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.