The arrangement of ovules within the ovary is known as placentation. The placentation are of different types namely, marginal, axile, parietal, basal, central and free central.

When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentaion is said to be axile (Figure A), as in china rose, tomato and lemon.

When the ovules are borne on central axis and septa are absent, as in Dianthus (carnation) and Primrose the placentation is called free central. (Figure B)

In marginal placentation (Figure C) the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, as in pea.

In parietal placentation (Figure D), the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two chambered due to the formation of the false septum, e.g., mustard and Argemone.