抄録
1. The karyological study in the hybrids of the following combinations were carried out.
Group 1. B. Napus, L. var. Napobassica, REICHB. n=19_??_×B. pekinensis, RUPR. n=10 _??_ B. Napus, L. var. Napobrassica, REICHB. _??_×B. nipposinica, BAILEY, n=10 _??_ B. Napus, L. var. oleifera, DC. n=19 _??_×B. rapa, L. n=10 _??_ B. pekinensis, RUPR. n=10 _??_×B. Napus, L. var. oleifera DC. n=19 _??_
Group 2. B. Napus, L. var. oleifera DC. n=19 _??_×B. Napus, L. var. oleifera DC. n=19 _??_ B. Napus, L. var. Napobrassica, REICHB. n=19 _??_×B. Napus, L. var. oleifera, DC. n=19 _??_
Group 3. B. Napus, L. var. Napobrassica, REICHB. n=19 _??_×B. juncea, COSS. n=18 _??_ B. juncea, Coss. n=18 _??_×B. Napus, L. var. Napobrassica, REICHB. E=19 _??_
2. The meiosis of the pollen mother cells are very similar in every hybrid of group 1. 10 bivalents and 9 univalents appearing in the heterotype division. After the bivalents were separated and passed to the pole normally, the univalents distributed irregularly with the splitting of a few chromosomes. Homotype division was carried on normally, though in a few cases the lagging chromosomes and the splitting of the univalents were observed. Restitution nucleus was found sometimes.
3. With the hybrids of the combination in group 2, no abnormality in the meiosis of the pollen mother cells was observed. 19 bivalents appeared in the heterotype division and the chromosomes were distributed normally in the heterotype and homotype divisions.
4. 10 bivalents and 17 univalents appeared in the heterotype division of the pollen mother cells of the hybrid group 3. After the former passed to both poles normally, the latter were distributed irregularly with the splitting of some chromosomes. In the homotype division, the general feature was normal though some lagging chromosomes and splitting of halves of chromosomes were to be seen. The occurrence of large nuclei and dyads, however, were also observed in a few cases.
5. Abnormal meiosis as in the F1 progenies of group 1 and 3 was also observed in the F2 hybrids of B. Napus, var. oleifera×B. pekinensis and B. juncea×B. Napus, var. Napobrassica. The number of the bivalents was the same or more and the univalents less than in the F1 progenies. In the heterotype division of B. juncea×B. Napus, var. Napobrassica the chromosomes were sometimes supernumerous. The polyads, from dyads to hexads, were also formed in F2 hybrids. Univalents often occurred in a ring in F2 progenies of B. juncea×B. Napus, var. Napobrassica. The number of univalents in a ring was less than those of F1 progenies. Some univalents of F2 progenies of B. Napus, var. oleifera×B. pekinensis were also arranged in a ring though the arrangement was rather irregular.
