This is a special type of inflorescence.
Here the receptacle is fleshy and forms hollow ball like structure with an apical opening.
Three types of flowers develop on the inner surface of the receptacle.
The female flowers are towards the base, male flowers are towards the orifice and short styled sterile female flowers are in between, e.g., Ficus sp.
The inflorescence is pollinated by a gall wasp (Blastophaga).