hitnatssiSuSSi a^t^twwi) t,^iti>r^ / n SJiUz^^n^C J^ /y^' (y,,^^.cAt^ y-iA^ci FIRST COURSE IN BIOLOGY BY L. H. BAILEY PART I. PLANT BIOLOGY WALTER M. COLEMAN PART IL ANIMAL BIOLOGY PART III. HUMAN BIOLOGY TORONTO THE MACMILLAN CO. OF CANADA, Ltd, 1910 Copyright, 1908, Bv THE MACMILLAN COMPANY. Set up and electrotyped. Published July, 1908. Reprinted October, 1908; February, September, 1909 ; January, 1910. NorijJOOU l^ttM J. S. Gushing Co. —Berwick .— The Test WITH THE Sus- pended Film OF LiMEWATER. 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 lime- water. 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 When withdrawn, the loop ought to hold a film of clear water.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 thfe 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 can- dle 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 COg get into the air .'' It is formed when- ever wood, coal, oil, or gas is burned. The amount of COg in ordinary air is very small, being only three parts in ten thousand. If the limewater in the PRELIMINARY EXPERIMENTS XXV 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 CHAPTER I wo TWO PLANTS OR PARTS ARE ALIKE Fig. I. — No Two Branches are Alike. (Hemlock.) If one compares any two plants of the same kind ever so closely, it will be found that they differ from each other. The difference is apparent in size, form, color, mode of branching, number of leaves, number of flowers, vigor, season of maturity, and the like ; or, in other words, all plants and animals vary from an assumed or standard type. If one compares ayiy two brandies or ttvigs on a tree, it will be found that they differ in size, age, form, vigor, and in other ways (Fig. i). If one compares atty two leaves, it will be found that they are unlike in size, shape, color, veining, hairiness, markings, cut of the margins, or other small features. In some cases (as in Fig. 2) the differences are so great as to be readily seen in a small black-and-white drawing. PLANT BIOLOGY If the pupil extends his observation to animals, he will still find the same truth ; for probably no two living objects are exact duplicates. If any person finds two objects that he thinks to be exactly alike, let him set to work to Fig. 2. — No Two Leaves are Alike. discover the differences, remembering that nothing in nature is so small or apparently trivial as to be overlooked. Variation, or differences between organs and also be- tween organisms, is one of the most significant facts in nature. Suggestions. — The first fact that the pupil should acquire about plants is that no two are alike. The way to apprehend this great fact is to see a plant accurately and then to compare it with NO TWO PLANTS OR PARTS ARE ALIKE 3 another plant of the same species or kind. In order to direct and concentrate the observation, it is well to set a certain number of attributes or marks or qualities to be looked for. 1. Suppose any two or more plants of corn are compared in the following points, the pupil endeavoring to determine whether the parts exactly agree. See that the observation is close and accurate. Allow no guesswork. Instruct the pupil to measure the parts when size is involved : (i) Height of the plant. (2) Does it branch? How many secondary stems or "suck- ers" from one root? (3) Shade or color. (4) How many leaves? (5) Arrangement of leaves on stem. (6) Measure length and breadth of six main leaves. (7) Number and position of ears ; color of silks. (8) Size of tassel, and number and size of its branches. (9) Stage of maturity or ripeness of plant. (10) Has the plant grown symmetrically, or has it been crowded by other plants or been obliged to struggle for hght or room ? (11) Note all unusual or interesting marks or features. (12) Always make note of comparative vigor of the plants. Note to Teacher. — The teacher should always insist on per- sonal work by the pupil. Every pupil should handle and stuay the object by himself. Books and pictures are merely guides and helps. So far as possible, study the plant or animal just where it grows naturally. Notebooks. — Insist that the pupils make full notes and preserve these notes in suitable books. Note-taking is a powerful aid in organizing the mental processes, and in insuring accuracy of obser- vation and record. The pupil should draw what he sees, even though he is not expert with the pencil. The drawing should not be made for looks, but to aid the pupil in his orderly study of the object ; it should be a means of self-expression. Laboratory. — Every school, however small, should have a laboratory or work-room. This work-room may be nothing more than a table at one side of the room where the light is good. Here the specimens may be ranged and studied. Often an aquarium and terrarium may be added. A cabinet or set of shelves should be provided for a museum and collection. The laboratory may be in part out of doors, as a school garden ; or the garden may be at the pupil's home, and yet be under the general direction of the teacher. CHAPTER II THE STRUGGLE TO LIVE Every plant and animal is exposed to ic7tfavorable con- ditions. It is obliged to contend with these conditions in order to live. No two plants or parts of plants are identically exposed to the conditions in which they live. The large branches Fig. 3. — a Battle for Life. in Fig. I probably had more room and a better exposure to light than the smaller ones. Probably no two of the leaves in Fig. 2 are equally exposed to light, or enjoy identical advantages in relation to the food that they re- ceive from the tree. Examine any tree to determine under what advantages or disadvantages any of the limbs may live. Examine similarly the different plants in a garden row (Fig. 3); or the different bushes in a thicket ; or the different trees in a wood. THE STRUGGLE TO LIVE The plant meets its conditions by succumbing to them (that is, by dying), or by adapting itself to them. The tree meets the cold by ceasing its active growth, hardening its tissues, dropping its leaves. Many her- baceous or soft-stemmed plants meet the cold by dying to the ground and withdrawing all life into the root parts. Some plants meet the cold by dying outright and provid- ing abundance of seeds to perpetuate the kind next season. Fig. 4. — The Reach for Light of a Tree on the Edge of a Wood. Plants adapt themselves to light by growing toward it (Fig. 4); or by hanging their leaves in such position that they catch the light ; or, in less sunny places, by expand- ing their leaf surface, or by greatly lengthening their stems so as to overtop their fellows, as do trees and vines. The adaptations of plants will afford a fertile field of study as we proceed. 6 PLANT BIOLOGY Struggle for existence and adaptation to conditions are among the most significant facts in nature. The sum of all the conditions in which a plant or an ani- mal is placed is called its environment, that is, its surround- ings. The environment comprises the conditions of climate, soil, moisture, exposure to light, relation to food supply, contention with other plants or animals. The organism adapts itself to its environment, or else it weakens or dies. Every weak branch or plant has undergone some hardship that it was not wholly able to withstand. Suggestions. — The pupil should study any plant, or branch of a plant, with reference to the position or condition under which it grows, and compare one plant or branch with another. With animals, it is common knowledge that every animal is alert to avoid or to escape danger, or to protect itself. 2. It is well to begin with a branch of a tree, as in Fig. i. Note that no two parts are alike (Chap. I). Note that some are large and strong and that these stand farthest towards Jight and room. Some are very small and weak, barely able to live under the competition. Some have died. The pupil can easily determine which ones of the dead branches perished first. He should take note of the position or place of the branch on the tree, and determine whether the greater part of the dead twigs are toward the center of the tree top or toward the outside of it. Determine whether acci- dent has overtaken any of the parts. 3. Let the pupil examine the top of any thick old apple tree, to see whether there is any struggle for existence and whether any limbs have perished. . 4. If the pupil has access to a forest, let him determine why there are no branches on the trunks of the old trees. Examine a tree of the same kind growing in an open field. 5. A row of lettuce or other plants sown thick will soon show the competition between plants. Any fence row or weedy place will also show it. Why does the farmer destroy the weeds among the corn or potatoes? How does the florist reduce competition to its lowest terms? what is the result? • CHAPTER III THE SURVIVAL OF THE FIT The plants that most perfectly meet their conditions are able to persist. TJiey perpetuate themselves. Their off- spring are likely to inherit some of the attributes that enabled them successfully to meet the battle of life. The Jit (those best adapted to their conditions) tend to survive. Adaptation to conditions depends on the fact of varia- tion; that is, if plants were perfectly rigid or invariable (all exactly alike) they could not meet new conditions. Conditions are necessarily new for every organism. It is impossible to picture a perfectly inflexible and stable succes- sion of plants or animals. Breeding. — • Man is able to modify plants and animals. All our common domestic animals are very unlike their original ancestors. So all our common and long-culti- vated plants have varied from their ancestors. Even in some plants that have been in cultivation less than a century the change is marked : coiiipare the com- mon black-cap raspberry with its common wild ances- tor, or the cultivated black- fig.s.— desirable and undesirable berry with the wild form. '^^^^^ "^ cotton plants, why? By choosing seeds from a plant that pleases him, the breeder may be able, under given conditions, to produce 7 PLANT BIOLOGY numbers of plants with more or less of the desired quali- ties ; from the best of these, he may again choose ; and so on until the race becomes greatly improved (Figs. 5, 6, 7). This process of continu- ously choosing the most suita- ble plants is known as selec- tion. A some- what similar process pro- ceeds in wild nature, and it is then known as natural se- lection. K Fig. 6. — Flax Breeding. /I is a plant grown for seed production; B, for fiber production. Why ? Suggestions. — 6. Every pu- pil should un- dertake at least one simple ex- periment in se- lection of seed. He may select kernels from the best plant of corn in the field, and also from the poorest plant, — having reference not so much to mere incidental size and vigor of the plants that may be due to accidental conditions in the field, as to the apparently constitutional strength and size, number of ears, size of ears, perfectness of ears and kernels, habit of the plant as to sucker- ing, and the like. The seeds may be saved and sown the next year. Every crop can no doubt be very greatly improved by a careful process of selection extending over a series of years. Crops are increased in yield or efficiency in three ways : better general care ; enriching the land in which they grow ; attention to breeding. Fig. 7. — Breed- ing. A, effect from breed- ing from smallest grains (after four years), average head; B, result from breeding from the plumpest and heaviest grains (after four years), average head. CHAPTER IV PLANT SOCIETIES In the long course of time in which plants have been accommodating themselves to the varying conditions in which they are obliged to grow, they have become adapted to every different environment. Certain plants, therefore, may live together or near each other, all enjoying the same general conditions and surroundings. These aggre- gations of plants that are adapted to similar general con- ditions are known as plant societies. Moisture and temperature are the leading factors in determining plant societies. The great geographical societies or aggregations of the plant world may con- veniently be associated chiefly with the moisture supply, as : wet-region societies, comprising aquatic and bog vegetation (Fig. 8); arid-region societies, zora^^xx^vn^^^^^xX. and most sand-region vegetation ; mid-region societies, comprising the mixed vegetation in intermediate regions (Fig. 9), this being the commonest type. Much of the characteristic scenery of any place is due to its plant societies. Arid-region plants usually have small and hard leaves, apparently preventing too rapid loss of water. Usually, also, they are characterized by stiff growth, hairy covering, spines, or a much-contracted plant-body, and often by large underground parts for the storage of water. Plant societies may also be distinguished with reference to latitude and temperature. There are tropical societies, temperate-region societies, boreal or cold-region societies, 9 10 PLANT BIOLOGY With ■ reference to altitude, societies might be classified as lowland (which are chiefly wet-region), intermediate (chiefly mid-region), siibalpine or mid-mountain (which are chiefly boreal), alpine or high-mountain. The above classifications have reference chiefly to great geographical floras or societies. But there are societies within societies. There are small societies coming within the experience of every person who has ever seen plants Fig. 8. — A Wet-region Society. growing in natural conditions. There are roadside, fence- row, lawn, thicket, pasture, dune, woods, cliff, barn-yard societies. Every different place has its characteristic vegeta- tion. Note the smaller societies in Figs. 8 and 9. In the former is a water-lily society and a cat-tail society. In the latter there are grass and bush and woods societies. Some Details of Plant Societies. — Societies may be com- posed of scattered and intermingled plants^ or of dense clumps or groups of plants. Dense clumps or groups are usually made up of one kind of plant, and they are then PLANT SOCIETIES II called colonies. Colonies of most plants are transient: after a short time other plants gain a foothold amongst them, and an intermingled society is the outcome. Marked exceptions to this are grass colonies and forest colonies, in which one kind of plant may hold its own for years and centuries. In a large newly cleared area, plants usually y?ri-/' estab- lish themselves in dense colonies. Note the great patches Fig. 9. — a Mid-region Society. of nettles, jewel-weeds, smart-weeds, clot-burs, fire-weeds in recently cleared but neglected swales, also the fire-weeds in recently burned areas, the rank weeds in the neglected garden, and the ragweeds and May-weeds along the re- cently worked highway. The competition amongst them- selves and with their neighbors finally breaks up the colonies, and a mixed and intermingled flora is generally the result. In many parts of the world the general tendency of neg- lected areas is to run into forest. All plants rush for the 12 PLANT BIOLOGY cleared area. Here and there bushes gain a foothold. Young trees come up ; in time these shade the bushes and gain the mastery. Sometimes the area grows to poplars or birches, and people wonder why the original forest trees do not return ; but these forest trees may be growing unob- served here and there in the tangle, and in the slow pro- cesses of time the poplars perish — for they are short-lived — and the original forest may be replaced. Whether one kind of forest or another returns will depend partly on the kinds that are most seedful in that vicinity and which, therefore, have sown themselves most profusely. Much depends, also, on the kind of undergrowth that first springs up, for some young trees can endure more or less shade than others. Some plants associate. They grow together. This is possible largely because they diverge or differ in charac- ter. Plants asso- ciate in two ways : by growing side by side ; by growing above or beneath. In sparsely popu- lated societies, plants may grow alongside each other. In most cases, however, there is overgrowth and undergrowth: one kind grows beneath another. Plants that have be- come adapted to shade are usually undergrowths. In a cat- tail swamp, grasses and other narrow-leaved plants grow in the bottom, but they are usually unseen by the casual Fig. io. — Overgrowth and Undergrowth in Three Series, — trees, bushes, grass. PLANT SOCIETIES 1 3 observer. Note the undergrowth in woods or under trees (Fig. lo). Observe that in pine and spruce forests there is almost no undergrowth, partly because there is very little light. On the same area the societies may differ at different times of the year. There are spring, summer, and fall soci- eties. The knoll which is cool with grass and strawber- ries in June may be aglow with goldenrod in September. If the bank is examined in May, look for the young plants that are to cover it in July and October; if in Septem- ber, find the dead stalks of the flora of May. What suc- ceeds the skunk cabbage, hepaticas, trilliums, phlox, violets, buttercups of spring } What precedes the wild sunflowers, ragweed, asters, and goldenrod of fall ">. The Landscape. — To a large extent the color of the land- scape is determined by the character of the plant societies. Evergreen societies remain green, but the shade of green varies from season to season ; it is bright and soft in spring, becomes dull in midsummer and fall, and assumes a dull yellow-green or a black-green in winter. Deciduous societies vary remarkably in color — from the dull browns and grays of winter to the brown greens and olive-greens of spring, the staid greens of summer, and the brilliant colors of autumn. The autumn colors are due to intermingled shades of green, yellow, and red. The coloration varies with the kind of plant, the special location, and the season. Even in the same species or kind, individual plants differ in color ; and this individuality usually distinguishes the plant year by year. That is, an oak which is maroon red this autumn is likely to exhibit that range of color every year. The au- tumn color is associated with the natural maturity and death of the leaf, but it is most brilliant in long and open 14 PLANT BIOLOGY falls — largely because the foliage ripens more gradually and persists longer in such seasons. It is probable that the autumn tints are of no utility to the plant. Autumn colors are not caused by frost. Because of the long, dry falls and the great variety of plants, the autumnal color of the American landscape is phenomenal. Ecology. '— The study of the relationships of plants and animals to each other and to seasons and environments is known as ecology (still written oecology in the dictionaries). It considers the habits, habitats, and modes of life of liv- ing things — the places in which they grow, how they migrate or are disseminated, means of collecting food, their times and seasons of flowering, producing young, and the like. Suggestions. — One of the best of all subjects for school instruc- tion in botany is the study of plant societies. It adds definiteness and zest to excursions. 7. Let each excursion be confined to one or two societies. Visit one day a swamp, another day a forest, another a pasture or meadow, another a roadside, another a weedy field, another a cliff or ravine. Visit shores whenever possible. Each pupil should be assigned a bit of ground — say lo or 20 ft. square — for special study. He should make a list showing (i) how many kinds of plants it contains, (2) the relative abundance of each. The lists secured in different regions should be com- pared. It does not matter greatly if the pupil does not know all the plants. He may count the kinds without knowing the names. It is a good plan for the pupil to make a dried specimen of each kind for reference. The pupil should endeavor to discover why the plants grow as they do. Note what kinds of plants grow next each other ; and which are undergrowth and which overgrowth ; and which are erect and which wide-spreading. Challenge every plant society. CHAEXEE^yL THE PLANT BODY The Parts of a Plant. — Our familiar plants are made up of several distinct parts. The most prominent of these parts are root, stem, leaf, flower, fruit, and seed. Familiar plants differ wonderfully in size and shape, — from fragile mushrooms, delicate waterweeds and pond-scums, to float- ing leaves, soft grasses, coarse weeds, tall bushes, slender cHmbers, gigantic trees, and hanging moss. The Stem Part. — In most plants there is a main central part or shaft on which the other or secondary parts are borne. This main part is the plant axis. Above ground, in most plants, the main plant axis bears the branches, leaves, a.nd flowers ; below ground, it bears the roots. The rigid part of the plant, which persists over winter and which is left after leaves and flowers are fallen, is the framework of the plant. The framework is composed of both root and stem. When the plant is dead, the frame- work remains for a time, but it slowly decays. The dry winter stems of weeds are the framework, or skeleton of the plant (Figs, ii and 12). The framework of trees is the most conspicuous part of the plant. The Root Part. — The root bears the stem at its apex, but otherwise it normally bears only root-branches. The stem, however, bears leaves, flowers, and fruits. Those living surfaces of the plant which are most exposed to light are green or highly colored. The root tends to grow downward, but the stem tends to grow upward toward light »5 i6 PLANT BIOLOGY and air. The plant is anchored or fixed in the soil by the roots. Plants have been called " earth parasites." The Foliage Part. — The leaves precede the flowers in point of time or life of the plant. The flowers always precede the fruits and seeds. Many plants die when the seeds have matured. The whole mass of leaves of any plant or any branch is known as its foliage. In some cases, as in crocuses, the flowers seem to precede the leaves ; but the leaves that made the food for these flowers grew the preceding year. The Plant Generation. — The course of a plant's life, with all the events through which the plant naturally passes, is known as the plant's life-history. The life-history em- braces various stages, or epochs, as dormant seed, germination, growth, flowering, fruiting. Some plants run their course in a few weeks or months, and some live for centuries. The entire life-period of a plant is called a generation. It is the whole period from birth to normal death, without reference to the various stages or events through which it passes. A generation begins with the young seed, not with germi- FiG. II. — Plant of a Wild Sunflower. Fig. 12. — Frame- work OF Fig. h. THE PLANT BODY 1/ nation. It ends with death — that is, when no life is left in any part of the plant, and only the seed or spore remains to perpetuate the kind. In a bulbous plant, as a lily or an onion, the generation does not end until the bulb dies, even though the top is dead. When the generation is of only one season's duration, the plant is said to be annual. When it is of two seasons, it is biennial. Biennials usually bloom the second year. When of three or more seasons, the plant is perennial. Examples of annuals are pigweed, bean, pea, garden sun- flower ; of biennials, evening primrose, mullein, teasel ; of perennials, dock, most meadow grasses, cat-tail, and all shrubs and trees. Duration of the Plant Body. — Plant structures which are more or less soft and which die at the close of the season are said to be herbaceous, in contradistinction to being ligneous or woody. A plant which is herbaceous to the ground is called an herb ; but an herb may have a woody or perennial root, in which case it is called an herbaceous perennial. Annual plants are classed as herbs. Examples of herbaceous perennials are buttercups, bleed- ing heart, violet, water lily, Bermuda grass, horse-radish, dock, dandelion, golden rod, asparagus, rhubarb, many wild sunflowers (Figs, ii, 12). Many herbaceous perennials have short generations. They become weak with one or two seasons of flowering and gradually die out. Thus, red clover usually begins to fail after the second year. Gardeners know that the best bloom of hollyhock, larkspur, pink, and many other plants, is secured when the plants are only two or three years old. Herbaceous perennials which die away each season to bulbs or tubers, are sometimes called pseud-annuals (that i8 PLANT BIOLOGY is, false annuals). Of such are lily, crocus, onion, potato, bull nettle, and false indigo of the Southern states. True annuals reach old age the first year. Plants which are normally perennial may become annual in a shorter- season climate by being killed by frost , rather than by dying naturally at the end of a season of growth. They are cli- matic annuals. Such plants are called plur-annuals in the short-season region. Many tropical perennials are plur- FiG. 13. — A Shrub or Bush. Dogwood osier. annuals when grown in the north, but they are treated as true annuals because they ripen sufficient of their crop the same season in which the seeds are sown to make them worth cultivating, as tomato, red pepper, castor bean, cotton. Name several vegetables that are planted in gardens with the expectation that they will bear till frost comes. Woody or ligneous plants are usually longer lived than herbs. Those that remain low and produce several or THE PLANT BODY 19 many similar shoots from the base are called shrubs, as lilac, rose, elder, osier(Fig. 13). Low and thick shrubs are bushes. Plants that produce one main trunk and a more or less elevated head are trees (Fig. 14). All shrubs and trees are perennial. Every plant makes an effort to propagate, or to perpetuate its kind ; and, as far as we can see, this is the end for which the plant itself lives. The seed or spore is the final product of the plant. ' i^i^ ^W^ Fig. 14. — A Tree. The weeping birch. Suggestions. — 8. The teacher may assign each pupil to one plant in the school yard, or field, or in a pot, and ask him to bring out the points in the lesson. 