One of the following events is precursor to seed habit and considered as important step in evolution.
Sporophyte becoming independent.
Megasporangia developing integuments.
Fertilisation and zygote formation in female gametophyte.
Formation of young embryos from zygote within the female gametophyte.
Formation of young embryos from zygote within the female gametophyte is considered as precursor to seed habit and an important step in evolution.