Chromosomal Configurations of Oenothera Species antd Crosses and Their Probable Significance

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Abstract
A tabulation of all chromosomal configurations of Oenothera species and crosses thus far observed is given, with a discussion of the significance of chromosomal cohesion. The data (from tables 1-11) are thought to indicate that chromosomal configurations are only relatively constant and not necessarily characteristic for any particular species. Whenever variable chromosomal configurations have occurred there have been recorded no particular phenotypi-cal changes with which they might be associated; also, the presence of 7 complete pairs of chromosomes in recognized heterozygotes indicates that heterozygosity plays no particular part in the formation of closed circles. The evidence seems to indicate that the complexes, as such (as recorded in tables 11-13), also bear no special relation to particular chromosomal configurations. It is therefore assumed that the formation of closed circles in the Oenotheras bears no particular relation to their observed genetical behavior. On the other hand, the data presented permit the assumption that closed circles are due to genic action as are phenotypical characters and are therefore heritable traits. Segmental interchange might possibly have an indirect relation to the formation of closed circles, in that the genes assumed to be the direct causal factors could, by segmental interchange, be transferred to other chromosomes, making possible other types of configurations in the succeeding generation.

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