Structure of 3-celled pollen grain :
(i) Pollen grains are normally spherical in shape.
(ii) Each pollen grain has a prominent two-layered wall.
(iii) The outer layer is called exine and the inner layer is called intine.
(iv) Exine is hard and made up of sporopollenin.
(v) Intine is thin, and it is made up of cellulose and pectin.
(vi) At certain places, exine is either absent or very thin and such places are called germ Pores.
(vii) A mature pollen grain has two cells - a vegetative cell and a generative cell.
(viii) The vegetative cell is larger, has abundant reserve food and a large irregular-shaped nucleus.
(ix) The generative cell is small and spindle-shaped and it floats in the cytoplasm of vegetative cell. It is a cell within the cell.
(x) The generative cell in some cases divides to form two male gametes, thus making the pollen 3-celled.