Here's one I picked up yesterday (see file attached, if you can make out the rather fuzzy picture). The fruit of the maple grows on the tree as a ball about 3-4cm across, but when it falls the outer coating of brown fluff easily falls off (as I know to my cost - I must remember the vacuum cleaner for my study floor!

) This is from a London Plane (to give it the name used at the Royal Botanic Gardens at Kew; I imagine in Madrid
platanus hispanica they use a different name.

)
The American Plane (sometimes called the 'buttonball' I believe) is closely related. The London Plane is a cross between the American Plane and
platanus orientalis.
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