Pollen mother cell → Pollen tetrad → Pollen grain

Explanation: The completed flow chart is as follows:

Pollen mother cell → Pollen tetrad → Pollen grain

Pollen mother cells are converted to pollen tetrad by meiosis division through the process of Microsporogenesis. The pollen tetrad are actually microspores tetrads.

Now as anther matures and dehydrates the pollen tetrads dissociate and form pollen grains.

When pollen grain is mature it contains two cells namely Vegetative cell and generative cell.