9. The teacher may put on the board the names of many common plants and ask the pupils to classify into annuals, pseud-annuals, plur-annuals (or climatic annuals), biennials, perennials, herbaceous perennials, ligneous perennials, herbs, bushes, trees. Every plant grown on the farm should be so classified : wheat, oats, corn, buckwheat, timothy, strawberry, raspberry, currant, tobacco, alfalfa, flax, crimson clover, hops, cowpea, field bean, sweet potato, peanut, radish, sugar-cane, barley, cabbage, and others. Name all the kinds of tree* you know. CHAPTER VI SEEDS AND GERMINATION The seed contains a miniature plant, or embryo. The embryo usually has three parts that have received names : the stemlet, or caulicle ; the seed-leaf, or cotyledon (usually I or 2) ; the bud, or plumule, lying between or above the cotyledons. These parts are well seen in the common bean (Fig. 15), particu- larly when the seed has been soaked for a few hours. One of the large cotyledons — OF THE Bean. comprising half of the bean — is shown at R, cotyledon; o, R. The cauUcle is at O. The plumule is muie^'V first showu at ^. The cotyledons are attached °°<^«- to the caulicle at F: this point may be taken as the first node or joint. The Number of Seed-leaves. — All plants having two seed-leaves belong to the group called dicotyledons. Such seeds in many cases split readily in halves, e.g. a bean. Some plants have only one seed-leaf in a seed. They form a group of plants called monocotyledons. Indian corn is an example of a plant with only one seed-leaf : a grain of corn does not split into halves as a bean does. Seeds of the pine family contain more than two cotyledons, but for our purposes they may be associated with the dicoty- ledons, although really forming a different group. These two groups — the dicotyledons and the mono- cotyledons — represent two great natural divisions of the vegetable kingdom. The dicotyledons contain the woody SEEDS AND GERMINATION 21 bark-bearing trees and bushes (except conifers), and most of the herbs of temperate climates except the grasses, sedges, rushes, lily tribes, and orchids. The flower-parts are usually in fives or multiples of five, the leaves mostly netted-veined, the bark or rind distinct, and the stem often bearing a pith at the center. The monocotyledons usually have the flower-parts in threes or multiples of three, the leaves long and parallel-veined, the bark not separable, and the stem without a central pith. Every seed \s, provided with food to support the germinat- ing plant. Commonly this food is starch. The food may be stored in the cotyledons^ as in bean, pea, squash ; or out- side the cotyledons, as in castor bean, pine, Indian corn. When the food is outside or around the embryo, it is usually called endosperm. Seed-coats; Markings on Seed. — The embryo and en- dosperm are inclosed within a covering made of two or more layers and known as the seed-coats. Over the point of the caulicle is a minute hole or a thin place in the coats known as the micropyle. This is the point at which fig. i6.— exter- the pollen-tube entered the forming ovule ^^^ parts of Bean, and through which the caulicle breaks in germination. The micropyle is shown at M in Fig. i6. The scar where the seed broke from its funiculus (or stalk that attached it to its pod) is named the hilum. It occu- pies a third of the length of the bean in Fig. i6. The hilum and micropyle are always present in seeds, but they are not always close together. In many cases it is difficult to identify the micropyle in the dormant seed, but its loca- tion is at once shown by the protruding caulicle as germi- nation begins. Opposite the micropyle in the bean (at the other end of the hilum) is an elevation known as the raphe. 22 PLANT BIOLOGY This is formed by a union of the funiculus, or seed-stalk, with the seed-coats, and through it food was transferred for the development of the seed, but it is now functionless. Seeds differ wonderfully in size, shape, color, and other characteristics. They also vary in longevity. These characteristics are peculiar to the species or kind. Some seeds maintain life only a few weeks or even days, whereas others will " keep " for ten or twenty years. In special cases, seeds have retained vitality longer than this limit, but the stories that live seeds, several thousand years old, have been taken from the wrappings of mummies are un- founded. Germination. — The embryo is not dead ; it is only dor- mant. When supplied with moisture^ warmth, and oxygen {air), it awakes and grows: this growth is germination. The embryo lives for a time on the stored food, but gradu- ally the plantlet secures a foothold in the soil and gathers food for itself. When the plantlet is finally able to shift for itself, germination is complete. Early Stages of Seedling. — The germinating seed first absorbs water, and swells. The starchy matters gradually become soluble. The seed-coats are ruptured, the caulicle and plumule emerge. During this process the seed respires freely, thj'owing off carbon dioxid (COg). The caulicle usually elongates, and from its lower end roots are emitted. The elongating caulicle is known as the hypocotyl (" below the cotyledons "). That is, the hypocotyl is that part of the stem of the plantlet lying between the roots and the cotyledon. The general direc- tion of the young hypocotyl, or emerging caulicle, is down- wards. As soon as roots form, it becomes fixed and its subsequent growth tends to raise the cotyledons above the ground, as in the bean. When cotyledons rise into the SEEDS AND GERMINATION 23 Fig. 17. — Pea. Grotesque forms assumed when the roots cannot gain entrance to the soil. air, germination is said to be epigeal (" above the earth "). Bean and pumpkin are examples. When the hypocotyl does not elongate greatly and the cotyledons remain under ground, the germi- nation is hypogeal ("be- neath the earth"). Pea and scarlet runner bean are examples (Fig. 48). When the germinating seed lies on a hard sur- face, as on closely com- pacted soil, the hypocotyl and rootlets may not be able to secure a foothold and they assume grotesque forms, (Fig. 17.) Try this with peas and beans. The first internode (" between nodes ") above the coty- ledons is the epicotyl. It elevates the plumule into the air, and the plumule- leaves expand into the first true leaves of the plant. These first true leaves, however, may be very unlike the later leaves in shape. Germination of Bean. — The common bean, as we have seen (Fig. 15), has cotyledons that occupy all the space inside the seed-coats. When the hy- pocotyl, or elongated caulicle, emerges, the plumule-leaves have begun to en- large, and to unfold (Fig. 18). The hypocotyl elongates rapidly. One end of it is held by the roots. The other is held by the seed-coats in the soil. It therefore takes the form of a loop, and the central part of the loop " comes up " first {a, Fig. 19). Presently the cotyledons come out of the seed-coats, Fig. 18. — Cotyledons OF Germinating Bean spread apart TO SHOW Elongat- ing Caulicle and Plumule. 24 PLANT BIOLOGY and the plant straightens and the cotyledons expand. These coty- ledons, or " halves of the bean," persist for some time {b, Fig. 19). They often become green and probably perform some function of foliage. Because of its large size, the Lima bean shows all these parts well. Germination of Castor Bean. — In the castor bean the hilum and micropyle are at the smaller end (Fig. 20). The bean " comes up " with a loop, which indicates that the hypocotyl greatly elongates. On examining germi- nating seed, however, it will be found that the cotyledons are contained inside a fleshy body, or sac {a. Fig. 21). This sac is the endosperm, its inner surface the thin, veiny coty- ledons are very closely pressed, ab- FlG. 19.- Germination of Bean. Fig. 20. — Sprout- ing OF Castor Bean. Against Fig. 21. — Germina- tion OF Castor Bean. Fig. 22. — Castor Bean. Endosperm at a, a; coty- ledons at b. Fig. 23. — Germination Complete in Casi\;r Bean. Endosperm at a. sorbing its substance (Fig. 22). The cotyledons increase in size as they reach the air (Fig. 23), and become func- tional leaves. I SEEDS AND GERMINATION 25 Germination of Monocotyledons. — Thus far we have stud- ied dicotyledonous seeds ; we may now consider the mono- cotyledonous group. Soak kernels of corn. Note that the micropyle and hilum are at the smaller end (Fig. 24). Make a longitudinal section through the 1 "—'■•—■■- Fig. 24. — Sprout- ing Indian Corn. Hilum at A; micro- pyle at d. Fig. 25. — Kernel OF Indian Corn. Caulicle at b; cotyle- don at a; plumule at /. Fig. 26.— Indian Corn, Caulicle at c\ roots emerging at m; plumule at/. single cotyledon is at a, the caulicle at b, the plumule at/. The cotyledon remains in the seed. The food is stored both in the cotyledon and as endosperm, chiefly the latter. The emerging shoot is the plumule,* with a sheath- ing leaf (/, Fig. 26). The root is emitted from the tip of the caulicle, c. The caulicle is held in a sheath (formed mostly from the seed-coats), and some of the roots escape through the upper end of this sheath {tn. Fig. 26). The epicotyl elongates, particularly if the seed is planted deep or if it is kept for a time confined. In Fig. 27 the epicotyl has elongated from n to/. The true plumule-leaf is at ^, but other leaves grow from its sheath. In Fig. 28 the roots are seen, emerging from the two ends of the caulicle- Fig. 27. — Indian Corn. o, plumule: « to/, epicotyl. 26 PLANT BIOLOGY sheath, c, in ; the epicotyl has grown to / ; the first plu- mule-leaf is at 0. In studying corn or other fruits or seeds, the pupil should note how the seeds are arranged, as on the cob. Count the rows on a corn cob. Odd or even in number } Always the same number.-' The silk is the style : find where it was attached to the kernel. Did the ear have any coverings } Explain. Describe colors and markings of kernels of corn ; and of peas, beans, castor bean. Gymnosperms. — The seeds in the pine cone, not being inclosed in a seed-vessel, readily fall out when the cone dries and the scales separate. Hence it is difficult to find cones with seeds in them after autumn has passed (Fig. 29). The cedar is also a gymno- sperm. Remove a scale from a pine cone and draw it and the seeds as they lie in place on the upper side of the scale. Examine the seed, preferably with a magnifying glass. Is there a hilum .-* The micropyle is at the bottom or little end of the seed. Toss a seed upward into the air. Why does it fall so slowly } Can you explain the peculiar whirl- ing motion by the shape of the wing } Repeat the ex- FiG. 28. — Germination is Com- plete. p, top of epicotyl ; o, plumule-leaf; ' tn, roots; c, lower roots. SEEDS AND GERMINATION 27 periment in the wind. Remove the wing from a seed and toss it and an uninjured seed into the air together. What do you infer from these ex- periments ? Suggestions. — Few subjects con- nected with the study of plant-life are so useful in schoolroom demonstrations as germination. The pupil should prepare the soil, plant the seeds, water them, and care for the plants. 10. Plant seeds in pots or shallow boxes. The box should not be very wide or long, and not over four inches deep. Holes may be bored in the bottom so it will not hold water. Plant a number of squash, bean, corn, pine, or other seeds about an inch deep in damp sand or pine sawdust in this box. The depth of planting should be two to four times the diameter of the seeds. Keep the sand or sawdust moist but not wet. If the class is large, use several boxes, that the supply of speci- mens may be ample. Cigar boxes and chalk boxes are excellent for individual pupils. It is well to begin the planting of seeds at least ten days in advance of the lesson, and to make four or five differ- ent plantings at intervals. A day or two before the study is taken up, put seeds to soak in moss or cloth. The pupil then has a series from swollen seeds to complete germination, and all the steps can be made out. Dry seeds should be had for comparison. If there is no special room for laboratory, nor duplicate ^nparatus for every pupil, each ex- periment may be assigned to a committee of two pupils to watch in the schoolroom. 11. Good seeds for study are those detailed in the lesson, and buckwheat, pumpkin, cotton, morning glory, radish, four o'clock, oats, wheat. It is best to use familiar seeds of farm and garden. Make drawings and notes of all the events in the germination. Note the 2ffects of unusual conditions, as planting too deep and too shallow and different sides up. For hypogeal germination, use the garden pea, scarlet runner or Dutch Fig. 29. — Cones of Hem- lock (above), White Pine, Pitch Pine. 28 PLANT BIOLOGY case-knife bean, acorn, horse-chestnut. Squash seeds are excellent for germination studies, because the cotyledons become green and leafy and germination is rapid. Its germination, as also that of the scarlet runner bean, is explained in " Lessons with Plants." Onion is excellent, except that it germinates too slowly. In order to study the root development of germinating plantlets, it is well to pro- vide a deeper box with a glass side against which the seeds are planted. 12. Observe the germination of any common seed about the house premises. When elms, oaks, pines, or maples are abundant, the germination of their seeds may be studied in lawns and along fences. 13. When studying germination, the pupil should note the differences in shape and size between cotyledons and plumule-leaves, and between plumule-leaves and the normal leaves (Fig. 30). Make drawings. 14. Make the tests described in the introductory experi- ments with bean, corn, the castor bean, and other seed for starch and proteids. Test flour, oatmeal, rice, sunflower, four o'clock, various nuts, and any other seeds obtainable. Record your results by ar- ranging the seeds in three classes, i. Much starch (color blackish or purple), 2. Little starch (pale blue or greenish), 3. No starch (brown or yellow). 15. Rate of growth of seedlings as affected by differences in tempera- ture. Pack soft wet paper to the depth of an inch in the bottom of four glass bottles or tumblers. Put ten soaked peas or beans into each. Cover each securely and set them in places having different temperatures that vary little. (A furnace room, a room with a stove, a room without stove but reached by sunshine, an unheated room not reached by the sun.) Take the temperatures occasion- ally with a thermometer to find difference in temperature. The tumblers in warm places should be covered very tightly to prevent the germination from being retarded by drying out. Record the number of seeds which sprout in each tumbler within i day ; 2 days ; 3 days ; 4 days, etc. 16. Is air necessary for the germination and groivth of seedlings ? Place damp blotting paper in the bottom of a bottle and fill it three fourths full of soaked seeds, and close it tightly with a rubber stopper or oiled cork. Prepare a " check experiment" by having another bottle with all conditions the same except that it is covered loosely that air may have access to it, and set the bottles side by side (why keep the bottles together?). Record results as in the preceding experiment. 17. What is tfu Fig. 30. — MusKMELON Seedlings, with the unlike seed-leaves and true leaves. r SEEDS AND GERMINATION' 29 nature of the gas given off by germinating seeds ? Fill a tin box or large-necked bottle with dry beans or peas, then add water ; note how much they swell. Secure two fruit-jars. Fill one of them a third full of beans and keep them moist. Allow the other to remain empty. In a day or two insert a lighted sphnter or taper into each. In the empty jar the taper burns : 'it contains oxygen. In the seed jar the taper goes out : the air has been replaced by carbon dioxid. The air in the bottle may be tested for carbon dioxid by removing some of it with a nibber bulb attached to a glass tube (or a fountain-pen filler) and bubbhng it through lime water. 18. Temperature. Usually there is a perceptible rise in temperature in a mass of germinating seeds. This rise may be tested with a thermometer. 19. Interior of seeds. Soak seeds for twenty-four hours and remove the coat. Distinguish the embryo from the endosperm. Test with iodine. 20. Of what utility is the food in seeds ? Soak some grains of corn overnight and remove the endosperm, being careful not to injure the fleshy cotyledon. Plant the incomplete and also some complete grains in moist sawdust and measure their growth at intervals. (Boiling the sawdust will destroy molds and bacteria which might interfere with experiment.) Peas or beans may be sprouted on damp blotting paper ; the cotyledons of one may be removed, and this with a normal seed equally advanced in germi- nation may be placed on a perforated cork floating in water in a jar so that the roots extend into the water. Their growth may be observed for several weeks. 21. Effect of darkness on seeds and seedlings. A box may be placed mouth downward over a smaller box in which seedlings are growing. The empty box should rest on half-inch blocks to allow air to reach the seedlings. Note any effects on the seedlings of this cutting off of the light. Another box of seedUngs not so covered may be used for a check. Lay a plank on green grass and after a week note the change that takes place beneath it. 22. Seedling of pine. Plant pine seeds. Notice how they emerge. Do the cotyledons stay in the ground ? How many cotyledons have they ? When do the cotyledons get free from the seed-coat ? What is the last part of the cotyledon to become free ? Where is the growing point or plumule ? How many leaves appear at once ? Does the new pine cone grow on old wood or on wood formed the same spring with the cone? Can you always find partly grown cones on pine trees in winter? Are pine cones when mature on two-year-old wood? How long do cones stay on a tree after the seeds have fallen out ? What is the advantage of the seeds falling before the cones? 23. Home experiments. If desired, nearly all of the foregoing experiments may be 30 PLANT BIOLOGY tried at home. The pupil can thus make the drawings for the notebook at home. A daily record of measurements of the change in size of the various parts of the seedhng should also be made. 24. Seed-testing. — It is important that one know before planting whether seeds are good, or able to grow. A simple seed-tester may be made of two'plates, one inverted over the other (Fig. 31). The lower plate is nearly filled with clean sand, which is covered with cheese cloth or blotting paper on which the seeds are placed. Canton flannel is sometimes used in place of sand and blotting paper. The seeds are then covered with another blotter or piece of cloth, and water is applied until the sand and papers are saturated. Cover with the second plate. Fig. 31. — a Home-made Set the plates where they will have about Seed-tester. the temperature that the given seeds would require out of doors, or perhaps a slightly higher temperature. Place 100 or more grains of clover, corn, wheat, oats, rye, rice, buckwheat, or other seeds in the tester, and keep record of the number that sprout. The result will give a percentage measure of the ability of the seeds to grow. Note whether all the seeds sprout with equal vigor and rapidity. Most seeds will sprout in a week or less. Usually such a tester must have fresh sand and paper after every test, for mold fungi are likely to breed in it. If canton flannel is used, it may be boiled. If possible, the seeds should not touch each other. Note to Teacher. — With the study of germination, the pupil will need to begin dissecting. For dissecting, one needs a lens for the examination of the smaller parts of plants and animals. It is best to have the lens mounted on a frame, so that the pupil has both hands free for pulling the part in pieces. An ordinary pocket lens may be mounted on a wire in a block, as in Fig. A. A cork is slipped on the top of the wire to avoid injury to the face. The pupil should be provided with two dissecting needles (Fig. B), made by securing an ordinary needle in a pencil-like stick. Another con- venient arrangement is shown in Fig. C. A small tin dish is used for the base. Into this a stiff" wire standard is soldered. The dish is filled with solder, to make it heavy and firm. Into a cork slipped on the standard, a cross wire is inserted, holding on the end a jeweler's glass. The lens can be moved up and down and sidewise. This outfit can be made for about seventy-five cents. Fig. D shows a convenient hand-rest or dissecting-stand to be SEEDS AND GERMINATION 31 used under this lens. It may be 16 in. long, 4 in. high, and 4 or 5 in. broad. \ ^ a Various kinds of dissecting microscopes are on the market, ana these are to be recommended when they can be afforded. I 5. — Dis- secting Needle % natural size. £). — Dissecting Stand. .^ C. — Dissecting Glass. /4. — Improvised Stand for Lens. Instructions for the use of the compound microscope, with which some schools may be equipped, cannot be given in a brief space ; the technique requires careful training. Such microscopes are not needed unless the pupil studies cells and tissues. CHAPTER VII THE ROOT — THE FORMS OF ROOTS The Root System. — The offices of the root are to hold the plant in place, and to gather food. Not all the food materials, however, are gathered by the roots. Fig. 32. — Tap-root System of Alfalfa. Fig. 33. — Tap-root of the Dandelion. The entire mass of roots of any plant is called its root system. The root system may be annual, biennial or peren- nial, herbaceous or woody, deep or shallow, large or small. Kinds of Roots. — A strong leading central root, which runs directly downwards, is a tap-root. The tap-root forms 32 THE ROOT— THE FORMS OF ROOTS 33 an axis from which the side roots may branch. The side or spreading roots are usually smaller. Plants that have such a root system are said to be tap-rooted. Examples are red clover, alfalfa, beet, turnip, radish, burdock, dandelion, hickory (Figs. 32, 33). A fibrous root system is one that is composed of many nearly equal slender branches. The greater number of plants have fibrous roots. Examples are many common grasses, wheat, oats, corn. The buttercup in Fig. 34 has a fibrous root system. Many trees have a strong tap-root when very young, but after a while it ceases to ex- tend strongly and the side roots develop until finally the tap-root character disappears. Shape and Extent of the Root Sys- tem. — The depth to which roots extend depends on the kind of plant, and the nature of the soil. Of most plants the roots extend far in all directions and lie comparatively near th^ surface. The roots usually radiate from a common point just beneath the surface of the ground. The roots grow here and there in search of food, often extending much farther in all directions than the spread of the top of the plant. Roots tend to spread farther in poor soil than in rich soil, for the same size of plant. The root has no such definite form as the stem has. Roots are usually very crooked, because they are constantly turned aside by obstacles. Examine roots in stony soil Fig. 34. — A Buttercup Plant, with fibrous roots. 34 PLANT BIOLOGY The extent of root surface is usually very large, for the feeding roots are fine and very numerous. An ordinary- plant of Indian corn may have a total length of root (measured as if the roots were placed end to end) of several hundred feet. The fine feeding roots are most abundant in the richest part of the soil. They are attracted by the food materials. Roots often will completely surround a bone or other morsel. When roots of trees are exposed, observe that most of them are horizontal and lie near the top of the ground. Some roots, as of willows, extend far iti search of water. They often run into wells and drains, and into the margins of creeks and ponds. Grow plants in a long narrow box, in one end of which the soil is kept very dry and in the other moist : observe where the roots grow. Buttresses. — With the increase in diameter, the upper roots often protrude above the ground and become bracing buttresses. These buttresses are usually largest in trees which always have been exposed to strong winds (Fig. 35). Because of growth and thickening, the roots elevate part of their diameter, and the washing away of the soil makes them to appear as if having risen out of the ground. Aerial Roots. — Although roots usually grow underground, there are some that naturally grow above ground. These usually occur on climbing plants, the roots becoming sup- ports or fulfilling the office of tendrils. These aerial roots usually turn away from the light, and therefore enter the Fig. 35. — The Bracing Base of a Field Pine. THE ROOT— THE FORMS OF ROOTS 35 crevices and dark places of the wall or tree over which the plant ,^ climbs. The trumpet creeper (Fig. 36), true or English ivy, and poison ivy climb by means of roots. Fig. 37.— Aerial RpoTs of an Orchid. In some plants all the roots are aerial ; that is, the plant grows above ground, and the roots gather food from the air. Such plants usually grow on trees. They are known as epiphytes or air-plants. The most fa- FiG. 36. — Aerial Roots . . OF Trumpet Creeper miliar examples are some of the tropi- OR tecoma. ^^j orchids, which are grown in glass- houses (Fig. 37). Rootlike organs of dodder and other parasites are discussed in a future chapter. 