Fertilization and seed development were studied inCrocus sativusL., after pollination withCrocus thomasiiTen. Fertilization was porogamous and resulted in the formation of zygote and primary endosperm nucleus; it was accompanied by degeneration of the receptive synergid and followed by degeneration of the antipodals. The endosperm developed precociously by free nuclear division, occuping a parietal position; subsequently it filled the central vacuole and became cellularized. The zygote divided after a quiescence period by formation of a transversal wall; its division was accompanied by degeneration of the persistent synergid. The embryo developed from the apical cell and, at maturity, was a cylindrical structure showing histological differentiation of the shoot apex. The seed coat was formed from both integuments. Both embryogeny and development of the endosperm and seed coat were entirely similar to those ofCrocus thomasii.