Main->Readings->4th Grade Readings->Plants->Part 3
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Flowering plants have one thing all other kinds of plants do not: flowers. Some flowers are colorful, but many others are so small and drab-looking you do not even know the plant has them.
Flowers are actually groups of special types of leaves. They have a different job from most leaves: A flower is the part of the plant where seeds are made.
A gladiola is one example of a flower
In a complete flower, there are four "whorls" made of special leaves. In the center is the first whorl, the stalk-like pistil. Around that, in the second whorl, are the stamens. Circling the stamens are the petals, which may be large and brightly colored but may also be small and brown, depending on the plant. The fourth whorl is the sepals, which protect the base of the flower. Some plants have flowers which do not have all these parts; they are called "incomplete" flowers.
Each part of the flower has a special job. The petals, for instance, surround and protect the other parts of the flower, and if they are brightly colored they work to attract insects or birds.
The stamens and the pistil of the flower are the parts that make seeds. The stamen is the male part of the flower. The thin stalk of the stamen is called the filament, and the sac on its tip is called the anther. The anther may have millions of grains of pollen. A pollen grain is a small object which holds the male cells of a plant. The pistil is the female part of the flower. The top of the pistil is called the stigma. The stalk of the pistil is called the style. At base of the pistil is the ovary, which contains tiny female cells called ovules. These parts are labeled in the picture below.
The stamen is the male part of the flower. At the tips are the anthers, which hold the pollen grains.The stalk is called the filament.
The pistil is the main part of the flower. The tip is the stigma, the stalk is the style, and the base is the ovary.
Inside the ovary are female cells called ovules.
Petals surround and protect the flower parts.
The sepals form a calyx around the base of the flower.
Pollen is carried from the stamens to other flowers of the same kind, by such things as insects, birds, and the wind. The process of moving pollen from stamen to pistil is called pollination.
When the pollen of another flower reaches the pistil, it lands on the stigma. Something peculiar happens next. The pollen grain forms a tube which grows down the style to the ovary. Two male cells from the pollen grain travel down the tube, and join with a female cell in the ovary. When male and female cells join, the process is called fertilization.
After fertilization, the joined cell and others like it grow and change and form a seed. The ovary gets thicker too, and the petals drop off because they are no longer needed. Gradually, the ovary forms a fruit with the seeds inside it. If you look at an apple, you will realize that the tiny leaf-like parts at the bottom are what is left of the sepals.
When you think of a fruit, you probably think of something sweet like an apple or an orange. However, to a botanist a "fruit" is the part of a plant that holds the seeds. Therefore, a cucumber is a fruit too, and so is a squash or a walnut.
Go on to Part 4: Photosynthesis
This page last modified on December 31, 2002