What part of the flower contains the male gametophyte?

Pollen grain

Explanation:

Male gametophyte in the flowering plant is much reduced and is dependent upon the sporophyte. Anthers of flowers contain pollen sac or microsporangia where microspore mother cells (MMC) are present. These microspore mother cells undergo meiosis to form four haploid microspores per MMC. Every microspore develops into an immature male gametophyte and is called a pollen grain. Each pollen grain consists of two cells: the tube cell and the generative cell. Once upon stigma, the germinated pollen grain with its pollen tube is the mature male gametophyte. The generative cell of the pollen grain divides to form two sperm cells.