The pollen tube may enter the ovule by following one of three routes given below : Porogamy-Pollen tube enters the ovule through micropyle, eg, most angiosperms. Mesogamy-Pollen tube enters the ovule through integuments (eg, Cucurbita) or through funiculus {eg, Pistacia). Chalazogamy-Pollen tube enters the ovule through chalazal tissues, eg, Casuarina, Beta vulgaris, Juglens regia, etc.