Apple stalk-branch junction. Coloured scanning electron micrograph (SEM) of a section through the junction between the stalk of an apple (lower half) and where it attaches to the branch (upper half) of a tree. With increasing maturity of the apple, the border area between branch and stem (brown) becomes corked. This cork layer interrupts the water supply of the apple and the result is a predetermined breaking point, which enables the apple to break free and fall to the ground when ripe. Magnification: x13, when printed 10 centimetres wide.