Not a seed head...this is the flower. What do the leaves look like? Maybe Mimosa pudica. Mimosa pudica - Wikipedia
I've advanced a little since I made that post. I now think it's either a 'Powderpuff' Mimosa strigillosa or possibly a Sensitive Briar, genus Shrankia Yours is a third that looks like it but I think the plant you suggest is larger -- see here. This one each flower is on a separate plant and only grows about 4 inches above the ground I'm posting a picture of the foliage which also has the same look but grows near the ground, more like ground cover.
