Floral structure of Takhtajania and its systematic position in Winteraceae

Floral structure of Takhtajania perrieri, the sole species of Winteraceae in Africa/Madagascar, was studied and compared with that in other Winteraceae. Floral organs are in more or less regular whorls, starting dimerous in the outer perianth region and changing to tetramerous and pentamerous in the inner perianth region and androecium. The innermost androecium whorl is often incomplete. The outer tepal pair is congenitally united, and pairs two and three are postgenitally united in their overlapping area in bud. At the transition from the female to the male phase of anthesis the club-shaped stamen filaments are inflated by cell enlargement, accompanied by starch consumption. The dimerous nature of the unilocular gynoecium is confirmed. The normal linear placentae of the two carpels are oblique to almost horizontal, and therefore the gynoecium does not conform to a usual paracarpous gynoecium with parietal placentation. The ovules are larger than those in other Winteraceae. However, the total evidence of floral features clearly shows the position of Takhtajania in the Winteraceae. Within the family it fits best in the Pseudowintera/Zygogynum-clade, which is sister to the Tasmannia/Drimys clade.