What is placentation? Describe the types of placentation.

(N/A) $\rightarrow$ The ovary contains one or more ovules attached to a flattened,cushion-like structure called the placenta.
$\rightarrow$ The arrangement of ovules within the ovary is known as placentation.
$\rightarrow$ The types of placentation are as follows:
$(i)$ Marginal Placentation: In this type,the placenta forms a ridge along the ventral suture of the ovary,and the ovules are borne on this ridge in 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,it is called axile placentation,e.g.,china rose,tomato,and lemon.
$(iii)$ Parietal Placentation: In this type,the ovules develop on the inner wall of the ovary or on its peripheral part. The ovary is one-chambered but becomes two-chambered due to the formation of a false septum,e.g.,mustard and Argemone.
$(iv)$ Free Central Placentation: When the ovules are borne on a central axis and septa are absent,the ovary is one-chambered; this is called free central placentation,e.g.,Dianthus and primrose.
$(v)$ Basal Placentation: In this type,the placenta develops at the base of the ovary,and a single ovule is attached to it,e.g.,sunflower and wheat.