Studies in Floral Anatomy. Iii. An Interpretation of the Gynaeceum in the Primulaceae

The Floral Morphology of the Polemoniaceae

“…32). Similar bundles have been reported by Dickson (1936) for the Primulaceous genus. She terms them "extra abortive stamen traces.…”

“…When the third whorl of stamens was present, there was no transgression of the law of alternation of whorls. Dickson (1936), working with the genus Samolus, one of the Primulaceae, reports a similar condition in regard to a third whorl of vestigial stamen traces. E. cicuiarium gives evidence that the reduction of staminal whorls is still going on.…”

“…DESCRIPTION OF VARIOUS CARYOPHYLLACEOUS AND GERANIACEOUS FORMs.-In an attempt to substantiate or discard some of the various hypotheses that have been offered in regard to the possible derivation of the Polemoniaceae, the floral anatomy of several genera of the Geraniaceae and the Caryophyllaceae has been considered. Recent work by Dickson (1936) gives sufficient evidence that the Primulaceae are not involved in the early history of the Polemoniaceae; hence descriptions of Primulaceous genera are not included. The relationship of this family to the 505 phylogenetic picture will be considered in the discussion.…”

“…In the Caryophyllaceae free central placentation is brought about by the breaking down of the loculi walls during the development of the gynaeceum. Both Dickson (1936) and (Douglas) (1936) have concluded that the free central placentation in the Primulaceae is merely a step in advance of that exhibited by the Caryophyllaceae. Evidence for this conclusion is found in the fact that the fused carpel margins are free from the ovary wall at the time of their separation from the receptacle in the Primulaceae, whereas in the Caryophyllaceae the carpel margins break down during the course of ovule development.…”

Again: ‘The New Morphology’

“…Placentation in the Primulaceae has gone a step further in specialization and the evidence from ontogeny of the loss of carpel walls is less obvious, but the ovules often lie on the placenta in two rows in median position opposite the midrib of each carpel, and in some genera there are sterile lines on the placenta where walls were present ancestrally (Douglas, 1936;Dickson, 1936). This position of the ovules and the sterile lines are part of the evidence of the former presence of partitions that are now lost.…”