Discuss the various types of pollen tube entry into ovary with the help of diagrams.

After pollen germination pollen tube enters into ovary by passing through style and enters into ovule by any one of the following three methods. They are :
A) Porogamy B) Chalazogamy C) Mesogamy
A) Porogamy: Pollen tube enters into ovule through micropyle of ovule. Eg : Ottelia
B) Chalazogamy : Pollen tube enters into ovule through chalaza. Eg : Casuarina
C) Mesogamy : Pollen tube enters into ovule through integuments. Eg : Cucurbits