In Casuarina fertilisation takes place through

In Casuarina, fertilization takes place through Chalazogamy.
The meaning of Chalazogamy is a process of fertilization in which the pollen tube penetrates the embryo sac through the tissue of the chalaza.
A process of fecundation in which the pollen tube penetrates the embryo sac through the tissue of the chalaza, instead of entering through the micropyle.