In the figure given below label the following parts : male gametes, egg cell, polar nuclei, synergid and pollen tube

The generative cell of a two-celled pollen divides in the pollen tube but not in a three-celled pollen. Give reasons.

$A$ : Initial growth of pollen tube takes place on expenditure of food present in the stigma and style.
$R$ : Pollen tube travels intracellularly and chemotactically.

Function of filiform apparatus is to

Diagram showing entry of pollen tube to the embryo sac. Identify $A$ to $G$ in the diagram

Give information about compatible and incompatible pollen.