36 PLANT BIOLOGY Some plants bear aerial roots, that may propagate the plant Qx may act as braces. They are often called prop-roots. The roots of Indian corn are familiar (Fig. 38). Many ficus trees, as the banyan of India, send out roots from their branches ; when these roots reach the ground they take hold and become great trunks, thus spreading the top of the parent tree over large areas. The muscadine grape of the Southern states often sends down roots from its stems. The man- grove tree of the tropics grows along seashores and sends down roots from the overhanging branches (and from the fruits) into the shal- low water, and thereby gradually marches into the sea. The tangled mass behind catches the drift, and soil is formed. Adventitious Roots. — Sometimes roots grow from the stem or other unusual places as the result of some accident to the plant, being located without known method or law. They are called adventitious (chance) roots. Cuttings of the stems of roses, figs, geraniums, and other plants, when planted, send out adventitious roots and form new plants. The ordinary roots, or soil roots, are of course not classed as adventitious roots. The adventitious roots arise on occa- sion, and not as a normal or regular course in the growth of the plant. No two roots are alike ; that is, they vary among them- selves as stems and leaves do. Each kind of plant has its Fig. 38. — Indian Corn, showing the brace roots at 00. THE ROOT— THE FORMS OF ROOTS 37 own form or habit of root (Fig. 39). Carefully wash away the soil from the roots of any two related plants, as oats and wheat, and note the differences in size, depth, direc- tion, mode of branching, num- ber of fibrils, color, and other r Fig. 39. — Roots of Barley at A and Corn at B. Carefully trace the differences. features. The character of the root system often governs the treatment that the farmer should give the soil in which the plant or crop grows. Roots differ not only in their form and habit, but also in color of tissue, character of bark or rind, and other features. It is excellent practice to t?y to identify different plants by means of their roots. Let each pupil bring to school two plants with the roots very carefully dug up, as cotton, corn, potato, bean, wheat, rye, timothy, pumpkin, clover, sweet pea, raspberry, strawberry, or other common plants. Root Systems of Weeds. — Some weeds are pestiferous because they seed abundantly, and others because their underground parts run deep or far and are persistent. Make out the root systems in the six worst weeds in your locality. CHAPTER ^11 THE ROOT. — FUNCTION AND STRUCTURE The function of roots is twofold, — to provide support or anchorage for the plant, and to collect and convey food ma- terials. The first function is considered in Chapter VII; we may now give attention in more detail to the second. The feeding surface of the roots is near their ends. As the roots become old and hard, they serve only as channels through which food passes and as holdfasts or supports for the plant. The root- hold of a plant is very strong. 0^/ \\Jil!Iiifil^^^'l^lBKII'' Slowly pull upwards on some plant, I ll/f,/\ wMMam^lt. and note how firmly it is anchored in the soil. Roots have power to choose their food; that is, they do not absorb all substances with which they come in contact. They do not take up great quantities of useless or harmful materials, even though these materials may be abundant in the soil ; but they may take up a greater quantity of some of the plant-foods than the plant can use to advantage. Plants respond very quickly to liberal feeding, — that is, to the application of plant-food to the soil (Fig 40). The poorer the soil, the more marked are the results, as a rule, of the application 38 Fig. 40. — Wheat growing UNDER Different Soil Treatments. Soil defi- cient in nitrogen ; com- mercial nitrogen applied to pot 3 (on right). THE ROOT— FUNCTION AND STRUCTURE 39 of fertilizers. Certain substances, as common salt, will kill the roots. Roots absorb Substances only in Solution. — Substances cannot be taken in solid particles. These materials are in solution in the soil water, and the roots themselves also have the power to dissolve the soil materials to some extent by means of substances that they excrete. The materials that /-fc| come into the plant through the roots are water atid mostly the min- eral substances, as compounds of po- tassium, iron, phosphorus, calcium, magnesium, sulfur, and chlorine. These mineral substances compose the ash when the plant is burned. The carbon is derived from the air through the green parts. Oxygen is derived from the air and the soil water. Nitrogen enters through the Roots. — All plants must have nitrogen; yet, although about four fifths of fig. 41. — nodules on roots . V . . ., 1 ^ ^ OF Red Clover. the air is nitrogen, plants are not able, so far as we know, to take it in through their leaves. It enters through the roots in combination with other ele- ments, chiefly in the form of nitrates (certain combinations with oxygen and a mineral base). The great family of leguminous plants, however (as peas, beans, cowpea, clover, alfalfa, vetch), use the nitrogen contained in the air in the soil. They are able to utilize it through the agency of nodules on their roots (Figs. 41, 42), These nodules contain bacteria, which appropriate the free or iincom- bined nitrogen and pass it on to the plant. The nitrogen 40 PLANT BIOLOGY Fig. 42. — Nodules on Vetch. becomes incorporated in the plant tissue, so that these crops are high in their nitrogen content. Inasmuch as nitrogen ih any form is expensive to purchase in fertilizers, the use of legu- minous crops to plow under is a very important agricul- tural practice in preparing the land for other crops. In order that leguminous crops may acquire atmos- pheric nitrogen more freely and thereby thrive better, the land is sometimes sown or inoculated with the nod- ule-fo rni ing bacteria . Roots require moisture in order to serve the plant. The soil water that is valu- able to the plant is not the free water, but the thin film of moisture :jtvhich adheres to each little particle of soil. The finer the soil, the greater the number of particles, and therefore the greater is the quantity of film moisture that it can hold. This moisture surround- ing the grains may not be perceptible, yet the plant can use it. Root absorption may continue in a soil which seems to be dust dry. Soils that are very hard and Fig. 43. — Two Kinds of Son, that have BEEN Wet and then Dried. The loamy soil above remains loose and capa- ble of growing plants ; the clay soil below has baked and cracked. THE ROOT— FUNCTION AND STRUCTURE 41 "baked" (Fig. 43) contain very little moisture or air, — not so much as similar soils that are granular or mellow. Proper Temperature for Root Action. — The root must be warm in order to perform its functions. Should the soil of fields or greenhouses be much colder than the air, the plant suffers. When in a warm atmosphere, or in a dry atmosphere, plants need to absorb much water from the soil, and the roots must be warm if the root-hairs are to supply the water as rapidly as it is needed. If the roots are chilled, the plant may wilt or die. Roots need Air. — Corn on land that has been flooded by heavy rains loses its green color and turns yellow. Besides diluting plant-food, the water drives the air from the soil, and this stiffocation of the roots is very soon ap- parent in the general ill health of the plant. Stirring or tilling the soil aerates it. Water plants and bog plants have adapted them- selves to their particular conditions. They get their air either by special surface roots, or from the water through stems and leaves. Rootlets. — Roots divide into the thinnest and fijiest fibrils : there are roots and there are rootlets. The smallest rootlets are so slender and dehcate that they break off even when the plant is very carefully Hfted from the soil. The rootlets, or fine divisions, are clothed with the root- hairs (Figs. 44, 45, 46). These root-hairs attach to the soil particles, ajid a great amount of soil is thus brought into actual contact with the plant. These are very deli- cate prolonged surface cells of the roots. They are borne for a short distance just back of the tip of the root. Rootlet and root-hair differ. The rootlet is a compact Fig. 44. — Root- hairs OF THE Radish. 42 PLANT BIOLOGY Fig. 45. — Cross-section of Root, enlarged, showing root-hairs. cellular structure. The root-hair is a delicate tubular cell (Fig. 45), within which is contained living matter {j>rotoplasm); and the protoplasmic lining membrane of the wall governs the entrance of water and substances in solu- tion. Being long and tube- like, these root-hairs are especially adapted for tak- ing in the largest quantity of solutions; and they are the principal means by which plant-food is absorbed from the soil, although the sur- faces of the rootlets them- selves do their part. Water plants do not produce an abundant system of root-hairs, and such plants depend largely on their rootlets. The root-hairs are very small, often invisible. They, with the young roots, are usually broken off when the plant is pulled up. They are best seen when seeds are germi- nated between layers of dark blotting paper or flannel. On the young roots, they will be seen as a mold-like or gossamer- like covering. Root-hairs soon die : they do not grow into roots. New ones form as the root grows. Osmosis. — The water with its nourishment goes through the thin walls of the root-hairs and rootlets by the process of osmosis. If there are two liquids of different density Fig. 46. — RoOT-HAlR, much en- larged, in contact with the soil particles ( j) . Air-spaces at a ; water-films on the particles, as at w. THE ROOT— FUNCTION AND STRUCTURE 43 on the inside and outside of an organic (either vegetable or animal) membrane, the liquids tend to mix through the membrane. The law of osmosis is that the most rapid flow is toward the denser solution. The protoplasmic lin- ing of the cell wall is such a membrane. The soil water being a weaker solution than the sap in the roots, the flow is into the root. A strong fertilizer sometimes causes a plant to wither, or "burns it." Explain. Structure of Roots. — The root that grows from the lower end of the caulicle is the first or primary root. Secondary roots branch from the primary root. Branches of second- ary roots are sometimes called tertiary roots. Do the sec- ondary roots grow from the cortex, or from the central cylinder of the primary root.-* Trim or peel the cortex from a root and its branches and determine whether the branches still hold to the central cylinder of the main root. Internal Structure of Roots. — A section of a root shows that it consists of a central cylinder (see Fig. 45) sur- rounded by a layer. This layer is called the cortex. The outer layer of cells in the cortex is called the epidermis, and some of the cells of the epidermis are prolonged and form the delicate root-hairs. The cortex resembles the bark of the stem in its nature. The central cylinder contains many tube-like canals, or " vessels " that convey water and food (Fig. 45). Cut a sweet potato across (also a radish and a turnip) and distinguish the central cylin- der, cortex and epidermis. Notice the hard cap on the tip of roots. Roots differ from stems in having no real pith. Microscopic Structure of Roots. — Near the end of any young root or shoot the cells are found to differ from each other more or less, according to the distance from the point. TJiis differentiation takes place iti the region just back of the growing point. To study growing points, use \ 44 PLANT BIOLOGY the hypocotyl of Indian corn which has grown about one half inch. Make a longitudinal section. Note these points (Fig. 47): {a) the tapering root-cap beyond the growing point ; {b) the blunt end of the root proper and the rec- tangular shape of the cells found there; {c) the group of cells in the middle of the first layers beneath the root- cap, — this group is the growing point; (^) study the slight differ- ences in the tissues a short dis- tance back of the growing point. There are four regions : the central cylinder, made up of several rows of cells in the center (//); the en- dodermis, {e) composed of a single layer on each side which separates the central cylinder from the bark ; the cortex, or inner bark, {e) of sev- eral layers outside the endodermis ; and the epidermis, or outer layer of bark on the outer edges {d). Make a drawing of the section. If a series of the cross-sections of the hypocotyl should be made and stud- ied, beginning near the growing point and going upward, it would be found that these four tissues become more distinctly marked, for at the tip the tissues have not yet assumed their characteristic form. The central cylinder contains the ducts and vessels which convey the sap. The Root-cap. — Note the form of the root-cap shown in the microscopic section drawn in Fig. 47. Growing cells, and especially those which are forming tissue by sub- dividing, are very delicate and are easily injured. The Fig. 47. — Growing Point OF Root of Indian Corn. d, d, cells which will form the epidermis; /, /, cells that will form bark; ?,?, endoder- mis; //, cells which will form the axis cylinder; /, initial group of cells, or growing point proper; c, root-cap. THE ROOT— FUNCTION AND STRUCTURE 45 cells forming the root-cap are older and tougher and are suited for pushing aside the soil that the root may pene- trate it. Region of most Rapid Growth. — The roots of a seedling bean may be marked at equal distances by waterproof ink or by bits of black thread tied moderately tight. The seedHng is then replanted and left undisturbed for two days. When it is dug up, the region of most rapid growth in the Fig. 48. —The Mark- ing OF THE Stem AND Root. Fig. 49. — The Result root can be deter- mined. Give a reason why a root camiot elongate throughout its length, — whether there is anything to pre- vent a young root from doing so. In Fig. 48 is shown a germinating scarlet runner bean with a short root upon which are marks made with waterproof ink ; and the same root (Fig. 49) is shown after it has grown longer. Which part of it did not lengthen at all .'' Which part lengthened slightly .'' Where is the region of most rapid growth.? Geotropism. — Roots turn to- ward the earth, even if the seed is planted with the micropyle up. This phenomenon is called posi- tive geotropism. Stems grow away from the earth. This is negative geotropism. 46 PLANT BIOLOGY Suggestions (Chaps. VII and VIII). — 25. Tests for food. Ex- amine a number of roots, including several fleshy roots, for the presence of food material, making the tests used on seeds. 26. Study of root-hairs. Carefully germinate radish, turnip, cabbage, or other seed, so that no delicate parts of the root will be injured. For this purpose, place a few seeds in packing-moss or in the folds of thick cloth or of blotting paper, being careful to keep them moist and warm. In a few days the seed has germinated, and the root has grown an inch or two long. Notice that, except at a dis- tance of about a quarter of an inch behind the tip, the root is covered with minute hairs (Fig. 44). They are actually hairs ; that is, root-hairs. Touch them and they collapse, they are so delicate. Dip one of the plants in water, and when removed the hairs are not to be seen. The water mats them together along the root and they are no longer evident. Root-hairs are usually destroyed when a plant is pulled out of the soil, be it done ever so carefully. They cling to the minute particles of soil (Fig. 46). The hairs show best against a dark background. 27. On some of the blotting papers, sprinkle sand ; observe how the root-hairs cling to the grains. Observe how they are flat- tened when they come in contact with grains of sand. 28. Root hold of plant. The pupil should also study the root hold. Let him carefully pull up a plant. If a plant grow alongside a fence or other rigid object, he may test the root hold by se- curing a string to the plant, letting the string hang over the fence, and then add- ing weights to the string. Will a stake of similar size to the plant and extending no deeper in the ground have such firm hold on the soil ? What holds the ball of earth in Fig. 50? 29. Roots exert pressure. Place a strong bulb of hyacinth or daffodil on firm-packed earth in a pot ; cover the bulb nearly to the top with loose earth \ place in a cool cellar ; after some days Fig. 50. — The Grasp of a Plant on the Parti CLES OF Earth. A grass plant pulled in a garden. THE ROOT— FUNCTION AND STRUCTURE 47 Fig. 51.— Plant grow- ing IN In- verted Pot. or weeks, note ihat the bulb has been raised out of the earth by the forming roots. All roots exert pressure on the soil as they grow. Explain. 30. Response of roots and stems to the force of gravity, or geotropisfn. Plant a fast-growing seedling in a pot so that the plumule extends through the drain hole and suspend the pot with mouth up {i.e. in the usual position). Or use a pot in which a plant is already growing, cover with cloth or wire gauze to prevent the soil from falling, and suspend the pot in an inverted position (Fig. 51). Notice the behavior of the stem, and after a few days remove the soil and observe the position of the root. 31. If a pot is laid on one side, and changed every two days and laid on its opposite side, the effect on the root and stem will be interesting. 32. If a fleshy root is planted wrong end up, what is the result ? Try it with pieces of horse-radish root. 33. By planting radishes on a slowly revolving wheel the effect of gravity may be neutralized. 34. Region of root most sensitive to gravity. Lay on its side a pot containing a growing plant. After it has grown a ioys days, wash away the earth surrounding the roots. Which turned downward most decidedly, the tip of root or the upper part? 35. Soil texture. Carefully turn up soil in a rich garden or field so that you have unbroken lumps as large as a hen's egg. Then break these lumps apart carefully with the fingers and determine whether there are any traces or remains of roots (Fig. 52). Are there any pores, holes, or channels made by roots ? Are the roots in them still living? 36. Compare an- other lump from a clay bank or pile • where no plants have been growing. Is there any differ- ence in texture? 37. Grind up this clay lump very fine, put it in a saucer, cover with water, and set in the sun. After a time it will have the appearance shown in the lower saucer in Fig. 43. Compare this with mellow garden soil. In which will plants grow best, even if the plant- food were the same in both ? Why ? 38. To test the effect of moisture on the plant, let a plant in a pot or box dry Fig. 52. — Holes in Soil made by Roots, now decayed. Somewhat magnified. 48 PLANT BIOLOGY out till it wilts ; then add water and note the rapidity with which it recovers. Vary the experiment in quantity of water applied. Does the plant call for water sooner when it stands in a sunny win- dow than when in a cool shady place? Prove it. 39. Immerse a potted plant above the rim of the pot in a pail of water and let it remain there. What is the consequence ? Why ? 40. To test the effect of temperature on roots. Put one pot in a dish of ice water, and another in a dish of warm water, and keep them in a warm room. In a short time notice how stiff and vigorous is the one whose roots are warm, whereas the other may show signs of wilting. 41. The process of osmosis. Chip away the shell from the large end of an egg so as to expose the uninjured membrane beneath for an area about as large as a dime. With sealing-wax, chewing-gum, or paste stick a quill about three inches long to the smaller end of the egg. After the tube is in place, run a hat pin into it so as to pierce both shell and membrane ; or use a short glass tube, first scraping the shell thin with a knife and then boring through it with the tube. Now set the egg upon the mouth of a pickle jar nearly full of water, so that the large end with the exposed membrane is beneath the water. After several hours, observe the tube on top of the egg to see whether the water has forced its way into the egg and increased its volume so that part of its contents are forced up into the tube. If no tube is at hand, see whether the contents are forced through the hole which has been made in the small end of the egg. Explain how the law of osmosis is verified by your result. If the eggshell contained only the membrane, would water rise into it? If there were no water in the bottle, would the egg-white pass down into the bot- tle ? 42. The region of most rapid growth. The pupil should make marks with waterproof ink (as Higgins' ink or indelible marking ink) on any soft growing roots. Place seeds of bean, radish, or cabbage between layers of blotting paper or thick cloth. Keep them damp and warm. When stem and root have grown an inch and a half long each, with waterproof ink mark spaces exactly one quarter inch apart (Figs. 48, 49). Keep the plantlets moist for a day or two, and it will be found that on the stem some or all of the marks are more than one quarter inch apart ; on the root the marks have -not separated. The root has grown beyond the last mark. Note to Teacher. — The microscopic structure of the root can be determined only by the use of the compound microscope ; but a good general conception of the structure may be 'had by a care- ful attention to the text and pictures and to explanations by the teacher, if such microscopes are not to be had. See note at close of Chapter X. CHAPTER IX THE STEM — KINDS AND FORMS; PRUNING The Stem System. — The stem of a plant is the part that bears the buds, leaves, flowers, and fruits. Its office is to hold these parts up to the light atid air ; and through its tissues the various food-materials and the life-giving fluids are distributed to the growing and working parts. The entire mass or fabric of stems of any plant is called its stem system. It comprises the trunk, branches, and twigs, but not the stalks of leaves and flowers that die and fall away. The stem system may be herbaceous or woody, annual, biennial, or perennial ; and it may assume many sizes and shapes. Stems are of Many Forms. — The general way in which a plant grows is called its habit. The habit is the appear- ance or general form. Its habit may be open or loose, dense, straight, crooked, compact, straggling, chmbing, erect, weak, strong, and the like. The roots and leaves are the important fimctional or tvorking parts ; the stem merely connects them, and its form is exceedingly variable. Kinds of Stems. — The stem may be so short as to be scarcely distinguishable. In such cases the crown of the plant — that part just at the surface of the ground — bears the leaves and flowers ; but this crown is really a very short stem. The dandelion. Fig. 33, is an example. Such plants are often said to be stemless, however, in order to distinguish them from plants that have long or conspic- E 49 • 50 PLANT BIOLOGY uous Stems. These so~called stemless platits die to the ground every year. Stems are erect when they grow straight up (Figs. 53, 54). They are trailing when they run along on the ground, Fig. 53. — Strict Simple Stem of Mullein. Fig. 54. — Strict Upright Stem OF Narrow-leaved Dock. as melon, wild morning-glory (Fig. 55). They are creep- ing when they run on the ground and take root at places, Fig. 55. — Trailing Stem of Wild Morning Glory {Convolvulus arvensis) . as the strawberry. They are decumbent when they lop over to the ground. They are ascending when they He mostly or in part on the ground but stand more or less upright at their ends ; example, a tomato. They are THE STEMS— KINDS AND FORMS; PRUNING 51 climbing when they cling to other objects for support (Figs. 36, 56). Trees in which the main trunk or the ** leader " continues to grow from its tip are said to be excurrent in growth. The branches are borne along the sides of the trunk, as in common pines (Fig. 57) and spruces. Excurrent means nmning out or running up. Trees in which the main trunk does not continue are said to be deliques- ^ cent. The branches arise from one common point or from each other. The stem is lost in the branches. The apple tree, plum (Fig. 58), maple, elm, oak, China tree, are familiar examples. DeHquescent means dissolving or melting away. Each kind of plant has its own peculiar habit or direction of growth; spruces al- ways grow to a single stem or trunk, pear Fig. 56. — a Climbing Plant (a twiner). nk, pear ^i>> Fig. 57. — Excurrent Trunk. A pine. Fig. 58. — Deliquescent Trunk OF Plum Tree. 52 PLANT BIOLOGY trees are always deliquescent, morning-glories are always trailing or climbing, strawberries are always creeping. We do not know why each plant has its own habit, but the habit is in some way associated with the plant's gene- alogy or with the way in which it has been obliged to live. The stem may be simple or branched. A simple stem usually grows from the terminal bud, and side branches either do not start, or, if they start, they soon perish. Mulleins (Fig. 53) are usually simple. So are palms. Branched stems may be of very different habit and shape. Some stem systems are narrow and erect ; these are said to be strict (Fig. 54). Others are diffuse, open, branchy, Izviggy. Nodes and Internodes. — The parts of the stem at which buds grow are called nodes or joints and the spaces be- tween the buds are internodes. The stem at nodes is usually enlarged, and the pith is usually interrupted. The distance between the nodes is influenced by the vigor of the plant : how .? Fig. 59. — Rhizome or Rootstock. Stems vs. Roots. — Roots sometimes grow above ground (Chap. VII); so, also, stems sometimes grow underground, and they are then known as subterranean stems, rhizomes, or rootstocks (Fig. 59). Stems normally bear leaves and buds, and thereby are they distinguished from roots; usually, also, they contain a pith. The leaves, however, may be reduced to mere scales, and the buds beneath them may be scarcely visible. THE STEMS— KINDS AND FORMS; PRUNING 53 Thus the "eyes" on a white potato are cavities with a bud or buds at the bottom (Fig. 60). Sweet potatoes have no evident "eyes" when first dug (but they may develop adventitious buds before the next grow- ing-season). The white potato is a stem : the sweet potato is probably a root. How Stems elongate. — Roots elongate by gi'owiitg near the tip. Stems elon- gate by growing more or less through- ^'^'* ^- ~ Sprouts o ^ e> C> d ARISING FROM THE out the young or soft part or "between buds, or eyes, of a joints " (Figs. 48, 49). But any part p^^'^^" *"^^'^- of the stem soon reaches a limit beyond which it cannot grow, or becomes "fixed"; and the new parts beyond elongate until they, too, become rigid. When a part of the stem once becomes fixed or hard, it never increases in length : that is, the trunk or woody parts never grow longer or higher ; branches do not become farther apart or higher from the ground. Stems are modified in form by the particular or incidental conditions under which they grow. The struggle for light is the chief factor in determining the shape and direction of any limb (Chap. II). This is well illustr,^ted in any tree or bush that grows against a building or on the mar- gin of a forest (Fig. 4). In a very dense thicket the innermost trees shoot up over the others or they perish. Examine any stem and endeavor to determine why it took its particular form. The stem is cylindrical, the outer part being bark and the inner part being wood or woody tissue. In the dicoty- ledonous plants, the bark is usually easily separated ffom the remainder of the cylinder at some time of the year ; in monocotyledonous plants the bark is not free. Growth in thickness takes place inside the covering and not on the very 54 PLANT BIOLOGY outside of the plant cylinder. It is evident, then, that the covering of bark must expand in order to allow of the expan- sion of the woody cylinder within it. The tis- sues, therefore, must be under constant pressure or tension. It has been determined that the pressure within a growing trunk is often as much as fifty pounds to the square inch. The lower part of the limb in Fig. 6i shows that the outer layers of bark (which are long since dead, and serve only as protective tissue) have reached the limit of their expanding capacity and have begun to split. The pupil will now be interested in the bark on the body of an old elm tree (Fig. 62); and he should be able to suggest one reason why stems remain cylindri- cal, and why the old bark becomes marked with furrows, scales, and plates. Most woody plants increase in diameter by the addition of an annual layer or ''ring'' on the outside of the woody cylinder, underneath the bark. The monocotyledo- nous plants comprise very few trees and shrubs in temperate climates (the palms, yuccas, and other tree- like plants are of this class), and they do not increase greatly in diameter and they rarely branch to any extent. Consult the woodpile for information as to the annual rings. Bark-bound Trees. — If, for any rea- son, the bark should become so dense and strong that the trunk cannot ex- pand, the tree is said to be " bark-bound." is not rare in orchard trees that have been neglected. Fig. 61.