BIOLOGY OF SEAWEEDS O F ECONOMIC IMPORTANCE
173
development to those of P. yexoensis. It is also possible to find admixture of monosporangia and sexual organs on the same frond with
this species, but not so frequently as with P. yezoensis.
During the initial stages of frond growth monosporangia are found
on plants between 0-1-5-6 cm in length, and the monospores produced
germinate to form new thalli. The main season of monospore production appears to last from September to November, and whilst a few
plants bearing monosporangia are to be found throughout the winter
and into the spring, the “ carpospores )’ are the main reproductive cells
through the winter months. Plants bearing monosporangia, spermatangia and “ carpogonia ” are found on the “ hibi )’ during November.
Thus there is an upsurge in the number of plants bearing the sexual
organs after the early production of monospores. An unusual feature,
however, is that during the following spring and summer there is a
second “wave ” of monospore production at a time when “ carpospore ” formation has ceased. This may be due to the persistence of the
monosporangium-bearing plants throughout the winter (possibly in
small numbers), but may also be a result of the somewhat earlier
maturation of the sporangia in the Gonchocelis-phase. There is, in fact,
some evidence that the shell-boring phase commences to liberate
spores in June, to be followed by the prodigious output of the autumn
months. Whilst the laver fronds of this species may be found on the
“ hibi ” during early summer, they usually disappear in July, and very
few are found after this. Some variation in the seasonal life is observed
with habitat. The plant is harvested from December until May.
Porphyra pseudolinearis. This species has the shortest growth
period on the “hibi” and in consequence there is a much shorter
harvesting time. The young plants appear on the “ hibi ” in midSeptember, but monospore production is not observed, and spermatangia and ‘‘ carpogonia ” are first seen in early October. Release of
carpospores is observed- from October until mid-March. The “ carpospores ” produce the Conchocelis-phase when germinated on suitable
substrata, and the filaments grow throughout the summer liberating
monospores in September and October. With this species harvesting is
limited to the months of November and December.
The seasonal life of the cultivated Porphyra species described above
is also reflected in the changes in population which are observed when
‘‘ hibi ” are spread at different times of the year, particularly in areas
where there is some abundance of the different species. Thus, on nets
spread in the first half of September the dominant plants will consist
of P. linearis and P. kunieda, and the P. tenera and P. yezoensis will
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development to those of P. yexoensis. It is also possible to find admixture of monosporangia and sexual organs on the same frond with
this species, but not so frequently as with P. yezoensis.
During the initial stages of frond growth monosporangia are found
on plants between 0-1-5-6 cm in length, and the monospores produced
germinate to form new thalli. The main season of monospore production appears to last from September to November, and whilst a few
plants bearing monosporangia are to be found throughout the winter
and into the spring, the “ carpospores )’ are the main reproductive cells
through the winter months. Plants bearing monosporangia, spermatangia and “ carpogonia ” are found on the “ hibi )’ during November.
Thus there is an upsurge in the number of plants bearing the sexual
organs after the early production of monospores. An unusual feature,
however, is that during the following spring and summer there is a
second “wave ” of monospore production at a time when “ carpospore ” formation has ceased. This may be due to the persistence of the
monosporangium-bearing plants throughout the winter (possibly in
small numbers), but may also be a result of the somewhat earlier
maturation of the sporangia in the Gonchocelis-phase. There is, in fact,
some evidence that the shell-boring phase commences to liberate
spores in June, to be followed by the prodigious output of the autumn
months. Whilst the laver fronds of this species may be found on the
“ hibi ” during early summer, they usually disappear in July, and very
few are found after this. Some variation in the seasonal life is observed
with habitat. The plant is harvested from December until May.
Porphyra pseudolinearis. This species has the shortest growth
period on the “hibi” and in consequence there is a much shorter
harvesting time. The young plants appear on the “ hibi ” in midSeptember, but monospore production is not observed, and spermatangia and ‘‘ carpogonia ” are first seen in early October. Release of
carpospores is observed- from October until mid-March. The “ carpospores ” produce the Conchocelis-phase when germinated on suitable
substrata, and the filaments grow throughout the summer liberating
monospores in September and October. With this species harvesting is
limited to the months of November and December.
The seasonal life of the cultivated Porphyra species described above
is also reflected in the changes in population which are observed when
‘‘ hibi ” are spread at different times of the year, particularly in areas
where there is some abundance of the different species. Thus, on nets
spread in the first half of September the dominant plants will consist
of P. linearis and P. kunieda, and the P. tenera and P. yezoensis will