抄録
(1) The intergeneric hybrid between Paraixeris denticulata and Lactuca squairosa were obtained. One of the hybrids was cytologically studied.
(2) In the root-tips of the hybrid there were not 14 chromosomes, the sum of the parental chromosomes, but were the variated number from 10 to 14 chromosomes. The majority of the root-tips, however, had 12 chromosomes among which two were fragmental ones. Assumption was made that the chromosomes of Lactuca squarrosa have been fragmented and eliminated in the foreign cytoplasm of Paraixeris denticulata.
(3) In more than half of the pollen mother cells, 6 bivaelnts or normal pairings were observed. The normal pairing of the less homologous chromosomes seems to be the characteristic nature in the chromosomes of Cichorieae. The cause of such a phenomenon was assumed to be the presence of homologous parts in every chromosome as duplications or the abundance of heterochromatic parts which produce the pairing power of the chromosomes.
The writer wishes to express his thanks to Prof. Sinotô under whose direction the present work was carried out. Thanks are due to the Japan Society for the Promotion of Scientific Research by a grant from which this work was partly supported.
