Euphorbia geniculata – ovule to seed

A comparative histogenetic study of ovules of some representatives of the genus Euphorbia reveals a remarkable similarity during the pre-fertilization stages. The inner integument is initiated first. Mitotic activity in the subdermatogen causes the initiation of integuments as well as the apical growth of the nucellus. Subsequent mitotic activity in the dermatogen contributes to the formation of the multi-layered micellar flanks, the distal region of integuments, and the caruncle. During the post-fertilization stages the basal part of the nucellus develops into a podium. The basal cells of the inner epidermis of the inner integument elongate appreciably, whereas its proximal cells add to the formation of a podium. The funicular vascular supply extends into the base of the inner integument. The suspensor of the embryo is embedded in the remnants of the nucellar beak which persists in the mature seed. Enucleate cytoplasmic vesicles project into the central vacuole of the nuclear endosperm. The dermal cells of the placental obturator elongate radially and form uni- and multi-cellular hairs. Development of the female gametophyte follows the Polygonum type.