天草増産に関する基礎的研究-V

Abstract

Some investigators have already reported that the ratio between the sexual and the asexual individuals, i.e. the cystocarpophytes and tetrasporophytes of Gelidium amansii, is much unbalanced on the natural rocks. From these observations they suggested that the occurrence of the alternation in generations of the life cycle of the present plant may be irregular. According to our investigations on the individuals of the G. amansii having grown on the artificial stone-bed, it was found that the female plants (cystocarpophyte) appear in greater number than the tetrasporophytes during one or two years after settling the bed (33-100%, mean value 64%. Fig. 1 and Table 1), while later they decreased gradually to 20-35% in three or four years after settling the bed, and finally, later than four years, the ratio carposporophyte to tetrasporophyte were about 18 (4-44): 57 (19-86), nearly the same as those on the natural rocks (Tables 1 and 2). Besides, it was also observed that among the new fronds sprouted out on the natural rocks after recovery from the “Isoyake Damage” (desert shore or burned shore) the number of cystocarpophyte and tetrasporophyte are almost equal.