The tapetum is the inner most wall layer of the microsporangia (pollen sacs) in anthers. These cells nourish the developing microspore mother cells and pollen grains. Besides this it forms the exine, secrete pollen kit and special proteins for pollen grains so as to recognize compatible stigmas

1. Sporopollenin is found in the exine of pollen grains.
2. It is one of the most resistant organic materials, that can withstand high temperature and action of strong acids and alkali; no enzyme is known to digest it.

Microsporogenesis :
(i)When the anther develops, each cell of sporogenous tissue functions as microspore mother cell (MMC) or pollen mother cell (PMC) and undergoes is meiotic divisions to form microspore tetrads.
(ii) The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis.
(iii) The microspores get arranged in a cluster of four cells and hence are microspore tetrad.
(iv) As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains
(v) In each microsporangium, thousands of pollen grains are formed and released with the dehiscence of anther.

(i) The process of formation of megaspores from Megaspore Mother Cell or MMC (diploid) is called megasporogenesis.
It occurs inside the nucellus of developing ovule of angiosperms. The process begins very early when nucellus is not conmpletely surrounded by the integuments. The MMC (a large cell containing dense cytoplasm and a prominent nucleus) enlarges in size and divides by meiosis. It first divides transversely into two cells called megaspore dyad. 
These two cells apgain divide transversely as a result, a linear row of four haploid cells megaspore tetrad is produced.

Out of the four megaspores one situated at the chalazal end remains functional and the rest three gradually degenerate. Such a development of embryo sac is called monosporic development, e.g. Pobygonum.
(ii)

(b) (i) The egg cell on fertilisation becomes the zygote, which later forms the embryo
(ii) The polar nuclei fuse to form a diploid secondary nucleus; on fertilisation by a male gamete, it forms the primary endosperm nucleus, which later forms the endosperm.

A received the embryo sac and B received the pollen grain.