Meiosis in polyploids

摘要: 1. The pollen mother-cell divisions in triploid tulips are described. At prophase only pairs of homologous chromosomes associate at any particular point, but different points. The fact that three threads lie side by proves each corresponds to a whole chromosome rather than half chromosome; the parasynaptic interpretation is thus substantiated. 2. After formation diplotene chiasmata, either all corresponding left attached as trivalents, or one may come entirely free. 3. Variation occurs number trivalents first metaphase, and chiasmata joining associated chromosomes. 4. The association agrees with stated requirements theory if we regard genetical evidence fromDrosophila applicable, pairing condition crossing-over. 5. InTulipa Clusiana DC. associations three, four five occur metaphase result earlier random amongst chromosomes.