The sandbox tree of tropical America is named after a desk accessory. Before blotting paper, people dried wet ink by shaking fine sand over the page, and the story goes that the tree’s unripe fruit, a ribbed pod shaped like a small pumpkin, was sawn open and hollowed out to hold that sand. Left on the branch, the same pod does something far less quiet. As it dries, tension builds along its segments until it splits with a crack like a gunshot and flings its flat seeds out fast enough to carry them tens of metres through the forest. Its Latin name, crepitans, means crackling. So the English name remembers the fruit at the one stage when it could be made polite: picked green, filled with sand, and set beside the inkwell, where it would never go off.