Conchocelis-Phase in the Life-History of Porphyra umbilicalis (L.) Kütz

Abstract

SEVERAL investigators, including Janczewski¹, Thuret and Bornet², Berthold³ and more recently Okamura, Onda and Higashi⁴, have successfully germinated the carpospores of various species of Porphyra and obtained thereby filamentous growths. However, it has never been clearly demonstrated step by step how the leafy thallus originated again, although some workers have succeeded in inducing further growth than others and made observations on which various theories have been based. Grubb⁵ describes the liberation of the contents of the terminal cell of a short swollen filament as well as empty swollen tips of others. Both Kylin⁶ and Rees^7,8 considered they saw evidence of the formation of monospores on the filaments, and it has been assumed that these germinated into the leafy thallus, although the possibility of such spores reproducing the filamentous stage cannot be ruled out. In Dangeard's⁹ view, the filamentous growth is protonemal, the leafy thallus developing on it as ‘buds'—a view contested by Rees⁷. At the other extreme, these filamentous growths from the carpospores have been considered pathological by Kunieda¹⁰, who asserts that the carpospores of the Japanese species, P. tenera Kjellmann, produced in the spring spend the summer in a resting condition. In the autumn, he considers they germinate direct into the leafy thallus, as do the monospores of all species which have been investigated. An earlier Japanese worker, Yendo¹¹, described the liberation of ciliated micro- and macrogametes from the original spore as well as other swollen cells of the filamentous growths ; but it seems possible such spores belonged to an endophytic fungus.