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A. D. BONEY
15. Eucheum
A number of species of Eucheum are used as sources of agar, and
the Malayan term for this genus is now used for its extractive (p. 11 1).
Eucheum plants have flattened or terete much branched thalli, and
reproductive organs are borne in small lateral branchlets. Species of
Eucheum have been collected for agar extraction in Western Australia
(Chapman, 1950), although there appear to be difficulties in collecting
large quantities of the seaweed ; some utilization is also reported from
Indonesia. This genus haa for long been used on relatively small scale
extractions in Asia, and some knowledge of its autecology would be
welcome.
16. Irid0phycu.s: ( = Iridaea)
This genus is mainly found in intertidal habitats in the southern
hemisphere and on the shores of the North Pacific Ocean. It is harvested
m a source of extractive in Japan, and recent work on the biology of
Iridophycw cornmpiae has been reported (Hasegawa and Fukuhara,
1962, 1963, 1966a,b,c ; Fukuhara, 1968a). Plants bearing sexual
organs and those with tetrasporangia are found throughout the year,
but there are periods when one or the other predominates. Young
fronds appear on the discoid holdfast in October and November, and
whilst growth is slow in the following months, the rate increases
rapidly in March and April, and maximum annual growth is observed
in May and June. Some deterioration of the fronds is observed in
August and September, but new frondage is formed at the same
time, so that " summer " and " winter " fronds are observed. The best
time for harvesting the plant is in May and June, since the main
fruiting period is during the autumn and winter, Plants beaxing
cystocrtrps are said to be heavier than those with tetrasporangia.
Released spores show a rapid attachment to the substratum after
shedding, and from the primary disc a number of growing points am
formed, each " point " producing two fronds. Fukuhara (1967, 1968b)
waa unable to recognize any diurnal fluctuation in the quantities of
spores released, nor any effects due to tidal periodicity or water
temperature. The optimal range for spore germination was found to
lie between 7°-150C, although some development was possible over the
ranges of 3"-7"C and 16O-23OC. Sea temperatures closely approximate
the optimal range found in experiment during the main periods of
spore liberation.
A. D. BONEY
15. Eucheum
A number of species of Eucheum are used as sources of agar, and
the Malayan term for this genus is now used for its extractive (p. 11 1).
Eucheum plants have flattened or terete much branched thalli, and
reproductive organs are borne in small lateral branchlets. Species of
Eucheum have been collected for agar extraction in Western Australia
(Chapman, 1950), although there appear to be difficulties in collecting
large quantities of the seaweed ; some utilization is also reported from
Indonesia. This genus haa for long been used on relatively small scale
extractions in Asia, and some knowledge of its autecology would be
welcome.
16. Irid0phycu.s: ( = Iridaea)
This genus is mainly found in intertidal habitats in the southern
hemisphere and on the shores of the North Pacific Ocean. It is harvested
m a source of extractive in Japan, and recent work on the biology of
Iridophycw cornmpiae has been reported (Hasegawa and Fukuhara,
1962, 1963, 1966a,b,c ; Fukuhara, 1968a). Plants bearing sexual
organs and those with tetrasporangia are found throughout the year,
but there are periods when one or the other predominates. Young
fronds appear on the discoid holdfast in October and November, and
whilst growth is slow in the following months, the rate increases
rapidly in March and April, and maximum annual growth is observed
in May and June. Some deterioration of the fronds is observed in
August and September, but new frondage is formed at the same
time, so that " summer " and " winter " fronds are observed. The best
time for harvesting the plant is in May and June, since the main
fruiting period is during the autumn and winter, Plants beaxing
cystocrtrps are said to be heavier than those with tetrasporangia.
Released spores show a rapid attachment to the substratum after
shedding, and from the primary disc a number of growing points am
formed, each " point " producing two fronds. Fukuhara (1967, 1968b)
waa unable to recognize any diurnal fluctuation in the quantities of
spores released, nor any effects due to tidal periodicity or water
temperature. The optimal range for spore germination was found to
lie between 7°-150C, although some development was possible over the
ranges of 3"-7"C and 16O-23OC. Sea temperatures closely approximate
the optimal range found in experiment during the main periods of
spore liberation.