Meiosis in Oenothera purpurata and Oe. blandina

This paper is a study of the essential stages of pollen meiosis in two Oenotheras which show seven pairs of chromosomes in diakinesis and the heterotypic metaphase. Its intention is to throw further light on the origin of the pairs and their relation to the method of synapsis. Although these forms agree in having seven pairs of chromosomes and no linkage ring, yet they show certain characteristic cytological differences, which will appear in the description. The problem of the origin of chromosome linkage or catenation (Gates, 1931), so characteristic of Oenothera, is also involved. Material and Methods . Oe. Purpurata was described by Klebahn (1925) from cultures derived from naturalised colonies of Oenothera on the Lunenburger Heide in North-western Germany. It is very much like Oe. Hookeri , but has small flowers. In crosses with Oe. Hookeri the smaller flowers of Oe. Purpurata are stated by Rudloff (1929, a ) to represent a monohybrid difference, the small flowers being dominant. By crossing it with various other forms, Rudloff found it to be homozygous, which he confirmed by showing that it had good pollen and seven free chromosome pairs in diakinesis.