|flower (flou'ər) Pronunciation Key
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The reproductive structure of the seed-bearing plants known as angiosperms. A flower may contain up to four whorls or arrangements of parts: carpels, stamens, petals, and sepals. The female reproductive organs consist of one or more carpels. Each carpel includes an ovary, style, and stigma. A single carpel or a group of fused carpels is sometimes called a pistil. The male reproductive parts are the stamens, made up of a filament and anther. The reproductive organs may be enclosed in an inner whorl of petals and an outer whorl of sepals. Flowers first appeared over 120 million years ago and have evolved a great diversity of forms and coloration in response to the agents that pollinate them. Some flowers produce nectar to attract animal pollinators, and these flowers are often highly adapted to specific groups of pollinators. Flowers pollinated by moths, such as species of jasmine and nicotiana, are often pale and fragrant in order to be found in the evening, while those pollinated by birds, such as fuschias, are frequently red and odorless, since birds have good vision but a less developed sense of smell. Wind-pollinated flowers, such as those of oak trees or grass, are usually drab and inconspicuous. See Note at pollination.