Early floral development and androecium organization in Fouquieriaceae (Ericales)

Early floral development with focus on the androecium was studied with the help of scanning electron microscopy and serial microtome sectioning in Fouquieria columnaris and F. splendens. Perianth organs appear in a spiral pattern on the floral apex. The spiral may be a clockwise or anti-clockwise. The androecium is best interpreted as two-whorled with all the stamens arranged in a single series. In F. splendens, two or more of the five epipetalous stamen positions are doubled, i.e. they are occupied by stamen pairs. Unusual features in the floral development of Fouquieriaceae include (1) a strong spiral component even in whorled organ categories and (2) a pronouncedly asymmetric floral apex during an early phase of floral development. From a phylogenetic point of view, it seems plausible that the common ancestor of Fouquieriaceae and its sister family Polemoniaceae was characterized by two alternating, pentamerous stamen-whorls.