The white fluffy thing in the photo is not the seed of the Stachytarpheta indica (common name: Common Snakeweed, Indian Snakeweed) from the Verbenaceae Family.
The seeds are dispersed by wind and it just so happened that the parent plant was nearby. The white fluffy hairs attached to the small seed carried it with the wind and it got lodged to this flower.
I was so preoccupied with the seed that I almost forgot to mention the parent plant Calotropis gigantea (common name: Crown Flower, Giant Milkweed) from the milkweed Family Asclepiadaceae. In fact, the seeds of Asclepias curassavica (common name: Blood Flower) look similar.