Stamens of a flower. The stamens (upper centre) are the male reproductive organs of a flower. Each stamen is composed of a stalk (filament), which holds an anther. The anther contains microsporangia, the producers of pollen. At the base of the stamens is the female reproductive organ (pistil). However, some species of plants are unisexual and a flower with only functional stamens is called a staminate flower.