Vascularisation de la fleur de Calla palustris (Araceae)

Abstract

Based on floral vascular system, the authors analysed the problem of pseudomonomeria, and the inter-generic relationships within the Calloideae. The hermaphrodite flowers of Calla do not have a perianth. The superior, unilocular ovary is surrounded by 10 to 12 extrorse stamens. Most of these flowers have an ovary wall which receives three carpellary traces. These three traces divides again to produce 9–12 bundles. At the base of the ovules, an oval vascular plexus can be seen on which the traces of the ovules are inserted. It originates from three carpellary bundles, even though it is connected to certain staminal traces. The anatomical study showed that the syncarpous gynoecium of Calla is composed of three carpels that are joined edge to edge. The bitegmic, anatropous, apotropous ascending ovules are located on a basal placenta. The number of ovules varies from 4 to 10. The basal placentation of Calla is of the basal-axile type. It derives from an axile placentation which is similar to that found in Lysichitum. Among the Calloideae, it is with Orontium aquaticum that Calla palustris shares the greatest number of characters: superior ovary, unilocular, tricarpellate gynoecium, basal placentation, and a reticulate pollen. In Orontium, the existence of 6 tepals and 6 stamens was noted while in Calla, 10–12 stamens were observed. It is possible that 6 of the 12 stamens of Calla, correspond to the 6 tepals of Orontium. The subfamily Calloideae is a heterogeneous taxon at the level of floral morphology.