Chromosome linkage in oenothera, with special reference to some F 1 hybrids

Oenothera has placed a large part in our initiation into many new fields of cytological and genetical research. Since ring-formation of chromosomes was first observed in this genus by Cleland a few years ago, it has become apparent as a characteristic of meiosis in several other Angiosperms, but whether these are entirely comparable to Oenothera is at present doubtful. It is to Oenothera that we look for the final solution of many of the difficulties encountered in any endeavour to correlate these phenomena with chromosome behaviour in more typical genera, for within the Onagra group are numerous inter-fertile species, each of which is characterised by its own particular chromosome configuration, which is constant throughout all the pollen mother-cells. Such rings are now known to occur also at reduction division in the embryo-sac mother-cell of a number of forms, and it has been found that similar configurations prevail on the male and female side in any particular species. This is observed by the author to be the ease inOe. rubricalyx (unpublished) and similar conditions have been described by Håbansson (1928) in several other derivatives ofOe. Lamarckiana . It seemed that a systematic study of the linkage of the chromosomes in a number of pure lines and in the hybrids between them was desirable, in that it might throw some light on the exact nature of pairing and chromosome linkage. Some such hybrids have already been described by Cleland (1927). This paper will deal with the chromosome behaviour in a number of F1 hybrids between pure lines in which the meiotic divisions have already been studied (Sheffield, 1927).