Complete the following flow chart

Pollen Mother cell $\to $ Pollen tetrad $\to $ Pollen grain $\to $ Vegetative cell

Pollen Mother cell $\to $ Pollen tetrad $\to $ Pollen grain $\to $   ……….

$A$ : The generative cell comes to lie freely in the cytoplasm of the tube cell.
$R$ : Cellulosic wall around generative cell is dissolved.

Intine of pollen grains is composed of

Pollen grains are generally _________ in outline measuring _________ micrometers in diameter.

Generally in the wall of the anther lobes how many middle layers are formed