Placentation is the arrangement of ovules within the ovary. Marginal placentation places them along a ridge on the ventral suture, as in pea. Axile placentation places them on a central axis in a multilocular ovary, as in china rose, tomato and lemon. Both attachment position and partitions matter.

In parietal placentation, ovules attach to the inner wall or periphery, as in mustard and Argemone. A false septum can make the mustard ovary appear two-chambered; chamber count alone should not change the classification to axile. Free-central placentation has ovules on a central axis without septa, as in Dianthus and Primrose. Basal placentation has an ovule attached at the base, as in sunflower and marigold.

In a transverse diagram, first locate the ovules, then trace their attachment. A central-looking cluster alone is not enough to distinguish axile from free-central; inspect whether septa divide the ovary into locules. A longitudinal section may be more helpful for basal placement. Use the supplied section orientation before interpreting apparent position.

Worked example: A central column without septa supports free-central placement. Adding septa and multiple locules changes the relevant comparison to axile.

NCERT trap: Mustard’s false septum does not convert wall attachment into axile placentation.

NEET method: Identify attachment first and true septa second; do not classify from chamber number alone.

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Morphology of Flowering Plants

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