Abstract
Ranunculus cantoniensis (2n=32), one kind of weeds commonly seen in a paddyfield, is an allied species to R. silerifolius (2n=16). The reciprocal crossings were carried out between the two species, and only two interspecific hybrids, one with 2n=24 and the other with 2n=32, were produced in the case where R, cantoniensis was a maternal plant. It was karyologically judged that the chromosome complement of the F1 with 2n=24 consisted of a half set of R. cantoniensis and a half set of R. silerifolius and the 8III configuration was observed at MI. The chromosome complement of the F1 with 2n=32 consisted of a half set of R. cantoniensis and the full set of R. silerifolius, and the 16II configuration was observed. Thus, it was considered that R, cantoniensis was primarily of an autotetraploid origin and the basic chromosome sets of R. cantoniensis and R. silerifolius were originally homologous each other, and that R. cantoniensis might be placed at the secondary stage in the process of cytogenetical diploidization.
