150
A. D. BONEY
region starts to decay and eventually growth of new tissue fails to
compensate for this process of apical breakdown. With general decay
of the blade and pneumatocyst the stipe is left bare in this region; and
on long stipes only a small proportion near the apex will ultimately
bear blades and pneumatocysts. On Tasmanian coasts decay of the
blade usually sets in 4 months after its date of initiation.
Quantitative data on the growth of young Macrocystis plants is also
available (Neushul and Haxo, 1963) from growth measurements made
in the sea by carefully transplanting the plants to submerged rafts and
under controlled laboratory conditions. When grown in the sea at a
depth of 15 m the plants doubled in area every 20-30 days, and in
length every 16-20 days during the autumn and winter months.
" Growth saturation " under laboratory conditions was measured at
1345 lux. Pressure effects were also found to be important, since
implosion of pneumatocysts would cause fronds to sink in the water
away from more adequate illumination. Growth studies are also
available for Macrocystis in New Zealand (Moore, 1943; Rapson et al.,
1943), and for Macrocystis integrifolia in British Columbia (Scagel,
1948).
The large plants described above represent the diploid sporophytic
generation-e.g. for Macrocystis integrifolia, 2n = 32 (Walker, 1952)and bear superficial sporangia in sori on specific blades (the sporophylls)
in the basal regions of the plant. Observations from a number of different regions indicate that fertile sporophylls are to be found at all
times of the y e a r 4 . g . Papenfuss (1942) for S. Africa, Brandt (1923)
and Neushul (1963) for California, and Cribb (1954) for Tasmania.
Brandt observed that zoospores germinated in early winter showed the
most rapid growth. Neushul described the various forms of sporophyll
and their productivity. In Southern California a conspicuous ring of
blue pigment surrounds the base of a fertile sporophyll. In many
instances up to 96% of the surface area of the sporophyll was found to
bear sporogenous tissue. Spore patches were observed to form and release their contents in about 2 weeks under controlled conditions.
The filamentous gametophytes have been described by Brandt
(1923), Delf and Levyns (1926) and Papenfuss (1942). Neushul (1963)
obtained growth of gametophytes, fertilization and young sporophytes
1-2 cm in length some 35-45 days after spore release from the sporophytes under a light intensity 1345 lux at 15°C. Gametophytes were
observed to grow at 237 lux-a much lower value than that required
for growth of the young sporophytes. Clendenning (1964) noted that
production of surface frondage from the sexual phase was a protracted
process, and a full " canopy " of fronds could take up to 2 years to
A. D. BONEY
region starts to decay and eventually growth of new tissue fails to
compensate for this process of apical breakdown. With general decay
of the blade and pneumatocyst the stipe is left bare in this region; and
on long stipes only a small proportion near the apex will ultimately
bear blades and pneumatocysts. On Tasmanian coasts decay of the
blade usually sets in 4 months after its date of initiation.
Quantitative data on the growth of young Macrocystis plants is also
available (Neushul and Haxo, 1963) from growth measurements made
in the sea by carefully transplanting the plants to submerged rafts and
under controlled laboratory conditions. When grown in the sea at a
depth of 15 m the plants doubled in area every 20-30 days, and in
length every 16-20 days during the autumn and winter months.
" Growth saturation " under laboratory conditions was measured at
1345 lux. Pressure effects were also found to be important, since
implosion of pneumatocysts would cause fronds to sink in the water
away from more adequate illumination. Growth studies are also
available for Macrocystis in New Zealand (Moore, 1943; Rapson et al.,
1943), and for Macrocystis integrifolia in British Columbia (Scagel,
1948).
The large plants described above represent the diploid sporophytic
generation-e.g. for Macrocystis integrifolia, 2n = 32 (Walker, 1952)and bear superficial sporangia in sori on specific blades (the sporophylls)
in the basal regions of the plant. Observations from a number of different regions indicate that fertile sporophylls are to be found at all
times of the y e a r 4 . g . Papenfuss (1942) for S. Africa, Brandt (1923)
and Neushul (1963) for California, and Cribb (1954) for Tasmania.
Brandt observed that zoospores germinated in early winter showed the
most rapid growth. Neushul described the various forms of sporophyll
and their productivity. In Southern California a conspicuous ring of
blue pigment surrounds the base of a fertile sporophyll. In many
instances up to 96% of the surface area of the sporophyll was found to
bear sporogenous tissue. Spore patches were observed to form and release their contents in about 2 weeks under controlled conditions.
The filamentous gametophytes have been described by Brandt
(1923), Delf and Levyns (1926) and Papenfuss (1942). Neushul (1963)
obtained growth of gametophytes, fertilization and young sporophytes
1-2 cm in length some 35-45 days after spore release from the sporophytes under a light intensity 1345 lux at 15°C. Gametophytes were
observed to grow at 237 lux-a much lower value than that required
for growth of the young sporophytes. Clendenning (1964) noted that
production of surface frondage from the sexual phase was a protracted
process, and a full " canopy " of fronds could take up to 2 years to