Placenta are soft cushion like tissues with which the ovules are attached to the inner surface of ovary wall.
The arrangement of ovules within the ovary is known as placentation. The placentations of different types, i.e., marginal, axile, parietal, basal and free central.
Marginal Placentation In this placentation, the placenta forms a ridge along the suture of the ovary and the ovules are borne on this ridge forming two rows, asin pea.
Axile Placentation In this placentation, the ovules are borne on central axis and marginal of placenta grow in word and fuse, thus making a multilocular Ovary, as in rose, tomato, etc.
Parietal Placentation In this placentation, the ovules develop on the inner wall of the ovule or on peripheral part. Ovary is one chambered but it becomes two chambered due to formation of a false septum known as replam, e.g., mustard.
Free Central Placentation In this type of placentation, the ovules are present on central axis of ovary and septa is absent so Ovary is unilocular, as in Dianthus and Primo.
Basal Placentation In this placentation, the placenta develops at the base of ovary an single ovule is attached to it, as in sunflower.
