Bonatea polypodantha flower centre

The flower centre of Bonatea polypodantha is largely occupied by the rostellum, a part of the column of the flower that includes anther (male) and gynoecium (female). The rostellum, a three-lobed structure here, but variously shaped in orchid types, generally serves to separate the male and female reproductive parts, preventing self-fertilisation.

Some yellow of the pollinia (a pollinium is a coherent mass of pollen grains), can be seen behind the rostellum in the photo. The protruding club-shaped stigma arms, two elongated processes, are positioned in the front, attached to the base of the lip.

Bonatea flowers are distinguished from those of the Habenaria genus by the chamber-like middle lobe of the three-lobed rostellum and the short, erect anther thecae (covering sheaths) that flank the rostellum in Bonatea (www.orchidspecies.com; Wikipedia).