Why are cells on the root tip of allium cepa used in studying mitosis?

The root tip cells of any plant are in a condition of constant division as they are meristematic cells. When observed, all mitotic processes can be studied distinctly.
Allium cepa is the onion plant. Its cells take up stain easily. Therefore, it becomes easier to observe them under the microscope. The nucleus is very clear and the dynamic changes there can be observed easily.