Which of the following layers of the microsporangium provides nutrition to the developing pollen grains?

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

In angiosperms,the male gametes are produced by the division of the ..........

Pollen grains are generally spherical,measuring about

Consider the following statements and choose the correct answer from the given options.
$Statement \ 1$: Innermost layer of microsporangium is tapetum.
$Statement \ 2$: Cells of tapetum possess dense cytoplasm, more than one nucleus, and nourish the developing pollen grains.

Majority of pollen grains are shed at