— Cracking OF THE Bark on an Elm Branch. Fig. 62. — Piece of Bark from an Old Elm Trunk. Such condition THE STEMS— KINDS AND FORMS; PRUNING 55 When good tillage is given to such trees, they may not be able to overcome the rigidity of the old bark, and, therefore, do not respond to the treatment. Sometimes the thinner-barked parts may outgrow in diameter the trunk or the old branches below them. The remedy is to release the tension. This may be done either by soften- ing the bark (by washes of soap or lye), or by separating it. The latter is done by slitting the bark-bound part (in spring), thrusting the point of a knife through the bark to the wood and then drawing the blade down the entire length of the bark- bound part. The slit is scarcely discernible at first, but it opens with the growth of the tree, filling up with new tissue beneath. Let the pupil consider the ridges which he now and then finds on trees, and determine whether they have any sig- nificance — whether the tree has ever been released or in- jured by natural agencies. The Tissue covers the Wounds and " heals " them. — This is seen in Fig. 63, in which a ring of tissue rolls out over the wound. This ring of healing tissue forms most rapidly and uniformly when the wound is smooth and regu- lar. Observe the healing on broken and splintered limbs ; also the difference in rapidity of healing between wounds on strong and weak limbs. There is difference in the rapidity of the healing process in different kinds of trees. Compare the apple tree and the peach. This tissue may in Fig. 63. — Proper Cutting of a Branch. The wound will soon be " healed." 56 PLANT BIOLOGY Fig. 64. — Erroneous Pruning. turn become bark-bound, and the healing may stop. On large wounds it progresses more rapidly the first few years than it does later. This roll or ring of tissue is called a callus. The callus grows from the liv- ing tissue of the stem just about the wound. It cannot cover long dead stubs or very rough broken branches (Fig. 64). Therefore, in pruning tJie brandies should be cut close to the trunk and made even and smooth ; all long stubs tnust be avoided. The seat of the wound should be close to the living part of the trunk, for the stub of the limb that is severed has no further power in itself of making healing tissue. The end of the remaining stub is merely covered over by the callus, and usually remains a dead piece of wood sealed in- side the trunk (Fig. 65). If wounds do not heal over speed- ily, germs and fungi obtain foothold in the dying wood and rot sets in. Hollow trees are those in which the decay- fungi have progressed into the inner wood of the trunk ; they have been infected {¥\g. 66). Large wounds should be protected with a covering of paint, melted wax, or other adhesive and lasting material. Fig. 65. Knot in a Hemlock Log. THE STEMS— KINDS AND FORMS; PRUNING 57 Fig, 66. — a Knot Hole, and the beginniiis; of a hollow trunk. to keep out the germs and fungi, A covering of sheet iron or tin may keep out the rain, but it will not ex- clude the germs of decay ; in fact, it may provide the very moist con- ditions that such germs need for their growth. Deep holes in trees should be treated .by having all the decayed parts removed down to the clean wood, the surfaces painted or otherwise sterilized, and the hole filled with wax or cement. Stems and roots are living, and they should not be wounded or mutilated unnecessarily. Horses should never be hitched to trees. Supervision should be exercised over persons who run telephone, telegraph, and electric light wires, to see that they do not mutilate trees. Electric light wires and trol- ley wires, when carelessly strung or improperly insulated, may kill trees (Fig. ^y). Suggestions. — Forms of stems. 43. Are tne trunks of trees ever per- fectly cylindrical? If not, what may cause the irregularities ? Do trunks often grow more on one side than the other? 44. Slit a rapidly growing limb, in spring, with a knife blade, and watch the re- sult during the season. 45. Consult the woodpile, and observe the variations in fig. 67.— Elm Tree killed thickness of the annual rings, and espe- by a Direct Current cially of the same ring at different places from an Electric in the circumference. Cross-sections of Railroad System. 58 PLANT BIOLOGY horizontal branches are interesting in this connection. 46. Note the enlargement at the base of a branch, and determine whether this enlargement or bulge is larger on long, horizontal limbs than on upright ones. Why does this bulge develop? Does it serve as a brace to the limb, and is it developed as the result of constant strain? 47. Strength of stems. The pupil should observe the fact that a stem has wonderful strength. Compare the propor- tionate height, diameter, and weight of a grass stem with those of the slenderest tower or steeple. Which has the greater strength ? Which the greater height? Which will withstand the most wind? Note that the grass stem will regain its position even if its top is bent to the ground. Note how plants are weighted down after a heavy rain and how they recover themselves. 48. Split a corn- stalk and observe how the joints are tied together and braced with fibers. Are there similar fibers in stems of pigweed, cotton, sun- flower, hollyhock ? Fig. 68. — Potato. What are roots, and what stems ? Has the plant more than one kind of stem ? more than two kinds ? Explain. CHAPTER X THE STEM — ITS GENERAL STRUCTURE There are two main types of stem structure in flowering plants, the differences being based on the arrangement of bundles or strands of tissue. These types are endof^enous and exogenous (page 20). It will require patient laboratory wbrTc to understand what these types and structures are. Endogenous, or Monocotyledonous Stems. — Examples of endogenous stems are all the grasses, cane-brake, sugar- cane, smilax or green-brier, palms, banana, canna, bam- boo, lilies, yucca, aspara- gus, all the cereal grains. For our study, a cornstalk may be used as a type. A piece of cornstalk, either green or dead, should be in the hand of each pupil while studying this lesson. Fig. 69 will also be of use. Is there a swelling at the nodes.? Which part of the internode comes nearest to being perfectly round.? There is a grooved channel running along one side of the internode : how is it placed with reference to the leaf.? with reference to the groove in the internode below it .? What do you find in each groove at its lower end.? (In a dried stalk only traces of this are usually seen.) Does any bud on a cornstalk besides the one at 59 Fig. 69. — Cross-section of Corn- stalk, showing the scattered fibro- vascular bundles. Slightly enlarged. 6o PLANT BIOLOGY the top ever develop ? Where do suckers come from ? Where does the ear grow ? Cut a cross-section of the stalk between the nodes (Fig. 69). Does it have a distinct bark ? ' The interior consists of soft "pith " and tough woody parts. The wood is found in strands or fibers. Which is more abundant } Do the fibers have any definite arrangement } Which strands are largest.? Smallest.'' The firm smooth nW( which cannot properly be called a bark) consists of small wood strands packed closely together. Grass stems are hollow cylinders ; and the cornstalk, because of the lightness of its contents, is also practically a cylinder. Stems of this kind are ad- mirably adapted for providing a strong support to leaves and fruit. This is in accordance with the well-known law that a hollow cylinder is much stronger than a solid cylinder of the same weight of material. Cut a thin slice of the inner soft part and hold it up to the light. Can you make out a number of tiny compartments or cells } These cells consist of a tissue called paren- chyma, the tissue from which when young all the other tissues arise and differentiate (Paren- chyma = parent -f- chyma, or tissue). The numerous walls of these cells may serve to brace the outer wall of the cylinder ; but their chief function in the young stalk is to give origin to other cells. When alive they are filled with cell sap and protoplasm. Trace the woody strands through the nodes. Do they ascend vertically } Do they curve toward the rind at certain places t Compare their course with the strands shown in Fig. 70. Tlie ivoody strands consist chiefly of tough fibrous cells that give rigidity Fig. 70. — Dia- gram TO SHOW THE Course of FlBRO-VASCU- LAR Bundles IN Monocoty- ledons. THE STEM— ITS GENERAL STRUCTURE 6i Fig. 71.— Diagram of Wood Strands or fibro-vascular Bundles in a Root, showing the wood {x) and bast (/) separated. I and strength to the plant, atid of long tubiilar interrupted canals that serve to convey sap upward from the root and to convey food downward from the leaves to the stem and roots. Monocotyledons, as shown by fossils, existed before dicotyledons appeared, and it is thought that the latter were developed from ancestors of the former. It will be interesting to trace the relationship in stem structure. It will first be necessary to learn something of the structure of the wood strand. Wood Strand in Monocotyledons and Dicotyledons. — Each wood strand (or fibro-vascular bundle) consists of two parts — the bast and the wood proper. The wood is on the side of the strand toward the center of the stem and con- tains large tubular canals that take the watery sap upward from the roots. The bast is on the side toward the bark and contains fine tubes through which diffuses the dense sap contain- ing digested food from the leaves. In the root (Fig. 71) the bast and the wood are separate, so that there are two kinds of strands. In monocotyledons, as already said, the strands (or bundles) are usually scattered in the stem with no definite arrangement (Figs. 72, 73). In dicotyledons the strands, or bundles, are arranged in a Fig. 72. — Part of Cross-section of Root- S'lOCK OF Asparagus, showing a few fibro vascular bundles. An endogenous stem. 62 PLANT BIOLOGY Q Fig. 73. — The Scattered Bundles or Strands, in monocotyledons at a, and the bun- dles in a circle in dicotyledons at b. Fig. 74. — Dicotyledonous Stem of One Year at Left WITH Five Bundles, and a two-year stem at right. t>, the pith; c, the wood part; 3, the bast part; a, one year's growth. ring. As the dicotyledonous seed germi- nates, five bundles are usually formed in its hypocotyl (Fig. 74); soon five more are interposed between them, and the multi- plication continues, in tough plants, until the bundles touch (Fig. 74, right). The inner parts thus form a ring of wood and the outer parts form the inner bark or bast. A new ring of wood or bast is formed on stems of di- cotyledons each year and the age of a cut stem is easily determined. When cross-sections of monocotyledonous and di- cotyledonous bundles are examined under the mi- croscope, it is readily seen Fig. 75. — FiBRO-VASCULAR Bundle of Indian Corn, much magnified. A, annular vessel ; A', annular or spiral vessel ; TT' , thick-walled vessels ; IV, tracheids or woody tissue ; F, sheath of fibrous tissue sur- rounding the bundle ; FT, fundamental tissue or pith ; S, sieve tissue ; P, sieve plate ; C, companion cell ; /, intercellular space, formed by tearing down of adjacent cells ; IV' , wood parenchyma. THE STEM— ITS GENERAL STRUCTURE 63 why dicotyledonous bundles form rings of wood and mono- cotyledonous cannot (Figs. 75 and 'j^^. The dicotyledon- ous bundle (Fig. ^6) has, running across it, a layer of brick- shaped cells called cambium, which cells are a specialized form of the parenchyma cells and retain the power of Fig. 76. — The Dicotyledonous Bundle or Wood Strand. Upper figure is of moonseed : f, cambium ; 790 None Holly 63,600 None Lilac 160,000 None Mistletoe 200 200 Tradescantia 2,000 2,000 Garden Flag (iris) ii,572 ii>572 The arrangement of stomates on the leaf differs with each kind of plant. Fig. 116 shows stomates and also the outlines of contiguous epidermal cells. The function or work of the stomates is to regulate the passage of zases Jnto and out of the plant. The directly active organs or parts are guard-cells, on either side the opening. One Fig. 116. — Stomates OF Geranium Leaf. method of opening is as follows : The LEAVES— STRUCTURE OR ANATOMY 89 thicker walls of the guard-cells (Fig. 114) absorb water from adjacent cells, these thick walls buckle or bend and part from each other at their middles on either side the opening, causing the stomate to open, when the air gases may be taken in and the leaf gases may pass out. When moisture is reduced in the leaf tissue, the guard cells part with some of their contents, the thick walls ^ straighten, and the faces of the two opposite | % ones come together, thus closing the stomate and preventing any water vapor from pass- ing out. WJien a leaf is actively at work making new organic compounds, the stomates are usually open; zvhen unfavorable condi- tions arise, they are usually closed. They also commonly close at night, when growth (or the utilizing of the new materials) is most likely to be active. It is sometimes safer to fumigate greenhouses and window gardens at night, for the noxious vapors are less likely to enter the leaf. Dust may clog or cover the stomates. Rains benefit plants by washing the leaves as well as by provid- ing moisture to the roots. Lenticels. — On the young woody twigs of many plants (marked in osiers, cherry, birch) there are small corky spots or eleva- tions known as lenticels (Fig. 117). They mark the loca- tion of some loose cork cells that function as stomates, for green shoots, as well as leaves, take in and discharge gases ; that is, soft green twigs function as leaves. Under some of these twig stomates, corky material may form and the opening is torn and enlarged: the lenticels are successors to the stomates. The stomates lie in the epi- FiG. 117. — Len- t i c e l s on Young Shoot OF Red Osier (CORNUS). 90 PLANT BIOLOGY dermis, but as the twig ages the epidermis perishes and the bark becomes the external layer. Gases continue to pass in and out through the lenticels, until the branch be- comes heavily covered with thick, corky bark. With the growth of the twig, the lenticel scars enlarge lengthwise or crosswise or assume other shapes, often becoming char- acteristic markings. Fibro-vascular Bundles. — We have studied the fibro- vascular bundles of stems (Chap. X). These stem bun- dles continue into the leaves, ramifying into the veins, carrying the soil water inwards and bringing, by diffusion, the elaborated food out through the sieve-cells. Cut across a petiole and notice the hard spots or areas in it; strip these parts lengthwise of the petiole : what are they .-" Fall of the Leaf. — In most common deciduous plants, when the season's work for the leaf is ended, the nutritious matter may be withdrawn, and a layer of corky cells is com- pleted over the surface of the stem where the leaf is attached. The leaf soon falls. It often falls even before it is killed by frost. Deciduous leaves begin to show the surface line of articulation in the early growing season. This articula- tion may be observed at any time during the summer. The area of the twig once covered by the petioles is called the leaf-scar after the leaf has fallen. In Chap. XV are shown a number of leaf-scars. In the plane tree (sycamore or buttonwood), the leaf-scar is in the form of a ring surround- ing the bud, for the bud is covered by the hollowed end of the petiole ; the leaf of sumac .is similar. Examine with a hand lens leaf-scars of several woody plants. Note the number of bundle-scars in each leaf-scar. Sections may be cut through a leaf-scar and examined with the micro- scope. Note the character of cells that cover the leaf- scar surface. LEAVES — STRUCTURE OR ANATOMY 9 I Suggestions. — To study epidermal hairs : 75. For this study, use the leaves of any hairy or woolly plant. A good hand lens will reveal the identity of many of the coarser hairs. A dissecting micro- scope will show them still better. For the study of the cell structure, a compound microscope is necessary. Cross-sections may be made so as to bring hairs on the edge of the sections ; or in some cases the hairs may be peeled or scraped from the epidermis and placed in water on a slide. Make sketches of the different kinds of hairs. 76. It is good practice for the pupil to describe leaves in respect to their covering : Are they smooth on both surfaces ? Or hairy? Woolly? Thickly or thinly hairy? Hairs long or short? Standing straight out or lying close to the surface of the leaf ? Simple or branched ? Attached to the veins or the plane surface ? Color? Most abundant on young leaves or old? 77. Place a hairy or woolly leaf under water. Does the hairy surface appear silvery? Why? Other questions : 78. Why is it good practice to wash the leaves of house plants? 79. Describe the leaf-scars on six kinds of plants : size, shape, color, position with reference to the bud, bundle-scars. 80. Do you find leaf-scars on mono- cotyledonous plants — corn, cereal grains, lilies, canna, banana, palm, bamboo, green brier? 81. Note the table on page 88. Can you suggest a reason why there are equal numbers of stomates on both surfaces of leaves of tradescantia and flag, and none on upper surface of other leaves? Suppose you pick a leaf of Hlac (or some larger leaf), seal the petiole with wax and then rub the under surface with vaseline ; on another leaf apply the vaseline to the upper surface ; which leaf withers first, and why ? Make a similar experiment with iris or blue flag. 82. Why do leaves and shoots of house plants turn towards the light? What happens when the plants are turned around ? 83. Note position of leaves of beans, clover, oxalis, alfalfa, locust, at night. CHAPTER XIII LEAVES — FUNCTION OR WORK We have discussed (in Chap. VIII) the work or function of roots and also (in Chap. X) the function of stems. We are now ready to complete the view of the main vital activities of plants by considering the function of the green parts (leaves and young shoots). Sources of Food. — The ordinary green plant has but two sources from which to secure food, — the air and the soil. When a plant is thoroughly dried in an oven, the water passes off ; this water came from the soil. The remaining part is called the dry substance or dry matter. If the dry matter is burned in an ordinary fire, only the ash remains; this ash came from the soil. The part that passed off as gas in the burning contained the elements that came from the air ; it also contained some of those that came from the soil — all those (as nitrogen, hydrogen, chlorine) that are transformed into gases by the heat of a common fire. The part that comes from the soil (the ash) is small in amount, being considerably less than lo per cent and sometimes less than i per cent. Water is the most abundant single constituent or substance of plants. In a corn plant of the roasting-ear stage, about 80 per cent of the substance is water. A fresh turnip is over 90 per cent water. Fresh wood of the apple tree contains about 45 per cent of water. Carbon. — Carbon enters abundantly into the composition of all plants. Note what happens when a plant is burned 92 LEAVES— FUNCTION OR WORK 93 without free access of air, or smothered, as in a charcoal pit. A mass of charcoal remains, almost as large as the body of the plant. Charcoal is almost pure carbon, the ash present being so small in proportion to the large amount of carbon that we look on the ash as an impurity. Nearly half of the dry substance of a tree is carbon. Carbon goes off as a gas when the plant is burned in air. It does not go off alone, but in combination with oxygen in the form of carbon dioxid gas, CO2. The green plant secures its carbon from the air. In other words, much of the solid matter of the plant comes from one of the gases of the air. By volume, carbon dioxid forms only a very small fraction of i per cent of the air. It would be very disastrous to animal life, however, if this percentage were much increased, for it excludes the life- giving oxygen. Carbon dioxid is often called "foul gas." It may accumulate in old wells, and an experienced person will not descend into such wells until they have been tested with a torch. If the air in the well will not support com- bustion, — that is, if the torch is extinguished, — it usually means that carbon dioxid has drained into the place. The air of a closed schoolroom often contains far too much of this gas, along with little solid particles of waste matters. Carbon dioxid is often known as carbonic acid gas. Appropriation of the Carbon. — The carbon dioxid of the air readily diffuses itself into the leaves and other green parts of the plant. The leaf is delicate in texture, and when very young the air can diffuse directly into the tissues. The stomates, however, are the special inlets adapted for the admission of gases into the leaves and other green parts. Through these stomates, or diffusion-pores, the out- side air enters into the air-spaces of the plant, and is finally absorbed by the little cells containing the living matter. 94 PLANT BIOLOGY Chlorophyll (" leaf green ") is the agent that secures the energy by means of which carbon dioxid is utilized. This material is contained in the leaf cells in the form of grains (p. 86) ; the grains themselves are protoplasm, only the coloring matter being chlorophyll. The chlorophyll bodies or grains are often most abundant near the upper surface of the leaf, where they can secure the greatest amount of light. Without this green coloring matter, there would be no reason for the large flat surfaces which the leaves possess, and no reason for the fact that the leaves are borne most abundantly at the ends of branches, where the light is most available. Plants with colored leaves, as coleus, have chlorophyll, but it is masked by other coloring matter. This other coloring matter is usually soluble in hot water: boil a coleus leaf and notice that it becomes green and the water becomes colored. Plants grown in darkness are yellow and slender, and do not reach maturity. Compare the potato sprouts that have grown from a tuber lying in the dark cellar with those that have grown normally in the bright light. The shoots have become slender and are devoid of chloro- phyll; and when the food that is stored in the tuber is exhausted, these shoots will have lived useless lives. A plant that has been grown in darkness from the seed will soon die, although for a time the little seedUng will grow very tall and slender: why .-' Light favors the production of chlorophyll, and the chlorophyll is the agent in the mak- ing of the organic carbon compounds. Sometimes chloro- phyll is found in buds and seeds, but in most cases these places are not perfectly dark. Notice how potato tubers de- velop chlorophyll, or become green, when exposed to light. Photosynthesis. — Carbon dioxid diffiises into the leaf ; during sunlight it is used, and oxygen is given off. How the LEAVES— FUNCTION OR WORK 95 carbon dioxid which is thus absorbed may be used in mak- ing an organic food is a complex question, and need not be studied here; but it may be stated that carbon dioxid and water are the constituents. Complex compounds are built up out of simpler ones. Chlorophyll absorbs certain light rays, and the energy thus directly or indirectly obtained is used by the living matter in uniting the carbon dioxid absorbed from the air with some of the zvater brought up from the roots. The ultimate result usually is starch. The process is obscure, but sugar is generally one step ; and our first definite knowledge of the product begins when starch is deposited in the leaves. The process of using the carbon dioxid of the air has been known as carbon assimilation, but the term now most used is photosynthesis (from two Greek words, meaning light and to put together). Starch and Sugar. — All starch is composed of carbon, hydrogen, and oxygen {C^H^qO^^. The sugars and the substance of cell walls are very similar to it in composition. All these substances are called carbohydrates. In making fruit sugar from the carbon and oxygen of carbon dioxid and from the hydrogen and oxygen of the water, there is a surplus of oxygen (6 parts CO2 + 6 parts H2O = CgH^.^Og 4- 6 O2). It is this oxygen that is given off into the air during sunlight. Digestion. — Starch is in the form of insoluble granules. When such food material is carried from one part of the plant to another for ptirposes of growth or storage, it is made soluble before it can be transported. When this starchy material is transferred from place to place, it is usually changed into sugar by the action of a diastase. This is a process (?