Q.The arrangements of ovules within the ovary is known as placentation. What does the term placenta refer to? Name and draw various types of placentations in the flower as seen in T.S. or V.S.

The placenta is the flattened, cushion-like structure inside the ovary to which one or more ovules remain attached. The way these ovules are arranged on the placenta within the ovary is called placentation, and several distinct types are recognised. In marginal placentation, the placenta forms a ridge along the ovary's ventral suture with ovules in two rows, as in pea. In axile placentation, the placenta is axial within a multilocular ovary, as in china rose, tomato and lemon. In parietal placentation, ovules develop on the ovary's inner wall, the ovary appearing two-chambered due to a false septum, as in mustard. In free central placentation, ovules sit on a central axis with no septa present, as in Dianthus. In basal placentation, the placenta develops at the base of the ovary with a single attached ovule, as in sunflower. …

Each ovary bears one or more ovules, and these ovules are not scattered loosely within the ovary but are attached to a specific structure.

• The placenta is described as a flattened, cushion-like tissue within the ovary, to which the ovules remain attached.
• Placentation is simply the term for how this placenta, and the ovules on it, are arranged within the ovary, and five distinct patterns are recognised.

In transverse or vertical section, each type would look distinct:

• Marginal placentation: the placenta forms a ridge running along the ventral suture of a single-chambered ovary, with ovules borne in two rows along this ridge, as in pea; a transverse section would show two rows of ovules along one edge of a single, undivided cavity.
• Axile placentation: the placenta is axial, running through the centre of a multilocular ovary, with ovules attached to it within each chamber, as in china rose, tomato and lemon; a transverse section would show several wedge-shaped chambers meeting at a central axis bearing ovules.
• Parietal placentation: ovules develop along the inner wall of the ovary, which starts out as a single chamber but becomes divided in appearance into two by a false septum, as in mustard and Argemone; a transverse section would show ovules attached near the outer wall rather than at a central axis.
• Free central placentation: ovules are borne on a central axis, but here the septa that would otherwise divide the ovary are entirely absent, as in Dianthus and Primrose; a transverse section would show a single chamber with a free-standing central column bearing ovules. …

Method: Two Independent Checks (Ovary Chambers + Placenta Position) Combine to Give All Five Types

This question is essentially the same content as describing placentation types but framed around drawing transverse and vertical section views, so the method is to combine two independent checks, rather than memorizing five names, and let their combination generate all five types systematically.

First, define the placenta itself in one line: the placenta is simply the cushion-like tissue inside the ovary that the ovules are physically attached to, nothing more complicated than the ovule's attachment point.

Check A, how many chambers does the ovary have, one, several with true walls or septa, or one but with a false septum making it look like two?

Check B, where is the placenta positioned within that chamber structure, on a ridge along one seam, on a central axis, along the outer wall, or right at the base? …