The Japanese call these flowers "muda-bana". An abortive flower is a flower that has a stamen but an under developed, or no pistil. It falls without producing fruit or seeds, due to its inability to fructify. Flowers require both male and female organs to reproduce, and the pistils and ovary serve as female organs, while the stamens are considered male organs.
Illustrative examples include Urginea nagarjunae and Trichilogaster acaciaelongifoliae.
References
Abortive flower Wikipedia(Text) CC BY-SA