(Hypanthium and staminal tube in Xylopia aromatica (Lam.) Mart. (Annonaceae)). A woody ring surrounding the carpels was observed in longitudinal sections of flowers of five species of Xylopia L.. The stamens and staminodes were spirally inserted on this ring. An anatomical study of the mature flowers of Xylopia aromatica (Lam.) Mart. was conducted to elucidate the nature of this structure, concentrating on the vascularization from the base of the receptacle to the stamens, staminodes and carpels. The woody ring was shown to be appendicular and of mixed origin. It consists of the fusion of the sepals, as well as external and internal petals and filaments in the basal region, thereby constituting the hypanthium. In the apical portion it is exclusively formed by the fusion of the filaments, thus constituting a staminal tube. The epidermal cells covering the stamens and staminodes have a lignified and thickened wall, distinguishing them from the other epidermal cells of the sepals, petals and carpels. Such cells also cover the woody ring, demonstrating its staminal origin. The woody texture of this ring is probably due to the presence of lignin in the walls of its epidermal cells. According to the literature, this ring has been interpreted as being of receptacular nature, without any anatomical support. The appendicular origin of the hypanthium is here reported for the first time for both of the genus Xylopia and Annonaceae.
Xylopia aromatica; Annonaceae; appendicular hypanthium; staminal tube
