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

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than plants in more cxpos ed placE: 5 or attached ImveY down the shore.
Dried specimens of all species range from light tannish brown
to almost black. Specimens previously preserved in fO~lalin often
dry g,"Ceenish"
Lamina shape is also highly variable. In three species with
vlh ich I am familiar, the d8gree of division of the lamina is largely
determined by wave force (South and Hay 1977) '"
ecolog'ical forms ot thallus occur r although intergrada tion between
them is common.
plants, chc:u,'aci:eristic of sernisheU:ered
pI Cl.ces, have an expanded deve lopment of the bJade,
in
the palmate region, and are only slightly divided.
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plants grow in areas l-lhere wave force is much st:ronge:c. Their
blades are deeply cleft into numerous narrow stri1ps or thongs. One
spp.r:ies (D. antarctica) has a thi.rd
form which grows on
s'teep cliffs where the jJUpact force of waves is exceptionally severe.
For more detailed description of these forms see 5"
Lamina margins may be diffen:mtiai:ed or undifferentiated
depending on the species. A aii feren tia ted margin is pa lerchan the
r.est of the lamina, and its surface is rough or even slightly callosec'!.
This character is only useful in areas where fish halJe not nibbled
away -che margins of the blades.
The lamina may be inflal:ed with honeycomh-.like tissue and
-cheref are buoyant I or it may be sol id and nonbuoyarJ t. Honeycomb
tissue can easily be detected by selecting a large specimen and
slicing down the middle of the blade parallel to its plane of
flatteni:og.
Apart from sponginess caused by the presence of honeycombing,
there are other textural differences bet',."e,-~n
The lall\inae
of some feel much firmer and more le."lthe:cy thCtil. others, and whereas
the surface of one species may be very smooth, that: of' another may
feel slightly rough.
The palm region of the blade may be smooth I OJ": it may be
covered Itli th fine cracks which are ilxranqed :I.n broken Goncent.):ic
rings. These are fine splits in the lnedstoderm e',no. outer cortex,
and are different frol'llthe 9:cooves on the stipe.
The presence or absence of stipi tate lateJ::al blades, OJ:' small
bud-like pxocesses on the lower ma:C9ins of the lamina