Abstract
Fused chromatids and chromatid fragments were found in a plant of Paeonia suffruticosa grown at the Bussey Institution. The inversions which produce the chromatid bridges occur in at least three of the five pairs of ehromosomes. Heterozygous inversions also cause partial asynapsis. The irregularities at meiosis cause about 66 per cent of pollen sterility. Most of the sterility is attributed to crossing over in heterozygous inversions paired nonhomologously.
The size of the chromatid fragments varies from a fraction of a micron to 9 microns in length. The uniform distribution of fragment size is attributed to crossing over in a number of short heterozygous inversions paired homologously, although there is some evidence that the variation in fragment size is caused by crossing over in non-homologously paired loops, or by inverted crossing over in non-homologously paired rods.
