BIOLOGY OF SEAWEEDS OF ECONOMIC IMPORTANCE
205
cortex the gradient was in the opposite direction. The alginic acid
content was higher in the inner regions of the stipe. Young and Langville (1958) studied the inorganic elements in Laminaria digitata from
the Atlantic Provinces of Canada, and found that the trace elements
were present in greater quantity in the stipe than in the frond. A
further observation was that the plants showed a property of accumulating arsenic from the surrounding medium to appreciably high
quantities.
Reports are available on the seasonal analyses of Macrocystis. In
earlier years the plant was extensively used as a source of potash, and
detailed analyses were carried out with this in mind (summaries in
Chapman, 1950, and Cribb, 1954). Present day usage is mainly concerned with the alginic acid content. Sannie (1950) reported that
M . pyrifera from the Kerguelen Islands contained 17.65y0 alginic acid
and 4.15% mannitol in the dried fronds, 18.79% and 5.78% in the
stipes, and 20.94% and 6.07% of the two compounds respectively in
the bladders. Cribb (1954) analysed M . pyrifera plants from Tasmania
and found an alginic acid variation of between 16.2% in the winter
and 29.4% in late autumn ; for mannitol the variations ranged from
6 to 11.55%. Wort (1955) described the results of a seasonal analysis of
the chemical composition of two giant kelps, Macrocystis integt-ifolia
and Nereocystis leutkeana, from the seas off British Columbia. The
analyses included dry weights, ash, total nitrogen, total phosphorus,
trace elements, alginic acid, fucoidin, mannitol, laminarin and lipoid
substances. In general the fronds showed higher contents than the
stipes, and in both structures there was a parallel seasonal variation.
The dry weight and ash contents were maximal in late autumn and
winter, and at a minimum in spring. The mannitol, laminarin and
fucoidin contents were highest in summer. The quantity of alginic acid
showed little variation throughout the year. Cribb (1954) indicated
the probable source of errors in the analyses of Hmrocystis pyrifera
reported above, and it is possible that, as with the related species in
British Columbia, there are no wide variations in alginic acid content
over the year.
B. Brown algae: the Fumles
Black (194813, 1949) studied the seasonal variation in chemical
constituents of the fucoid algae commonly found on Scottish shores.
Thus, with Ascophyllum rwdosum it was found that the principal
extractives (mannitol, laminarin, alginic acid) showed slight seasonal
variation ; in consequence from the chemical aspect the plant could be
harvested at any time of the year. The slight increases in mannitol
205
cortex the gradient was in the opposite direction. The alginic acid
content was higher in the inner regions of the stipe. Young and Langville (1958) studied the inorganic elements in Laminaria digitata from
the Atlantic Provinces of Canada, and found that the trace elements
were present in greater quantity in the stipe than in the frond. A
further observation was that the plants showed a property of accumulating arsenic from the surrounding medium to appreciably high
quantities.
Reports are available on the seasonal analyses of Macrocystis. In
earlier years the plant was extensively used as a source of potash, and
detailed analyses were carried out with this in mind (summaries in
Chapman, 1950, and Cribb, 1954). Present day usage is mainly concerned with the alginic acid content. Sannie (1950) reported that
M . pyrifera from the Kerguelen Islands contained 17.65y0 alginic acid
and 4.15% mannitol in the dried fronds, 18.79% and 5.78% in the
stipes, and 20.94% and 6.07% of the two compounds respectively in
the bladders. Cribb (1954) analysed M . pyrifera plants from Tasmania
and found an alginic acid variation of between 16.2% in the winter
and 29.4% in late autumn ; for mannitol the variations ranged from
6 to 11.55%. Wort (1955) described the results of a seasonal analysis of
the chemical composition of two giant kelps, Macrocystis integt-ifolia
and Nereocystis leutkeana, from the seas off British Columbia. The
analyses included dry weights, ash, total nitrogen, total phosphorus,
trace elements, alginic acid, fucoidin, mannitol, laminarin and lipoid
substances. In general the fronds showed higher contents than the
stipes, and in both structures there was a parallel seasonal variation.
The dry weight and ash contents were maximal in late autumn and
winter, and at a minimum in spring. The mannitol, laminarin and
fucoidin contents were highest in summer. The quantity of alginic acid
showed little variation throughout the year. Cribb (1954) indicated
the probable source of errors in the analyses of Hmrocystis pyrifera
reported above, and it is possible that, as with the related species in
British Columbia, there are no wide variations in alginic acid content
over the year.
B. Brown algae: the Fumles
Black (194813, 1949) studied the seasonal variation in chemical
constituents of the fucoid algae commonly found on Scottish shores.
Thus, with Ascophyllum rwdosum it was found that the principal
extractives (mannitol, laminarin, alginic acid) showed slight seasonal
variation ; in consequence from the chemical aspect the plant could be
harvested at any time of the year. The slight increases in mannitol