Well, it's true. But read on. Oak-apples grow, often in clusters, from buds on small branches of oak trees and, green at first, they ripen to a rosy color. Marbles, most often found on young trees, grow at the tips of small branches and are corky, hard and brown when mature. Spangles are small and disc-like, and grow on the undersides of oak leaves often in groups of eighty or more.
Cherries also grow on the leaves, and currants usually grow on the catkins.
As you probably realize, the Oak-apples, Marbles, Spangles, Cherries and Currants are not what they sound like. They are galls. They result from abnormal growth caused by the invasive and irritating effect that certain insects can have on the tissues of an oak tree.