ИСТИНА

According to recent molecular phylogenetic data, the rare Australian endemic Maundia triglochinoides does not form a clade with taxa traditionally classified as members of the family Juncaginaceae. Therefore, views on morphological evolution and taxonomy of Alismatales require re-assessment. As the morphology of Maundia is poorly known and some key features are controversially described in the literature, flowers and fruits were studied using light and scanning electron microscopy. Except in the inflorescence tip (where the flower groundplan is variable), flowers possess two tepals in transversal-abaxial position, six stamens in two trimerous whorls and four carpels in median and transversal positions. Maundia shares the same and highly unusual floral groundplan with Aponogeton spp., a homoplastic similarity that can be explained by spatial constraints in developing inflorescences. The shared possession of orthotropous ovules supports the molecular phylogenetic placement of Maundia as sister to a large clade including Potamogetonaceae and related families. The nucellar coenocyte of Maundia appears to be unique among monocots. Although carpels of Maundia are united via floral centre, like in Juncaginaceae, fruits of Maundia differ from those of Juncaginaceae. At maturity, carpels of Maundia do not separate from the flower centre. Fruits are indehiscent. Pericarp and seed coat histology provide some other features not described so far in Juncaginaceae. As Maundia exhibits a mosaic of features characteristic of other families of tepaloid core Alismatales, its segregation as a separate family is plausible. Affinities to related taxa are discussed.