What is placentation ? Describe types of placentation.

$\rightarrow$ Ovary bears one or more ovules attached to a flattened cushion like placenta.
$\rightarrow$ The arrangement of ovules within the ovary is called placentation.
$\rightarrow$  The types of placentation are as follow:
$(i)$ Marginal Placentation : In marginal placentation the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows e.g. pea, bean.
$(ii)$ Axile Placentation : When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentaion is said to be axile. e.g. china rose, tomato and lemon.
$(iii)$ Parietal Placentation : In parietal placentation, 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.
$(iv) $ Free Central Placentation : When the ovules are borne on central axis and septa are absent ovary is one-chambered so it is called free central e.g. Dianthus and Primrose.
$(v)$ Basal Placentation : In basal placentation, the placenta develops at the base of ovary and a single ovule is attached to it, e.g. Sunflower, Wheat.