Supplies: As many flowers, of some kind (hibiscus, lilies) that clearly show the calyx, corolla, stamens and pistils. The larger the flowers are that show these parts the better. Make sure there are enough flowers for each student Magnifying lenses for each student. Utility knife for yourself
Necessity of Flowers-(
Tell the students) Many flowers are among the most beautiful and delicate of natural objects. While flowers delight us by their beauty and fragrance, they serve a very important use both to man and to the plant that bears them. Without flowers, plants could not bear the fruits and vegetables we prize so much for food, and the seeds. Without seeds, most kinds of plants would soon disappear, for they could form no more little plants to take the place of those who die.
Parts of the Flower-(
Explain to the students) Flowers are prettiest when left whole, but in this lesson we are to to learn the names and uses of the different parts of the flower,so we shall need to pull the flowers to pieces somewhat. A flower, when complete, has four main parts, each of which has a name and use. These four main parts are composed of smaller parts, each of which also has its name. (
Handout flowers and lenses)
The Calyx and the Sepal- (
Direct students attention to the base of the flower)(
Explain to students) At the base of the flower, we find a green part, called the calyx. In some flowers, the calyx is composed of several more or less leaf like parts, each of which is called a sepal. The calyx is green in most flowers. The calyx forms a sort of cup that supports the rest of the flower. (Have students study calyx under lens, then direct them to remove the sepals and count them)
The Corolla and the Petals-(
Tell the students) The corolla consists of distinct parts called petals. In many plants, like the morning glory and pumpkin, the petals are joined. The corolla is usually of some other color than green. This helps to make the
flower more easily seen, so that insects can find it. (Tell students to study petals under lens, then carefully remove them and count them)
The
stamen and their Parts-(
Tell the students) Inside the corolla is a group of slender organs, called the stamen. Each stamen consist of three parts; the long and slender portion attached to the calyx, below, called the filament; the swollen portion at the top, called the anther; and a dust like
substance found on or within the anther, called pollen.
The function of the stamen is to produce pollen, without which
seeds can not be formed. Some flowers have many stamens, while others do not have so many. (Tell the students to carefully remove the stamens and look at them under the lens.Help students locate the two parts of the stamen)
The Pistil and its Parts.-(Explain to the students) the column like part in the center of the flower is called the pistil. This, also consist of three main parts. The enlarged top is called the stigma; the egg shaped base is called the ovary; and the slender part connecting the
stigma and the ovary is called the style. The ovary contains a smaller egg shaped part, called the ovule, which may later become the seed. Many flowers have more than one pistil, and many ovaries contain more than one ovule. The pistil forms and protects the ovules until they become seeds.(Help students locate the three parts of the pistil. Cut the ovaries so that the students can view cross sections and look for the formation of ovules)
Pollination-When the pistil is mature, a drop of a sticky liquid forms on the stigma, so that a grain of
pollen that happens to touch it sticks fast. If the pollen grain is from the same flower as the pistil, or from another flower of the same kind, it puts out a long tube that grows through the style into the ovary, where it comes in contact with the ovule, after which the ovule grows into a seed. The alighting of the pollen grain on the stigmas is called pollination.
If no pollen grain of the same kind alights on the stigma, the ovule does not become a seed, and dies. Bees and some other insects visit the flowers to get honey or pollen from them which they use as food. In entering the flowers, they become more or less dusted with the pollen, and as they rub against the stigma, they aid much in pollination. These insects help flowers form fruit or seeds, as so their visits to the flowers are very useful.
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