Abstract
Crepidiastrum platyphyllum occurs only in Bôsô and Miura Peninsula, the northern limit of the genus. In the southern parts there occurs only Crepidiastrum Keiskeanum. The individualities of these species are presumed to be kept by the isolation, geographical or physiological or both. But the results of artificial hybridization of these two species eliminate the possibility of the physiological isolation.
The studies of meiosis of this hybrid gave further examples of the residual pairing, which was abundantly observed in the progenies of intergeneric hybrids of the species of this group. The characteristic feature of the residual pairing is the diminution of multivalents during the progress of meiotic prophase, the result being the normal anaphase inspite of the occurrence of many multivalents at diplotene.
