The Botany of Iceland - 01.12.1912, Side 105

MARINE ALGAL VEGETATION
91
upper littoral zone, but not known below the limit of low-tide I
have also designated semi-Iittoral as they might be expected to
grow lower down.1
C. The Sublittoral Species.
These species play the principal röle in the sublittoral vegeta-
tion. This may be characterized in a somewhat similar manner as
the vegetation of the upper littoral zone, although conversely as
regards red and green algæ, viz. by a large number of red algæ
and an extremely small number of green algæ and by the occur-
rence of a mass of Laminariaceœ. In Table 7, these species are
marked with an s before the name. Their number is shown by
the following íigures: —
Red2 Brown Green Blue-green.. . Littoral 5 14 33 6 Species Semi-littoral 30 31 15 Sublittoral 39 22 3
Total. . . 58 76 64
From a comparison of tlie number of species of the sublittoral
zone with that of the littoral and semi-littoral zones it'is seen that
it is sinallest in the littoral zone, somewliat larger in the sublittoral
zone and considerably larger in the semi-littoral zone. Species of
green algæ occur most abundantly in the littoral zone, and their
number is infinitesimal in the sublittoral zone. Red algæ are most
nnmerous in the sublittoral zone and very scarce in the littoral
zone. The brown algæ are more evenly distributed in the different
zones, yet they are richest in species in the semi-littoral zone. The
blue-green algæ are found exclusively in the littoral zone.
In the semi-littoral zone the large brown algæ do not occur in
masses like, for example, the belt of Fucus in the upper littoral
1 As regards the majority of the species (see Table 7) it is easy to decide
whether they are littoral, semi-littoral or sublittoral, but therc are some species,
nevertheless, which it is difficult to refer definiteiy to any one of the three zones
mentioned, and therefore it is sometimes a matter of opinion whetlier they should
be reckoned in the one or the otlier. By perusing the table these species are
easih’ detected.
2 Two species, Delesseria Baerii and Bonnemaisonia asparagoides are not in-
cluded as their hahitat is unknown to me (see 31, pp. 140. 141).