194
A. D. BONEY
with the free-living form, and these are properties shared with the
attached forms of the plant, which also show regenerative growth after
wounding or casting of spent sporogenous tissue. Regenerated branches
which arise by active growth of the central axial filaments of the main
axis are distinguishable in later years because of the basal ring formed
by the remnants of older tissue which survive. The propagulae referred
t o above may become branched prior to their detachment from the
parent plant; in the mass of free-living material these propagulae
apparently form plants of a distinctly radial form. The free-living forms
of Furcellaria were considered by Austin (1960a) to be able to survive
because of a number of features of their biology. The plants must be
able to grow without attachment to the substratum, and live without
orientation to light or gravity. The thalli must be able to survive
almost continual rolling on the seabed, and partial burying in the mud
and sand. Finally, the plant must be able to carry out constant vegetative multiplication without loss of clonal vigour. These same features
must also apply to other free-living seaweeds, e.g. Phyllophora nervosa.
It would appear that the free-living form of Furcellaria is able to
contain by vegetative means the changes in standing crop following the
intensive harvesting by the collectors. Up to now there is no evidence
that the biomass has been critically lowered by the exploitation of the
last 14-15 years (p. 128). It is possible that this removal of part of the
population may have proved beneficial and encouraged growth of new
and more vigorous young branches. There seems no evidence that the
attached forms make any contribution to this free-living population.
The possibility remains, however, that the spores produced by the
attached intertidal forms drift down into sublittoral habitats and there
germinate to form the unattached plants directly. Burrows (1958)
has shown that the sublittoral algal population in Liverpool Bay can
be appreciably added to in this way. Austin (1955, 1960b,c,d) has
made a detailed study of the reproduction of the attached form in
the British Isles. The species show a typical alternation between
tetrasporophytes, male and female plants and carposporophytes. The
diploid tetrasporophytes are far more numerous than the gametophytes,
and the male and female plants occur in approximately equal numbers.
Fruiting appears to be a protracted process ; thus, the tetrasporangia
are initiated in April and steadily increase in size throughout the summer
and early autumn. The first division of the sporangia occurs during a
limited period in November (9th to 15th day), and this includes a
reduction division. The periodicity is apparently linked with a neap
tide cycle, and divisions of the nuclei were restricted to a few hours per
day (9 p m . to midnight). Liberation of the tetraspores occurs about
A. D. BONEY
with the free-living form, and these are properties shared with the
attached forms of the plant, which also show regenerative growth after
wounding or casting of spent sporogenous tissue. Regenerated branches
which arise by active growth of the central axial filaments of the main
axis are distinguishable in later years because of the basal ring formed
by the remnants of older tissue which survive. The propagulae referred
t o above may become branched prior to their detachment from the
parent plant; in the mass of free-living material these propagulae
apparently form plants of a distinctly radial form. The free-living forms
of Furcellaria were considered by Austin (1960a) to be able to survive
because of a number of features of their biology. The plants must be
able to grow without attachment to the substratum, and live without
orientation to light or gravity. The thalli must be able to survive
almost continual rolling on the seabed, and partial burying in the mud
and sand. Finally, the plant must be able to carry out constant vegetative multiplication without loss of clonal vigour. These same features
must also apply to other free-living seaweeds, e.g. Phyllophora nervosa.
It would appear that the free-living form of Furcellaria is able to
contain by vegetative means the changes in standing crop following the
intensive harvesting by the collectors. Up to now there is no evidence
that the biomass has been critically lowered by the exploitation of the
last 14-15 years (p. 128). It is possible that this removal of part of the
population may have proved beneficial and encouraged growth of new
and more vigorous young branches. There seems no evidence that the
attached forms make any contribution to this free-living population.
The possibility remains, however, that the spores produced by the
attached intertidal forms drift down into sublittoral habitats and there
germinate to form the unattached plants directly. Burrows (1958)
has shown that the sublittoral algal population in Liverpool Bay can
be appreciably added to in this way. Austin (1955, 1960b,c,d) has
made a detailed study of the reproduction of the attached form in
the British Isles. The species show a typical alternation between
tetrasporophytes, male and female plants and carposporophytes. The
diploid tetrasporophytes are far more numerous than the gametophytes,
and the male and female plants occur in approximately equal numbers.
Fruiting appears to be a protracted process ; thus, the tetrasporangia
are initiated in April and steadily increase in size throughout the summer
and early autumn. The first division of the sporangia occurs during a
limited period in November (9th to 15th day), and this includes a
reduction division. The periodicity is apparently linked with a neap
tide cycle, and divisions of the nuclei were restricted to a few hours per
day (9 p m . to midnight). Liberation of the tetraspores occurs about