This fruit was growing on a tree in the Luxembourg Gardens in Paris. It's about the size of a cricket ball. Thanks Derek
Looks like Maclura pomifera. Common name Osage orange. See..... http://en.wikipedia.org/wiki/Osage-orange
Two weeks ago, Albert k from Cape Town, S. Africa sent in a similar photo. I had no previous idea that osage orange had such a wide range---just knew it from fencerows out around my grandparents' home in southern Illlinois. Truly, it is a small world.
It is fairly widely grown as an ornamental tree. I've seen one or two planted in Britain, too. It is however native only in a small area of the south-central USA.
