Drew3) has demonstrated that when carpospores of Porphyra umbilicalis (L.) Kutz. germinate on shell matrices, they penetrate into shell and give rise to Conchocelis-phase, described by Batters and Rosenvinge2) under the name of Conchocelis rosea. Drew presented further details of Conchocelis-phase and described the development of 'fertile cell-rows', but she did not find the liberation of spores from them. Recently, many investigators have observed that spores are formed in 'fertile cell-row' of Conchocelis-phase and they germinate into Porphyra thalli. In addition to 'fertile cellrows', Drew has shown 'plantlets' developed in the intestices of shells and on the surface of shell flakes in the cultures, but no spore formed on them. The present writer studied on the 'plantlets' of Porphyra these several years in the laboratory. Six species of Porphyra were studied; P. suborbiculata Kjellm., P. tenera Kjellm., P. kuniedai Kurogi (round type of P. tenera), P. seriata Kjellm., P. yezoensis Ueda prox. and P. pseudolinearis Ueda. Schreiber's, Drew's and Provassoli's solutions were used, for the cultures and usually they were charged every two weeks. The culture glass vessels were placed at 300-500 lux in light intensity. The temperature of the culture water was shown in Table 1. The results of observation are summarized as follows: 1. 'Plantlets' have develped on the surface of the shell, and they have been found to be in connexion with 'fertile cell-rows' inside the shell. 2. Although the 'plantlets' are observed all species of Porphyra used in this study, they are well developed especially in stenohaline species, such as P. suborbiculata, P. seriata and P. pseudolinearis. 3. In P. tenera, P. kuniedai and P. yezoensis prox., 'plantlets' have arisen on the shell after 'fertile cellrows' discharged spores. 4. The cells of these 'plantlets' are varied in diameter and length under the different culture conditions. Each cell of them contains a stellate plastid with a pyrenoid, but some narrow cells have no pyrenoid. 5. Asexual spores are liberated from the 'plantlets' during the autumn months and they have developed into leafy thalli of Porphyra. 6. The 'plantlets' did not develop directly to leafy thalli in the same culture in which Conchospores have given rise to them. 7. During the period of late autumn and winter, immature branches of 'plantlets' become narrow in size. Finally they grow to normal Conchocelis-filaments which are able to penetrate again into the shell. 8. It seems that the 'plantlet' and 'fertile cell-row' are essentially the same which is the Conchosporangium in Conchocelis-phase of Porphyra.

長崎大学水産学部研究報告, v.11, pp.128-136; 1961