Meiosis inOenothera purpurataandOe. blandina

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Abstract
Both spp. have 7 free pairs of chromosomes in meiosis. There is a much larger amount of interlocking of pairs during diakinesis and heterotypic metaphase in blandina than in purpurata. This difference is due ultimately to a stronger attraction between homologous chromosomes at meiosis in purpurata than in blandina. Definite evidence of para-synapsis in Oenothera was found. Pairing of divaricated threads was seen in the zygotene stage, and some evidence of doubleness in the stages following. In the "second contraction" stage of the pachynema the spireme is not continuous as hitherto supposed, but 7 loops representing the pairs of chromosomes are more or less completely interlocked, thus giving the appearance of a continuous spireme, except when certain pairs are free from the beginning. Rod pairs, which occur in blandina with a frequency of about 3 in 1000, indicate that occasionally there is no chiasma between the point of spindle fibre attachment and an end of a chromosome. It is concluded that while the ends of chromosomes in Oenothera pair side by side, asynapsis characterizes their median portions.

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