Anatomical and ontogenetic investigations on the morphology of the flowers and the fruit of Scyphostegia borneensis Stapf (Scyphostegiaceae)

New details could be derived from the study of fixed male and female flowers of Scyphostegia borneensis Stapf. Of prime importance among these is the exact structure of the female reproductive units. They correspond to what are generally recognized as ovules. These anatropous ovules have a constriction separating funicle and raphe, an aril (loid) of mixed character, a distal integumental extension, and a fivelobed exostome. Their placentation is basal. Together, they are enclosed by an urceolate wall consisting of three-trace units which are apically stigmatic. These sterile units form septs growing downwards between the tips of the ovules, giving rise to locules which are open below. The morphological interest of some of these details was discussed. The embryosack development could be followed. The fruit appeared to be a fleshy capsule. The striking similarity with certain formations in the Monimiaceae is not based on affinity. As to the above characters the alleged affinity with the Flacourtiaceae could not be checked because comparable characters in that family have never been studied. However, there is a correspondence with such details known in the Tamaricaceae. Moreover, in the Tamaricaceae the placentation is intermediate between basal and parietal. This was considered to favour the inclusion of the Scyphostegiaceae in the Parietales. Of all the Parietales families they must be nearest to the Flacourtiaceae, as judged from external characters.