Outlines of Lessons in Botany, Part I; from Seed to Leaf For the Use of Teachers, or Mothers Studying with Their Children

[Footnote 1: This section may be omitted, and the lessons begun with Seedlings, if the teacher prefer.]

What is Botany? The pupils are very apt to say at first that it is learning about flowers. The teacher can draw their attention to the fact that flowers are only a part of the plant, and that Botany is also the study of the leaves, the stem, and the root. Botany is the science of plants. Ask them what the Geranium is. Tell them to name some other plants. The teacher should keep a few growing plants in the schoolroom for purposes of illustration.

Ask them what else there is in the world besides plants. By this question the three kingdoms, animal, vegetable, and mineral, are brought up. It will give occasion for a discussion of the earth and what it contains, the mountains, formed of rocks and soil, the plants growing on the earth, and the animals that inhabit it, including man. Let them name the three kingdoms with some example of each. Which of these kingdoms contain living things? The words organic and inorganic can be brought in here. An organ ([Greek: Ergon], meaning work) is any part that does a special work, as the leaves, the stem of a plant, and the eye, the ear of animals. An organism is a living being made up of such organs. The inorganic world contains the mineral kingdom; the organic world includes the vegetable and animal kingdoms.

One's aim in these lessons should always be to tell the pupils as little as possible. Try to lead them to think out these things for themselves.

Ask them how plants differ from animals. They will say that plants are fixed to one place, while animals can move about; that plants have no will or consciousness, and that animals have. These answers are true when we compare the higher animals with plants, but the differences become lost as we descend in the scale and approach the border land where botanist and zoologist meet on a common ground. Sea-anemones are fixed to the rock on which they grow, while some of the lower plants are able to move from place to place, and it is hardly safe to affirm that a jelly-fish is more conscious of its actions than is a Sensitive Plant, the leaves of which close when the stem is touched.

There is no real division between animals and plants. We try to classify the objects about us into groups, according to the closeness of their relationships, but we must always remember that these hard lines are ours, not Nature's. We attempt, for purposes of our own convenience, to divide a whole, which is so bound together that it cannot be separated into parts that we can confidently place on different sides of a dividing line.

1. Plants as Food-Producers.--The chief distinguishing characteristic of plants is one that the pupils may be led to think out for themselves by asking them what animals feed upon. To help them with this, ask them what they had for breakfast. Oatmeal is mentioned, perhaps. This is made from oats, which is a plant. Coffee and tea, bread made from wheat, potatoes, etc., all come from plants.[1] Beef, butter and milk come from the cow, but the cow lives upon grass. The plant, on the other hand, is nourished upon mineral or inorganic matter. It can make its own food from the soil and the air, while animals can only live upon that which is made for them by plants. These are thus the link between the mineral and animal kingdoms. Ask the scholars if they can think of anything to eat or drink that does not come from a plant. With a little help they will think of salt and water. These could not support life. So we see that animals receive all their food through the vegetable kingdom. One great use of plants is that they are food-producers.

[Footnote 1: Reader in Botany, for use in Schools. Selected and adapted from well-known authors. Ginn & Co., Boston, New York and Chicago, 1889. I. Origin of Cultivated Plants.]

This lesson may be followed by a talk on food and the various plants used for food.[2]

[Footnote 2: The Flour Mills of Minneapolis: Century Magazine, May, 1886. Maize: Popular Science News, Nov. and Dec., 1888.]

2. Clothing.--Plants are used for clothing. Of the four great clothing materials, cotton, linen, silk, and woollen, the first two are of vegetable, the last two of animal origin. Cotton is made from the hairs of the seed of the cotton plant.[1] Linen is made of the inner fibre of the bark of the flax plant. It has been cultivated from the earliest historical times.

[Footnote 1: Reader in Botany. II. The Cotton Plant.]

3. Purification of the Air.--The following questions and experiments are intended to show the pupils, first, that we live in an atmosphere, the presence of which is necessary to support life and combustion (1) and (2); secondly, that this atmosphere is deprived of its power to support life and combustion by the actions of combustion (2), and of respiration (3); thirdly, that this power is restored to the air by the action of plants (4).

We have the air about us everywhere. A so-called empty vessel is one where the contents are invisible. The following experiment is a good illustration of this.

(1) Wrap the throat of a glass funnel with moistened cloth or paper so that it will fit tightly into the neck of a bottle, and fill the funnel with water. If the space between the funnel and the bottle is air-tight, the water will not flow into the bottle.

Do not explain this in advance to the pupils. Ask them what prevents the water from flowing into the bottle. If they are puzzled, loosen the funnel, and show them that the water will now flow in. In the first case, as the air could not escape, the water could not flow in; in the second, the air was displaced by the heavier water.

