akene

Fruit (cremocarp) of Osmorrhiza; the two akene-like ripe carpels separating at maturity from a slender axis or carpophore.

It is what the botanists call an akene, which simply means just one seed with a tight envelope about it.

Akene of Virgin's-bower, retaining the feathered style, which aids in dissemination.

The fruit of Composit (though not of a single carpel) is also an akene.