Answer:
Androecium:
Androecium is the third whorl, which is the male reproductive part of the flower.
Unit:
Its units are called stamen.
Stamen:
Each stamen has a thread like filament at the free end of which anther is attached.
Anther:
Anther has pollen sacs in which haploid microspores (pollen grains) are produced through meiosis.
Process:
Each microspore germinates into the male gametophyte generation. During it, the nucleus of microspore undergoes mitosis ans produces two nuclei i.e. a tube nucleus and a generative nucleus. The generative nucleus again undergoes mitosis and produces two sperms. So, a germinated microspore has a tube nucleus and two sperms. All these structures are the male gametophyte generation of the plant.