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

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CHAPTER FIVE
MORPHOLOGY
5.1 INTRODUCTION
Since Chamisso's 1822 account of D. antaY>CJtiea (as Pueus
anta:t'eticuB), there have been fficmy descriptions of its external
morphology. Previous tllorphologica.l info:t"ma.tion on D, wi llano is
scarce, and the original descript.ion (Lindauer 1949) was inadequate.
With few exceptions, previous workers failed to appreciate the high
degree of morphological plasticity exhibited by the more widely
distributed D. antarctica. This diversity is documented here for
New Zealand populations, and an att~npt is made to relate this
variation to certain physical and biological factors. The features
most important in this respect are: overall plant size, the degree of
subdivision of the lamina, the shape of the palmate region, the e,(tent
of inflatory or honeycomb tiSSUe, stipe size (especially relative to
the size of the lamina) and the shape and size of holdfasts.
Anatomical studies made during the course of this investigation
largely substantiated the earlier observations of Naylor (1949; 1953)
and Herriott (1923), Remarks here are mainly restricted to points
indicating discrepancies or additions to the published accounts.
5. 2 REMARKS CONCERNING THE ANATOMY OF DURVILLAEA
Holdfasts of individual DuroiUaBQ plants often fuse ,\lith each
other to form a composite holdfast mass. and this fusion of differen't
holdfasts is often so complete that it is difficult to detect where
Lhey are joined (Herriott 1923:552), (Fig, 5,.lh)
Fusion. between holdfasts may. occur at all stages throughout the
life of Dur>vittaea plants, and appears to be a more common occurrence
with D. antaratica than D. wi llana, Up to four holdfasts have been
found fused when plants were only 0,5-LO em long, and only CJ. few
weeks old. The fact that rhizoids of different germlings become
in.terwoven under culture conditions, suggests that fusion lnay even
occur at the gerrnling stage.
The holdfasts of two DurvitZaea species are capable of fusing
to form a composite holdfast,
D. antaretiaa and D. wiZZana holdfasts
o.re occasionally found fused togethel:: in the transition region between
the t.wo zon e s ,