Flower, part of a plant that is concerned with reproduction. Each flower is borne on a stalk or pedicel, the tip of which is expanded to form a receptacle that bears the floral organs. The sepals are the first of these organs and are normally green and leaflike. Above the sepals there is a ring of petals, which are normally colored and vary greatly in shape. The ring of sepals is termed the calyx, and the ring of petals, the corolla. Collectively the calyx and corolla are called the perianth. Above the perianth are the reproductive organs comprising the male organs, the stamens (collectively known as the androecium) and the female organs, the carpels (the gynoecium). Each stamen consists of a slender stalk, or filament, that is capped by the pollen-producing anther. Each carpel has a swollen base, the ovary, that contains the ovules that later form the seed. Each carpel is connected by a style to an expanded structure called the stigma. Together, the style and the stigma are sometimes termed the pistil. There are 3 main variations of flower structure. In hypogynous flowers (e.g., the buttercup) the perianth segments and stamens are attached below a superior ovary, while in perigynous flowers (e.g., the rose) the receptacle is cuplike, enclosing a superior ovary, with the perianth segments and stamens attached to a rim around the receptacle. In epigynous flowers (e.g., the dandelion) the inferior ovary is enclosed by the receptacle and the other floral parts are attached to the ovary. In many plants, the flowers are grouped together to form an inflorescence (flower cluster). Pollen produced by the stamens is transferred either by insects or the wind to the stigma, where pollination takes place. Many of the immense number of variations of flower form are adaptations that aid either insect or wind pollination.