Exalbuminous seeds are of

When the pollen grains are not transferred from anthers to the stigma in flower due to the barrier or fence, it is referred as or when some natural barrier exists between androecium and gynoecium to check self pollination, it is known as

A schematic illustration of the pollen grain is called

$A$ : In sporoderm, pectocellulosic layer is surrounded by sporopollenin.
$R$ : Exine is differentiated into outer ektexine and inner endexine.

Which layer of cells possess dense cytoplasm and generally have more than one nucleus ?