The present investigation was carried on to clarify the effects of temperature, chlorinity of sea water and light upon the maturity of gametophytes and the early development of sporophytes of Undaria pinnatifida.
Results obtained may be summarized as follows:
1) Reproduction of sexual organs in gametophytes, both ? and ?, occurs usually below 20°C., and it does not occur higher above 23°C. (Fig. 2-A)
Sporophytes can develop below 20°C. They grow normally within 10-17°C. (Fig. 2-B)
(2) The maturation of gametophytes and the growth of sporophytes are affected by lower chlorinity less than 15‰. Cl. (Fig. 3-A, B)
(3) The maturation of gametophytes and the growth of sporophytes seem to be greatly affected by intensity and colour of illumination. A. rather higher intensity seems to be necessary for the formation of female sexual organs and for the development of sporophytes, as the processes are delayed or do not occur in dark or in reduced light. But the antheridia can be formed even in dark. (Fig. 4, 5)
4) Among variously coloured light, orange light was found unfit for the development of gametophytes and sporophytes.