Abstract
Pollen sterility in a plant of Allium cepa was found to be associated with a high incidence of univalents. Initial pairing of the chromosomes took place at early prophase but in 70% of the cells the chromosomes separated completely prior to metaphase I. This dissociation of paired chromosomes occurred either on account of failure of chiasmata or of their precocious terminalization. Desynapsis was of the ‘medium-strong’ type. Anaphase I was typified by unequal chromosome distribution, lagging and a high frequency of precociously dividing univalents. The first nuclear division resulted in the fromation of 1-8 micronuclei. A second nuclear division occurred rarely.
