The Reproduction and Morphogeny in Codium fragile

Abstract

1. The field observations on the vegetation and sexuality of Codium fragile have been made for several years during 1940-1949 and 1951-1953 in the central region of the Pacific coast of Japan.The young plants begin to appear during early winter and spring, then they become luxuriant during early summer and late autumn. The reproductive organs (gametangia) are produced usually from May till December. As for the sexuality, most plants are dioecious and some are monoecious, while the sexual ratio and the ratio of monoecious to dioecious plants are varied in places or seasons.2. The gametes are anisomorphic, and the conjugation takes place between a macro (female)- and a micro (male)- gamete. The zygote develops into a tufty plant composed of non-septate, sympodially branched filaments. Though the shape of the free filament is variable, the contents of the filament or chromatophores are identical to those of C. fragile. This tufty vaucherioid plant survives over four years becoming much denser, but not into Codium-form probably owing to the unfavourable conditions in the culture vessel.3. From the field and laboratory observations, it is suggested that the frond of Codium may be made up by the interweaving of the sympodially branched filaments, producing in the beginning the prostrate basal portion then one or more erect portions. And also it is suggested that these filaments may be originate in a zygote or in a few zygotes: that is to say homogeneous or heterogeneous. If this assumption is acceptable, much variety in sex differentiation in Codium fragile seems to be explained by such flexibility in the process of the morphogeny.