The arrangement of ovules within the ovary is known as placentation. What does the term placenta refer to? Name and describe various types of placentations in flowers as seen in $T.S.$ or $V.S$.

(N/A) $\rightarrow$ Placenta: The placenta is a flat,cushion-like tissue to which one or more ovules are attached.
$\rightarrow$ The arrangement of ovules within the ovary is called placentation.
$\rightarrow$ The types of placentation are as follows:
$(i)$ 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 placentation 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 the 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 basal placentation,the placenta develops at the base of the ovary,and a single ovule is attached to it,e.g.,sunflower,wheat.