1. The frequency of chiasmata and of univalents is similar in pollen and embryo sac mother cells ofLilium testaceum.
2. Cells with fewest chiasmata have those chiasmata most strongly localized either proximally or distally.
3. Hence pairing must have begun either near the centromere or near an end. The contact point is optional.
4.M chromosomes come into contact more readily near the ends,S chromosomes near the centromere.
5. ButM chromosomes pair more slowly, so that the frequency of their chiasmata falls away more rapidly in low chiasma cells than that ofS’s.
6. Samples of cells used for the study of meiosis in species and crosses must therefore be regarded as representing cross-sections of the process of pairing secured by a variable interruption of the process. Statistical treatment can be used to indicate the order of pairing and the means of interruption.
Volume 101, 2022
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