CHAPTER I. NO TWO PLANTS OR PARTS ARE ALIKE P 1

II. THE STRUGGLE TO LIVE P 4

III. SURVIVAL OF THE FIT P 7

IV. PLANT SOCIETIES P 9

V. THE PLANT BODY P 15

VI. SEEDS AND GERMINATION P 20

VII. THE ROOT--THE FORMS OF ROOTS P 32

VIII. THE ROOT--FUNCTION AND STRUCTURE P 38

IX. THE STEM--KINDS AND FORMS--PRUNING P 49

X. THE STEM--ITS GENERAL STRUCTURE P 59

XI. LEAVES--FORM AND POSITION P 73

XII. LEAVES--STRUCTURE AND ANATOMY P 86

XIII. LEAVES--FUNCTION OR WORK P 92

XIV. DEPENDENT PLANTS P 106

XV. WINTER AND DORMANT BUDS P 111

XVI. BUD PROPAGATION P 121

XVII. HOW PLANTS CLIMB P 129

XVIII. THE FLOWER--ITS PARTS AND FORMS P 133

XIX. THE FLOWER--FERTILIZATION AND POLLINATION P 144

XX. FLOWER-CLUSTERS P 155

XXI. FRUITS P 163

XXII. DISPERSAL OF SEEDS P 172

XIII. PHENOGAMS AND CRYPTOGAMS P 176

XXIV. STUDIES IN CRYPTOGAMS P 182

PART II. ANIMAL BIOLOGY

I. INTRODUCTION A 1

II. PROTOZOANS A 10

III. SPONGES A 17

IV. POLYPS A 22

V. ECHINODERMS A 34

VI. WORMS A 42

VII. CRUSTACEANS A 51

VIII. INSECTS A 63

IX. MOLLUSKS A 97

X. FISHES A 109

XI. BATRACHIANS A 126

XII. REPTILES A 139

XIII. BIRDS A 150

XIV. MAMMALS A 184

PART III. HUMAN BIOLOGY

I. INTRODUCTION H 1

II. THE SKIN AND KIDNEYS H 16

III. THE SKELETON H 28

IV. THE MUSCLES H 39

V. THE CIRCULATION H 51

VI. THE RESPIRATION H 70

VII. FOOD AND DIGESTION H 89

VIII. THE NERVOUS SYSTEM H 117

IX. THE SENSES H 142

X. BACTERIA AND SANITATION H 158

GENERAL INDEX i

GENERAL INTRODUCTION

=PRELIMINARY EXPERIMENTS=

These experiments are inserted for those pupils who have not had instruction in chemistry and physics, to give them a point of view on the subjects that follow. At least a general understanding of some of these subjects is necessary to a satisfactory elementary study of biology.

=Elements and Compounds.=--The material world is made up of elements and compounds. An _element_ is a substance that cannot be separated into two or more substances. A _compound_ is formed by the union of two or more elements. All the material or substance of which the earth and its inhabitants is composed is formed of the chemical elements; this substance taken all together is known as _matter_.

_Carbon_ and _iron_ are examples of elements. Compare a bit of charcoal, which is one form of carbon, with a new iron nail. Which is brighter? Heavier for its size? Tougher? More brittle? Harder? More readily combustible? Resistant to change when left exposed to air and dampness? There are two other forms of carbon: graphite or black lead (used in pencils and stove polish); and diamond, which occurs in crystals and is the hardest known substance. Iron does not have varied forms like carbon. _Sulfur_ is another element. What is its color? Has it odor? Taste? Will it dissolve in water? Is it heavy or light? Will it burn? What is the color of the flame? Of the fumes? _Phosphorus_, another element, burns so readily that it ignites by friction and is used in matches. Rub the tip of a match with the finger. What is the odor of phosphorus? Phosphorus exists in nature only in combination with other elements. Lead, tin, silver, gold, copper, zinc, nickel, platinum, are elements.

There are less than eighty known elements; but the compounds formed of them are innumerable. Carbon is found in all substances formed by the growth of living things. That there is carbon in sugar, for example, can easily be shown by charring it on a hot shovel or a stove until its water is driven off and only charcoal is left. Part of the starch in a biscuit remains as charcoal when it has been half burned.

=Oxygen and the Air.=--The great activity of pure oxygen in attacking other substances can be shown by passing into a fruit-jar a lighted splinter, a piece of lighted magnesium ribbon, an old watch spring (or a bit of picture wire), the end of which has been dipped in sulfur and lighted. About one fifth of the air is oxygen and about four fifths is _nitrogen_ and other inactive gases. Pure nitrogen will quickly extinguish a lighted splinter thrust into it. It is the oxygen in the air that supports all forms of burning. Less than one half of one per cent of the air is an inactive gas called carbon dioxid, a compound of carbon and oxygen. It is formed not only when wood or coal is burned, but also by the life processes of animals and plants.

