The Botany of Iceland - 01.12.1912, Blaðsíða 161

MARINE ALGAL VEGETATION
147
is generally known, the species has very strong haptera, often ar-
ranged in rows, which issue from the lower part of the stipe, so
that the haptera appear one above the other in vertical succession.
They then look like a vertical row of obliquely placed props, one
above the other; such rows issue in all directions from the stipe.
By this it must be understood that, as the plant grows, new hap-
tera appear, usually in the regular succession mentioned, until such
time as the plant attains its normal size. The development of the
haptera must necessarily keep pace with the rest of the growth,
because the larger the plant becomes so much the more is it rnoved
by the waves, and so much the stronger must tlie props become
if the plant is not to be torn up. The youngest props are the
longest, and are situated at the extreme (upper) end of tlie row.
That the growth of the organs of attachment is contemporaneous
with the increase in size of the individual applies also, of course,
to the other Laminariaceœ, but scarcely anywhere is it seen so
distinctly as in this species.
In its main features L. hyperborea behaves in Iceland — at any
rate in S. and SW. Iceland — in the same manner as it is recorded
by Börgesen (12, p. 755) to behave in the Færöes.
The Under-vegetation. No doubt an abundant under-vege-
tation occurs everywhere, cliiefly formed of crustaceous algæ as a
lower layer, and of branching or membranaceous Rhodophyceœ and a
few Phœophyceœ in addition as an upper layer. Here, as in the Fucus-
belt, it must be assumed that the under-vegetation is of no real
value to the upper; while, on the other liand, the latter affords
protection to the under-vegetation — in the Fucus-belt against de-
siccation and too strong light, and in the Laminariaceœ-community
against strong movements of tlie water. The subdued light caused
by the Laminaria fronds is, no doubt, also of importance in the
upper portion of the Lamman'ö-belt, in so far, at any rate, that
the species with a more downward range may endeavour to attain
greater heights. In the lower portion of the Laminaria-belt the sub-
dued light does not seem to affect the under-vegetation very much
which seems to thrive there just as well as in open places where
Laminariaceœ are absent; to have the waves moderated may be
beneficial to the under-vegetation, especially in shallow water. During
excessive ebb-tides opportunities may occur in many places of seeing
how tlie Laminaria fronds moderate the motion of the waves, that
is when this is not too violent, as, for example, when it approxi-
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