200
A. D. BONEY
following May, when the plants reach maximum size and are the most
numerous on the shore. Thereafter there is a decline in population, and
plants bearing carposporangia and those with tetrasporangia are found.
The larger plants are found in the lower part of the shore zone. Since
the plants grow in habitats where there is some degree of exposure to
air, large boulders are sometimes placed on shelves of rock which may
not be sufficiently uncovered by the sea at times of low water in order
to provide more suitable conditions for the growth of Gloiopeltis
(Yendo, 1914). Culture studies have shown that spore attachment by
Gloiopeltis occurs in considerable quantities on quartzite, and few other
algal spores can so effectively attach themselves to this type of rock.
Prolonged ecological observations on G. furcata have shown that
this high-zoned plant first forms a closed community on the shore, but
may in time become overgrown by Ulva pertusa (Uzike, 1956). In
experiments in which " belt transects " were cleared down the shore
and all the seaweed growth removed, the zones of the dominating
species (including G. furcata) tended to widen appreciably after recolonization (Katada and Matsui, 1953).
Suto (1949) observed some periodicity in spore release with this
species. Fertile fronds collected at low tide were observed to release
their spores in the laboratory 30 min before the next flood tide. If the
spores obtained in this way were then " sown '' just before a flood tide
by broadcasting them over the shore, it was estimated that about 30%
of the sown spores would attach themselves to the rock. I n the following
autumn young plants would appear, and these would occur in numbers
equal to about ten plants per em2 of substratum. Suto (1950a) stated
that a daily release of spores was obtained, and that attachment was
most likely immediately after release from the sporangia. Matsui
(1956, 1957, 1959) reported on the discharge of spores from both
Gloiopeltis furcata and G. tenax. With G. tenax exposure to air and
drying tended to induce release of tetraspores, whereas with G . furcata
drying delayed the time of spore shedding. With both species, however,
an increased spore output was observed when the fronds were dried
under " shade '' conditions. I n general, the quantities of spores
released were observed to increase appreciably at the time of " spring "
tides. Information of this nature is of value for the methods of sowing
spores described above.
VI. QUANTITATIVE CRANQES IN SEAWEED EXTRACTIVES AND OTHER
CONSTITUENTS DUE TO SEASON AND ENVIRONMENT
The principal extractives of brown and red algae were briefly
discussed earlier (p. 111). Any quantitative estimate of the seasonal
A. D. BONEY
following May, when the plants reach maximum size and are the most
numerous on the shore. Thereafter there is a decline in population, and
plants bearing carposporangia and those with tetrasporangia are found.
The larger plants are found in the lower part of the shore zone. Since
the plants grow in habitats where there is some degree of exposure to
air, large boulders are sometimes placed on shelves of rock which may
not be sufficiently uncovered by the sea at times of low water in order
to provide more suitable conditions for the growth of Gloiopeltis
(Yendo, 1914). Culture studies have shown that spore attachment by
Gloiopeltis occurs in considerable quantities on quartzite, and few other
algal spores can so effectively attach themselves to this type of rock.
Prolonged ecological observations on G. furcata have shown that
this high-zoned plant first forms a closed community on the shore, but
may in time become overgrown by Ulva pertusa (Uzike, 1956). In
experiments in which " belt transects " were cleared down the shore
and all the seaweed growth removed, the zones of the dominating
species (including G. furcata) tended to widen appreciably after recolonization (Katada and Matsui, 1953).
Suto (1949) observed some periodicity in spore release with this
species. Fertile fronds collected at low tide were observed to release
their spores in the laboratory 30 min before the next flood tide. If the
spores obtained in this way were then " sown '' just before a flood tide
by broadcasting them over the shore, it was estimated that about 30%
of the sown spores would attach themselves to the rock. I n the following
autumn young plants would appear, and these would occur in numbers
equal to about ten plants per em2 of substratum. Suto (1950a) stated
that a daily release of spores was obtained, and that attachment was
most likely immediately after release from the sporangia. Matsui
(1956, 1957, 1959) reported on the discharge of spores from both
Gloiopeltis furcata and G. tenax. With G. tenax exposure to air and
drying tended to induce release of tetraspores, whereas with G . furcata
drying delayed the time of spore shedding. With both species, however,
an increased spore output was observed when the fronds were dried
under " shade '' conditions. I n general, the quantities of spores
released were observed to increase appreciably at the time of " spring "
tides. Information of this nature is of value for the methods of sowing
spores described above.
VI. QUANTITATIVE CRANQES IN SEAWEED EXTRACTIVES AND OTHER
CONSTITUENTS DUE TO SEASON AND ENVIRONMENT
The principal extractives of brown and red algae were briefly
discussed earlier (p. 111). Any quantitative estimate of the seasonal