At the time of dehiscence, a pollen grain in angiosperm could be 2-celled when it contains one tube cell and one generative cell or it could be 3-celled when the generative cell divides mitotically to give rise to the two male gametes, and hence, one tube cell and two male gametes make pollen grain a 3-celled structure. At 2-celled stage, one small generative cell and one large tube cell are placed within the pollen grains.