http://www.xavier.edu/green/flora/ginkgobiloba

Ginkgo: alternate, simple fan-shaped deciduous leaf usually divided into two lobes.  Gymnosperm ?fossil tree? first grew over 200 million years ago during the Permian, before the age of dinosaurs. It was a sacred tree to the Buddhists who cultivated it in temples.  It is now used as an ornamental tree and thought to be extinct in the wild.  Only the male is planted because the female fruit contains butyric acid and smells awful when crushed.   Fertilization occurs when free-swimming sperm find the cherry-shaped female fruit, often after the fruit has fallen to the ground.  Non-native to the Midwest.  Introduced from Eastern China.