The arrangement of ovules within the ovary is known as placentation. The placentation can be seen by taking a transverse section and vertical section of ovary.
Types of placentation
1. Marginal placentation: Placenta forms ridge along the ventral suture of the ovary in monocarpellary unilocular pistil and the ovules are born on ridge forming two rows, as in pea, Crotalaria.
2. Axile placentation: In this type the ovary is multilocular, and the placenta is axial. The ovules are arranged at the center of multilocular ovary e.g., members of family Malvaceae, lemon orange, tomato, China rose.
3. Parietal placentation: In this type the ovules develop on the inner wall of the ovary or on peripheral part. Here ovary is one chambered but it become two chambered due to the formation of false septum. e.g., mustard, radish and Argemone.
4. Free central placentation: The placenta arises from the base pf ovary, projects into the cavity as a swollen axis. Ovules are born on central axis and septa is absent, the placentation is said to be free central placentation as in Dianthus, Primula etc.
5. Basal Placentation: When placenta develops at the base of ovary and single ovule attached to it in unilocular ovary such placentation is known as basal placentation. e.g., sunflower, marigold etc.
