Flower

A flower is the reproductive part of the plant. Flowers are bisexual but some flowers are unisexual. It contains calyx, corolla, androecium, & gynoecium.

The flower is the reproductive part of the plant. Usually, flowers are bisexual but some flowers are unisexual too. It usually contains calyx, corolla, androecium, and gynoecium.

1. Calyx: It is the outermost whorl. It is green in color. It protects the flower during the bad stage.
2. Corolla: It is the part of the inner to the calyx. It is colorful. It has a strong odor. Corolla helps in pollination by attracting visiting insects.
3. Androecium: The male reproductive part of a flower is called androecium. It is a collection of stamens. A stamen is made from filaments, anther, and connective. The anther contains pollen grains.
4. Gynoecium (Pistil): The female reproductive part is called gynoecium or pistil. It consists of carpals. Carpals are made from the ovary, style, and stigma. The ovary contains ovules.

Pollination

The process of transfer of pollen grains from another to the stigma of flowers is called pollination.

There are two types of pollination, they are:

1. Self-Pollination
2. Cross-Pollination 

1. Self-Pollination

The process of transfer of pollen grains from the anther to the stigma of the same flower or different of the same plant is called self-pollination.

Mostly, bisexual flowers have self-pollination. External agents aren’t required for it. It doesn’t bring variation in offspring.

2. Cross-Pollination

The process of transfer of pollen grains from the anther of a flower to the stigma of another of the different plants of the same species is called cross-pollination.

Mostly, unisexual flowers have cross-pollination. External agents are required for cross-pollination. It brings variation in offspring.