• 1
    Artificial autotetraploids of three species of Primula have been made and crossed reciprocally with their diploid parents.
  • 2
    Data on the character of the seeds produced, derived from dissection and embryo-logical examination, are presented. It is shown that the seeds from reciprocal diploid-autotetraploid crosses fall into two classes, type A and type B, which resemble in general features and pattern of development those from reciprocal crosses between the diploid species. They are normally practically empty at maturity, and no triploid offspring have been obtained.
  • 3
    Diploid-autotetraploid crosses in general are discussed, and it is pointed out that the nature and goodness of their seeds varies greatly from genus to genus. The crosses can be arranged in four groups on a basis of triploid productivity.
  • 4
    The embryological data on these crosses are also briefly reviewed. While some general similarities can be recognized, there is so much diversity that no generalizations about the pattern of breakdown can be made.