Structural Variatin in the Chromosomes of Campanula persicifolia

Abstract

CHROMOSOME behaviour at meiosis has been described in Campanula persicifolia to show the relationships of diploid, triploid, and tetraploid forms.¹ The haploid number is eight. In the diploid, as a rule the chromosomes are associated at both ends forming rings, but occasionally association at one end gives a rod. In the tetraploid, the majority of the chromosomes still associate in pairs, but this is varied by the formation of rings and chains of four as well as by failure of pairing. In the triploid the third chromosome is occasionally associated with its homologues in a chain, but more usually free. The end-to-end association always found at metaphase follows terminalisation of from two to five interstitial chiasmata found at a diplotene stage characteristic of parasynapsis. This terminalisation accounts for the failure of quadrivalents by the cancellation of chiasmata.² We may therefore speak of the chromosomes as being joined at metaphase by terminal chiasmata with an approximate average of two to each chromosome.