The intersexual plant of R. Acetosa generally bears flowers of three types, namely male, female and bisexual ones. The male and female flowers are morphologically normal, but the bisexual ones sometimes show various grades of degeneration (Fig. 1-6). Numbers of these different flowers in each plant are variable and usually female flowers are few or absent. Accordingly we have determined the degrees of intersexuality in each plant by calculating the percentage of bisexual flowers. The chromosome numbers of 50 different individuals in various grades of intersexuality are denoted in the following table: It is pecuriar that some diploid individuals show a low intersexuality. The chromosomal elements of such individuals, however, appear similar to that of the male plant (Fig. 7-10). Some intersexual plants of R. Acetosa are fertile. I have obtained many progenies. Among the progenies of triploid intersexual plants, 15-, 16- and 20-chromosomal individuals were found (Fig. 11). Further investigations of these progenies will be reported later. VII. Chromosomes of R. montanus. The numbers of diploid chromosomes in female, male and intersexual plants of R. montanus were determined respectively to be 14, 15 and 22. The behavior of chromosomal elements is quite identical with that in the case of R. Acetosa (Fig. 12-14). Therefore the chromosomal formulae of these plants should perhaps be as follows:-_??_14=12a+2X _??_15=12a+X+2Y _??_22=18a+2X+2Y VIII. Chromosomes of an intersexual plant of R. acetosella. This summer (1929) I collected some fertile intersexual plants of R. acetosella from two different places in South Saghalien. One of them was fixed and studied cytologically. In the heterotypic nuclear division in pollen mother cells we found 20 bivalents and one univalent (Fig. 15). Some bivalents associate with each other and form one or more tetrapartite ring-complexes (Fig. 16). In the anaphase, the univalent goes freely to one pole. Therefore the daughter plates have usually 21 and 20 chromosomes (Fig. 17, 18). We are not yet sure whether all the intersexual plants of R. acetosella have 41 chromosomes or not.
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.