Exospermum, of the primitive vesselless angiosperm family Winteraceae, has been described as differing from other genera in the family in having ovules scattered over the internal walls of the carpels. Studies of developing carpels with the scanning electron microscope revealed that ovules are initiated in a single row on each of the two placentas, as in other Winteraceae; subsequently, the numerous crowded ovules become aligned in different directions. This results in the superficial appearance of diffuse placentation; however, even at anthesis, the bases of the funicles are inserted on each placenta in a more or less uniseriate row. Flower structure is summarized.