Pelargonium capitatum ripe fruit

Ripening of the Pelargonium capitatum fruit results in the five mericarps splitting and moving away from the calyx, the style and each other.

The thin slice of skin of the style attached to each seed remains attached to it like a tail until after dispersal. When these surface sections of the style loosen from the central column, the ovary disintegrates and the calyx lets go to free the five mericarps. The seed at the end is danced around in the air by the spiralling, thin attachment that frees its long silky hairs in the process.

The entire unit or mericarp is now ready to be launched into a new life. The hairs will aid in the flight over an undetermined distance from the mother plant; if all goes well to a good spot far enough for plants not to inhibit each other. Once on the ground the twisting of the mericarp tail acts like a “ploughing” screw, helping the pointed seed to become buried, i.e. “planted”.

In the photo the top end of the mericarp’s tail still hangs on to the tip of the style and the hairs spread from the twisting action before the moment comes for the wind to take it.

Other soft hair, shorter and downy, is visible in the photo, covering pedicels and calyces. This is markedly different to the long, shiny hairs on the mericarps (Wikipedia; www.geraniumsonline.com).