For an interesting discussion on the origin of flowering plants, the reader is referred to Peter Crane, et.al. In order to understand angiosperm reproduction and their life cycle, knowledge of floral anatomy is necessary. The following diagram indicates the major structures, which are defined in the Glossary . Flowers may be perfect, containing both male and female structures, or imperfect, containing only one sex. Furthermore, they may be complete, possessing sepals, petals, stamens and pistils, or incomplete, lacking one or more of these structures.
Sepals enclose and protect the remaining flower during the bud stage.
The collection of sepals is called the calyx. Further interior lie the petals, which together comprise the corolla. The corolla is usually the showy part of the flower and serves to attract potential pollinators. The calyx and corolla are collectively known as the perianth. Centermost on the flower is the female reproductive organ, or pistil, which may consist of one to several carpels.