/ digestion. It is much like the change of starchy foodstuffs to sugary foods by the saliva. 96 PLANT BIOLOGY Distribution of the Digested Food. — After being changed to the soluble form, this material is ready to be used in growth^ either in the leaf, in the stem, or in the roots. With other more complex products it is then distributed throughout all of the growing parts of the plant ; and when passing down to the root, it seems to pass more readily through the inner bark, in plants which have a defi- nite bark. This gradual down- ward diffusion through the inner bark of materials suitable for growth is the process referred to when the " descent of sap " is men- tioned. Starch and other products are often stored in one growing season to be used in the next sea- son. If a tree is constricted or strangled by a wire around its trunk (Fig. ii8), the digested food cannot readily pass down and it is stored above the girdle, causing an enlargement. Assimilation. — The food from the air and that from the soil unite in the living tissues. The "sap" that passes upwards from the roots in the growing season is made up largely of the soil water and the salts which have been absorbed in the diluted solutions (p. 6y). This upward- moving water is conducted largely through certain tubular canals of the young wood. These cells are never continu- ous tubes from root to leaf ; but the water passes readily from one cell or canal to another in its upward course. The upward-moving water gradually passes to the grow- ing parts, and everywhere in the living tissues, it is of Fig. ii8. — Trunk Girdled BY A Wire. See Fig. 85. LEAVES — FUNCTION OR WORK 97 course in the most intimate contact with the soluble carbo- hydrates and products of photosynthesis. In the build- ing up or reconstructive and other processes it is therefore available. We may properly conceive of certain of the simpler organic molecules as passing through a series of changes, gradually increasing in complexity. There will be formed substances containing nitrogen in addition to carbon, hydrogen, and oxygen. Others will contain also sulfur and phosphorus, and the various processes may be thought of as culminating in protoplasm. Protoplasm is the living matter in plants. It is in the cells, and is usually semifluid. Starch is not living matter. The complex process of building up the protoplasm is called assimilation. Respiration. — Plants need oxygen for respiration, as animals do. We have seen that plants need the carbon dioxid of the air. To most plants the nitrogen of the air is inert, and serves only to dilute the other elements ; but the oxygen is necessary for all life. We know that all animals need this oxygen in order to breathe or respire. In fact, they have become accustomed to it in just the proportions found in the air; and this is now best for them. When animals breathe the air once, they make it foul, because they use some of the oxygen and give off carbon dioxid. Likewise, all living parts of the pla7it must have a constant supply of oxygen. Roots also need it, for they respire. Air goes in and out of the soil by diffusion, and as the soil is heated and cooled, causing the air to expand and contract. The oxygen passes into the air-spaces and is absorbed by the moist cell membranes. In the living cells it makes possible the formation of simpler compounds by which energy is released. This energy enables the plant to 98 PLANT BIOLOGY work and grow, and the final products of this action are carbon dioxid and water. As a result of the use of this oxygen by night and by day, plants give off carbon dioxid. Plants respire ; but since they are stationary, and more or less inactive, they do not need as much oxygen as animals, and they do not give off so much carbon dioxid. A few plants in a sleeping room need not disturb one more than a family of mice. It should be noted, however, that germinating seeds respire vigorously, hence they consume much oxy- gen ; and opening buds and flowers are likewise active. Transpiration. — Much more water is absorbed by the roots than is used in growth, a7id this surplus water passes from the leaves into the atmosphere by an evaporation process known as transpiration. Transpiration takes place more abundantly from the under surfaces of leaves, and through the pores or stomates. A sunflower plant of the height of a man, during an active period of growth, gives off a quart of water per day. A large oak tree may transpire 1 50 gallons per day during the summer. For every ounce of dry matter produced, it is estimated that 15 to 25 pounds of water usually passes through the plant. When the roots fail to supply to the plant sufficient water to equalize that transpired by the leaves, the plant wilts. Transpiration from the leaves and delicate shoots is in- creased by all of the conditions which increase evapora- tion, such as higher temperature, dry air, or wind. The stomata open and close, tending to regulate, transpiration as the varying conditions of the atmosphere affect the moisture content of the plant. However, in periods of drought or of very hpt-^wrcather, and especially during a hot wind, the closing of these stomates cannot sufflciently prevent evaporation. The roots may be very active and yet fail to absorb sufficient moisture to equalize that given i LEAVES — FUNCTION OR WORK 99 off by the leaves. The plant shows the effect (how ?). On a hot dry day, note how the leaves of corn " roll " tow- ards afternoon. Note how fresh and vigorous the same leaves appear early the following morning. Any injury to the roots, such as a bruise, or exposure to heat, drought, or cold may cause the plant to wilt. Water is forced up by root pressure or sap pressure. (Exercise 99.) Some of the dew on the grass in the morn- ing may be the water forced up by the roots ; some of it is the condensed vapor of the air. The wilting of a plant is due to the loss of water front the cells. The cell walls are soft, and collapse. A toy balloon will not stand alone until it is inflated with air or liquid. In the woody parts of the plant the cell walls may be stiff enough to support themselves, even though the cell is empty. Measure the contraction due to wilt- ing and drying by tracing a fresh leaf on page of note- book, and then tracing the same leaf after it has been dried between papers. The softer the leaf, the greater will be the contraction. Storage. — We have said that starch may be stored in twigs to be used the following year. The very early flowers on fruit trees, especially those that come before the leaves, and those that come from bulbs, as crocuses and tulips, are supported by the starch or other food that was organ- ized the year before. Some plants have very special stor- age reservoirs, as the potato, in this case being a thickened stem although growing underground. (Why a thickened stem.-* p. 84.) It is well to make the starch test on winter twigs and on all kinds of thickened parts, as tubers and bulbs. Carnivorous Plants. — Certain plants capture insects and other very small animals and utilize them to some extent as food. Such are the sundew, that has on the leaves lOO PLANT BIOLOGY sticky hairs that close over the insect ; the Venus's flytrap of the Southern states, in which the halves of the leaves close over the prey like the jaws of a steel trap ; and the various kinds of pitcher plants that col- lect insects and other organic matter in deep, water-filled, flask- like leaf pouches (Fig. 119). The sundew and Venus's fly- trap are sensitive to contact. Other plants are sensitive to the touch without being insectivo- rous. The common cultivated sensitive plant is an example. This is readily grown from seeds (sold by seedsmen) in a warm place. Related wild plants in the south are sensitive. The utility of this sensitiveness is not understood. Parts that Simulate Leaves. — We have learned that leaves are endlessly modified to suit the conditions in which the plant is placed. The most marked modifications are in adaptation to light. On the other hand, other organs often perform the functions of leaves. Green shoots function as leaves. These shoots may look like leaves, in which case they are called cladophylla. The foliage of common asparagus is made up of fine branches : the real morpho- logical leaves are the minute dry functionless scales at the bases of these branchlets. (What reason is there for calling them leaves .-') The broad " leaves " of the florist's smilax are cladophylla : where are the leaves on this plant .-" In most of the cacti, the entire plant body performs the func- tions of leaves until the parts become cork-bound. Fig. 119. — The Common Pitcher Plant {Sarracenia purpurea) of the North, show- ing the tubular leaves and the odd, long-stalked flowers. LEAVES— FUNCTION OR WORK lOI Leaves are sometimes modified to perform other functions than the vital processes : they may be tendrils, as the terminal leaflets of pea and sweet pea; or spines, as in barberry. Not all spines and thorns, however, represent modified leaves: some of them (as of hawthorns, osage orange, honey locust) are branches. Suggestions. — To test for chlorophyll. 84. Purchase about a gill of wood alcohol. Secure a leaf of geranium, clover, or other plant that has been exposed to sunlight for a few hours, and, after dipping it for a minute in boiling water, put it in a white cup with sufficient alcohol to cover. Place the cup in a shallow pan of hot water on the stove where it is not hot enough for the alcohol to take fire. After a time the chlorophyll is dissolved by the alcohol, which has become an intense green. Save this leaf for the starch experiment (Exercise 85). Without chlorophyll, the plant cannot appropriate the carbon dioxid of the air. Starch and photosynthesis. 85. Starch is present in the green leaves which have been exposed to sunlight ; but in the dark no starch can be formed from carbon dioxid. Apply iodine to the leaf from which the chlorophyll was dissolved in the previous experiment. Note that the leaf is colored purplish brown throughout. The leaf contains starch. 86. Se- cure a leaf from a plant which has been in the dark- ness for about two days. Dissolve the chlorophyll as before, and attempt to stain this leaf with iodine. No purplish brown color is pro- duced. This shows that the starch manufactured in the leaf may be entirely removed during darkness. 87. Secure a plant which has been kept in darkness for twenty- four hours or more. Split a small cork and pin the two halves on opposite sides of one of the leaves, as shown in Fig. 120. Place the plant in the sunlight again. After a morning of bright sunshine dissolve the chlorophyll in this leaf with alcohol ; then stain the leaf with the iodine. Notice that the leaf is stained deeply except where the cork was ; there sunlight and carbon dioxid were excluded, Fig. 121. There is no starch in the Fig. 120. — Exclud- ing Light and CO2 FROM Part OF A Leaf. Fig. 121. — The Result. I02 PLANT BIOLOGY covered area. 88. Plants or parts of plants that have developed no chlorophyll can form no starch. Secure a variegated leaf of coleus, ribbon grass, geranium, or of any plant showing both white and green areas. On a day of bright sunshine, test one of these leaves by the alcohol and iodine method for the presence of starch. Observe that the parts devoid of green color have formed no starch. However, after starch has once been formed in the leaves, it may be to be again the living changed into soluble substances and removed, converted into starch in certain other parts of tissues. To test the giving off of oxygen by day. 89. Make the experiment illus- trated in Fig. 122. Under a fun- nel in a deep glass jar containing fresh spring or stream water place fresh pieces of the common waterweed elodea (or anacharis). Have the funnel considerably smaller than the vessel, and sup- port the funnel well up from the bottom so that the plant can more readily get all of the carbon dioxid available in the water. Why would boiled water be undesirable in this experiment? For a home-made glass funnel, crack the bottom off a narrow-necked bottle by press- ing a red-hot poker or iron rod against it and leading the crack around the bottle. Invert a test- tube over the stem of the fun- nel. In sunlight bubbles of oxygen will arise and collect in the test-tube. If a sufficient quantity of oxygen has collected, a lighted taper inserted in the tube will glow with a brighter flame, showing the presence of oxygen in greater quantity than in the air. Shade the vessel. Are bubbles given off"? For many reasons it is impracticable to continue this experiment longer than a few hours. 90. A simpler experiment may be made if one of the waterweeds Cabomba (water-lily family) is available. Tie a lot of branches together so that the basal ends shall make a small bundle. Place these in a large vessel of spring water, and insert a test-tube of water as before over the bundle. The bubbles will arise from the cut surfaces. Obsen^e the bubbles on pond scum and water- weeds on a bright day. To illustrate the results of respiration Fig. 122. -To SHOW THE ElSCAPE OF Oxygen. LEAVES— FUNCTION OR WORK 103 Fig. 123. — To illus- TRAiE A Product OF Respiration. Fig. 124. — Rh:spi ra- tion OF Thick Roots. (CO2). 91. In a jar of germinating seeds (Fig. 1 23) place carefully a small dish of limewater and cover tightly. Put a similar dish in another jar of about the same air space. After a few hours compare the cloudi- ness or precipitate in the two vessels of limewater. 92. Or, place a growing plant in a deep covered jar away from the light, and after a it'N hours in- sert a lighted candle or splinter. 93. Or, perform a similar experiment with fresh roots of beets or turnips (Fig. 124) from which the leaves are mostly removed. In this case, the jar need not be kept dark ; why ? To test transpiratioti. 94. Cut a succulent shoot of any plant, thrust the end of it through a hole in a cork, and stand it in a small bottle of water. Invert over this a fruit jar, and observe that a mist soon accumulates on the inside of the glass. In time drops of water form. 95. The ex- periment may be varied as shown in Fig. 125. 96. Or, invert the fruit jar over an entire plant, as shown in Fig. 126, taking care to cover the soil with oiled paper or rubber cloth to prevent evaporation from the soil. 97. The test may also be made by placing the pot, properly protected, on bal- fig. 125. -To illustrate Transpiration. I04 PLANT BIOLOGY Fig 126. — Tt) ILI.USTRAIE Transpiration. ances, and the loss of weight will be noticed (Fig. 1 2 7). 98. Cut a winter twig, seal the severed end with wax, and allow the twig to lie several days ; it shrivels. There must be some upward movement of water even in winter, else plants would shrivel and die. 99. To illustrate sap pressure. The upward movement of sap water often .takes place under considerable force. The cause of this force, known as root pressure, is not well understood. The pressure varies with different plants and under, different conditions. To illustrate : cut off a strong-growing small plant near 3^ the ground. By ^ means of a bit of rubber tube attach a glass tube with a bore of approxi- mately the diame- ter of the stem. Pour in a Uttle water. Observe the rise of the water due to the pressure from be- low (Fig. 128). Some plants yield a large amount of water under a pressure sufficient to raise a column several feet ; others force out little, but under consider- able pressure (less easily de- monstrated). The vital pro- cesses (/. . Pear-bud. 142. In Fig. 143 it is opening. In Fig. 145 Fig. 142. — Fruit-bud OF Pear. Fig. 143. — The opening of THE Pear Fruit-bud. Fig. 144. — Open- ing Pear Leaf-bud. WINTER AND DORMANT BUDS 115 it is more advanced, and the woolly unformed flowers are appearing. In Fig. 146 the growth is more advanced. Fig. 146. — a sin- gle Flower IN THE Pear CLUSTER, as seen at 7 A.M. on the day of its opening. At 10 o'clock it will be fully ex- panded. Fig. 147. — The opening of THE Flower- bud OF Apricot. Fig. 148. — Apricot Flower-bud, enlarged. Buds that contain or produce only leaves are leaf-buds. Those which contain only flowers are flower buds or fruit-buds. The latter occur on peach, almond, apricot, and many very early spring-flowering plants. The single flower is emerging from the apricot bud in Fig. 147. A longi- tudinal section of this bud, enlarged, is shown in Fig. 148. Those that contain both leaves and flowers are mixed buds, as in pear, apple, and most late spring- flowering plants. Fruit buds are usually thicker or stouter than leaf-bicds. They are borne in different positions on different plants. In some plants (apple, pear) they are on the ends of short branches or spurs ; in others (peach, red maple) they are along the sides of the last year's ,, T X-- , F'<^- 149- — Fruit-buds growths. In Fig. 149 are shown and leaf-buds of pear. ii6 PLANT BIOLOGY three fruit-buds and one leaf-bud on E, and leaf-buds on A. See also Figs. 150, 151, 152, 153, and explain. Fig. 150. — Fruit-buds of Apple ON Spurs : a dormant bud at the top. Fig. 151. — Clus- ter OF Fruit- buds OF SWEET Cherry, with one pointed leaf-bud in cen- ter. Fig. 152. — Two Fruit-buds OF Peach with a leaf- bud between. . Fig. 153. — Opening of Leaf-buds and Flower-buds of Apple. "77/^ burst of spring'' means in large part the opening of the buds. Everything was made ready the fall before. The embryo shoots and flowers were tucked azvay, and the food was stored. The warm rain falls, and the shutters open and the sleepers wake : the frogs peep and the birds come. Arrangement of Buds. — We have found that leaves are usually arranged in a definite order ; buds are borne in the axils of leaves : therefore buds must exhibit phyllotaxy. J WINTER AND DORMANT BUDS 117 Moreover, branches grow from buds: branches, therefore, should show a definite arrangement; usually, however, they do not show this arrangement because not all the buds grow and not all the branches live. (See Chaps. II and III.) It is apparent, however, that the mode of arrangement of buds determines to some extent the form of the tree: com- pare bud arrangement in pine or fir with that in maple or apple. Fig. 154. •Oak Spray. How are the leaves borne with reference to the annual growths ? The uppermost buds on any twig, if they are well matured, are usually the larger and stronger and they are the most likely to grow the next spring; therefore, branches tend to be arranged in tiers (particularly well marked in spruces and firs). See Fig. 1 54 and explain it. Winter Buds show what has been the Effect of Sunlight. — Buds are borne in the axils of the leaves, and the size or vigor of the leaf determines to a large extent the size of the bud. Notice that, in most instances, the largest buds are nearest the tip (Fig. 157). If the largest ones are not near the tip, there is some special reason for it. Can you state it .-* Examine the shoots on trees and bushes. Il8 PLANT BIOLOGY Suggestions. — Some of the best of all observation lessons are those made on dormant twigs. There are many things to be learned, the eyes are trained, and the specimens are everywhere accessible. 123. At whatever time of year the pupil takes up the study of branches, he should look for three things : the ages of the various parts, the relative positions of the buds and leaves, the different sizes of similar or comparable buds. If it is late in spring or early- in summer, he should watch the development of the buds in the axils, and he should determine whether the strength or size of the bud is in any way related to the size and vigor of the subtending (or supporting) leaf. The sizes of buds should also be noted on leafless twigs, and the sizes of the former leaves may be inferred from the size of the leaf-scar below the bud. The pupil should keep in mind the fact of the struggle for food and hght, and its effects on the developing buds. 124. The bud and the branch. A twig cut from an apple tree in early spring is shown in Fig. 155. The most hasty obser- vation shows that it has various parts, or members. It seems to be divided at the point / into two parts. It is evident that the part from/ to h grew last year, and that the part below/ grew two years ago. The buds on the two parts are very unlike, and these differences challenge investigation. — In order to under- stand this seemingly lifeless twig, it will be necessary to see it as it looked late last summer (and this condition is shown in Fig. 156). The part from / \.o h, — which has just completed its growth, — is seen to have its leaves growing singly. In every axil (or angle which the leaf makes when it joins the shoot) is a bud. The leaf starts first, and as the season advances the bud forms in its axil. When the leaves have fallen, at the approach of winter, the buds remain, as seen in Fig. 155. Every bud on the last year's growth of a winter twig, therefore, marks the position occupied by a leaf when the shoot was growing. — The part below /, in Fig. 156, shows a wholly different arrangement. The leaves are two or more together {aaaa), and there are buds without leaves {bbbb). A year ago this part looked like the present shoot from / to h, — that is, the leaves were single, with a bud in the axil of each. It is now seen that some of these bud-hke parts are longer than others, and that the longest ones are those which have leaves. It must be because of the leaves that they have increased in length. The body e has lost its leaves through some accident, and its growth has ceased. In other words, the parts at aaaa are hke the shoot /h, except that they are shorter, and they are of the same age. One grew from the end or terminal bud of the main branch, and the others from the side or lateral buds. Parts or bodies that bear leaves are, therefore, branches. — The buds at bbbb have no leaves, and they remain the same WINTER AND DORMANT BUDS 119 size that they were a year ago. They are dormant. The only way for a mature bud to grow is by making leaves for itself, for a leaf D/ '^i Fig. 155. — An Apple Twig. Fig. 156. — Same twig before leaves fell. will never stand below it again. The twig, therefore, has buds of two ages, — those at bbbb are two seasons old, and those on the 120 PLANT BIOLOGY tips, of all the branches (aaaa, h), and in the axil of every leaf, are one season old. It is only the terminal buds that are not axillary. When the bud begins to grow and to put forth leaves, it gives rise to a branch, which, in its turn, bears buds. — It will now be interesting to determine why certain buds gave rise to branches and why others remained dormant. The strongest shoot or branch of the year is the terminal one {fh). The next in strength is the uppermost lateral one, and the weakest shoot is at the base of the twig. The dormant buds are on the under side (for the twig grew in a horizontal position). All this suggests that those buds grew which had the best chance, — the most sunlight and room. There were too many buds for the space, and in the struggle for existence those that had the best oppor- tunities made the largest growths. This struggle for existence began a year ago, however, when the buds on the shoot below/" were forming in the axils of the leaves, for the buds near the tip of the shoot grew larger and stronger than those near its base. The growth of one year, therefore, is very largely determined by the conditions under which the buds were formed the previous year. Other bud characters. 125. It is easy to see the swelling of the buds in a room in winter. Secure branches of trees and shrubs, two to three feet long, and stand them in vases or jars, as you would flowers. Renew the water frequently and cut off the lower ends of the shoots occasionally. In a week or two the buds will begin to swell. Of red maple, peach, apricot, and other very early-flowering things, flowers may be obtained in ten to twenty days. 126. The shape, size, and color of the winter buds are different in every kind of plant. By the buds alone botanists are often able to distinguish the kinds of plants. Even such similar plants as the different kinds of willows have good bud characters. 