For an amaryllis flower to release pollen, the anther that holds the pollen must first mature and open. This splitting open of the anther is called dehiscence. It is very important for dehiscence to occur at the proper time, so that mature pollen can disperse and pollinate the stigma. The pore opening (stomium) on the amaryllis anther is longitudinal. It looks like a line, up and down, on the anther.
The stomium splits open due to the swelling pollen and anther dehydration. At first the stomium remains closed, due to adherence of the walls on each side of the stomium. But then as dehydration occurs, the outward walls start to bend outward, so the anther turns "inside out." The pollen that was once contained inside is now on the outside and free to disperse. As this happens, the walls also shrink and the anther shortens considerably. All of this, amazingly, takes place in a matter of hours.
One anther starting to split open and another anther fully closed.
The up & down line on the closed anther is the stomium - it remains closed due to adherence of the walls on each side.
Two anthers opening, a third anther fully closed.
Top left anther fully opened and walls bent "inside out." Now open, this anther has shortened considerably.
Top right anther almost open, but not bent "inside out" yet.
Bottom anther just starting to split open.
Closeup of anther splitting open.
Anther in background fully opened.
Four anthers fully opened, 2 anthers left to go.
All of this happened over the course of 4 hours -- AMAZING!