Sinningia Naughty Bits

On top is a flower of Sinningia bullata as it appears to the observer.

Below is the flower with the corolla removed, to show the reproductive parts of the flower. The mostly straight structure is the style; it ends in a sticky blob called the stigma.  The multiple slightly curved structures below the style are the stamens, each made up of a slender stalk called a filament and ending in a pollen-bearing clump called an anther.

This sectioned flower of Sinningia bullata shows both the anthers and the stigma.  The stigma, at the end of the style, protrudes beyond the anthers.  The anthers are joined into a single clump, which is characteristic of sinningias.

The stigma being beyond the anthers means that the flower is in its female phase, ready for the stigma to receive pollen from other flowers, transferred by a pollinator, in this case a hummingbird.

Note that the filaments connect directly to the corolla tube, while the style connects to the ovary at the base of the flower.

Also note the position of the anthers within the corolla tube.  A hummingbird thrusting its beak into this flower will have its beak dusted with pollen.  Compare the picture below.

Here the anthers of Sinningia cardinalis 'Innocent' are held just beneath the overhanging upper lip or galea.  The stigma, at the end of the style, protrudes beyond the anthers.  The anthers are joined into a single clump, which is characteristic of sinningias.

The stigma is just barely visible behind the filaments.  Since the anthers protrude further, this flower is in its male phase, ready to dispense pollen onto a pollinator for transfer to the stigma of another flower.

In the case of this species, the hummingbird's beak goes into the flower as far as the lower lip will allow.  The positioning of the anthers means that the pollen gets dusted on the hummingbird's forehead instead of the beak.  As a result, a species without a galea (like S. bullata) may be able to inhabit the same geographical area as a species with a galea (like S. cardinalis) without hybridizing.

This shows the stigma of Sinningia bullata, at the end of the style.  Pollen grains deposited on the sticky surface of the stigma "germinate" and grow down into the style, creating a long pollen tube which eventually tries to penetrate an ovule and deliver its load of DNA to the waiting "female" cells.

In animals, single-celled sperm fertilize single-celled ovules.  In flowering plants, however, pollen grains fertilize eight-celled ovules, resulting in so-called "double fertilization".  In some plant families, this extra fertilization results in a food supply (endosperm) for the embryo in the seed when it germinates.

This stigma is cup-shaped.  The main alternative shape for stigmas in the family Gesneriaceae is a two-lipped arrangement, something like an open clamshell.