Apomixis is also called as adventive embryony is method of fertilization from cells or than egg cells. Adventive embryony is possible when embryo develops from integuments or nucellus.

The transfer of pollen grains from anr of one flower to stigma of anor flower of  same plant is called geitonogamy.

The octants (eight embryonic) cells divide periclinally (type of cell division that occurs parallel to cells) to produce a dermatogen or an outer layer of protoderm. The inner cells differentiate into ground meristem (periblem) and procambium (plerome).

The phenomenon of occurrence of more than one embryo in seed is known as polyembryony. It is of two types: sporophytic and gametophytic polyembryony. In sporophytic polyembryony, embryos arise from zygote or proembryo or from initial sporophytic cells of ovule such as nucellus and integument. Nucellar polyembryony is also known as adventitive polyembryony in which nucellar cells develop into embryos at expense of ors by accumulating dense cytoplasm and starch. These cells divide repeatedly and develop into embryonic mass. For example, citrus, mango and jamun. When embryos arise from gametophytic cell of embryo sac with or without fertilization,  it is known as gametophytic polyembryony.