The diploid number of chromosomes of several species of Iris have been determined as follows: Iris Kaempferi var. hortensis 24, I. Kaempferi var. spontanea 24, I. sibirica var. orientaris 28, I. laevigata 32, I. gracilipes 36, I. florentina 48, I. japonica 54. Among these species, Iris japonica and I. florentina form trivalent chromosomes in the prophase of the heterotypic nuclear division in their pollen-mother-cells. Therefore their chromosomes must be considered as triploid. It is a remarkable fact that all the individuals of a distinct species have triploid chromosomes.
As is already known (KIHARA and ONO, 1923, 1925), the diploid number of chromosomes of Rumex Acetosa, L. is 15 (=12a+X+2Y) in the male and 14 (=12a+2X) in the female. The present authors have investigated the diploid numbers of chromosomes of a number of intersexual plants, which are found sometimes growing wild. Mostly they are 22 (triploid) and in one case 29 (tetraploid). The formulae of these chromosomes should be perhaps, as follows: 22=18a+2X+2Y 29=24a+3X+2Y Large, equal-armed, V-shaped X-chromosomes can be identified usually with no difficulty. The intersexual plants should have arisen therefore from the union of the diploid and haploid or both diploid gametes, the intersex being caused by the broken balance between the autosomes and sex-chromosomes.