The Osage orange, Maclura pomifera, is what is botanically known as a "multiple" fruit. It's the result of many, many tiny female flowers jammed together into a cluster. After pollination, the flowers swell, and all of them coalesce into this massive structure. It can sometimes be the size of a large orange, or even a grapefruit.
According to an article on eu.tallahassee.com¸each of the tiny ovaries inside produces a single seed. The fresh, ripened fruit is quite solid, usually an attractive yellow color, and filled with plenty of sticky, white latex. Don't even think about eating one of these things. Although we humans find it inedible, it comes from a plant that is related to the very edible breadfruit.
