Contributions to Cytology and Genetics from the Departments of Plant-Morphology and of Genetics, Botanical Institute, Faculty of Science, Tokyo Imperial University, No. 65

抄録

1. In the heterotypic prophase of the pollen mother cells in Carica papaya, Myrica rubra and Aucuba japonica, achromatic threads are all single in nature showing no parallel arrangement. In Beta vulgaris nucleolar budding is observed in the same stage.
2. End-to-end connection of univalent chromosomes is visible in the prophase of the pollen mother cells in all four species studied, so that the mode of gemini-formation is telosyndetic.
3. The haploid number of chromosomes is counted as follows: Carica papaya …… 9 Myrica rubra …… 8 Aucuba japonica …… 16 Beta vulgaris …… 9
4. The diploid number of chromosomes in Carica papaya is 18.
5. No sex chromosomes are found in the male of three dioecious plants, Carica papaya, Myrica rubra and Aucuba japonica.
6. The axes of both homotypic spindles in each of four species observed may be located in various angles to each other, namely they are parallel, perpendicular or oblique to each other.
7. Pollen tetrads are formed in all cases by the aid of protoplasmic furrowings instead of cell plates. The furrowing process may be initiated at interkinesis.
8. Tetraploid number of chromosomes is often found in the tapetal cells of Carica papaya.
9. In the postsynaptic prophase of Beta vulgaris three kinds of bivalent chromosomes can be distinguished, i. e. 4 rings, 4 rods and one small v-shaped one.