=Favorable and Unfavorable Conditions for Evaporation.=--Pour the same quantity of water (half a glassful) into three saucers and two bottles. Place one saucer near a hot stove; place the other two in a cool place, having first covered one of them with a dish. Place one of the bottles by the stove and the other by the remaining saucers. After some hours, examine the saucers and bottles and compare and record the results. Explain. State three conditions that are favorable to evaporation. State three ways in which evaporation may be prevented or decreased.

=Tests for Acid, Alkaline, and Neutral Substances.=--For _acid tests_, use sour buttermilk (which contains _lactic acid_), or _hydrochloric acid_ diluted in ten parts water, or _strong vinegar_ (which contains _acetic acid_). Has the acid a characteristic (“sour”) _odor_ and _taste_ (test it only when very dilute)? Rub dilute acid between the fingers; how does it feel? Is there any effect on the fingers? Obtain litmus paper at a druggist’s. Dip a strip of red litmus and of blue litmus paper into the acid. What result?

For _alkaline tests_, dissolve in a glass of water a spoonful of baking soda or some laundry soap; or dissolve an inch stick of caustic soda in a glass of water. Test odor and “feel” of last solution as with the acid; likewise test effect of alkaline solution on red and blue litmus paper. Record results. Alkalies are strong examples of a more general class of substances called _bases_, which have the opposite effect from acids.

Test pure water. Has it odor? A taste? Test it with red and blue litmus paper. Water is a _neutral_ substance: that is, it is neither an acid nor an alkali (or base).

After making appropriate tests, write _ac_, _al_, or _neu_ after each name in the following list (or write in three columns): vinegar, soda, saliva, sugar, juice of apple, lemon, and other fruits, milk, baking powder, buttermilk, ammonia, salt water.

Pour some of the alkaline solution into a dish, gradually add dilute acid (or sour buttermilk), stirring with glass rod and testing with litmus until the mixture does not turn red litmus blue nor blue litmus red. The acid and alkali are then said to have _neutralized_ each other, and the resulting substance is called a _salt_. The salt may be obtained by evaporating the water of the solution. Most common minerals are salts. If the last experiment is tried with soda and sour buttermilk, the demonstration will show some of the facts involved in bread making with the use of these substances.

=Test for Starch.=--Starch turns blue with iodine. The color may be driven away by heat, but will return again as the temperature lowers. Procure a few cents’ worth of tincture of iodine and dilute it. Get a half dozen pieces of paper and cardboard, all different, and test each for starch by placing it over mouth of bottle and tipping the bottle up. If much starch is present the spot will be blue-black or dark blue; if little starch, pale blue; if no starch, brown or yellowish.

Make pastes with wheat flour, potato starch, and corn starch. Treat a little of each with a solution of rather dilute tincture of iodine. Try grains from crushed rice with the same solution. Are they the same color? Cut a thin section from a potato, treat with iodine and examine under the microscope.

=To study Starch Grains.=--Mount in cold water a few grains of starch from each of the following: potato, wheat, arrowroot (buy at drug store), rice, oats, corn. Study under microscope the sizes, forms, layers, fissures, and location of nuclei, and make a drawing of a few grains of each.

=Test for Grape Sugar.=--Make a thick section of a bit of the edible part of a pear and place it in a bath of Fehling’s solution. After a few moments boil the liquid containing the section for one or two minutes. It will turn to an orange color, showing a deposit of an oxid of copper and perhaps a little copper in the metallic form. A thin section treated in like manner may be examined under the microscope, and the fine particles, precipitated from the sugar of the pear, may be clearly seen. (_Fehling’s solution_ is made by taking one part each of these three solutions and two parts of water: (1) Copper sulfate, 9 grams in 250 cubic centimeters of water; (2) sodium hydroxid, 30 grams in 250 c.c. water; (3) Rochelle salts, 43 grams in 250 c.c. water.)

=Test for Nitrogenous Substances, or Proteids.=--Put a little white of egg into a test tube and heat slowly. What change takes place in the egg? Put another part of the white of egg into a test tube and add dilute nitric acid. Compare the results of the two experiments. White of egg is an example of a proteid; that is, it is the form of nitrogen most commonly found in plant and animal tissue, and it can be formed only by life processes. Do acid and heat harden or soften most substances? Either of the above tests reveal proteid, if present. Does cooking tend to soften or toughen lean meat?