Ask the pupils why the air in a crowded room becomes so difficult to breathe. Could a person live if he were shut up in an air-tight room for a long time? Fresh air is necessary to life. The teacher may explain that it is the oxygen in the air that supports life. Air is composed one-fifth of this gas and four-fifths of nitrogen. The gases are mixed and the nitrogen simply dilutes the oxygen, as it were.

Fresh air is necessary to support combustion as well as life. Ask them why we put out a fire by throwing a blanket or a rug over it. The following experiment illustrates this.

(2) Take a small, wide-mouthed bottle, covered with a card or cork. To this cover fasten a piece of bent wire with a taper on the end. Light the taper and lower it into the jar. It will burn a few seconds and then go out. Raise and light it again, and it will be extinguished as soon as it is plunged into the bottle. This shows that the oxygen of the air is used up by burning substances, as it is by breathing animals.

The following experiment shows that fire will not burn in an atmosphere of gas from our lungs.

(3) Fill a bottle with gas by breathing into it through a bit of glass tubing, passed through a card or cork, and reaching to the bottom of the bottle. The bottle will be dimmed with moisture, showing the presence of aqueous vapor. A lighted match plunged into the bottle will be immediately extinguished. A better way, which, however, takes some skill in manipulation, is to fill the bottle with water, cover it with a flat piece of glass, and invert the bottle in a dish of water, taking care that no air bubbles enter. Then, through a bit of glass tubing, blow into the bottle till the water is expelled. Cover the mouth with the glass under water, and holding it tightly down, invert the bottle quickly. Set it down, light a match, take away the glass, and at the same instant plunge in the match. If no air has been allowed to enter, the match will go out at once. No animal could live in an atmosphere which could not support combustion.

From these experiments the pupils have seen that the life-sustaining quality of the air is used up by combustion and respiration. To bring in the subject of purification by plants, ask them why all the oxygen in the world is not exhausted by the people and the fires in it. After the subject has been explained, the following experiment can be prepared and put aside till the next lesson.

(4) Fill two bottles with air from the lungs, as in (3) having previously introduced a cutting from a plant into one of the bottles. Allow them to stand in the sun for a day or two. Then test both bottles with a burning match. If properly done, the result will be very striking. The end of the cutting should be in the water of the dish. This experiment will not succeed excepting with bottles such as are used for chemicals, which have their mouths carefully ground. Common bottles allow the air to enter between the bottle and the glass.[1]

[Footnote 1: See note on page 13.]

4. Fuel.--Light a match and allow it to burn until half charred. Blow it out gently, so as to leave a glowing spark. When this spark goes out it will leave behind a light, gray ash. We have to consider the flame, the charred substance, and the ash.

Flame is burning gas. In all ordinary fuels, carbon and hydrogen, in various combinations and free, make the principal part. The first effect of the heat is to set free the volatile compounds of carbon and hydrogen. The hydrogen then begins to unite with the oxygen of the air, forming water, setting free the carbon, which also unites with oxygen, forming carbonic acid gas. The burning gases cause the flame. The following experiment will illustrate this.

(5) Fit a test-tube with a tight cork, through which a bit of glass tubing, drawn out into a jet, is passed, the tubing within being even with the cork. Place some bits of shaving in the tube, cork it, and make the cork perfectly air-tight by coating it with bees wax or paraffine. Heat the test-tube gently over an alcohol lamp. The wood turns black, and vapor issues from the jet, which may be lighted (Fig. 4). Care should be taken to expel all the air before lighting.

(6) That the burning hydrogen forms water by uniting with the oxygen of the air, may be shown by holding a cold glass tumbler over the jet, or over any flame. The glass will be dimmed by drops of moisture.

The charred part of the wood is charcoal, which is one form of carbon. Our ordinary charcoal is made by driving off all the gases from wood, by burning it under cover where only a little air can reach it. The volatile gases burn more readily than the carbon, and are the first substances to be driven off, so that the carbon is left behind nearly pure. In the same way we have driven off all the gases from the half-burned match and left the carbon. The teacher should have a piece of charcoal to show the pupils. It still retains all the markings of the wood.

If the combustion is continued, the carbon also unites with the oxygen of the air, till it is all converted into carbonic acid gas. This was the case with the match where we left the glowing spark. The gray ash that was left behind is the mineral matter contained in the wood.

(7) We can show that this gas is formed by pouring lime water into a bottle in which a candle has been burned as in (2). The water becomes milky from a fine white powder formed by the union of the carbonic acid gas with the lime, forming carbonate of lime. This is a chemical test.