164
A. D. BONEY
in vessels in which its Conchocelis-phase had been cultured, the
direct link between the two was not clearly demonstrated.
At present the critical problem in Porphyra life-histories is seen in
the lack of any convincing data on the sexual process, and the stage
at which meiosis takes place. The data on this have been summarized
by Drew (1956) and Dixon (1963b), and each has stressed the absence
of any reliable information. Drew (1956) described two types of spore
which were formed in the Porphyra life-history ; monospores are formed
by a simple rounding-off of the contents of a vegetative cell, and smaller
spores formed by successive divisions of the contents of a mother cell.
Prior to the formation of the last type of spore many claims have been
made that fusion took place between the contents of the mother cell and
those of the spermatium, and that a reduction division then preceded
formation of the “ carpospores ”. This term has been used with reservations by a number of workers in the field. For one species for which
detailed cytological studies are available (P. purpurea) there is no
evidence of a reduction division. Krishnamurthy (1959) obtained the
same chromosome number in the cells of the leafy thallus, in the cells
producing spermatia, in the spore mother cells and the newly released
and germinating spores, and in the Conchocelis-phase. Magne (1952)
recorded only mitotic divisions in the nuclei of the “ carpospore ”producing cells of Porphyra linearis, but did indicate that a fertilization
process was to be observed. This lack of any convincing data on the
sexual fusion in Porphyra raises a problem in descriptive work, since it
is claimed that a fusion of spermatia and the contents of mother cells
does occur in the cultivated species of Porphyra in Japan and China.
A number of features of this fusion process have been described,
except the fusion of gamete nuclei.* Thus in the following account the
terms “ carpogonia ” and “ carpospore ” are used with the reservations outlined above. As pointed out by Dixon (1963b), no clear
explanation of the mass of conflicting data is possible without a
considerable amount of further critical work on the problem.
The significance of Drew’s observations on the Conchocelis-phase
in the Porphyra life-history will be indicated in the following pages. Its
importance to the Japanese seaweed industry has been immense, and a
tangible reminder of this is the granite memorial to the late Dr. K. M.
Drew erected by fishermen at Uzuchi, near Tokyo.
More recent reviews on the Porphyra life-history have been supplied
by Conway (1964a, b, c), with particular emphasis on the species
growing in the British Isles. I n this work also the question of gametic
* Fertilization in P q h y r a yezoensks has been described recently (Yebu, H. end
Tokide, J. (1963) BOCK F ~ o .
FGh. Hokkaido U ~ C ~ V .
14, 131-6).
A. D. BONEY
in vessels in which its Conchocelis-phase had been cultured, the
direct link between the two was not clearly demonstrated.
At present the critical problem in Porphyra life-histories is seen in
the lack of any convincing data on the sexual process, and the stage
at which meiosis takes place. The data on this have been summarized
by Drew (1956) and Dixon (1963b), and each has stressed the absence
of any reliable information. Drew (1956) described two types of spore
which were formed in the Porphyra life-history ; monospores are formed
by a simple rounding-off of the contents of a vegetative cell, and smaller
spores formed by successive divisions of the contents of a mother cell.
Prior to the formation of the last type of spore many claims have been
made that fusion took place between the contents of the mother cell and
those of the spermatium, and that a reduction division then preceded
formation of the “ carpospores ”. This term has been used with reservations by a number of workers in the field. For one species for which
detailed cytological studies are available (P. purpurea) there is no
evidence of a reduction division. Krishnamurthy (1959) obtained the
same chromosome number in the cells of the leafy thallus, in the cells
producing spermatia, in the spore mother cells and the newly released
and germinating spores, and in the Conchocelis-phase. Magne (1952)
recorded only mitotic divisions in the nuclei of the “ carpospore ”producing cells of Porphyra linearis, but did indicate that a fertilization
process was to be observed. This lack of any convincing data on the
sexual fusion in Porphyra raises a problem in descriptive work, since it
is claimed that a fusion of spermatia and the contents of mother cells
does occur in the cultivated species of Porphyra in Japan and China.
A number of features of this fusion process have been described,
except the fusion of gamete nuclei.* Thus in the following account the
terms “ carpogonia ” and “ carpospore ” are used with the reservations outlined above. As pointed out by Dixon (1963b), no clear
explanation of the mass of conflicting data is possible without a
considerable amount of further critical work on the problem.
The significance of Drew’s observations on the Conchocelis-phase
in the Porphyra life-history will be indicated in the following pages. Its
importance to the Japanese seaweed industry has been immense, and a
tangible reminder of this is the granite memorial to the late Dr. K. M.
Drew erected by fishermen at Uzuchi, near Tokyo.
More recent reviews on the Porphyra life-history have been supplied
by Conway (1964a, b, c), with particular emphasis on the species
growing in the British Isles. I n this work also the question of gametic
* Fertilization in P q h y r a yezoensks has been described recently (Yebu, H. end
Tokide, J. (1963) BOCK F ~ o .
FGh. Hokkaido U ~ C ~ V .
14, 131-6).