|The Parts of a Flower
A typical flower grows on a receptacle, or torus, an enlarged part of the flower stalk. The flower consists of four whorls, or sets, of parts. These whorls are (1) the calyx, (2) the corolla, (3) the stamens, and (4) the pistils.
The outermost whorl is the calyx. Within the calyx is the corolla. The calyx and corolla together form the perianth. The stamens, or male reproductive organs, lie within the corolla. The pistils, or female parts of the flower, make up the innermost whorl of parts.
The Calyx is usually made up of small, green, leaflike sepals. These sepals protect the delicate inner parts of the flower bud. When the bud matures, the sepals usually spread apart widely, and may drop off. To prevent such insects as ants and beetles from climbing into the flower from below, the sepals may bend backward or bear special bristly structures.
The Corolla usually consists of a group of colorful petals. The bright colors of the corolla attract insects and birds that pollinate the flower. Some flowers, such as the anemones, have no corolla. Their sepals have become petal-like in color and function. In many plants of the lily family, the sepals and petals are almost identical in size, shape, and color. Such sepals and petals together are called tepals. Lizard's-tail flowers have neither calyx nor corolla, and botanists call them naked flowers.
The petals of a flower may unite to form a structure resembling a tube, saucer, pouch, or other object. In the morning-glory, the corolla looks like a bell; in the moccasin flower, like a slipper; in the canary-bird vine, like a tiny flying canary; and in the sacred datura, like a long trumpet. The doubled flowers of our gardens, such as carnations and cabbage roses, may have hundreds of petals.
The Stamens may vary in number from one to more than a thousand. They are usually separate from each other. But in some flowers they grow together to form a ring or cup. In others, such as lobelias, lupines, and mallows, they join to form a tube.
In most plants, each stamen has a long, narrow filament, or stalk. Most filaments are like threads, but some are flat and look like paper. Others may have winged or toothlike edges. On top of the filament is an enlargement called the anther. The anther usually consists of four baglike structures called pollen sacs or micro-sporangia. Dustlike pollen is produced in the sacs. Stamens are called staminodes if they lack anthers or if the anthers fail to produce pollen.
The Pistils may vary in number from one to many. In some flowers, several separate pistils may join together to form a single compound pistil. Each pistil normally consists of three parts: the stigma, the style, and the ovary.
The stigma, at the top, may be large and feathery or small and hard to see. When the stigma is "ripe," its sticky upper surface catches and holds any pollen grains that fall on it. Beneath the stigma, the long, slender style leads to a round or long chamber called the ovary. Sometimes the pistil has no style, and the stigma rests directly on top of the ovary. The ovules (egg cells) that develop into seeds, grow inside the ovary.
|The Robinson Library > Science > Botany > Plant Anatomy|
This page was last updated on 03/11/2014.