A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...

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where the impact force of waves is less severe.
The high impact form is found almost exclusively on cliff
coasts, particularly on the seaward faces of rocky projections which
jut out into narrow channels or guts. They contrast markedly with
other D. antarctica specimens grOWing on the channel sides. and
consequently parallel to the direction of the wave (Figs. 5.7; 5.9).
In areas of yet higher impact force, D. antarotioa does not occur.
(ii) Thonged fO~l(Figs. 5.6d-f~ 5.Ba.c)
The narrow D. antarctioa hand on steep outer coasts of New
Zealand, the s ubantar cti c islands, the Chatham Is lands and southern
South America is dominated by a form which I have called thonged I.
These plants commonly exceed 5 m and may weigh 25 kg. Their laminae
are variably divided into numerous (at Tautuku there are commonly
more than 150) long. narrow (1-5 em) whip-like thongs. These are
highly honeyoombed, and appear circular or oval in cross section.
The thickness of this honeycombing commonly exceeds 15 rom. At
three localities where wave force is very strong, the degree of
lamina division and honeycombing of more than 50% of D. antarctica
plants was rated between "medium" and "high" (Fig. 5.4).
Stipes are large, reaching 50 l'I\1T\1 thick, and occasionally 80 rom
thick. Hold£asts are dome shaped or distinctly conical.
Chamisso's illustration of Fucue antaroticuB (Fig. 310) is identical
to thonged specimens in southern New Zealand. The size of the palmate
region varies considerably depending on the age of the plant
(Fig. 5.4). Sometimes only the distal third of the lamina is split
into the narrow whip-like thongs, while in older specimens, the
thongs extend the full length of the lamina. When the palmate
region is small, as in chamisso's illustration, then it is usually
solid and leathery. More expansive palmate regior,:. are frequently
slightly honeycombed.
In South and Hay (1977) these plants were described as "braided".
We have subsequently decided that the long narrow divisions of
the laminae are more accurately described as thongs rather than
braids.