The flowers of the Scrophulariaceae show a great diversity in form, es
pecially of the corolla. The most common pollinators are bees collecti
ng nectar, pollen, or oil; other pollinators are moths and butterflies
, hummingbirds, syrphid flies, and (in one case) ants. The occurrence
of bell-shaped corollas in most tribes of the Scrophulariaceae and in
related families indicates that this is the basic (ancestral) flower f
orm. Derived from it are narrow tubular corollas, wide flaring ones, c
orollas closed to unsuitable visitors by a palate (an upcurving of the
tube), corollas forming a keel around the style and anthers either on
the upper or lower side of the flower, corollas inflated to form a ba
lloon, and corollas with one or two spurs. Convergences due to selecti
on by the same or similar pollinators limit the usefulness of most of
these floral features in analyzing the systematic relationships of the
tribes of the Scrophulariaceae. Nevertheless, their diversity of form
s exemplifies the evolutionary potential of fused perianth parts.