The falling of leaves from a tree in autumn is not an example of diffusion. Diffusion refers to the movement of particles from an area of high concentration to an area of low concentration. In the case of leaves falling from a tree, the leaves are not moving from an area of high concentration to an area of low concentration. Instead, the leaves are being detached from the tree due to the formation of a layer of cells called the abscission layer at the base of the petiole (the stalk that connects the leaf to the stem). The formation of the abscission layer causes the leaves to become separated from the tree, resulting in their fall.

Examples of diffusion include:

- The spreading of perfume in a room

- The movement of oxygen from the lungs to the blood

- The absorption of nutrients from the soil into plant roots