Porogamy is the entry of pollen tube into ovule through micropyle e.g., Lily. It is the most common form of entry. Mesogamy is the entry of pollen tube into ovule through the sides after piercing through the integuments, e.g., Cucurbita. Chalazogamy is entry of pollen tube into the ovule through the chalaza e.g., Casuarina. Pseudogamy is the precocious development of embryo (before pollination) but the pollination is an absolute requirement of endosperm development, e.g., Poa sp., Allium tuberosum, Parthenium etc.