Meiosis in Hypericum punctatum

Abstract

In both micro- and megasporogenesis, chromosomes fail to pair at "diakinesis." Instead they become fastened end-to-end in a chain. At first metaphase, alternating chromosomes tend to pass to opposite poles. Irregularities often occur so that at second metaphase the haploid count is often 7 and 9 instead of the usual 8. Lagging of chromosomes may occur. Extra nuclei are sometimes formed. Second division sometimes shows extra, small spindles, and dwarf nuclei may be formed. At maturity nearly \ the pollen grains are morphologically sterile. Meiosis in general resembles that found by Cleland and others in certain Oenothera species. The cytological situation resembles conditions found in natural hybrids.