Hello,
I'm not much of a gardener and just do the donkey stuff for swmbo.
I do hope this is an appropriate group.
She picked up a leaf with attached seeds in NW London a few days back whilst
visiting friends.

I have put a photo up at
http://www.flickr.com/photos/31263451@N07/?saved=1

It looks V much to me like sweet chestnut seed but the leaf does not.
Leaf and twiglet were firmly attached when gathered from the pavement, they
have now separated.

Many thanks,

Nick.