168
A. D. B O m Y
continue to grow throughout the summer and it liberates its monospores (or " conchospores ") from mid-September to early November,the time of spreading the " hibi ". The copious release of spores in the
sea was known long before the association of the Conchocelis- phase with
the Porphyru plants had been demonstrated. Various interpretations
as to the origins of these spores have been given. Thus Kusakabe
(1929) suggested that Porphyru plants from the previous spring sowing
of " carpospores " were the sources, and Ueda (19294 stated that this
autumnal " flush " of spores came from Porphyra plants which were
able to survive through the summer months.
Sea temperatures fall from 25OC to 15'C during the early part of the
growth season in the Matsushima district of Japan. It is in this same
temperature range that both maturation of spores of the Conchcelisphase and their liberation are observed (Kurogi and Hirano, 1956a, b).
Whilst dense spore settlements are obtained when " hibi " are spread
from mid-September to early October in North Japan, in South Japan
the time of spore settlement is mainly observed in October (Kurogi,
1961). Even during this time monospore production and settlement
have been observed to show periodicity. " Hibi " spread on the 2nd,
3rd and 4th days following the 1st or 15th days of a lunar month
apparently show the most dense spore settlements. Dense spore settlements are also obtained after heavy seas, but a marked fall in the
spore population is observed after heavy rain.
The period of growth of Porphyra tenera in Japan is a relatively
short season which coincides with reduction in day length and a fall in
sea temperature. Since the Conchcelis-phase grows throughout the
summer months it is evident that day length and temperature must
influence this phase in the life history. Iwasaki (1956) has given experimental verification of this. Young germlings (0.5 cm in length)
obtained from monospores of the Conchocelis-phase were grown at
controlled temperature (14'-16"C) in a light regime of 13 h daily
illumination, using an incandescent light source (400-500 ft candles).
Control plants were illuminated for 8 h daily. Thalli of the narrowfronded Porphyra developed in the control material whereas the longday samples produced plants of irregular shape which became pale in
colour; after 40 days these plants produced spores, (considered to be
functionally the same as"' carpospores '7, which on germination again
formed the Conchocelis-phase. The 13 h daily illumination corresponds
with that obtained in late April in localities where the plant is cultivated
in Japan; at this time also degeneration of the fronds proceeds at a
rapid pace. By contrast the Conchcelis-phase grows best under longday conditions.
A. D. B O m Y
continue to grow throughout the summer and it liberates its monospores (or " conchospores ") from mid-September to early November,the time of spreading the " hibi ". The copious release of spores in the
sea was known long before the association of the Conchocelis- phase with
the Porphyru plants had been demonstrated. Various interpretations
as to the origins of these spores have been given. Thus Kusakabe
(1929) suggested that Porphyru plants from the previous spring sowing
of " carpospores " were the sources, and Ueda (19294 stated that this
autumnal " flush " of spores came from Porphyra plants which were
able to survive through the summer months.
Sea temperatures fall from 25OC to 15'C during the early part of the
growth season in the Matsushima district of Japan. It is in this same
temperature range that both maturation of spores of the Conchcelisphase and their liberation are observed (Kurogi and Hirano, 1956a, b).
Whilst dense spore settlements are obtained when " hibi " are spread
from mid-September to early October in North Japan, in South Japan
the time of spore settlement is mainly observed in October (Kurogi,
1961). Even during this time monospore production and settlement
have been observed to show periodicity. " Hibi " spread on the 2nd,
3rd and 4th days following the 1st or 15th days of a lunar month
apparently show the most dense spore settlements. Dense spore settlements are also obtained after heavy seas, but a marked fall in the
spore population is observed after heavy rain.
The period of growth of Porphyra tenera in Japan is a relatively
short season which coincides with reduction in day length and a fall in
sea temperature. Since the Conchcelis-phase grows throughout the
summer months it is evident that day length and temperature must
influence this phase in the life history. Iwasaki (1956) has given experimental verification of this. Young germlings (0.5 cm in length)
obtained from monospores of the Conchocelis-phase were grown at
controlled temperature (14'-16"C) in a light regime of 13 h daily
illumination, using an incandescent light source (400-500 ft candles).
Control plants were illuminated for 8 h daily. Thalli of the narrowfronded Porphyra developed in the control material whereas the longday samples produced plants of irregular shape which became pale in
colour; after 40 days these plants produced spores, (considered to be
functionally the same as"' carpospores '7, which on germination again
formed the Conchocelis-phase. The 13 h daily illumination corresponds
with that obtained in late April in localities where the plant is cultivated
in Japan; at this time also degeneration of the fronds proceeds at a
rapid pace. By contrast the Conchcelis-phase grows best under longday conditions.