Green brains.....that is what my children call hedge apples. This time of year it is common in Kentucky to find the osage-orange trees (Maclura pomifera) dropping their hedge apple fruit. The fruit was named hedge apple both because of the large round shape (4"-5" diameter) and the fact that most osage-orange trees can be found along hedge and fence rows, and that is precisely where I stumbled upon this particular example.
As I cut open the fruit, it oozed a white sap quite profusely. This liquid dries very quickly into a sticky pitch-like substance which will not wash off with soap and water and would make a very effective water-proofing substance. I had to resort to mineral spirits to clean my knife. In the days of yore, hedge apples would be placed under beds to keep the spiders away. Scientific studies have shown that the sap of the fruit does indeed contain a substance which repels several insect species as effectively as our synthetic DEET insect repellent. However, you won't find me slathering the sap on my skin or clothing!