Calyx and corolla are the two accessory whorls of a flower that possess the units, sepals and petals, respectively. These organs provide protection to the inner reproductive whorls. The mode of arrangement of sepals and petals, with respect to one another in the bud condition of a flower, is known as aestivation. Valvate, imbricate, twisted, quincuncial and vexillary are the different types of aestivation.

The ovary is the swollen basal portion of the carpel of the gynoecium in which ovules are located. The ovules remain attached to the inner wall of the ovary to a parenchymatous outgrowth called the placenta. Placentation is the arrangement of the ovules on the placenta. Different types of placentations are found in plants such as: Marginal: Here, the placenta develops along the junction of the two margins of the carpel. Axile: In this, the placenta develops from the central axis of a multilocular ovary and the ovules placed along the axis. Parietal: The placenta develops in the inner wall of the ovary. Basal: The placenta develops from the base of one chambered ovary. Free central: The placenta develops from the central axis of one chambered ovary.

The process of the transfer of pollen grains from the anther of the stamen to the stigma of the carpel of the same flower or of a different flower of the same or closely related species is called pollination. Pollination is of two types: self-pollination and cross-pollination. If the pollination takes place within a plant, then it is called self-pollination. If self-pollination takes place within the same flower, is called autogamy. When pollination takes place between different plants of the same or allied species, then it is called cross-pollination. It is also called allogamy.

Herkogamy is an outbreeding device of a bisexual flower that prevent self-pollination. In this condition, the pollen grains are unable to reach the stigma of the same flower because of spatial separation of the anthers and stigma. The anthers and stigma are arranged in different height or position is an example of herkogamy. It encourages cross-pollination. Example: Gloriosa superba.