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Flowers
Flowers, which generally are the showiest part of a plant, have sexual reproduction as their sole function. Their beauty and fragrance have evolved not to please humans but to ensure continuance of the species. Fragrance and color attract pollinators (insects or birds) that play an important role in the reproductive process.
Flowers are important for plant classification. The system of plant nomenclature we use today was developed by Carl von Linné (Linnaeus) and is based on flowers and/or reproductive parts of plants. One reason his system is successful is because flowers are the plant part least influenced by environmental changes. Thus, a knowledge of flowers and their parts is essential for anyone interested in plant identification.
Structure
As a plant's reproductive part, a flower contains a stamen (male flower part) and/or pistil (female flower part), plus accessory parts such as sepals, petals, and nectar glands (Figure 19).
The stamen is the male reproductive organ. It consists of a pollen sac (anther) and a long supporting filament. This filament holds the anther in position, making the pollen available for dispersement by wind, insects, or birds.
The pistil is a plant's female part. It generally is shaped like a bowling pin and is located in the flower's center. It consists of a stigma, style, and ovary. The stigma is located at the top and is connected by the style to the ovary. The ovary contains eggs, which reside in ovules. If an egg is fertilized, the ovule develops into a seed.
Sepals are small, green, leaflike structures located at the base of a flower. They protect the flower bud. Collectively, the sepals are called a calyx.
Petals generally are the highly colored portions of a flower. Like nectar glands, petals may contain perfume. Collectively, the petals are called a corolla. The number of petals on a flower often is used to help identify plant families and genera. Flowers of dicots typically have four or five sepals and/or petals, or multiples thereof. In monocots, these floral parts typically come in threes or multiples of three.
additional resources
floral parts ...
http://gened.emc.maricopa.edu/bio/bio181/BIOBK/anglc_1.gif
ovary ...
http://csdl.tamu.edu/FLORA/tfplab/ovary.jpg
floral parts...
e.g., pistil, stamen, petal, and sepal
http://csdl.tamu.edu/FLORA/tfplab/reproch.htm#basic
