In angiosperms, during development of embryo the suspensor cells develop from

The oospore divides transversely forming two cells, a terminal cell and basal cell. The cell towards the micropylar end of the embryo sac is the suspensor cell (i.e., basal cell) and the other one makes to the embryo cell (i.e., terminal cell). The terminal cell by subsequent divisions gives rise to the embryo, while the basal cell contributes the formation of suspensor.