Another test for proteid is nitric acid, which _turns proteid_ (and hardly anything else) _yellow_. Proteid when burned has a characteristic odor; this will be noticed if lean meat or cheese is charred in a spoon. The offensive odor from decomposing proteid is also characteristic, whether it comes from stale beans, meat, mushrooms, or other things containing proteid.

=Test for Fats and Oils.=--Place a little tallow from a candle on unglazed paper and warm. Hold the paper up to the light and examine it. What effect has the fat had on the paper? Place a little starch, sugar, powdered chalk, or white of egg on paper and repeat the experiment; is the effect the same? Place some of the tallow in a spoon, and heat. Compare the effect of heat on fat and proteid. Water also makes paper semi-transparent, but it soon evaporates: fat does not evaporate.

Another test for fats is to mount a thin section of the endosperm of castor-oil seed in water and examine with high power. Small drops of oil will be quite abundant. Treat the mount with alcanin (henna root in alcohol). The drops of oil will stain red. This is a standard test for fats and oils.

=To make or liberate Oxygen.=--If there is a chemistry class in school, one of its members will doubtless be glad to prepare some of the gas called _oxygen_, and furnish several glass jars filled with it to the biology class. If it is desired to make oxygen, the following method may be employed: Provide a dry glass flask of three to four ounces capacity. It should have a glass delivery tube, inserted through a one-holed rubber stopper, and so bent as to pass under the surface of water contained in a deep dish. Fill several pint fruit-jars with water, cover with pieces of stiff pasteboard, and turn mouth downwards in the dish of water. From one half to two thirds ounces of an equal mixture of potassium chlorate and manganese dioxid (procured at drug store) is put in the flask and heated by means of a gas or alcohol lamp. When the oxygen begins to form, collect some in jars by inserting the end of delivery tube under the jars as they stand in water. _Caution_: Remove delivery tube from water before cooling the flask, to prevent any water being drawn back.

=Oxidation.=--That something besides wood or coal is necessary to a fire can be shown by shutting off entirely the draught of a stove. Fire and other forms of combustion depend on a process called _oxidation_. This consists in the uniting of oxygen with other substances. When wood decays, the carbon in it oxidizes (unites with oxygen) and _carbon dioxid gas_ is formed. When wood burns, the oxidation is more rapid. When iron oxidizes, _iron rust_ is formed. When hydrogen is oxidized, water is formed. Kerosene oil contains hydrogen, and water is formed when it is burned. Almost every one has noticed the cloud of moisture which collects on the chimney when the lamp is first lighted. By using a chimney which has been kept in a cold place, the moisture becomes apparent; soon the chimney becomes hot and the water no longer collects, but it continues to pass into the room as long as the lamp burns. Fats also contain hydrogen. Hold a piece of cold glass or an inverted tumbler above the flame of a tallow candle. Does water collect on it?

Oxidation may be said to be the basis of all life processes for this reason: oxidation gives rise to heat and sets free energy, and all living things need heat and energy in order to grow and live. The heat of animals is very noticeable. The oxidation in plants also forms a slight amount of heat. In both animals and plants oxidation is much slower than in ordinary fires. That heat is formed even in slow oxidation is shown by fires which arise spontaneously in masses of decaying material. The rotting of wood is not only accompanied by heat but sometimes by light, as when “fox fire” is emitted. Rub the end of a match on your finger in the dark. Explain the result. Strike a match and notice the white fumes which rise for an instant. These fumes are not ordinary smoke (particles of carbon), but they are oxid of phosphorus. Why will water (oxid of hydrogen) not burn? Sand is oxid of silicon. Explain how throwing sand on a fire puts it out. [See also experiments with candle and breath, in The Principles of Biology.]

=Inorganic and Organic Matter.=--=Test for Minerals.=--The earth was once in a molten condition, which would have destroyed any combustible material if any had then existed. Before plants and animals existed, the earth consisted mostly of incombustible minerals, known as _inorganic matter_. Substances formed by animals and plants are _organic matter_, so called because built up by organized or organ-bearing or living things; starch is an example, being formed in plants. Organic substances are composed chiefly of carbon, oxygen, hydrogen, and nitrogen. (See page 1 of “Animal Biology.”) Coal-oil, and all combustible materials have their origin in life. Hence, burning to find whether there is an incombustible residue is also a _test for minerals_. Meat, bread, oatmeal, bone, wood, may be tested for mineral matter by burning in a spoon held over a hot fire, or flame of gas or lamp. The substance being tested should be burned until all black material (which is organic carbon and not a mineral) has disappeared. Any residue will be _mineral matter_.

