Gynoecium is the female reproductive part of the flower and is made up of one or more carpels. A carpel consists of three parts: stigma, style and ovary. Ovary is the enlarged basal part, on which there is an elongated tube, the style. The style connects the ovary to the stigma. The stigma is usually at the tip of the style and is the receptive surface for pollen grains. Each ovary bears one or more ovules attached to a flattened, cushion-like placenta. When more than one carpel is present, they may be free (as in lotus and rose) and are called apocarpous. When carpels are fused (as in mustard and tomato) they are called syncarpous. After fertilisation, the ovules develop into seeds and the ovary matures into a fruit.
Placentation: The arrangement of ovules within the ovary is known as placentation. The placentation is of different types: marginal, axile, parietal, basal, central and free central.
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, as in pea.
In axial placentation the ovules are attached to placenta in a multilocular ovary as in china rose, tomato and lemon.
In parietal placentation, the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of the false septum, e.g., mustard and Argemone.
In free central placentation the ovules are borne on central axis and septa are absent, as in Dianthus and Primrose.
In basal placentation, the placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.