127. Distinguish and draw fruit-buds of apple, pear, peach, plum, and other trees. If different kinds of maples grow in the vicinity, secure twigs of the red or swamp maple, and the soft or silver rnaple, and compare the buds with those of the sugar maple and Norway maple : What do you learn ? FiG. 157. — Buds of the Hickory. CHAPTER XVI BUD PROPAGATION We have learned (in Chap. VI) that plants propagate by means of seeds. They also propagate by means of bud parts, — as roots tocks {rhizomes), roots, runners, layers, bulbs. The pupil should determine how any plant in which he is interested naturally propagates itself (or spreads its kind). Determine this for raspberry, blackberry, strawberry, June- grass or other grass, nut-grass, water lily, May apple or mandrake, burdock, Irish potato, sweet potato, buckwheat, cotton, pea, corn, sugar-cane, wheat, rice. Plants may, be artificially propagated by similar means, as by layers, cuttings, and grafts. The last two we may discuss here. Cuttings in General. — A bit of a plant stuck into the ground stands a chance of growing ; and this bit is a cutting. Plants have preferences, however, as to the kind of a bit which shall be used, but there is no ivay of telling what this preference is except by trying. I n some instances this prefer- ence has not been discovered, and we say that the plant cannot be propagated by cuttings. Most plants prefer that the cutting be made of the soft or growing parts (called "wood" by gardeners), of which the "slips" of geranium and coleus are examples. Others grow equally well from cuttings of the hard or mature parts or wood, as currant and grape; and in some instances this mature wood may be of roots, as in the blackberry. In some cases cuttings are made of tubers, as in the Irish 122 PLANT BIOLOGY potato (Fig, 60), Pupils should make cuttings now and then. If they can do nothing more, they can make cut- tings of potato, as the farmer does; and they can plant them in a box in the window. The Softwood Cutting. — The softwood cutting is made from tissue that is still growing, or at least from that which is not dormant. // comprises one or two joints, with Fig. 158. — Geranium Cutting. Fig. 159. — Rose Cittting. a leaf attached (Figs. 158, 159). It must not be allowed to wilt. Therefore, it must be protected from direct sun- light and dry air until it is well established ; and if it has many leaves, some of them should be removed, or at least cut in two, in order to reduce the evaporating surface. The soil should be uniformly moist. The pictures show the depth to which the cuttings are planted. For most plants, the proper age or maturity of wood for the making of cuttings may be determined by giving the twig a quick bend: if it snaps and hangs by the bark, it is in proper condition; if it bends without breaking, it is too young and soft or too old ; if it splinters, it is too old and woody. The tips of strong upright shoots usually make the best cuttings. Preferably, each cutting should have a joint or node near its base; and if the internodes are very short it may comprise two or three joints. BUD PROPAGATION 123 Fig. 160. — CuttinG-box. The stem of the cutting is inserted one third or more its length in clean sand or gravel , and the earth is pressed firmly about it. A newspaper may be laid over the bed to ex- clude the light — if the sun strikes it — and to prevent too rapid evaporation. The soil should be moist clear through, not on top only. Loose sandy or gravelly soil is used. Sand used by masons is good material in which to start most cuttings; or fine gravel — sifted of most of its earthy matter — may be used. Soils are avoided which contain much decay- ing organic matter, for these soils are breeding places of fungi, which attack the soft cutting and cause it to " damp off," or to die at or near the surface of the ground. If the cuttings are to be grown in a window, put three or four inches of the earth in a shallow^ box or a pan. A soap box cut in two lengthwise, so that it makes a box four or five inches deep — as a gardener's flat — is excellent (Fig. 160). Cuttings of common plants, as geranium, coleus, fuchsia, carnation, are kept at a living-room temperature. As long as the cuttings look bright and green, they are in good condition. It may be a month before roots form. When roots have formed, the plants begin to make new leaves at the tip. Then they may be transplanted into other boxes or into pots. The verbena in Fig. 161 is just ready for transplanting. Fig. i6i.— Verbena Cutting ready for transplanting. 124 I PLANT BIOLOGY Fig. 162. — Old Geranium Plant cut back to make it throw out Shoots from which Cuttings can be made. dow plants are those which old. The geranium and fuchsia cut- tings which are made in January, February, or March will give compact blooming plants for the next winter ; and thereafter new ones should take their places (Fig. 163). The Hardwood Cutting. — Best re- sults with cuttings of mature wood are It is not always easy to find growing shoots from which to make the cut- tings. The best practice, in that case, is to cut back an old plant, then keep it warm, and well watered, and thereby force it to throw out new shoots. The old geranium plant from the window garden, or the one taken up from the lawn bed, may be treated this way (see Fig. 162). The best plants of geranium and coleus and most win- are not more than one year Fig. 163. — Early Winter Geranium, from a spring cutting. B UD PR OP A GA TION 125 secured when the cuttings are made in the fall and then buried until spring in sand in the cellar. These cuttings are usually six to ten inches long. They are not idle while they rest. The lower end calluses or heals, and the roots form more readily when the cutting is planted in the spring. But if the proper season has passed, take cuttings at any time in winter, plant them in a deep box in the window, and watch. They will need no shading or special care. Grape, currant, gooseberry, willow, and poplar readily take root from the hardwood. Fig. 164 shows a currant cutting. It has only one bud above the ground. The Graft. — When the cutting is inserted in a plant rather than- in the soil, it is a graft ; and the graft may grow. In this case the cutting grows fast to the other plant, and the two become one. When the cutting is inserted in a plant, it is no longer called a cutting, but a cion; and the plant in which it is inserted is called the stock. Fruit trees are grafted /;/ order that a ce7'tain variety or kind may be per- petuated, as a Baldwin or Ben Davis vari- ety of apple, Seckel or Bartlett pear, Navel or St. Michael orange. Plants have preferences as to the stocks on which they tvill grow ; but zve can find out what their choice is only by making the experiment. The pear grows well on the quince, but the quince does not thrive on the pear. The pear grows on some of the hawthorns, but it is an unwilling subject on the apple. Tomato plants will grow on potato plants and potato plants on tomato plants. Fig. 164. — Cur- rant Cutting. 126 PLANT BIOLOGY « When the potato is the root, both tomatoes and potatoes may be produced, although the crop will be very small; when the tomato is the root, neither potatoes nor tomatoes will be produced. Chestnut will grow on some kinds of oak. In general, one species or kind is grafted on the same species, as apple on apple, pear on pear, orange on orange. The forming, growing tissue of the stem (on the plants we have been discussing) is the cambium (Chap. X), lying on the outside of the woody cylinder beneath the bark. In order that union may take place, the cambium of the cion and of the stock must come together. Therefore the cion is set in the side of the stock. There are many ways of shaping the cion and of preparing the stock to receive it. These ways are dictated largely by the relative sizes of cion and stock, although many of them are matters of personal preference. The underlying principles are two : securing close contact between the cambiums of cion and stock ; covering the wounded surfaces to prevent evapora- tion and to protect the parts from disease. On large stocks the commonest form of grafting i4 the cleft-graft. The stock is cut off and split ; and in one or both sides a wedge-shaped cion is firmly inserted. Fig. 165 shows the cion ; Fig. 166, the cions set in the stock; Fig. 167, the stock waxed. It will be seen that the lower bud — that lying in the wedge — is covered by the wax; but being nearest the food supply and least exposed to weather, it is the most likely to grow : it will push through the wax. Cleft-grafting is practiced in spring, as growth begins. The cions at^e cut previously, when perfectly dormant, and from the tree which it is desired to propagate. The cions are kept in sand or moss in the cellar. Limbs of various BUD PROPAGATION 127 sizes may be cleft-grafted, — from one half inch up to four inches in diameter ; but a diameter of one to one and one half inches is the most convenient size. All the leading or main branches of a tree top may be grafted. If the remaining parts of the top are gradually cut away and the cions grow well, the entire top will be changed over to the new variety. Fig. 165.— ClON OF Apple. Fig. 166.— The CiON Inserted. Fig. 167. — The Par IS Waxed. Another form of grafting is known as budding. In this case a single bud is used, and it is slipped underneath the bark of the stock and securely tied (not waxed) with soft material, as bass bark, corn shuck, yarn, or raffia (the last a commercial palm fiber). Budding is performed when the bark of the stock will slip or peel (so that the bud can be inserted), and when the bud is mature enough to grow. Usually budding is performed in late summer or early fall, when the winter buds are well formed ; or it may be practiced in spring with buds cut in winter. In ordinary summer budding (which is the usual mode) the "bud" or cion forms a union with the stock, and then lies dormant till the following spring, as if it were still on its own twig. 128 PLANT BIOLOGY Budding is mostly restricted to young trees in the nursery. In the spring following the budding, the stock is cut off just above the bud, so that only the shoot from the bud grows to make the future tree. This prevailing form of budding (shield-budding) is shown in Fig. i68. Suggestions. — 128. Name the plants that the gardener propagates by means of cuttings. 129. By means of grafts. 130. The cutting-box may be set in the window. If the box does not receive direct sunlight, it may be covered with a pane of glass to prevent evaporation. Take care that the air is not kept too close, else the damping- off fungi may attack the cuttings, and they will rot at the surface of the ground. See that the pane is raised a little at one end to afford ventila- tion ; and if the water collects in drops on the under side of the glass, remove the pane for a time. 131. Grafting wax is made of beeswax, resin, and tallow. A good recipe is one part (as one pound) of rendered tallow, two parts of bees- wax, four parts of rosin ; melt together in a kettle ; pour the liquid into a pail or tub of water to so- lidify it ; work with the hands until it has the color and "grain" of taffy candy, the hands being greased when necessary. The wax will keep any length of time. For the Httle grafting that any pupil would do, it is better to buy the wax of a seedsman. 132. Grafting is hardly to be recom- mended as a general school diversion, as the mak- ing of cuttings is ; and the account of it in this chapter is inserted chiefly to satisfy the general curiosity on the subject. 133. In Chap. V we had a definition of a plant generation : what is " one generation " of a grafted fruit tree, as Le Conte pear, Baldwin, or Ben Davis apple? 134. The Elberta peach originated about i88o : what is meant by " originated " ? 135. How is the grape, propagated so as to come true to name (explain what is meant by "coming true")? currant? strawberry? raspberry? blackberry? peach? pear? orange? fig? plum? cherry? apple? chest- nut? pecan? Fig. i68. — Bud- ding. The " bud " ; the opening to re- ceive it ; the bud tied. CHAPTER XVII HOW PLANTS CLIMB We have found that plants struggle or contend for a place in which to Hve. Some of them become adapted to grow in the forest shade, others to grow on other plants, as epiphytes, others to climb to the light. Observe how woods grapes, and other forest climbers, spread their foli- age on the very top of the forest tree, while their long flexile trunks may be bare. There are several ways by which plants climb, but most climbers may be classified into four groups : ( i) scramblers, (2) root climbers, (3) tendril climbers, (4) twiners. Scramblers. — Some plants rise to light and air by rest- ing their long and weak stems on the tops of bushes and quick-growing herbs. Their stems may be elevated in part by the growing twigs of the plants on which they recline. Such plants are scramblers. Usually they are provided with prickles or bristles. In most weedy swamp thickets, scrambling plants may be found. Briers, some roses, bed- straw or galium, bittersweet {Solajtum Dulcamara, not the Celastrus), the tear-thumb polygonums, and other plants are familiar examples of scramblers. Root Climbers. — Some plants climb by means of true roots. These roots seek the dark places and therefore enter the chinks in walls and bark. The trumpet creeper is a famiHar example (Fig. 36). The true or English ivy, which is often grown to cover buildings, is another instance. Still another is the poison ivy. Roots are K 129 I30 PLANT BIOLOGY "^ Fig. 169. — Tendril, to show where the coil is changed. distinguished from stem tendrils by their irregular or indefinite positioti as well as by their mode of growth. Tendril climbers. — A slender coiling part that serves to hold a climbing plant to a support^is known as a tendril. The free end swings or curves until it strikes some object, when it attaches itself and then coils and draws the plant close to the support. The spring of the coil also allows the plant to move in the wind, thereby enabhng the plant to maintain its hold. Slowly pull a well-matured tendril from its support, and note how strongly it holds on. Watch the tendrils in a wind-storm. Usually the tendril attaches to the support by coiling about it, but the Virginia creeper and Boston ivy (Fig. 170) attach to walls by means of disks ... on the ends of the tendrils. Since both ends of the tendril are fixed, when it finds a support, the coil- ing would tend to twist it in two. It will be found, how- ever, that the tendril coils in different di- rections in different parts of its length. In Fig. 169, show- ing an old and stretched-out tendril, the change of direction in the coil occurred at a. In long tendrils of cucumbers and melons there may be several changes of direction. Tendrils may represent either branches or leaves. In the Fig. 170.— Tendril OF Boston Ivy. HOW PLANTS CLIMB 131 Virginia creeper and grape they are branches ; they stand opposite the leaves in the position of fruit clusters, and sometimes one branch of a fruit cluster is a tendril. These tendrils are therefore homologous with fruit-clusters, and fruit-clusters are branches. In some plants tendrils are leaflets (Chap. XI). Ex- amples are the sweet pea and common garden pea. In Fig. 171, observe the leaf with its two great L stipules, petiole, six normal Jeaflets, and two '^^ or three pairs of leaflet tendrils and a termi- nal leaflet tendril. The cobea, a common garden climber, has a similar arrangement. In some cases tendrils are stipules, as prob- ably in the green briers (smilax). The petiole or midrib may act as a tendril, as in various kinds of clem- atis. In Fig. 172, the common wild clematis or " old man vine," this mode is seen. Twiners. — The entire plant or shoot may wind about a support. Such a plant is a twiner. Examples are bean, hop, morning-glory, moon- flower, false bittersweet or waxwork {Celastrm), some honeysuckles, wistaria, Dutchman's pipe, dodder. The free" tip of the twining branch sweeps about in curves, much as the tendril does, until it finds support or becomes old and rigid. Each kind of plant usually coils in only one direction. Most plants coil against the sun, or from the observer's left across his front to his right as he faces the plant. Fig. 171. — Leaves of Pea, — very large stipules, op- posite leaflets, and leaflets represented by tendrils. 132 PLANT BIOLOGY Examples are bean, morning-glory. The hop twines from the observer's right to his A left, or with the sun. Fig. 172. — Clematis climbing by Leaf-tendril. Suggestions. — 136. Set the pupil to watch the behavior of any plant that has tendrils at different stages of maturity. A vigorous cucumber plant is one of the best. Just beyond the point of a young straight tendril set a stake to compare the position of it. Note whether the tendril changes position from hour to hour or day to day. 137. Is the tip of the tendril perfectly straight? Why? Set a small stake at the end of a strong straight tendril, so the tendril will just reach it. Watch, and make drawing. 138. If a tendril does not find a support, what does it do ? 139. To test the movement of a free tendril, draw an ink line lengthwise of it, and note whether the line remains always on the concave side or the convex side. 140. Name the tendril-bearing plants that you know. 141. Make similar observations and experiments on the tips of twining stems. 142. W^hat twining plants do you know, and which way do they twine ? 143. How does any plant that you know get up in the world? 144. Does the stem of a climbing plant con- tain more or less substance (weight) than an erect self-supporting stem of the same height ? Explain. CHAPTER XVIII THE FLOWER — ITS PARTS AND FORMS The function of the flower is to produce seed. It is probable that all its varied forms and colors contribute to this supreme end. These forms and colors please the human fancy and add to the joy of living, but the flower exists for the good of the plant, not for the good of man. The parts of the flower are of two general kinds — those that are directly concerned in the production of seeds, and those that act as covering and protecting organs. The former parts are known as the essential organs ; the latter as the floral envelopes. Envelopes. — The floral envelopes usually bear a close resemblance to leaves. These envelopes are very com- monly of two series or kinds — the Older and the inner. The outer series, known as the calyx, is usually smaller and green. It usually comprises the outer cover of the flower bud. The calyx is the lowest whorl in Fig. 173. p^^ 173. -flower of The inner series, known as the a buitercup in Sec- corolla, is usually colored and more special or irregular in shape than the calyx. It is the showy part of the flower, as a rule. The corolla is the second or large whorl in Fig. 173. The calyx may be composed of several leaves. Each leaf is a sepal. If it is of one piece, it may be lobed or divided, in which case the divisions are called calyx -lobes. 133 134 PLANT BIOLOGY In like manner, the corolla may be composed of petals, or it may be of one piece and variously lobed. A calyx of one piece, no matter how deeply lobed, is gamosepalous. A corolla of one piece is gamopetalous. When these series are of separate pieces, as in Fig. 173, the flower is said to be polysepalous and polypetalous. Sometimes both series are of separate parts, and sometimes only one of them is so formed. The floral envelopes are ho- viologoiis with leaves. Sepals and petals, at least when more than three or five, are in more than one whorl, and one whorl stands below another so that the parts overlap. They are borne on the expanded or thickened end of the flower stalk ; this end is the torus. In Fig. 1 73 all the parts are seen as attached to the torus. This part is sometimes called the re- ceptacle, but this word is a common-language term of several meanings, whereas torus has no other meaning. Sometimes one part is attached to another part, as in the fuchsia (Fig. 174), in which the petals are borne on the calyx-tube. Subtending Parts. — Sometimes there are leaf-like parts just below the calyx, looking like a second calyx. Such parts accompany the carnation flower. These parts are bracts (bracts are small specialized leaves); and they form an involucre. We must be careful that we do not mistake them for true flower parts. Sometimes the bracts are large and petal-like, as in the great white blooms of the Fig. 174. — Flower of Fuchsia in Section. THE FLOWER — ITS PARTS AND FORMS 135 flowering dogwood : here the real flowers are several, small and greenish, forming a small cluster in the center. Essential Organs. — The essential organs are of two series. The outer series is composed of the stamens. The inner series is composed of the pistils. Stamens bear the pollen, which is made up of grains or spores, each spore usually being a single plant cell. The stamen is of two parts, as is readily seen in Figs. 173, 174, — the enlarged terminal part or anther, and the stalk or filament. The filament is often so short as to seem to be absent, and the anther is then said to be sessile. The anther bears the pollen spores. It is made up of two or four parts (known as sporangia or spore-cases), which burst and discharge the pollen. When the pollen is shed, the stamen dies. The pistil has three parts : the lowest, or seed- bearing part, which is the ovary; the stigma at the upper extremity, which is a flattened or expanded surface, and usually rough- ened or sticky ; the stalk- like part or style, connect- ing the ovary and stigma. Sometimes the style is apparently wanting, and the stigma is said to be sessile on the ovary. These parts are shown in the fuchsia (Fig. 1 74). The ovary or seed vessel is at a. A long style, bearing a large stigma, projects from the flower. See also Figs. 175 and 176. Stamens and pistils probably are homologous with leaves. A pistil is sometimes conceived to represent anciently a Fig. 175. — The Structure of a Plum Blossom. se, sepals; p, petals; sta, stamens; o, ovary; J, style; st, stigma. The pistil consists of the ovary, style, and stigma. It contains the seed part. The stamens are tipped with anthers, in which the pollen is borne. The ovary, o, ripens into the fruit. 136 PLANT BIOLOGY Fig. 176. — Simple Pistils of But- tercup, one in longitudinal sec- tion. leaf as if rolled into a tube ; and an anther, a leaf of which the edges may have been turned in on the midrib. The pistil may be of one part or com- partment, or of many parts. The different units or parts of which it is composed are carpels. Each carpel is homologous with a leaf. Each carpel bears one or more seeds. A pistil of one carpel is simple ; of two or more carpels, compound. Usu- ally the structure of the pistil may be de- termined by cutting horizontally across the lower or seed- bearing part, as Figs. 177, 178 explain. A flower may contain a simple pistil (one carpel), as the pea (Fig. 177); several simple pis- tils (several separate carpels), as the buttercup (Fig. 176); or a compound pistil with carpels united, as the Saint John's wort (Fig. 1 78) and apple. How many carpels in an apple } A peach .? An okra pod } A bean pod } The seed cavity in each carpel is called a locule (Latin locus, a place). In these locules the seeds are borne. Conformation of the Flower. — A flower that has calyx, corolla, stamens, and pistils is said to be complete (Fig. 173); all others are incomplete. In some flowers both the floral envelopes are wanting : such are naked. When one of the floral envelope series is wanting, the remaining series is said to be calyx, and the flower is therefore apetalous (without petals). The knot- FiG. 177. — Pistil of Garden Pea, the stamens being pulled down in order to dis- close it ; also a section showing the single compartment (com- pare Fig. 188). Fig. 178. — Compound Pistil of a St. John's Wort. It has 5 carpels. THE FLOWER — ITS PARTS AND FORMS 137 weed (Fig. 179), smartweed, buckwheat, elm are examples. Some flowers lack the pistils : these are stami- nate, whether the envelopes are missing or not. Others lack the stamens : these are pistillate. Others have neither stamens nor pistils: these are sterile (snowball and hydrangea). Those that have both stamens and pistils are per- fect, whether or not the envelopes are missing. Those that lack eitherstamensor pistils are imper- fect or diclinous. Staminate and pistillate flowers Fig. 179. — Knotweed, a very eommon but inconspicu- ous plant along hard walks and roads. Two flowers, enlarged, are shown at the right. These flowers are are imperfect or very small and borne in the axils of the leaves. diclinous When staminate and pistillate flowers are borne on the same plant, e.g. oak (Fig. 180), corn, beech, chestnut, hazel, walnut, hickory, pine, begonia (Fig. 181), watermelon. Fig. 180. — Staminate Catkins of Oak. The pistillate flowers are in the leaf axils, and not shown in this pic- ture. Fig. 181. — Begonia Flowers., Staminate at A ; pistil- late below, with the winged ovary at B. 138 PLANT BIOLOGY ,[;;>l»''i"J>t: gourd, pumpkin, the plant is monoecious ("in one house "). When they are on different plants, e.g. poplar, cottonwood, bois d'arc, willow (Fig. 182), the plant is dioecious ("in two houses "). Some varieties of strawberry, grape, and mul- berry are partly dioecious. Is the rose either monoecious or dioecious } Flowers in which the parts of each series are alike are said to be regular (as in Figs. 173, 174, 175). Those in which some parts are unlike other parts of the same series are irregular. Their regularity may be in calyx, as in nasturtium (Fig. 183); in corolla (Figs. 184, 185); in the ^ II stamens (compare nasturtium, catnip, Fig. 185, sage); in the pistils. Irregu- larity is most frequent in the corolla. Fig. 182. — Catkins of a Willow. A staminate flower is shown at s, and a pistillate flower at /. The staminate and pistillate are on different plants. Fig. 183. — Flower of Garden Nasturtium. Separate petal at a. The calyx is produced into a spur. Fig. 185, — Flower of Catnip. Fig. 184. — The Five Petals OF THE Pansy, detached to show the form. THE FLOWER — ITS PARTS AND FORMS 1 39 Various Forms of Corolla. — The corolla often assumes very definite or distinct forms, especially when gamopet- alous. It may have a long tube with a wide-flaring limb, when it is said to be funnelform, as in morning-glory and pumpkin. If the tube is very narrow and the limb stands at right angles to it, the corolla is salverform, as in phlox. If the tube is very short and the limb wide- spreading and nearly circular in outline, the corolla is rotate or wheel-shaped, as in potato. A gamopetalous corolla or gamosepalous calyx is often cleft in such way as to make two prominent parts. Such parts are said to be lipped or labiate. Each of the lips or lobes may be notched or toothed. In 5-membered flowers, the lower lip is usually 3-lobed and the upper one 2-lobed. Labiate flowers are characteristic of the mint family (Fig. 185), and the family therefore is called the Labiatae. (Lit- erally, labiate means merely "lipped," without specifying the number of lips or lobes ; but it is commonly used to desig- nate 2-hpped flowers.) Strongly 2-parted polypetalous flowers may be said to be labiate ; but the term is often- est used for gamopetalous co- rollas. Labiate gamopetalous flowers that are closed in the throat (or entrance to the tube) are said to be grinning or personate (per- sonate means masked, or person- ^^°- ^86. -Personate Flower ^ OF Toadflax. like\ Snap-dragon is a typical example; also toadflax or butter-and-eggs (Fig. 186), and many related plants. Personate flowers usually have definite relations to insect pollination. Observe how an insect forces his head into the closed throat of the toad- flax. I40 PLANT BIOLOGY The peculiar flowers of the pea tribes are explained in Figs. 187, 188. Spathe Flowers. — In many plants, very simple (often naked) flowers are borne in dense, more or less fleshy spikes, and the spike is inclosed in or attended by a leaf, sometimes corolla-like, known as a spathe. The spike of flowers is technically known as a spadix. This type of flower is characteristic of the great arum family, which is Fig. 187. — Flowers of the Common Bean, with one flower opened (a) to show the structure. Diagram of Alfalfa Flower IN Section: C, calyx, D, standard; W, wing; K, keel; T, sta- men-tube; F, filament of tenth stamen; X, stigma; K, style; O, ovary; the dotted lines at E show position of stamen-tube, when pushed upward by insects. Enlarged. chiefly tropical. The commonest wild representatives in the North are Jack-in-the-pulpit, or Indian turnip, and skunk cabbage. In the former the flowers are all diclin- ous and naked. In the skunk cabbage all the flowers are perfect and have four sepals. The common calla is a good example of this type of inflorescence. Compositous Flowers. — The head (anthodium) or so- called "flower" of sunflower (Fig. 189), thistle, aster, dandelion, daisy, chrysanthemum, goldenrod, is com- posed of several or many little flowers, or florets. These THE FLOWER — ITS PARTS AND FORMS 141 Fig. 189. — Head of Sunflower. florets are inclosed in a more or less dense and usually green involucre. In the thistle (Fig. 190) this involucre is prickly. A longitudinal section discloses the flo- rets, all attached at bot- tom to a common torus, and densely packed in the involucre. The pink tips of these florets con- stitute the showy part of the head. Each floret of the this- tle (Fig. 190) is a com- plete flower. At a is the ovary. At <^ is a much-divided plumy calyx, known as the pappus. The corolla is long- tubed, rising above the pappus, and is enlarged and 5-lobed at the top, c. The style pro- jects at e. The five anthers are united about the style in a ring at d. Such anthers are said to be syngenesious. These are the various parts of the florets of the Com- positae. In some cases the pappus is in the form of barbs, bristles, or scales, and sometimes it is wanting. The pappus, as we shall see later, assists in distributing the seed. Often the florets are not all alike. The corolla of those in the outer circles may be developed into a long, straplike, or tubular part, and the head then has the ap- FiG. 190. — Longitudinal Section OF Thistle Head; also a Floret OF Thistle. 