POSTION OF GYNOECIUM ON THE THALAMUS:
Based on the position gynoecium on the thalamus in relation to other floral parts, flowers are divided into three types, as follows:
1. Hypogynous Flowers, 2. Perigynous Flowers and 3. Epigynous Flowers.
HYPOGYNOUS FLOWERS:
Thalamus is convex or conical.The gynoecium is present at the tip of the thalamus.
The remaining floral parts like calyx, corolla, androecium are arranged at the base of the gynoecium.In this flower, ovary is completely present outside the thalamus. So it is called 'SUPERIOR OVARY'. Examples:Hibiscus, Datura.
PERIGYNOUS FLOWERS:
Thalamus is concave or saucer shaped.The gynoecium is located centrally in the thalamus. The remaining floral parts like calyx, corolla, androecium are arranged along the margins.In this flower, ovary wall is adnated to thalamus only at the base.
In this flower, ovary is present partly inside and partly outside the thalamus. So the ovary is called HALF-INFERIOR or HALF SUPERIOR OVARY.
Example:Tephrosia.
EPIGYNOUS FLOWERS:
The thalamus is deep cup like in appearance.
The ovary of the gynoecium is completely embedded in the thalamus.
The wall of the ovary is completely fused with thalamus.The remaining floral parts like calyx, corolla and androecium are arranged along the margins of the thalamus.
The ovary is completely inside the thalamus. So the ovary is called 'INFERIOR OVARY'. Example:Tridax.

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