NOTES ON THE EVOLUTION OF ANDROECIAL ORGANIZATION IN THE MAGNOLIOPHYTINA (ANGIOSPERMS)

This paper aims to summarize briefly and to update our ideas about and roecial architecture formulated in earlier publications. Ontogenetic e vidence of stamen development, viz. the initiation, arrangement and re lationship of stamens to other floral morphemes, can be translated int o a semophyletic scheme reflecting the phylogeny of the androecium. Th e ancestral androecium is discussed in the light of recent theories ab out angiosperm phylogeny. Two divergent androecial processes are propo sed for the angiosperms starting from a spiral androecium with a moder ate number of stamens. However, transitions exist between spiral polya ndry, numerous stamens in whorls, and chaotic polyandry. From an andro ecium with several alternating whorls of paired and single stamens, ou ter stamen pairs are retained following the successive loss of inner s tamen whorls. Single stamens instead of pairs occur at the very end of this line and represent a more advanced condition. This line is mostl y present in tri-and dimerous flowers. From the same starting point di plostemony (with two alternating whorls of single stamens) originated, again giving rise to various states usually present in pentamerous or tetramerous flowers.