Micromorphology of stylar head complex.
SEM micrographs illustrating surface topographical features, both in freshly-fixed, critical point dried material (A & B), and in unprocessed samples from herbarium specimens (C & D). In Vanguerieae the stigma (s) terminates the pollen presenter (p), the whole being referred to as the “stylar head complex”. In freshly-fixed pollen presenters taken from buds just prior to anther dehiscence, as in the case of A and B, the outer surfaces are largely devoid of adherent material. (A) Stylar head complex from an almost mature flower bud showing the slightly longitudinally-grooved pollen presenter and the terminal stigmatic lobes. (B) Enlarged portion of the stylar head complex illustrating the sharp boundary between the pollen presenter with its relatively large, convex, outer tangential epidermal cell walls, and the stigmatic lobes with their much smaller, rather papillate epidermal cells. (C) Surface of pollen presenter from an open flower showing secretions (initially somewhat sticky), especially in sinuses between epidermal cells. (D) Enlarged surface of pollen presenter showing secretions apparently exuded from the epidermal cells; these appear globular, or thread-like and often somewhat moniliform.