The arrangement of ovules inside the ovary of a flower is known as placentation. The different types of placentation are:
(1) Marginal placentation- The placenta forms a ridge along through the ventral suture of the ovary, ovules are borne on the ridge to form two rows. Example: Pea
(2) Axile placentation- The placenta is axial and ovules are attached to it in a multilocular ovary. Example: Lemon
(3) Parietal placentation- Ovules develop on the inner wall of the ovary or on the peripheral. It is single-chambered, but due to the formation of a false septum, it becomes two-chambered. Example: Mustard
(4) Basal placentation- Placenta develops at the base of the ovary wherein a single ovule is attached to it. Example: Marigold
(5) Free central placentation - Ovules are borne on the central axis and septa are absent Example: Primrose