BIOLOGY OF SEAWEEDS O F ECONOMIC IMPORTANCE
213
regions of the shore where the agar-weeds were growing. He found that
spores occurred in greater numbers near the top of a submerged reef
bearing large numbers of Amphiroa plants, and that these spores
tended to drift in the surface layers over considerable distances from
the point where they were released. The harmful effects of Amphiroa
and related genera is due to their calcareous nature, and calcification of
the cell walls is observed at the earliest stages of plant growth (Furuya,
1960).
IX. SEAWEEDS AS POOD AND UURES
A. Seaweeds as h u m n food
Although marine algae have been utilized as a direct source of food
by coast dwellers in different parts of the world for many years, in
general the seaweeds are a poor source of nutrition. Whilst the carbohydrate contents of the thalli are fairly large, the quantities of protein
and fat are relatively small; and although carbohydrates are good
sources of energy, the algal polysaccharides are poorly digested by
man. The food value of marine algae lies mainly in their mineral salt
and vitamin content. The variety of ways in which seaweeds are directly
utilized have been described by Chapman (1950), Newton (1951, 1963)
and Scagel (1961). The value of the trace element content of Macrocystis in treatment of anaemia, debility, digestive upsets and geriatrio
conditions has been reported by Siefert and Wood (1956).
I n recent years there have been reports of tests on the edibility
of marine algae used as human food. Thus the flavour of the green
seaweeds Ulva pertusa and Enteromorpha prolifera has been studied by
Obata et al. (1951), and was considered to be due to the production of
dimethyl sulphide. The flavour was scarcely detectable in fresh thalli,
but gradually developed when left in seawater. On sterilized portions
of the thallus the flavour developed only after inoculation with bacteria.
The free amino-acid content of Porphyra tenera was analysed by
Tsuchiya and Sasaki (1957), who identified a number of " sweet ''
and " flavour-producing " amino acids. Miura (1961), describing a
new species of Porphpra ( P . tenuipedalis), found its taste inferior to
that of other Japanese lavers. Hampson (1957) reported that in
South Wales the lavers collected during the summer months showed a
definite loss of flavour, and a souring of the thalli took place in hot
weather. This is put forward as a reason for people not utilizing the
lavers when there was no " r " in the month. Information is also available on the extractive content and quality of kombu in Japan (Oishi
et al., 1961a). The ratio of amino-nitrogen to total nitrogen was always
higher in better quality kombu. Further investigations were carried
213
regions of the shore where the agar-weeds were growing. He found that
spores occurred in greater numbers near the top of a submerged reef
bearing large numbers of Amphiroa plants, and that these spores
tended to drift in the surface layers over considerable distances from
the point where they were released. The harmful effects of Amphiroa
and related genera is due to their calcareous nature, and calcification of
the cell walls is observed at the earliest stages of plant growth (Furuya,
1960).
IX. SEAWEEDS AS POOD AND UURES
A. Seaweeds as h u m n food
Although marine algae have been utilized as a direct source of food
by coast dwellers in different parts of the world for many years, in
general the seaweeds are a poor source of nutrition. Whilst the carbohydrate contents of the thalli are fairly large, the quantities of protein
and fat are relatively small; and although carbohydrates are good
sources of energy, the algal polysaccharides are poorly digested by
man. The food value of marine algae lies mainly in their mineral salt
and vitamin content. The variety of ways in which seaweeds are directly
utilized have been described by Chapman (1950), Newton (1951, 1963)
and Scagel (1961). The value of the trace element content of Macrocystis in treatment of anaemia, debility, digestive upsets and geriatrio
conditions has been reported by Siefert and Wood (1956).
I n recent years there have been reports of tests on the edibility
of marine algae used as human food. Thus the flavour of the green
seaweeds Ulva pertusa and Enteromorpha prolifera has been studied by
Obata et al. (1951), and was considered to be due to the production of
dimethyl sulphide. The flavour was scarcely detectable in fresh thalli,
but gradually developed when left in seawater. On sterilized portions
of the thallus the flavour developed only after inoculation with bacteria.
The free amino-acid content of Porphyra tenera was analysed by
Tsuchiya and Sasaki (1957), who identified a number of " sweet ''
and " flavour-producing " amino acids. Miura (1961), describing a
new species of Porphpra ( P . tenuipedalis), found its taste inferior to
that of other Japanese lavers. Hampson (1957) reported that in
South Wales the lavers collected during the summer months showed a
definite loss of flavour, and a souring of the thalli took place in hot
weather. This is put forward as a reason for people not utilizing the
lavers when there was no " r " in the month. Information is also available on the extractive content and quality of kombu in Japan (Oishi
et al., 1961a). The ratio of amino-nitrogen to total nitrogen was always
higher in better quality kombu. Further investigations were carried