142 PLANT BIOLOGY pearance of being one flower with a border of petals. Of such is the sunflower (Fig. 189), aster, bachelor's button or cornflower, and field daisy (Fig, 211), These long corolla- limbs are called rays. In some cultivated composites, all the florets may develop rays, as in the dahlia and chrysan- themum. In some species, as dandelion, all the florets naturally have rays. Syngenesious arrangement of an- thers is the most characteristic single feature of the composites. Double Flowers. — Under the stimulus of cultivation and increased food supply, flowers tend to become double. True doubling arises in two ways, mor- phologically : ( I ^sta- mens or pistils may produce petals (Fig. 191) ; (2) adventi- tious or accessory petals may arise in the circle of petals. Both of these cate- gories may be pres- ent in the same flower. In the full double hollyhock the petals derived from the staminal col- umn are shorter and make a rosette in the center of the flower. In Fig. 192 is shown the doubling of a daffodil by the modification of stamens. Other modifications of flowers are sometimes known as doubling. For example, double dahlias, chrysanthemums, and sunflowers are forms in which the disk flowers have developed rays. The snow- ball is another case. In the wild snowball the external flowers of the cluster are large and sterile. In the culti- FiG. 191. — Petals arising from the Stami- nal Column of Hollyhock, and accessory petals in the corolla-whorl. THE FLOWER — ITS PARTS AND FORMS 1 43 vated plant all the flowers have become large and sterile. Hydrangea is a similar case. Fig. 192. — Narcissus or Daffodil. Single flower at the right. Suggestions. — 145. If the pupil has been skillfully conducted through this chapter by means of careful study of specimens rather than as a mere memorizing process, he will be in mood to chal- lenge any flower that he sees and to make an effort to understand it. Flowers are endlessly modified in form ; but they can be understood if the pupil looks first for the anthers and ovaries. How may anthers and ovaries always be distinguished? 146. It is excellent practice to find the flowers in plants that are commonly known by name, and to determine the main points in their struc- ture. What are the flowers in Indian corn? pumpkin or squash? celery ? cabbage ? potato ? pea ? tomato ? okra ? cotton ? rhubarb ? chestnut? wheat? oats? 147. Do all forest trees have flowers? Explain. 148. Name all the monoecious plants you know. Dioecious. 149. What plants do you know that bloom before the leaves appear ? Do any bloom after the leaves fall ? 150. Ex- plain the flowers of marigold, hyacinth, lettuce, clover, asparagus, garden calla, aster, locust, onion, burdock, lily-of-the-valley, crocus, Golden Glow rudbeckia, cowpea. 151. Define a flower. Note to the Teacher. — It cannot be urged too often that the specimens themselves be studied. If this chapter becomes a mere recitation on names and definitions, the exercise will be worse than useless. Properly taught by means of the flowers themselves, the names become merely incidental and a part of the pupil's language, and the subject has living interest. CHAPTER XIX THE FLOWER — FERTILIZATION AND POLLINATION Fertilization. — Seeds result from the union of two ele- ments or tarts. One of these elements is a cell-nucleus of the pollen-grain. The other ele- ment is the cell-nucleus of an egg- cell, borne in the ovary. The pollen-grain falls on the stigma (Fig, 193). It absorbs the juices exuded by the stigma, and grows by sending out a tube (Fig. 194). This tube grows downward through the style, absorbing food as it goes, and finally reaches the egg-cell in the interior of an ovule in the ovary (Fig. 195), and fertilization, or union of a nucleus of the pollen and the nucleus of the egg-cell in the ovule, takes place. The ovule and embryo within then develops into a seed. The growth of the pollen-tube is often spoken of as germination of the pollen, but it is not germination in the sense in which the word is used when speaking of seeds. Better seeds — that is, those that produce stronger and more fruitful plants — often re- sult when XhQ pollen comes from another flower. Fertilization effected between different flowers is cross -fertilization ; that resulting from the 144 Fig. 193'. — B, Pollen escap- ing from anther; A, pollen germinating on a stigma. Enlarged. Fig. 194.— A Pollen- grain AND THE Grow- iNG Tube. THE FL O WER — PER TILIZA TION AND POLLINA TION 1 45 application of pollen to pistils in the same flower is close- fertilization or self-fertilization. It will be seen that the cross-fertilization relationship may be of many degrees — between two flowers in the same cluster, between those in different clusters on the same branch, between those on different plants. Usually fertilization takes place only between plants of the same species or kind. In many cases there is, in effect, a7i apparent selection of pollen when pollen from two or more sources is applied to the stigma. Sometimes the foreign pollen, if from the same kind of plant, grows, and fertiliza- tion results, while pollen from the same flower is less promptly effec- tive. If, however, no foreign pol- len is present, the pollen from the same flower may finally serve the same purpose. In order that the pollen may grow, tJie stigma must be ripe. At this stage the stigma is usually moist and some- times sticky. A ripe stigma is said to be receptive. The stigma may remain receptive for several hours or even days, depending on the kind of plant, the weather, and how soon pollen is received. Watch a certain flower every day to see the anther locules open and the stigma ripen. When fertilization takes place, the stigma dies. Observe, also, how soon the petals wither after the stigma has received pollen. Pollination. — The transfer of the pollen from anther to stigma is known as pollination. The pollen may Fig. 195. — Diagram to represent fertiliza- TION. J, stigma; j/, style; tfz', ovary; o, ovule; /, pollen-grain; pt, pollen-tube; e, egg-cell; m, micropyle. 146 PLANT BIOLOGY fall of its own weight on the adjacent stigma, or it may be carried from flower to flower by wind, insects, or other agents. There may be self-pollination or cross-pol- lination, and of course it must always precede fertilization. Usually the pollen is discharged by the burst- ing of the anthers. The commonest method of discharge is through a slit on either side of the anther (Fig. 193). Sometimes it discharges 'through a pore at the apex, as in azalea (Fig. Fig. 196. — Anther of 1 96), rhododendron, huckleberry, wintergreen. Azalea, Jj^ some plants a part of the anther wall raises opening by • i i / terminal or falls as a ltd, as m barberry (Fig. 197), blue P*''^^^- cohosh, May apple. The opening of an anther (as also of a seed-pod) is known as dehiscence {de, from ; hisco, to gape). When an anther or seed pod opens, it is said to dehisce. Most flowers are so constructed as to increase the chances of cross-pollination. We have seen that the stigma may have the power of choosing foreign pollen. The commonest means of necessitating cross-pollina- tion is the different times of maturing of stamens and pistils in the same flower. In most cases the stamens mature first: the flower is then proterandrous. When the pistils mature first, the flower is proterogynous. {Aner, andr, is a Fig. 197. — Greek root often used, m combmations, for sta- barberry men, and e^yne for pistil.) The difference in Stamen, "^•^ ^ ^ . with anther time of ripening may be an hour or two, or it opening by may be a day. The ripening of the stamens ^''^^• and pistils at different times is known as dichogamy, and flowers of such character are said to be dichogamous. There is little chance for dichogamous flowers to pollinate themselves. Many flowers are imperfectly dichogamous — THE FL 0 WER — PER TILIZA TION AND POLLINA TION 1 47 some of the anthers mature simultaneously with the pistils, so that there is chance for self-pollination in case for- eign pollen does not arrive. Even when the stigma receives pollen from its own ilower, cross-fer- tilization may result. The hol- lyhock is proter- androus. Fig. 198 shows a flower recentlv ^^^' ^9^— ^L^^'^^OF hollyhock; proterandrous. expanded. The center is occupied by the column of sta- mens. In Fig. 199, showing an older flower, the long styles are conspicuous. Some flowers are so constructed as to prohibit self-polli- nation. Very irregular flowers are usually of this kind. With some of them, the petals form a sac to inclose the anthers and the pol- len cannot be shed on the stigma but is retained until a bee forces the sac open ; the pollen is rubbed on the hairs of the bee and transported. Regular flowers usu- ally depend mostly on dichogamy and the selective power of the pistil to insure crossing. Flowers that are very Fig. 199. — Older Flower of Hollyhock. 148 PLANT BIOLOGY irregular and provided with nectar and strong perfume are usually pollinated by insects. Gaudy colors probably attract insects in many cases, but perfume appears to be a greater attraction. The insect visits the flower for the nectar (for the making of honey) and may unknowingly carry the pollen. Spurs and sacs in the flower are necta- ries (Fig, 200), but in spurless flowers the nectar is usually secreted in the bottom of the flower cup. This compels the insect to pass by the anther and Fig. 200.— Flower of rub against the pollen before it reaches Larkspur. ,, 1. c ..' ^i. 1.1 the nectar, bometimes the anther is a long lever poised on the middle point and the insect bumps against one end and lifts it, thus bringing the other end of the lever with the pollen sacs down on its back. Flowers that are pollinated by insects are said to be entomophilous (" insect lov- ing"). Fig. 200 shows a larkspur. The envelopes are separated in Fig. 201. The long spur at once suggests insect pollination. The spur is a sepal. Two hollow petals project into this spur, ap- parently serving to guide the bee's tongue. The two smaller petals, in front, are peculiarly colored and perhaps serve the bee in locating the nectary. The stamens ensheath the pistils (Fig. 202). As the insect stands on the flower and thrusts its head into the center, Fig. 201. — Envelopes of a Larkspur. There are five wide sepals, the upper one be- ing spurred. There are four small petals. THE FLOWER — FERTILIZATION AND POLLINATION 149 the envelopes are pushed downward and outward and the pistil and stamens come in contact with its abdomen. Since the flower is proterandrous, the pollen that the pistils receive from the bee's abdomen must come from another flower. Note a somewhat similar ar- rangement in the toadflax or butter-and- eggs. In some cases (Fig. 203) the stamens are longer than the pistil in one flower and shorter in another. If the insect visits such flowers, it gets pollen on its head from the long-stamen flower, and deposits this pollen on the stigma in the long-pistil flower. Such flowers are di- morphous (of two forms). If pollen from its own flower and from another flower both fall on the stigma, the proba- bilities are that the stigma will choose the foreign pollen. Fig. 202. — Stamens OF Larkspur, sur- rounding the pistils. Fig. 203.— Dimorphic Flowers of Primrose. Many flozvers are pollinated by the wind. They are said to be anemophilous ("wind loving "). Such flowers pro- ISO PLANT BIOLOGY duce great quantities of pollen, for much of it is wasted. They usually have broad stigmas, which expose large surfaces to the wind. They are usually lacking in gaudy colors and in perfume. Grasses and pine trees are typical examples of anemophilous plants. In many cases cross-polHnation is insured because the stamens and pistils are in different flowers (diclinous). Monoecious and dioecious plants may be polli- nated by wind or insects, or other agents (Fig. 204). They are usually wind - pollinated, although willows are often, if not mostly, insect- pollinated. The Indian corn is a monoecious plant. The staminate flowers are in a terminal panicle (tassel). The pistillate flowers are in a dense spike (ear), inclosed in a sheath or husk. Each " silk " is a style. Each pistillate flower produces a kernel of corn. Some- times a few pistillate flowers are borne in the tassel and a few staminate flowers on the tip of the ear. Is self-fertili- zation possible with the corn } Why does a " volunteer " stalk standing alone in a garden have only a few grains on the ear .'' What is the direction of the prevailing wind in summer .-• If only two or three rows of corn are Fig. 204. — Flowers of Black Walnut : two pis- tillate flowers at A, and staminate catkins at B. THE FL O WER — PER T I LIZ A TION AND POLLINA TION I 5 I planted in a garden where prevailing winds occur, in which direction would they better run ? Although most flowers are of such character as to insure or increase the chances of cross-pollination, there are some that absolutely forbid crossing. These flowers are usually borne beneath or on the ground, and they lack showy colors and per- fumes. They are known as cleistogamous flowers (meaning " hidden flow- ers "). The plant has normal showy flowers that may be insect-pol- linated, and in addition is provided with these simplified flowers. Only a few plants bear cleis- togamous flowers. Hog- peanut, common blue violet, fringed winter- green, and dalibarda are Fig. 205. — Common Blue Violet. The . , •, , -L • i • 1 familiar flowers are shown, natural size. the best subjects m the The corolla is spurred. Late in the season, Northern states. Fi"". cleistogamous flowers are often borne on , , . the surface of the ground. A small one is 205 shows a cleiStOga- shown at a. A nearly mature pod is shown mOUS flower of the blue at b. Both a and b are one third natural violet at a. Above the true roots, slender stems bear these flowers, that are provided with a calyx, and a curving corolla which does not open. Inside are the stamens and pistils. Late in the season the cleistogamous flowers may be found just underneath the mold. They never rise above ground. The following summer one may find a seedling plant, in 152 PLANT BIOLOGY some kinds of plants, with the remains of the old cleistog- araous flower still adhering to the root. Cleistogamous flowers usually appear after the showy flowers have Fig. 206. — Pods of Peanuts ripening underground. passed. They seem to insure a crop of seed by a method that expends Httle of the plant's energy. The pupil will be interested to work out the fruiting of the pea^ nut (Fig. 206). Unbaked fresh peanuts grow readily and can easily be raised in the North in a warm sandy garden. Suggestions. — 152. Not all the flowers produce seeds. Note that an apple tree may bloom very full, but that only rela- tively few apples may result (Fig. 207). More pollen is produced than is needed to fertilize the flotvers ; this increases the chances that sufficient Fig. 207. -Stkuggi.e for Existence among the Apple Flowers. THE FL O WER — FEE T I LIZA TION AND POLLINA TION I 5 3 stigmas will receive acceptable pollen to enable the plant to perpetuate its kind. At any time iii summer, or even in fall, examine the apple trees carefully to determine whether any dead flowers or flower stalks still remain about the apple ; or, examine any full-blooming plant to see whether any of the flowers fail. 153. Keep watch on any plant to see whether insects visit it. What kind? When? What for? 154. Determine whether the calyx serves any purpose in protecting the flower. Very carefully remove the calyx from a bud that is normally exposed to heat and sun and rain, and see -whether the flower'then fares as well as others. 155. Cover a single flower on its plant with a tiny paper or muslin bag so tightly that no insect can get in. If the flower sets fruit, what do you conclude? 156. Remove carefully the corolla from a flower nearly ready to open, preferably one that has no other flowers very close to it. Watch for insects. 157. Find the nectar in any flower that you study. 158. Remove the stigma. What happens? 159. Which of the following plants have perfect flowers : pea, bean, pumpkin, cotton, clover, buckwheat, potato, Indian corn, peach, chestnut, hickory, watermelon, sunflower, cab- bage, rose, begonia, geranium, cucumber, calla, willow, cotton- wood, cantaloupe ? What have the others ? 160. On wind- polHnated plants, are either anthers or stigmas more numerous ? 161. Are very small colored flowers usually borne singly or in clusters ? 162. Why do rains at blooming time often lessen the fruit crop ? 163. Of what value are bees in orchards ? 164. The crossing of plants to impro7)e varieties or to obtain new varieties. — It may be desired to perform the operation of polli- nation by hand. In order to insure the most definite results, every effort should be made rightly to apply the pollen which it is desired shall be used, and rigidly to exclude all other pollen. (a) The first requisite is to remove the anthers from the flower which it is proposed to cross, and they must be removed before the pollen has been shed. The flower-bud is therefore opened and the anthers taken out. Cut off the floral envelopes with small, sharp- pointed scissors, then cut out or pull out the anthers, leaving only the pistil untouched ; or merely open the corolla at the end and pull out the anthers with a hook or tweezers ; and this method is often the best one. It is best to delay the operation as long as possible and yet not allow the bud to open (and thereby expose the flower to foreign pollen) nor the anthers to discharge the pollen. ((5) Th^ ^GVi&x must next be covered with a paper bag to prevent the access of pollen (Figs. 208, 209). If the stigma is not receptive at the time (as it usually is not), the desired pollen is not applied at once. The bag may be removed from time to time to allow of examination of the pistil, and when the stigma is mature, which is told by its glutinous or roughened appearance, 154 PLANT BIOLOGY the time for pollination has come. If the bag is slightly moist- ened, it can be puckered more tightly about the stem of the plant. The time required for the stigma to mature varies from several hours to a l^^fi days, (r) When the stigma is ready, an unopened anther from the desired flower is crushed on the finger nail or a knife blade, and the pollen is rubbed on the stigma by means of a tiny brush, the point of a knife blade, or a sliver of wood. The Fig. ao8. — a Paper Bag, with string inserted. Fig. 209. — The Bag tied OVER a Flower. flower is again covered with the bag, which is allowed to remain for several days until all danger of other pollination is past. Care must be taken completely to cover the stigmatic surface with pollen, if possible. The seeds produced by a crossed flower pro- duce hybrids, or plants having parents belonging to different varieties or species. 165. One of the means of securing new forms of plants is by making hybrids. Why ? Fig. 210. — Fig. The fig is a hollow torus with flowers borne on the inside, and pollinated by insects that enter at the apex. CHAPTER XX FLOWER-CLUSTERS Origin of the Flower-cluster. — We have seen that branches arise from the axils of leaves. Sometimes the leaves may be reduced to bracts and yet branches are borne in their axils. Some of the branches grow into long limbs ; others be- come short spurs ; others bear flowers. In fact, a flower is it- self a specialized branch. Flowers are usually borne near the top of the plant. Often they are produced in great num- bers. It results, therefore, that flower branches usually stand close together, forming a clus- ter. The shape and arrange- ment of the flower-cluster differ with the kind of plant, since each plant has its own mode of branching. Certain definite or well-marked types of flower-clusters have re- ceived names. Some of these names we shall discuss, but the flower-clusters that perfectly match the definitions are the exception rather than the rule. The determining of the 155 Fig. 211. —Terminal Flowers OF THE Whiteweed (in Some places called ox-eye daisy). 156 PLANT BIOLOGY kinds of flower-clusters is one of the most perplexing sub- jects in descriptive botany. We may classify the subject around three ideas : solitary flowers, centrifugal or deter- minate clusters, centripetal or indeterminate clusters. Solitary Flowers. — In many cases flowers are borne singly; they are separated from other flowers by leaves. They are then said to be solitary. The solitary flower may be either at the end of the main shoot or axis (Fig. 211), when it is said to be terminal ; or from the side of the shoot (Fig. 212), when it is said to be lateral or axillary. Centripetal Clusters. — If the flower-bearing axils were rather close together, an open or leafy flower-cluster might result. If the plant continues to grow from the tip, the older flowers are left farther and farther behind. If the cluster were so short as to be flat or convex on top, the out- ermost flowers would be the older. A flower-cluster in which the lower or outer flowers open first is said to be a centripetal cluster. It is some- times said to be an indeterminate cluster, since it is the result of a type of growth which may go on more or less continuously from the apex. The simplest form of a definite centripetal cluster is a raceme, which is an open elongated cluster in which the flowers are borite singly on very short branches and open from below (that is, from the older part of the shoot) Fig. 212. — Lateral Flower of AN Abutilon. a greenhouse plant. FL O WER- CL US TERS 157 upwards (Fig. 213). The raceme may be terminal to the main branch; or it may be lateral to it, as in Fig. 214. Racemes often bear the flowers on one side of 5mMw&i(«v/,M^^f>N the stem, thus form- ing a single row. When a cen- tripetal flower- cluster is long and dense and the flowers are sessile or nearly so, it is called a spike (Fig. 215). Common examples of spikes are plantain, migno- nette, mullein. A very sJiort and dense spike is a head. Clover (Fig. 216) is a good example. The sunflower and related plants bear many small flowers in a very dense and often flat head. Note that in the sunflower (Fig. 189) the outside or exterior flowers Fig. 213. — RActinE of Currant, Terminal or lateral ? Fig. 214. — Lateral Racemes (in fruit) of Barberry. Fig. 215.— Spike of Plantain. 158 PLANT BIOLOGY open first. Another special form of spike is the catkin, which usually has scaly bracts, the whole cluster being deciduous after flowering or fruiting, and the flowers (in typical cases) having only stamens or pistils. Examples are the "pussies" of willows (Fig. 182) and flower-clusters of oak (Fig. 180), walnuts (Fig. 204), poplars. Fig. 216. — Head of Clo- ver Blossoms. Fig. 217. — CorVmb of Candy- tuft. When a loose, elongated centripetal flower-cluster has some primary branches simple, and others irregularly branched, it is called a panicle. It is a branching raceme. Because of the earlier growth of the lower branches, the panicle is usually broadest at the base or conical in outline. True panicles are not very common. When an indeterminate flower-cluster is short, so that FL O WER- CL US TERS 1 59 the top is convex or flat, it is a corymb (Fig. 217). The outermost flowers open first. Centripetal flower-clusters are sometimes said to be corymbose in mode. When the branches of an indeterminate cluster arise from a common point, like the frame of an umbrella, the cluster is an umbel (Fig. 218). Typical umbels occur in carrot, parsnip, caraway and other plants of the parsley family : the family is known as the Umbelliferae, or umbel-bearing Fig. 218.