I would recommend looking at this paper, and in particular the section "A SHORT INTRODUCTION TO OENOTHERA GENETICS":
The genetics of Oenothera is a genetics of entire haploid genomes (Renner complexes), which inherit as single units and are entitled with names such as hjohansen, Galbicans, or Gflavens (for terminology, see materials and methods). All loci of a Renner complex are in linkage disequilibrium.
Figure 1 from that paper shows what that looks like in meiosis, in terms of its impact on chromosome pairing- basically chromosome pairing forms rings of chromosomes linked by translocations.
Additionally, it appears that plastid inheritance is biparental to some extent. These also contain pollen-lethal factors related to autosomes, such that cytonuclear incompatibilities kill pollen recombinants between a Renner complex and plastids (eggs are unaffected, Figure 2, 3):
Consequently, the F1 generation is identical to the parental generation without segregation of traits, since chromosomes separate as a set without intermixing.
The set of plastids ("plastome") will then break down in the F2 such that assortment can happen.
Selfing of appropriate flowers ensures that only plastome I is inherited to the next generation. However, in F2 the nuclear genome splits into the progenies CC-I and AC-I...
Since the ring of 14 chromosomes should inhibit free segregation of individual chromosomes and practically homologous recombination between haploid genomes in the hybrid AC, the coding potential of the A and C genomes is not mixed and a seemingly unchanged, homozygous CC genotype, now associated with plastome I, occurs in F2.
So it's rather complex. Hopefully that sheds some light on it, but it's understandable if it's still confusing!