Reproductive anatomy and relationships of Setchellanthus caeruleus (Setchellantitaceae)

Floral, seed, and fruit anatomy of the unispecific Mexican genus Setchellan thus are described. The genus has floral features that are characteristic o f some traditionally defined Capparales or close allies of an expanded orde r Capparales, viz., a (5-)6(-7)-merous flower with a 3-merous gynoecium and an androecium comprising (5-)6(-7) fascicles of stamens that develop centr ifugally; a short androgynophore and well-developed gynophore; a 3-loculed gynoecium with a 3-lobed style and 3 conduplicate valves that separate from the vascular placental column at maturity much as do the valves of Cleome or Brassicaceae. Setchellanthus, however, has straight seeds with a spatula te embryo and a non-fibrous exotegmen; it lacks the reniform seeds with fib rous exotegmen characteristic of the core Capparales. Vascular bundles in t he fruit wall are amphivasal and show an extensive secondary growth that pr oduces tracheids like those of the secondary xylem of stems; bordered pits are present in the wall of the inner epidermis cells. The floral and seed a natomy as well as the distinctive fruit anatomy support a position of Setch ellanthus that is near-basal to the core Capparales.