210
A. D. BONEY
et aZ., 1949). During April, when new frondage was forming, both yield
and the gelling qualities of the extract were low for plants from an
area harvested the previous year, but the physical properties of
extracts from untouched plants collected at the same time of year were
somewhat higher. Material collected a few weeks later gave extracts
with a higher gel strength. Subsequently the gel strength increased,
and reached a maximum value in September, falling off slowly through
the winter and then more rapidly with the approach of spring. A
similar seasonal analysis for Chondrus showed that both yield and gel
strength tended to improve from spring to autumn.
For Gelidium cartilagineum, the agarophyte used in the United
States, Cooper and Johnstone (1944) have shown that the major yields
of agar are obtained from plants harvested in the summer months, the
time of the year when the peak period of assimilatory activity is recorded. For Gelidium umansii, the agarophyte collected in Japan, Asano
et al. (1951) have reported a steady rise in agar content through
the summer, reaching a maximum in autumn and then falling again in
the winter months. The crude protein contents were the inverse of this.
Both from the point of view of chemical contents, and in order to allow
the necessary regeneration of new frondage, harvesting of Gigurtina
in the British Isles would best be carried out in July, August and early
September. I n Japan, the autumn would appear to be the most favourable time for collecting Gelidium umansii. With the red algae, as with
other crop plants, the time of harvesting must take into account the
best season for maximum yield of agar, to enable regeneration of new
frondage, and not to interfere with spore output. These times would
appear to vary with Gelidium species from different parts of the world.
VII. TECHNIQUES USED IN HARVESTINQ SEAWEED
Many of these have been indicated in earlier pages. Mechanical
cutters will be effective only when dense crops of weed are available,
e.g. Nacrocystis and Laminaria sp. Large-scale harvesting of Hacrocystis on the coast of California has been described by Tseng (1947),
and methods for harvesting Laminuria have been investigated by the
Institute of Seaweed Research in Scotland (Booth, 1964a). Dredging
by means of outboard trawls has been utilized with free-living seaweeds,
e.g. Furcellaria fastigiata f. aegagrophila in Danish waters (Austin,
1960a). Intertidal fucoid algae are reaped by means of hand cutting
methods such as those described above where there are fairly dense
" stands " of the seaweed. The need for controlled cutting of the
fucoid algae has already been described, whilst the continued heavy
cropping of the FurceZZuria fastigiuta f. aegagrophila seems to have left
A. D. BONEY
et aZ., 1949). During April, when new frondage was forming, both yield
and the gelling qualities of the extract were low for plants from an
area harvested the previous year, but the physical properties of
extracts from untouched plants collected at the same time of year were
somewhat higher. Material collected a few weeks later gave extracts
with a higher gel strength. Subsequently the gel strength increased,
and reached a maximum value in September, falling off slowly through
the winter and then more rapidly with the approach of spring. A
similar seasonal analysis for Chondrus showed that both yield and gel
strength tended to improve from spring to autumn.
For Gelidium cartilagineum, the agarophyte used in the United
States, Cooper and Johnstone (1944) have shown that the major yields
of agar are obtained from plants harvested in the summer months, the
time of the year when the peak period of assimilatory activity is recorded. For Gelidium umansii, the agarophyte collected in Japan, Asano
et al. (1951) have reported a steady rise in agar content through
the summer, reaching a maximum in autumn and then falling again in
the winter months. The crude protein contents were the inverse of this.
Both from the point of view of chemical contents, and in order to allow
the necessary regeneration of new frondage, harvesting of Gigurtina
in the British Isles would best be carried out in July, August and early
September. I n Japan, the autumn would appear to be the most favourable time for collecting Gelidium umansii. With the red algae, as with
other crop plants, the time of harvesting must take into account the
best season for maximum yield of agar, to enable regeneration of new
frondage, and not to interfere with spore output. These times would
appear to vary with Gelidium species from different parts of the world.
VII. TECHNIQUES USED IN HARVESTINQ SEAWEED
Many of these have been indicated in earlier pages. Mechanical
cutters will be effective only when dense crops of weed are available,
e.g. Nacrocystis and Laminaria sp. Large-scale harvesting of Hacrocystis on the coast of California has been described by Tseng (1947),
and methods for harvesting Laminuria have been investigated by the
Institute of Seaweed Research in Scotland (Booth, 1964a). Dredging
by means of outboard trawls has been utilized with free-living seaweeds,
e.g. Furcellaria fastigiata f. aegagrophila in Danish waters (Austin,
1960a). Intertidal fucoid algae are reaped by means of hand cutting
methods such as those described above where there are fairly dense
" stands " of the seaweed. The need for controlled cutting of the
fucoid algae has already been described, whilst the continued heavy
cropping of the FurceZZuria fastigiuta f. aegagrophila seems to have left