Flower- is the reproductive structure of angiosperms or flowering plant.  Compared to the reproductive structures of other plants. the flower is unique in several ways. Its consists of four kinds of modified leaves. two of which ( stamens and pistils) bear pollen and seeds. Several non flowering plants also produce pollen and seeds on modified leaves. but in the angiosperms the pletely encloses the ovule, which becomes the seed. The term Angiosperms is derived from the greek and means "seed in a vessel".

Four kinds of modified leaves make up a complete leaves

Primary reproductive structures

1. Pistil  
2. Stamens

Secondary Structures

1. Petals
2. Sepals

Pistil is the female reproductive structure; It has a stigma which through pollen tube grows; and ovary with one or more ovules.

Stamens- also vary in several ways, although not as markedly as ovaries.

Petals or Sepals- taken together form the corolla which take numerous and often beautiful forms.

If flowers is lacking anyone of the four basic parts, it is said to be incomplete. Flowers that have both stamens and pistils but lack petals or sepals are described as perfect incomplete flowers. Imperfect flowers can be either male or female. If both male and female flowers occur on the same plant , the plant is said to be monoecious; if male and female  flowers  are on separate plants the species is dioecious.