=Protoplasm.=--Inside the cells of plants and animals is the _living substance_, known as _protoplasm_. It is a structureless, nearly or quite colorless, transparent jelly-like substance of very complex and unstable composition. Eighty per cent or more is water; the remainder is proteid, fats, oils, sugars, and salts. Protoplasm has the power of _growth and reproduction_; it can make _living substance from dead or lifeless substances_. It has the _power of movement_ within the cell, and it is influenced (or is irritable) by heat, light, touch, and other stimuli. When protoplasm dies the organism dies.

=Physics= is the science that treats of the _properties_ and _phenomena_ (or behavior) of matter or of objects; as of such properties or phenomena or agencies as heat, light, force, electricity, sound, friction, density, weight, and the like.

=Chemistry= is the science that treats of the _composition_ of matter. All matter is made up, as we have seen, of elements. Very few elements exist in nature in a free or uncombined form. The nitrogen and oxygen of the air are the leading uncombined elements.

In order to express the chemical combinations clearly, _symbols_ are used to represent each element, and these symbols are then combined to represent the proportions of each in the compound. If C stands for carbon and O for oxygen, the carbon dioxid might be represented by the formula COO. In order to avoid the repetition of any letter, however, a number is used to denote how many times the element is taken: thus the formula always used for carbon dioxid is CO₂. The formula for hydrogen oxid, or water, is H₂O; that for starch is C₆H₁₀O₅. N stands for nitrogen; P, for phosphorus; K, potassium; Fe, iron; S, sulfur.

=Biology= is the science that treats of life; that is, of all knowledge of plants and animals of all kinds. (See page 1, “Animal Biology.”)

HOW A CANDLE BURNS

Some of the foregoing suggestions may be readily explained and illustrated by simple experiments with a burning candle. The following directions for such experiments are by G. W. Cavanaugh.

The materials needed for this exercise are: a piece of candle about two inches long, a lamp chimney (one with a plain top is best), a piece of white crockery or window glass, a piece of fine wire about six inches long, a bit of quicklime about half the size of an egg, and some matches. All of these, with the possible exception of the quicklime, can be obtained in any household. If you perform the experiment requiring the lime, be sure that you start with a fresh piece of quick or stone lime, which can be had of any lime or cement dealer. During the performance of the following simple experiments, the pupil should describe what he sees at each step. The questions inserted in the text are offered merely as suggestions in the development of the desired ideas. The answers are those which it is desired the pupils shall reach or confirm by their own observation.

I. _Oxygen_

Light the candle and place it on a piece of blotting paper (_A_). What do you see burning? Is anything burning besides the candle? The answer will probably be “no.” Let us see.

Place the lamp chimney over the lighted candle, and partly cover the top by a piece of stiff paper, as in Fig. A. Ask the pupils to observe and describe how the flame goes out; _i.e._ that it is gradually extinguished and does not go out instantly. Why did the flame go out? The probable thought will be, “Because there was no air.” (If there was no air within the chimney, some could have entered at the top.)

[Illustration: _A._--THE BEGINNING OF THE CANDLE EXPERIMENT.]

[Illustration: _B._--SUPPLYING AIR UNDERNEATH THE CHIMNEY.]

Place two pencils beside the relighted candle and on them the chimney (_B_). What is the difference between the way in which the candle burns now and before the chimney was placed over it? It flickers, or dances about more. What makes boys and girls feel like dancing about when they go out from a warm schoolroom? What makes the flame dance or flicker when the chimney is raised by the pencils? Because it gets fresh air under the chimney.

Repeat the first experiment, in which the flame grows gradually smaller till it is extinguished. Why does the flame die out now? Is it really necessary to have fresh air in order to keep a flame burning?

To prove this further, let the candle be relighted. Place the chimney over it, now having the top completely closed by a piece of paper. Have ready a lighted splinter or match, and just as soon as the candle is extinguished remove the paper from the chimney top and thrust in the lighted splinter. Why does the light on the splinter go out? What became of the freshness that was in the air? It was destroyed by the burning candle.

Evidently there is some decided difference between unburned air and burned air, since a flame can continue to burn only in air that has the quality known as freshness. This quality of fresh air is due to oxygen, represented by O. Why was the splinter put out instantly, while the candle flame died out gradually? When the splinter was thrust in, the air had no freshness or oxygen at all, while when the candle was placed under the chimney, it had whatever oxygen was originally in the air within the chimney.

Endeavor to have this point clearly understood: that the candle did not go out as long as the air had any oxygen and that the splinter was extinguished immediately because there was no oxygen left.

