After arriving at the top of ovary the pollen tube may enter the ovule by following three ways: [a] By micropyle: The entry of pollen tube into ovule through micropyle is called porogamy. [b] By chalaza: The entry of pollen tube in the ovule through chalaza is called chalazogamy. [c] By integument: The entry of pollen in the ovule through integument is called mesogamy.