The Botany of Iceland - 01.12.1912, Qupperneq 94

V. THE VERTICAL DISTRIBUTION OF THE SPECIES.
If we walk along the beach at low-tide we see a belt Iaid bare,
the breadth of which varies according to the degrees of declivity
of the coast and according to the tides — that is according to
whether it is spring-tide or neap-tide. At spring-tide the belt is
broad and at neap-tide narrow. The low-water mark of neap-tide
divides the belt laid bare into two parts, an upper part which is
laid bare during every low-tide and a lower part which is laid bare
only at and about spring-tide. The upper part, between the upper
limit of growth of the algal vegetation and the low-water mark of
neap-tide, which almost coincides with the lower edge of the Fucaceœ-
belt, I call the Upper Littoral Zone. The lower part, from the
lower edge of the Fucaceœ-belt to the usual1 low-water mark of
spring-tide, I call the Lower Littoral Zone. Below low-water mark
of spring-tide begins the vegetation which is constantly submerged.
That the vegetation of the lower littoral zone is closely connected
with that in the upper part of the constantly-submerged zone is
natural and will be discussed subsequently.
In the following table a dash (—) denotes a habitat (depth) in
which the species has been found many times, and a dot (•) one
in which it has been found either once or comparatively rarely.
Table 7. The Vertical Distribution of the Species.
Litto- ral zone Depth (metre)
iipper lower o 2 1 1 i 'ö 7 o ca «o lO CM _l (M o o M 31—35 .10 40 41—45 o irt 1 o if5 o o o 1 o o o co o r- l lO oo oo
Rhodophyceæ. I
1 Bangia fuscopurpurea —|
sl Porphyra miniata — — —
1 No notice is taken of the extraordinarily low ebb-tides which occasionally
occur and by which large Laminariœ are often exposed.