What is the function of filament?

Assertion (A): In some plants the generative cell divides and forms the two male gametes during pollen tube growth in stigma.

Reason(R): In plants which shed pollen in three cell stage, the pollen tube will have two male gametes from the beginning.

The correct option among the following is:

Match the following lists:

The correct match is:

Assertion $\left(\mathrm{A}\right):$ Xenogamy involves transfer of pollen grains from the flower of one plant to the stigma of another plant.

Reason $\left(\mathrm{R}\right):$ This is the only type of pollination which brings genetically different types of pollen grains to the stigma.

The correct answer is:

Assertion $\left(\mathrm{A}\right):$ Pollengrains are well preserved as fossils

Reason $\left(\mathrm{R}\right):$ The exine of pollen grains is made up of sporopollenin, which can withstand high temperatures, strong acids and alkali.

Observe the diagram of the young anther given below:

 Which layer nourishes the developing pollen grain.