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

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confined to the merist.oderm, then by peeling in this manner, the plants
would lose their means of growth. This does not happen because the
cells which are exposed subsequently divide t.o form a ne\'] band of cells.
It is therefore inadvisable to make a strong distinction b~twec~
the rneristoderm and the outer cortex. Herriott (1923:556) nlaoe ho
distinction at all, and referred sir!Wly to cortical or assimilatory
tissue.
5.3
(a)
Gennling development:
Naylor (1953a) and De1e'pine (1964) described the early development
of young sporelings.
Zygotes of D. antarotica and D. willana which I
cultured at Kaikoura in the 1973 winter and spring, developed at a
faster rate than those cultured by Naylor, but apart from this my own
observations (Fig. 5.3) substantiated their work.
OVa axe released in packages of four, surrounded by the endochiton
(Fig. 5.3al. The exochiton is left behind in the conceptacle. within
an hour or less, the endochiton ruptures, releasing the four ova ~lIhich
can then be fertilized. The time taken for th~ endochiton to rupture
is highly variable.
With some plants, isolated ova were observed
almost im.mediately after the concepto.cles began releasing.
It is
probable tha"t in some cases, the endochi ton ruptures inside the
coneptacle, or at the ostiole. Occasionally, the entire oogonium
(i.e. with both exochiton and endochiton) is discharged.
No significant difference behJeen the size of either these
packages or individual ova was found bebleen the two species (Table 5.1).
Table 5.1
Length of oogonia (without exochiton) and diameter of
ova of D, antarctica and D, willana.
Species
Mean length of ova
package ()Jm)
n
Ovum diarn.
(l-ffi\)
n
96.0 ± 208
30
34.0 ± 0.6
30
D. wi llana
94.B ± 3.4
17
35.1 ± 0 .. 8
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