Abstract
In two dioecious species, i. e. Plagiochila ovalifolia (n=9) and Plag. japonica (n=9) have been found the structural sex-chromosomes; the largest heterochromosome of female and of male gametophytes of these species are sex-chromosomes X and Y respectively. The X and Y are, in the nuclear plate, the same in chromosomal morphology, but the difference between their heterochromat in was observed. The chromosome formulae of these species are as follows;
Plagiochila ovalifolia _??_8+X _??_8+Y
Plag. japonica _??_8+X _??_8+Y
