FEMALE DOMINANT POPULATION OF COLPOMENIA-PEREGRINA (SCYTOSIPHONALES, PHAEOPHYCEAE)

The ratio of fertile male to female gametophytes of Colpomenia peregri na (Sauvageau) Hamel (Scytosiphonales, Phaeophyceae) was investigated through its reproductive season at Oshoro in Hokkaido, Japan. It was a bout 1:19 in the samples examined with determination by the size of ga metangia. Thirty-three culture strains were established from sporophyt ic discoid thalli collected from the field. Both female and male gamet ophytes appeared in 10 strains of these cultures, and only female game tophytes appeared in the remaining 23 strains. However, there was no s train in which only male gametophytes appeared in culture. These 10 st rains and 23 strains were considered to be derived from zygotic sporop hytes and female parthenosporophytes, respectively. Germination of unf used female and unfused male gametes was examined in culture. The abil ity for germination was much lower in male gametes than that in female gametes. Although, the cause of the female dominance of this species at Oshoro was discussed considering the presence or absence of female- like, asexual plants, the female dominance is chiefly due to the frequ ent occurrence of parthenogenesis of female gametes.