An ovary with ovules arranged along its walls is said to have ------------ placentation.

Analyze the question: It asks for the type of placentation where ovules are attached along the walls of the ovary.

Concept: Placentation is the arrangement of ovules inside the ovary. The main types are:

• Marginal: The ovules are attached along one margin (suture) of a single carpel, as in pea and beans (a simple ovary with one chamber).
• Axile: The ovary is divided into chambers, and the ovules are attached to a central axis where the partitions meet, as in hibiscus, tomato and orange.
• Parietal: The ovary has one chamber, and the ovules are attached to the inner walls of the ovary, as in pawpaw and cucumber.
• Free central: The ovary has one chamber, and the ovules are attached to a central column that does not reach the walls, as in primrose and Dianthus.
• Basal: A single ovule sits at the base of the ovary, as in sunflower.

Solution: The question says the ovules are arranged "along its walls." This matches the definition of parietal placentation, where ovules are borne on the inner wall of a one-chambered ovary formed from fused carpels.

Marginal placentation (D) is a close distractor. It is found in a single carpel, with ovules along one edge, usually described as along the "margin" or "suture," not generally along the walls. Axile (A) and free central (C) involve a central axis, not the walls. "Central" (B) is not a standard type on its own.

Answer: E. parietal

Exam tip: Think "Parietal = Perimeter/wall." Parietal means "of the wall." Remember pawpaw for parietal and hibiscus/tomato for axile.