Abstract: The development of the ovule, megaspore and megagametophyte in Populus del-toides Bartr. cv. ’Lux’ (ex.I-69/55), Populus × euramericana (Dode) Guinier. cv. ’San Martino’ (ex. I-72/58) and Populus × euramericana (Dode) Guinier (ex. I-214) of Aigeiros poplars was observed. The ovule is anatropous, unitegmic and crassinu-cellate. Both integuments originate from the epidermis. The archesporium is considered to be unicellular. The primary sporogenous cell functions as the megaspore mother cell which forms a linear tetrad. The chalazal member of the megaspore tetrad is functional and develops into a polygonum-type embryo sac. During the later stages of development the megagametophyte projects through the nucellus into the micropyle. The archesporium is considered to be multicellular, but more than one archesporial cell may develop and thus two linear tetrads of megaspores may be found in few ovules of I-72. In some ovules of I-72, the second megaspore in the charazal region of the tetrad is functional.