たかねすいばノ性染色體ニ就キテ (豫報)

抄録

1. The diploid number of chromosomes in the male plant of Rumex monlanus DESF. is 15 and that of the female 14 as in Rumex acelosa L. Of the 15 chromosomes in the male plant, 12 are autosorties and the remaining 3 sex chromosomes, and of the 14 chromosomes in the female, 12 are autosomes and the rest sex chromosomes. The two sex chromosomes in the somatic division of the female plant are V-shaped (X-chromosomes) and among the three sex chromosomes in the male plant, one is V-shaped (X-chromosome) while the two are J-shaped (Y₁ and Y₂-chromosomes): The latter are smaller than the X-chromosome but larger than any of the autosomes.
2. At the heterotypic metaphase in the pollen-mother-cell, 6 gemini and one tripartite chromosome are observed, and at the heterotypic anaphase, the median (X-chromosome) of the tripartite chromosome goes to the one pole and the terminal ones (Y₁ and Y₂-chromosomes) to the other, as in the case of R. aceiosa L. Sometimes one or two of the 6 gemini form the chromosome-bridge at the heterotypic anaphase but the tripartite chromosome has no connection with it.
3. Such three sex chromosomes (X, Y₁ and Y₂-chromosomes) have each a remarkable constriction and actual separation from the point of constriction often takes place. Acoordingly, chromosome numbers larger than the usual are to be found at the metaphase of mitosis in young pollen-grains and root-tip-cells. In Lapathum, a sub-genus of Rumex, haploid chromosome numbers are 10, 20, 30, 40, 50, 60 and 100 but in the sub genus Aceiosa they are 7, (8), 9, 10 and 21 (KIHARA and ONO, 1926; ONO, 1928); that is to say, the former sub-genus shows polyploidy while the latter does not. Thus an interesting relation between the remarkable constriction of sex chromosomes and non-polyploidy may be suggested.
4. Considerably larger young pollen-grains are often observed among the anormal ones. The ratio of the volume of these larger grains and normal ones is 2.5: 1. These larger grains are supposed to have the diploid chromosome-number caused by imperfect heterotypic or homotypic division of the pollen-mother-cell, and may have a certain significance in the origin of the polyploid plants.