BIOLOGY OF SEAWEEDS OF ECONOMIC IMPORTANCE
193
Picking the fronds which leaves the holdfasts undamaged ensures that
the density of the erect frondage will have recovered by the next year.
MacFarlane tested this by a number of methods ; in the first both fronds
and attaching discs were removed, and in the second the fronds were
cut by means of shears very close to the holdfasts. Methods of raking
were also tested, either by detaching the frondage without injury to
the holdfast, or by " over-raking ", with damage to and removal of the
attaching discs. The method which did least damage to the attaching
discs again ensured the most complete recovery of the plants, and dense
frondage was available after 6 months, whereas any serious damage
to the attaching discs delayed recovery for up to 2 years. The summer
months are the best times for harvesting Chndrus in the British Isles,
but the plant is a less valuable source than Gigartina. The large quantities of Chndrus available on the shores of Nova Scotia have already
been described (p. 130).
13. Furcellaria
The importance of Furcellaria fastigiata f. aegagrophila to the
Danish seaweed industry has already been mentioned (p. 128). The
most complete biological study of this free-living form was that made
by Austin (1960a) whilst continuing studies carried out on the seasonal
life of the attached forms of the same species (Austin, 1955, 1960a,b).
Since this plant is of potential economic value in other localities
(Kireeva, 1958) the extent to which the standing crop can sustain the
regular and intensive harvesting carried out in the Central Kattegat is
clearly of some importance. Austin found that 99% of the 1-14 cwt
" haul " obtained after a 10-min " sweep '' consisted of the free-living
plant. The lengths of the individual fronds varied from 1-16 cm
(mean 6 cm), compared with lengths of 15-25 cm as seen on attached
forms of the species growing in the same area. The branches of the
free-living form were appreciably thinner than those of the attached
form, and also characterized by numerous dichotomies. Large numbers
of adventitious branches were also observed, bearing basal " hapteron "like outgrowths which served to attach the branches to those of neighbouring plants. Numerous small outgrowths or " propagulm ", readily
detachable, were also observed on the upper branches, and were
considered to be a means of vegetative propagation.
All of the free-living material examined was sterile, so that maintenance of the standing crop is brought about solely by vegetative
means. This can in part be explained by the process of fragmentation
as new branches are formed after degeneration of the older parts of
the plant. In addition regenerative growth and proliferation are seen
A.x.B.-~
I
193
Picking the fronds which leaves the holdfasts undamaged ensures that
the density of the erect frondage will have recovered by the next year.
MacFarlane tested this by a number of methods ; in the first both fronds
and attaching discs were removed, and in the second the fronds were
cut by means of shears very close to the holdfasts. Methods of raking
were also tested, either by detaching the frondage without injury to
the holdfast, or by " over-raking ", with damage to and removal of the
attaching discs. The method which did least damage to the attaching
discs again ensured the most complete recovery of the plants, and dense
frondage was available after 6 months, whereas any serious damage
to the attaching discs delayed recovery for up to 2 years. The summer
months are the best times for harvesting Chndrus in the British Isles,
but the plant is a less valuable source than Gigartina. The large quantities of Chndrus available on the shores of Nova Scotia have already
been described (p. 130).
13. Furcellaria
The importance of Furcellaria fastigiata f. aegagrophila to the
Danish seaweed industry has already been mentioned (p. 128). The
most complete biological study of this free-living form was that made
by Austin (1960a) whilst continuing studies carried out on the seasonal
life of the attached forms of the same species (Austin, 1955, 1960a,b).
Since this plant is of potential economic value in other localities
(Kireeva, 1958) the extent to which the standing crop can sustain the
regular and intensive harvesting carried out in the Central Kattegat is
clearly of some importance. Austin found that 99% of the 1-14 cwt
" haul " obtained after a 10-min " sweep '' consisted of the free-living
plant. The lengths of the individual fronds varied from 1-16 cm
(mean 6 cm), compared with lengths of 15-25 cm as seen on attached
forms of the species growing in the same area. The branches of the
free-living form were appreciably thinner than those of the attached
form, and also characterized by numerous dichotomies. Large numbers
of adventitious branches were also observed, bearing basal " hapteron "like outgrowths which served to attach the branches to those of neighbouring plants. Numerous small outgrowths or " propagulm ", readily
detachable, were also observed on the upper branches, and were
considered to be a means of vegetative propagation.
All of the free-living material examined was sterile, so that maintenance of the standing crop is brought about solely by vegetative
means. This can in part be explained by the process of fragmentation
as new branches are formed after degeneration of the older parts of
the plant. In addition regenerative growth and proliferation are seen
A.x.B.-~
I