canaliculata bears fruit and carries on vegetative work the
whole year at Reykjavík. In December—January the fruiting indi-
viduals were comparatively few, but there was a quantity of young
plants almost all of which were in the “rosette” stage. It is per-
haps doubtful if this species belongs to tliis group at all.
Group 2. The Fucaceœ belong to this group (with the exception
of Pelvetia (?)). Fucus spiratis produces fruit in spring, summer and
autumn. In December (1911) it was sterile, and young plants were
found in quantities.
Ascophijllum nodosum, Fucus vesiculosus and Fucus inftatus, all
these behave almost similarly. In December and January I saw,
here and there, individuals with very young receptacles, but by far
the greater part were sterile. In spring and early summer these
species are found everywhere witli full-grown receptacles. In the
latter half of August they are sterile everywhere and at that time
only a few individuals, which must be regarded as stragglers, are
found bearing receptacles. Of F. inftatus I saw no stragglers in Au-
gust. In September also they are sterile. In tlie first half of Octoher