180
A. D. BONEY
dense pigmentation. Long periods in darkness (20-23 h) resulted in a
more stunted growth and greenish colour of the filaments. Actual
growth was best observed under long-day conditions, whilst the rates of
growth varied with the different light intensities used. Formation of
monosporangia commenced only when the filaments were kept under
short-day conditions, and in cultures kept in the dark for 14-23 h/day
monosporangia were obtained in large numbers at all levels of filaments
growth within the shell. Shortening of the dark period at this time,
(e.g. to 9-12 h) resulted in monosporangia being formed only on the
innermost branches, but any further reduction in the dark period
markedly reduced sporangium formation. The general results quoted
above appear to be true of the five species of Porphyra cultivated in
Japan. These experimental results show some measure of agreement
with what is known about the seasonal life of the cultivated lavers in
Japan, since the main period of growth of the Conchocelis-phase is in the
summer, but that formation of sporangia and release of spores is mainly
observed under short-day conditions (Fig. 10). For example, Taneka
(1959) studied the condition of the Conchocelis filaments in mollusc
shells kept on the seabed over the course of a year and verified much of
the experimental data summarized above ; growth of the filaments was
also observed, however, between Kovember and March, indicating
that some development of the filaments follows the earliest settlements
of '' carpospores " on shell surface. Iwasaki (1961) and Iwasaki and
Matsudaira (1963) studied the growth of the free-living filaments of
Porphyra tenera obtained by germination of the " carpospores ".
Their results are a general confirmation of those already quoted above,
with growth of the filaments under long-day conditions ; and growth of
the leafy Porphyra thallus and formation of the monosporangia on the
filaments under short-days. Release of spores from the monosporangia
appears to be affected by photoperiodism (p. 168). When the freeliving Conchocelis filaments were kept under a long-day regime for a
protracted period under controlled temperature conditions three types
of plant " body '' were obtained, (a) inflated spherical cells, (b) " strawberry "-like structures, and (c) " special " sporangia. The first two
structures were obtained at temperatures greater than 18°C. The
inflated spherical structures produced single spores which formed
Conchocelis filaments on germination, and the spore-like bodies produced by the " strawberry " structures also produced similar filaments.
The " special " sporangia showed a different type of behaviour. Two
types of plantlet were obtained, depending on whether the spores were
grown under long- or short-day conditions. It was also observed that
fragments of the Conchocelis filaments could reproduce by vegetative
A. D. BONEY
dense pigmentation. Long periods in darkness (20-23 h) resulted in a
more stunted growth and greenish colour of the filaments. Actual
growth was best observed under long-day conditions, whilst the rates of
growth varied with the different light intensities used. Formation of
monosporangia commenced only when the filaments were kept under
short-day conditions, and in cultures kept in the dark for 14-23 h/day
monosporangia were obtained in large numbers at all levels of filaments
growth within the shell. Shortening of the dark period at this time,
(e.g. to 9-12 h) resulted in monosporangia being formed only on the
innermost branches, but any further reduction in the dark period
markedly reduced sporangium formation. The general results quoted
above appear to be true of the five species of Porphyra cultivated in
Japan. These experimental results show some measure of agreement
with what is known about the seasonal life of the cultivated lavers in
Japan, since the main period of growth of the Conchocelis-phase is in the
summer, but that formation of sporangia and release of spores is mainly
observed under short-day conditions (Fig. 10). For example, Taneka
(1959) studied the condition of the Conchocelis filaments in mollusc
shells kept on the seabed over the course of a year and verified much of
the experimental data summarized above ; growth of the filaments was
also observed, however, between Kovember and March, indicating
that some development of the filaments follows the earliest settlements
of '' carpospores " on shell surface. Iwasaki (1961) and Iwasaki and
Matsudaira (1963) studied the growth of the free-living filaments of
Porphyra tenera obtained by germination of the " carpospores ".
Their results are a general confirmation of those already quoted above,
with growth of the filaments under long-day conditions ; and growth of
the leafy Porphyra thallus and formation of the monosporangia on the
filaments under short-days. Release of spores from the monosporangia
appears to be affected by photoperiodism (p. 168). When the freeliving Conchocelis filaments were kept under a long-day regime for a
protracted period under controlled temperature conditions three types
of plant " body '' were obtained, (a) inflated spherical cells, (b) " strawberry "-like structures, and (c) " special " sporangia. The first two
structures were obtained at temperatures greater than 18°C. The
inflated spherical structures produced single spores which formed
Conchocelis filaments on germination, and the spore-like bodies produced by the " strawberry " structures also produced similar filaments.
The " special " sporangia showed a different type of behaviour. Two
types of plantlet were obtained, depending on whether the spores were
grown under long- or short-day conditions. It was also observed that
fragments of the Conchocelis filaments could reproduce by vegetative