The Botany of Iceland - 01.12.1912, Síða 182

168
H.JÓNSSON
stagnea and Leathesia (living from June to Septeniber). In addition
there are species which may be su}>posed to be annual, as for
example, Pundaria, Stidyosiphon, Scgtosiphon (?), Phyllitis, the ma-
jority of the Didyosiphonaceœ, Chorda-species, etc.
Of Red Algæ the following must be presumed to be annual: —
Bangia, Porphyra-species, Porphyropsis, Conchocelis, Chantransia-
species, Ceramium-species and possibly several more. As regards
Porphyra umbilicalis it should, however, be stated that it has been
found at all seasons of the year and at Reykjavík it occurs as
luxuriantly in December—January as during the spring.
R. Perennial Algæ. With regard to some of the speeies it
is difficult to decide whether they are perennial or annual, as our
knowledge of them is incomplete; consequently it is sometimes a
matter of opinion whelher they are to be included in the one or
in the other group. Only a few of the Green Algæ are perennial,
as for instance, the majority of the Acrosiphonia-species. The latter,
besides being reproduced by spores, have also abundant vegetative
reproduction by means of offslioots; and some of them, as for in-
stance, A. albescens and others, live all the jæar round in the semi-
littoral zone.
Of the Rrown Algæ the Fucaceœ and the Laminariaceœ are
perennial. It is, however, doubtful whether we are justified in in-
cluding Saccorrhiza dermatodea among the perennials. At Reykjavík
I have seen only old fruiting specimens in the winter, and judging
from their appearance it is very probable that they die during the
winter; nothing can, however, be stated with certainty regarding
this point.
In the fjords of E. Iceland large individuals of this species were
growing in the sublittoral zone; I believe they were more than one
year old, but I could not prove this. In Greenland (Rosenvinge,
61, p. 852) perennial or upwards of a year old individuals of this
species occur.
With regard to several other species of Rrown Algæ it is not
easy to say at present whether they are annual or perennial. I
think, however, that the following may be classed as perennial: —
Lithoderma, Ralfsia-species, Sphacelaria-species, Chœtopteris, Desma-
restia aculeata, D. ligulata, Chordaria flagelliformis (?).
I think that the majority of the Red Algæ are perennial or
can, at any rate, live through more than one growth-period. I shall,