In a bisexual flower, the male reproductive part is the stamen, which consists of the anther and the filament.
\begin{itemize}
\item (a) Anther: The anther is the part of the stamen that produces pollen grains. Pollen grains contain the male gametes.
\item (b) Ovary: The ovary is part of the pistil (female reproductive part) and contains ovules, which house the female gamete (egg cell).
\item (c) Stigma: The stigma is the receptive tip of the pistil where pollen lands.
\item (d) Filament: The filament is the stalk that supports the anther.
\end{itemize}
The male gametes are developed within the pollen grains, which are produced in the anther.
\[ \boxed{\text{anther}} \]