抄録
The cytological studies in three species of the genus Cucumis, one species and one cultivar of the genus Citrullus have been carried out. The possibility that the base number seven, the lowest in the family, has given rise to the base number 12 by fragmentation or the latter has given rise to the former by reduction in the genus Cucumis, has been analysed and discussed in this paper. In the genus Citrullus polynemy has been assumed for the difference in the size of the chromosomes. As regards the phylogenetic relationship between the two taxa, it is suggested that C. vulgaris var. fistulosus should be given a distinct specific rank, because of distinct differences in total chromatin matter, chiasmata frequency and breeding behaviour.