Relight the candle. A former question may now be repeated: Is anything else burning besides the candle?

When the subject of the necessity of fresh air and consequently of oxygen for the burning of the candle seems to be understood, the following questions, together with any others which suggest themselves, may be asked: What is the reason that draughts are opened in stoves? Why is the bottom of a “burner” on a lamp always full of holes?

II. _Carbon_

Let us now observe the blackened end of a burned match or splinter. This black substance is usually known by the name of charcoal. If handled, it will blacken the fingers. Try this. The same substance is found on the bottoms of kettles which have been used over a wood fire, but it is there a fine powder.

Let us see what was burning when the candle was lighted, besides the oxygen in the air. Relight the candle and hold the porcelain or glass about an inch above the bright part of the flame. What happens to it there? Next, lower it directly into the flame (_C_). What is the black stuff that gets on the glass? Look closely and see whether it is not deposited here also as a fine powder. Will this deposit from the candle blacken the fingers?

[Illustration: _C._--THE CARBON (OR SOOT) IS DEPOSITED ON THE GLASS.]

Instead of using the name _charcoal_ for this black substance, let us call it _carbon_, the better name, because there are several kinds of carbon, and charcoal is only that kind which is rather light and easily blackens the hands.

The carbon from the candle flame came mostly from the wax or tallow; only a very small part came from the wick. It cannot be seen in the tallow, neither can it be seen in unburned wood, and yet it can be found when the wood is partly burned.

Why, now, is the glass blackened when held in the flame and not when held directly above it? It is because the carbon from the candle has not been completely burned at the middle of the flame; but it is burned beyond the bright part of the flame. When the glass is held in the flame, the carbon that is not yet completely burned is deposited on it, because it is cooler than that in the surrounding flame.

A fine deposit of carbon can be had from any of the luminous parts of the flame; and it is these thousands of little particles of carbon, getting white hot, which glow like coals in the stove and make the light. Just as soon as they are completely burned, there is no more light, as coals cease to glow when burned to ashes.

III. _Carbon dioxid_

[Illustration: _D._--THE TEST WITH THE SUSPENDED FILM OF LIMEWATER.]

Let us now inquire what becomes of the carbon that we find in the bright part of the flame and of the oxygen that was in the air in the lamp chimney. When the candle was extinguished within the chimney, there was no oxygen left, as shown by the lighted splinter, which was put out immediately. Neither could any of the particles of carbon be found except on the wick. Yet they both still exist within the chimney, but in an entirely different condition. While the candle was burning, the little particles of carbon that we find ascending in the flame are joining with the oxygen of the air and making an entirely new substance. This new substance is a gas and cannot be seen in the air.

Of what two substances is this new substance made? It is CO₂.

Place a bit of quicklime in about half a glass of water on the day previous to the experiment. When ready for use there will be a white sediment at the bottom and a thin white scum on the top of the clear limewater. The pupils should see this white scum, as a question about it will follow. Make a loop in the end of the piece of wire by turning it around the point of a lead pencil. Remove the scum from the limewater with a piece of paper and insert the loop into the clear water. When withdrawn, the loop ought to hold a film of clear water. Pass the wire through a piece of cardboard or stiff paper, and arrange as shown in _D_.

Place the chimney over the lighted candle. Lower the loop into the chimney and cover the top of the chimney with the paper. Withdraw the wire two minutes after the candle goes out. Note the cloudy appearance of the film of water on the wire. The cloudiness was caused by the carbon dioxid formed while the candle was burning.

Omitting the candle, hang the freshly wetted wire in the empty chimney. Let the film of limewater remain within the chimney for the same length of time as when the candle was used. It does not become cloudy now. The cloudiness in clear limewater is a test or indication that carbon dioxid is present.

What caused the white scum on the limewater which stood overnight?

How does the CO₂ get into the air? It is formed whenever wood, coal, oil, or gas is burned.

The amount of CO₂ in ordinary air is very small, being only three parts in ten thousand. If the limewater in the loop be left long enough in the air, it will become cloudy. The reason it clouds so quickly when the candle is being burned is that a large amount of CO₂ is formed. Besides being made by real flames, CO₂ is formed every time we breathe out air. Renew the film of water in the loop and breathe against it gently for two or three minutes.

The presence of CO₂ in the breath may be shown better by pouring off some of the clear limewater into a clean glass and blowing into it through a straw.

Why does water put out a fire? The answer is, not alone because it wets and shuts off the supply of free oxygen, but because it cools the carbon, which must be hot in order to unite with the oxygen, and prevents the oxygen of the air from getting as near the carbon as before.

PLANT BIOLOGY