Fascinating. Where'd they come from? What's the plant look like? Not mandevilla is it? Phil J

a friend gave them to me in northern france, but i never saw the plant and he did not know anything about it.

Stumped at the moment. Let's see if Fractal's watching, he might know. PJ

I saw a plant with seed pods like these when I went to The Garden Party to Make a Difference in the gardens of Prince Charles' residence, Clarence House and the neighbouring gardens. It was in the garden of Marlborough House. I took 2 pictures intending to put them up on here to see if anyone could id it, but forgot. I've just uploaded them here -
http://www.growsonyou.com/photo/slideshow/182534-mystery-plant/member/beattie and the following (or is it preceding?) photo. The seed pods were just splitting in mid September.

It's an Asclepias, or close relative, but I can't tell which one from the pods alone. Mandevillea and it's kin have pods in "Siamese twin" pairs.

Thanks Tugbrethil. I googled images of Asclepias seed pods and came up with possible matches with A.syriaca or A.speciosa. They may not be the only possible answer - there may be others but they look good enough for me. Pity we didn't see the flowers, but never mind. :-)

Came to this too late! I agree, looks like Asclepias.