— Remains of a Last Year's Umbel of Wild Carrot. family. In the carrot and many other Umbelliferae, there are small or secondary umbels, called umbellets, at the end of each of the main branches. (In the center of the wild carrot umbel one often finds a single, blackish, often aborted flower, comprising a i-flowered umbellet.) Centrifugal or Determinate Clusters. — When the ter- minal or central flower opens first, the cluster is said to be centrifugal. The growth of the shoot or cluster is deter- minate, since the length is definitely determined or stopped by the terminal flower. Fig. 219 shows a determinate or centrifugal mode of flower bearing. i6o PLANT BIOLOGY Dense centrifugal clusters are usually flattish on top because of the cessation of growth in the main or central axis. These com- pact flower-clusters are known as cymes. Centrifugal clusters are sometimes said to be cymose in mode. Apples, pears (Fig. 220), and elders bear flowers in cymes. Some cyme-forms are like umbels in general appear- ance. A head-like cymose clus- ter is a glomerule ; it blooms from the top downwards rather than from the base upwards. Mixed Clusters. — Often the cluster is mixed, being determi- nate in one part and indeterminate in another part of the same clus- ter. The main cluster may be indeterminate, but the branches determinate. The cluster has the appearance of a panicle, and is usually so called, but it is really a thyrse. Lilac is a familiar example of a thyrse. In some cases the main cluster is determinate and the branches are indeterminate, as in hydrangea and elder. Inflorescence. — The mode or method of flower arrangement is known as the inflorescence. That is, the inflorescence is cymose, co- rymbose, paniculate, spicate, solitary, determinate, inde- terminate. By custom, however, the word " inflorescence " Fig. 219. — Determinate or Cymose Arrangement. — Wild geranium. Fig. 220. — Cyme of Pear. Often imperfect. FL 0 WER- CL US TERS 1 6 1 3l3 123!»(»12l i . ;. 221. — Forms of Centripetal Flower-clusters. z, raceme; 2, spike; 3, umbel; 4, head or anthodium; 5, corymb. Fig. 222. — Centripetal Inflorescence, to«/«»«^rf. 6, spadix ; 7, compound umbel ; 8, catkin. Fig. 223. — Centrifugal Inflorescence. I, cyme; 2, scirpioid raceme (or half cyme). 1 62 PLANT BIOLOGY has come to be used for the flower-cluster itself in works on descriptive botany. Thus a cyme or a panicle may be called an inflorescence. It will be seen that even solitary flowers follow either indeterminate or determinate methods of branching. The flower-stem. — The stem of a solitary flower is known as a peduncle ; also the general stem of a flower- cbister. The stem of the individual flower in a cluster is a pedicel. In the so-called stemless plants the peduncle may arise directly from the ground, or crown of the plant, as in dandelion, hyacinth, garden daisy; this kind of peduncle is called a scape. A scape may bear one or many flowers. It has no foUage leaves, but it may have bracts. Suggestions. — 166. Name six columns in your notebook as follows : spike, raceme, corymb, umbel, cyme, solitary. Write each of the following in its appropriate column : larkspur, grape, rose, wistaria, onion, bridal wreath, banana, hydrangea, phlox, China berry, Hly-of-the-valley, Spanish dagger (or yucca), sorghum, tuberose, hyacinth, mustard, goldenrod, peach, hollyhock, mul- lein, crepe myrtle, locust, narcissus, snapdragon, peppergrass, shepherd's purse, coxcomb, wheat, hawthorn, geranium, carrot, elder, millet, dogwood, castor bean ; substitute others for plants that do not grow in your region. 167. In the study of flower- clusters, it is well to choose first those that are fairly typical of the various classes discussed in the preceding paragraphs. As soon as the main types are well fixed in the mind, random clusters should be examined, for the pupil must never receive the impres- sion that all flower-clusters follow the definitions in books. Clus- ters of some of the commonest plants are very puzzhng, but the pupil should at least be able to discover whether the inflorescence is determinate or indeterminate. Figures 221 to 223 (from the German) illustrate the theoretical modes of inflorescence. The numerals indicate the order of opening. CHAPTER XXI FRUITS The ripened ovary, with its attachments, is known as the fruit. // contains the seeds. If the pistil is simple, or of one carpel, the fruit also will have one com- partment. If the pistil is compound, or of more than one carpel, the fruit usually has an equal number of com- partments. The com- partments in pistil and fruit are known as lo- cules (from Latin locus, meaning "a place"). The simplest kind of fruit is a ripened \-loculed ovary. The first stage in complex- ity is a ripened 2- or many-loculed ovary. Very complex forms may arise by the attachment of other parts to the ovary. Sometimes the style persists and becomes a beak (mustard pods, dentaria. Fig. 224), or a tail as in clematis ; or the calyx may be attached to the ovary ; or the ovary may be embedded in the receptacle, and ovary and receptacle together consti- tute the fruit : or an involucre may become a part of the 163 Fig. 224. — Dentaria, or Tooth-wort, in fruit. 1 64 PLANT BIOLOGY fruit, as possibly in the walnut and hickory (Fig. 225), and cup of the acorn (Fig. 226). The chestnut and the beech bear a prickly involucre, but the nuts, Fig. 225. — Hickory-nut. The nut is the fruit, con- tained in a husk. Fig. 226. — Live-oak Acorn. The fruit is the " seed " part ; the involucre is the "cup." or true fruits, are not grown fast to it, and the involucre can scarcely be called a part of the fruit. A ripened ovary is a pericarp. A pericarp to which other parts adhere has been called an accessory or reenforced fruit. (Page 169.) Some fruits are dehiscent, or split open at maturity and liberate the seeds ; others are indehiscent, or do not open. A dehiscent pericarp is called a / pod The parts into' which such a pod breaks or splits are known as valves. In inde- hiscent fruits the seed is liberated by the decay of the envelope, or by the rupturing of the envelope by the germinating seed. Indehiscent winged peri- American Elm. carps are known as samaras or key fruits. Maple (Fig. 227), elm (Fig. 228), and ash (Fig. 93) are examples. Fig. 227. — Key of Sugar Maple. Fig. 228. — Key of Common FRUITS 165 Fig. 229. — Akenes of buitercup. Fig. 230. — Akenes OF Buttercup, one in longitudi- nal section. Pericarps. — The simplest pericarp is a dry, one- seeded, indehiscent body. It is known as an akene. A head of akenes is shown in Fig. 229, and the structure is explained in Fig. 230. Akenes may be seen in buttercup, hepatica, anemone, smartweed, buckwheat. A i-loculed pericarp which dehisces along the front edge (that is, the inner edge, next the center of the flower) is a follicle. The fruit of the larkspur (Fig. 231) is a follicle. There are usually five of these fruits (sometimes three or four) in each larkspur flower, each pistil ripening into a follicle. If these pistils were united, a single compound pistil would be formed. Columbine, peony, ninebark, milk- weed, also have follicles. A i-loculed pericarp that de- hisces on both edges is a legume. Peas and beans are typical exam- ples (Fig. 232); in fact, this character gives name to the pea family, — Leguminosae. Often the valves of the legume twist forcibly and expel the seeds, throwing them some distance. The word " pod " is sometimes restricted to legumes, but it is better to use it generi- cally for all dehiscent pericarps, A compound pod — dehiscing peri- carp of two or more carpels — is a capsule (Figs. 233, 234, Fig. 232. — A.... Bean Pod. Fig. 233. — Capsule of Castor -OIL Bean AFTER Dehiscence. i66 PLANT BIOLOGY Fig. 234. — Cap- sule OF Morn- ing Glory. 236, 237). Some capsules are of one locule, but they may have been compound when young (in the ovary stage) and the partitions may have vanished. Sometimes one or more of the carpels are uniformly crowded out by the exclusive growth of other carpels (Fig. 235). The seeds or parts which are crowded out are said to be aborted. There are several ways in which cap- sules dehisce or open. When they break along the partitions (or septa), the mode is known as septi- cidal dehiscence (Fig. 236) ; In septicidal dehiscence the fruit separates into parts representing the original carpels. These carpels may still be entire, and they then dehisce individu- ally, usually along the inner edge as if they were follicles. When the compartments split in the middle, betiveen the partitions, the mode is loculicidal dehiscence (Fig. 237). In some cases the dehiscence is at the top, when it is said to be apical (al- though several modes of dehis- cence are here included). When the IV hole top comes off, as in purs- lane and garden portulaca (Fig. 238), the pod is known as a pyxis. In some cases apical dehiscence is by means of a hole or clefts. The peculiar capsule of the mustard family, or Cruci Fig. 235. — Three-carpeled Fruit OF Horse-chestnut. Two locules are closing by abortion of the ovules. Fig. 236. — St. John's Wort. Sep- ticidal. Fig. 237. — Loculici- dal Pod of Day-lily. FRUITS 167 ferae, is known as a silique when it is distinctly longer than broad (Fig. 224), and a silicle when its breadth nearly Fig. 238. — Pyxis of Portu- LACA OR Rose-moss. Fig. 239. — Berries of Goose- berry. Remains of calyx at c. equals or exceeds its length. A cruciferous capsule is 2-carpeled, with a thin partition, each locule containing seeds in two rows. The two valves detach from below upwards. Cabbage, turnip, mustard, water-cress, radish, rape, shepherd's purse, sweet alyssum, wall- flower, honesty, are examples. Fig. 240.— Berry of the Ground Cherry OR Husk Tomato, contained in the inflated calyx. The pericarp may \iQ fleshy and indehiscent. A pulpy pericarp with several or many seeds is a berry (Figs. 239, 240, 241). To the horticulturist a berry is a small, soft, edible fruit, without Fig. 241. — Orange; example of a berry. 1 68 PLANT BIOLOGY particular reference to its structure. The botanical and horticultural conceptions of a berry are, therefore, unlike. In the botanical sense, gooseberries, currants, grapes, to- matoes, potato-balls, and even eggplant fruits and oranges (Fig. 241) are berries; strawberries, raspberries, black- berries are not. A fleshy pericarp containing one relatively large seed or stone is a drupe. Examples are plum (Fig. 242), peach, cherry, apricot, olive. The walls of the pit in the plum, peach, and cherry are formed from the inner coats of the ovary, and the flesh from the outer coats. Drupes are also known as stone-fruits. Fruits that are formed by the sub- sequent union of separate pistils are aggregate fruits. The carpels in aggregate fruits are usually more or less fleshy. In the raspberry and blackberry flower, the pistils are essentially distinct, but as the pistils ripen they co- here and form one body (Figs. 243, 244). Fig. 242. — Plum; exam- ple of a drupe. Fig. 244. — Aggrkgate Fruit of Mulberry; and a separate fruit. Fig. 243. — Fruit OF Rasp- berry. Each of the carpels or pistils in the raspberry and blackberry is a Httle drupe, or drupelet. In the rasp- berry the entire fruit separates from the torus, leaving the torus on the plant. In the blackberry and dew- FRUITS 169 berry the fruit adheres to the torus, and the two are re- moved together when the fruit is picked. Accessory Fruits. — When the pericarp and some other part grow together, the fruit is said to be accessory or reenforced. An example is the straw- berry (Fig. 245). The edible part is a greatly enlarged toms, and the pericarps are akenes embedded in it. These akenes are commonly called seeds. Various kinds of reenforced fruits have received special names. One of these is the hip, characteristic of roses. In this case, the torus is deep and hollow, Hke an urn, and the separate akenes are borne inside it. The mouth of the receptacle may close, and the walls sometimes become fleshy ; the fruit may then be mistaken for a berry. The fruit of the pear, apple, and quince is known as a Fig. 245. — Straw- berry; fleshy torus in which akenes are embedded. Fig. 246. — Section of AN Apple. Fig. 247. — Cross-section OF AN Apple, pome. In this case the five united carpels are completely buried in the hollow torus, and the torus makes most of the edible part of the ripe fruit, while the pistils are repre- sented by the core (Fig. 246). Observe the sepals on the top of the torus (apex of the fruit) in Fig. 246. Note the outlines of the embedded pericarp in Fig. 247. I/O PLANT BIOLOGY Gymnospermous Fruits. — In pine, spruces, and their kin, there is no fruit in the sense in which the word is used in the preceding pages, because there is no ovary. The ovules are naked or uncovered, in the axils of the scales of the young cone, and they have neither style nor stigma. The pollen falls directly on the mouth of the ovule. The ovule ripens into a seed, which is usually winged. Because the ovule is not borne in a sac or ovary, these plants are called gymnosperms (Greek for "naked seeds"). All the true cone-bearing plants are of this class ; also certain other plants, as red cedar, juniper, yew. The plants are monoecious or sometimes dioecious. The staminate flowers are mere naked stamens borne beneath scales, in small yellow catkins which soon fall. The pistillate flowers are naked ovules beneath scales on cones that persist (Fig. 29). Gymnospermous seeds may have several cotyledons. Suggestions. — 168. Study the following fruits, or any five fruits chosen by the teacher, and answer the questions for each : Apple, peach, bean, tomato, pumpkin. What is its form ? Locate the scar left by the stem. By what kind of a stem was it attached ? Is there any remains of the blossom at the blossom end? De- scribe texture and color of surface. Divide the fruit into the seed vessel and the surrounding part. Has the fruit any pulp or flesh? Is it within or without the seed vessel? Is the seed vessel simple or subdivided? What is the number of seeds? Are the seeds free, attached to the wall of the vessel, or to a support in the center? Are they arranged in any order? What kind of wall has the seed vessel ? What is the difference between a peach stone and a peach seed? 169. The nut fruits are always available for study. Note the points suggested above. Determine what the meat or edible part represents, whether cotyledons or not. Figure 248 is suggestive. 170. Mention all the fleshy fruits you know, tell where they come from, and refer them to their proper groups. 171. What kinds of fruits can you buy in the market, and to what groups or classes do they belong? Of which ones are the seeds only, and not the pericarps, eaten ? 172. An ear of corn is always available for study. What is it — a fruit or a collection of fruits ? How are the grains arranged on the cob ? How many rows do you count on each of several ears ? Are all the rows on an ear FRUITS 171 equally close together ? Do you find an ear with an odd number of rows ? How do the parts of the husk overlap ? Does the husk serve. as protection from rain ? Can birds pick out the grains? How do insect enemies enter the ear ? How and when do weevils lay eggs on corn ? 173. Study a grain of corn. Is it a seed ? Describe the shape of a grain. Color. Size. Does its surface show any projections or depressions ? Is the seed-coat thin or thick ? Transparent or opaque ? Locate the hilum. Where is the silk scar ? What is the silk ? Sketch the grain from the two points of view that show it best. Where is the embryo ? Does the grain have endosperm ? What is dent com ? Flint corn ? How many kinds of corn do you know ? For what are they used ? Fig. 248. — Pecan Fruit. Note to Teacher. — There are few more interesting subjects to beginning pupils than fruits, — the pods of many kinds, forms, and colors, the berries, and nuts. This interest may well be utilized to make the teaching alive. All common edible fruits of orchard and vegetable garden should be brought into this dis- cussion (some of the kinds are explained in " Lessons with Plants"). Of dry fruits, as pods, burs, nuts, collections may be made for the school museum. Fully mature fruits are best for study, particularly if it is desired to see dehiscence. For com- parison, pistils and partially grown fruits should be had at the same time. If the fruits are not ripe enough to dehisce, they^ may be placed in the sun to dry. In the school it is well to have a collection of fruits for study. The specimens may be kept in glass jars. Always note extenor of fruit and its parts : interior of fruit with arrangement and attachment of contents. CHAPTER XXII DISPERSAL OF SEEDS It is to the plant's advantage to have its seeds distributed as widely as possible. // has a better chance of surviving in the struggle for existence. It gets away from competi- tion. Many seeds and fruits are of such character as to increase their chances of wide dispersal. The commonest means of dissemination may be classed under four heads : explosive fruits ; transportation by. wind ; tratisportation by birds; burs. Fig. '249. — Explosion of THE Balsam Pod. Fig. 250. — Explosive Fruits of Oxalis. An exploding pod is shown at c. The dehiscence is shown at b. The structure of the pod is seen at a. Explosive Fruits. — Some pods open tvith explosive force ' and discharge the seeds. Even bean and everlasting peas do this. More marked examples are the locust, witch hazel, garden balsam (Fig. 249), wild jewel-weed or impa- tiens (touch-me-not), violet, crane's-bill or wild geranium, bull nettle, morning glory, and the oxalis (Fig. 250). The 172 DISPERSAL OF SEEDS 1 73 oxalis is common in several species in the wild and in cultivation. One of them is known as wood sorrel. Figure 250 shows the common yellow oxalis. The pod opens loculicidally. The elastic tissue suddenly contracts when dehiscence takes place, and the seeds are thrown violently. The squirting cucumber is easily grown in a garden (pro- cure seeds of seedsmen), and the fruits discharge the seeds with great force, throwing them many feet. Wind Travelers. — Wind - transported seeds are of two general kinds : those that are provided with zvings, as the flat seeds of catalpa (Fig. 251) and cone-bear- ing trees and the samaras of ash, elm, tulip-tree, ailanthus, and maple ; and those which have feathery buoys or para- cJmtes to enable them to float in the air. Of the latter kind are the fruits of many composites, irt which the pappus is copious and soft. Dandelion and thistle are examples. The silk of the milkweed and probably the hairs on the cotton seed have a similar office, and also the wool of the cat-tail. Recall the cottony seeds of fig. 251. — winged ., -11 J 1 Seeds OF Catalpa. the willow and poplar. Dispersal by Birds. — Seeds of berries and of other small fleshy fruits are carried far and xvide by birds. The pulp is digested, but the seeds are not injured. Note how the cherries, raspberries, blackberries, June-berries, and others spring up in the fence rows, where the birds rest. Some berries and drupes persist far into winter, when they supply food to cedar birds, robins, and the winter birds. Red cedar is distributed by birds. Many of these pulpy 174 PLANT BIOLOGY fruits are agreeable as human food, and some of them have been greatly enlarged or " improved " by the arts of the cultivator. The seeds are usually indigestible. Burs. — Many seeds and fruits bear spines, hooks, and hairs, which adhere to the coats of animals and to clothing. The burdock has an involucre with hooked scales, contain- ing the fruits inside. The clotbur is also an involucre. Both are compositous plants, allied to thistles, but the whole head, rather than the separate fruits, is transported. In some com- positous fruits the pappus takes the form of hooks and spines, as in the " Spanish bayonets " and " pitch- forks." Fruits of various kinds are known as "stick tights," as of the agrimony and hound's-tongue. Those who walk in the woods in late sum- mer and fall are aware that plants have means of disseminating them- selves (Fig. 252). If it is impossible to iden- tify the bure which one finds on clothing, the seeds may be planted and specimens of the plant may then be grown. Suggestions. — 174. What advantage is it to the plant to have its seeds widely dispersed? 175. What are the leading ways in which fruits and seeds are dispersed? 176. Name some explosive fruits. 177. Describe wind travelers. 178. What seeds are car- ried by birds? 179. Describe some bur with which you are familiar. 180. Are adhesive fruits usually dehiscent or indehis- cent? 181. Do samaras grow on low or tall plants, as a rule? 182. Are the cotton fibers on the seed or on the fruit? 183. Name the ways in which the common weeds of your region are disseminated. 184. This lesson will suggest other ways in which Fig. 252. — Stealing a Ride. DISPERSAL OF SEEDS 175 seeds are transported. Nuts are buried by squirrels for food ; but if they are not eaten, they may grow. The seeds of many plants are blown on the snow. The old stalks of weeds, standing through the winter, may serve to disseminate the plant. Seeds are carried by water down the streams and along shores. About woolen mills strange plants often spring up from seed brought in the fleeces. Sometimes the entire plant is rolled for miles before the winds. Such plants are " tumbleweeds." Examples are Russian thistle, hair grass or tumblegrass (Fanicum capillare), cyclone plant (^Cydoloma platyphylluni), and white amaranth {Amarantus albus). About seaports strange plants are often found, having been introduced in the earth that is used in ships for ballast. These plants are usually known as "ballast plants." Most of them do not persist long. 185. Plants are able to spread themselves by means of the great numbers of seeds that they produce. How many seeds may a given elm tree or apple tree or raspberry bush produce ? Fig. 253. — The Fruits OF THE Cat-tail are LOOSENED BY WiND AND Weather. CHAPTER XXIII PHENOGAMS AND CRYPTOGAMS Fig. 254. — Christmas Fern. — Dryopteris acrostichoides ; known also as Aspidium. The plants thus far studied produce flowers; and the flowers produce seeds by means of which the plant is prop- agated. There are other plants, however, that produce no seeds, and these plants (including bac- teria) are probably more numer- ous than the seed-bearing plants. These plants propagate by means of spores, which are generative cells ^ usually simple, containing no em- bryo. These spores are very small, and sometimes are not visible to the naked eye Prominent among the spore- propagated plants are ferns. The common Christmas fern (so called because it remains green during winter) is shown in Fig. 254. The plant has no trunk. The leaves spring directly from the ground. The leaves of ferns are called fronds. They vary in shape, as other leaves do. Some of the fronds in Fig. 254 are seen to be narrower at the top. If these are examirred more closely (Fig. 255), 176 Fiu. 255. — Fruiting Frond OF Christmas Fern. Sori at a. One sorus with its in- dusium at b. PHENOGAMS AND CRYPTOGAMS 177 it will be seen that the leaflets are contracted and are densely covered beneath with brown bodies. These bodies are collections of sporangia or spore-cases. Fig. 256. — Common Poi.ypode Fern. Polypodium vulgare. Fig. 257. — SoRi and Spo- rangium OF POLYPODE. A chain of cells lies along the top of the sporangium, which springs back elasti- cally on drying, thus dis- seminating the spores. Fig. 258. — The Brake Fruits underneath THE Re volute Edges of the Leaf. The sporangia are collected into little groups, known as sort (singular, sorus) or fruit-dots. Each sorus is covered with a thin scale or shield, known as an indusium. This indusium sepa- rates from the frond at its edges, and the sporangia are exposed. Not all ferns have indusia. The polypode (Figs. 256, 257) does not; the sori are naked. In the brake (Fig. 258) and maidenhair (Fig. 259) the edge of the frond turns over and forms an indusium. The nephrolepis or sword fern of greenhouses is allied to the polypode. The sori are in a single row on either side the midrib (Fig. 260). The indu- sium is circular or kidney- shaped and open at one edge Fig. 259.— Fruiting Pinnules of Maidenhair Fern. 178 PLANT BIOLOGY Fig. 260. — Part of Frond of Sword Fern. To the pupil : Is this illustration right side up ? or finally all around. The Boston fern, Washington fern, Pierson fern, and others, are horticultural forms of the common sword fern. In some ferns (Fig. 261) an entire frond becomes contracted to cover the sporangia. The sporangium or spore-case of a fern is a more or less globular body and usually with a stalk (Fig. 257). // con- tains the spores. When ripe it bursts and the spores are set free. In a moist, warm place the spores germinate. They produce a small, flat, thin, green, more or less heart- shaped membrane (Fig. 262). This is the prothallus. Sometimes the prothallus is an inch or more across, but oftener it is less than a dime in size. Although easily seen, it is commonly unknown ex- cept to botanists. Prothalli may often be found in greenhouses where ferns are grown. Look on the moist stone or brick walls, or on the firm soil of undisturbed pots and beds ; or spores may be sown in a damp, warm place. On the under side of the prothallus two kinds of organs are borne. These are the Fig. 262. — Prothallus of a , . , FERN. Enlarged. archegonium (contammg egg- Archegonia at a ; antheridia at b. Cells) aud the ailtheridium (con- FiG. 261. — Fertile and Sterile Fronds of the Sensitive Fern. i PHENOGAMS AND CRYPTOGAMS 1 79 taining sperm-cells). These organs are minute specialized parts of the prothallus. Their positions on a particular prothallus are shown at a and b in Fig. 262, but in some ferns they are on separate prothalli (plant dioecious). The sperm-cells escape from the antheridiiim and in the water that collects on the prothallus are carried to the archegoniiim, where fertilization of the egg takes place. From the ferti- lized egg-cell a plant grows, becoming a "fern." In most cases the prothallus soon dies. The prothallus is the gametophyte (from Greek, signifying the fertilized plant). The fern plant, arising from the fertilized Q,gg in the archegonium, becomes a perennial plant, each year pro- ducing spores from its fronds (called the sporophyte) ; but these spores — which are merely detached special kinds of cells — produce the prothallic phase of the fern plant, from which new individuals arise. A fern is fertilized but once in its lifetime. The "fern" bears the spore, the spore gives rise to the prothallus, and the egg-cell of the prothallus (when fertiUzed) gives rise to the fern. A similar alternation of generations runs all through the vegetable kingdom, although there are some groups of plants in which it is very obscure or apparently wanting. It is very marked in ferns and mosses. In algae (includ- ing the seaweeds) the gametophyte is the " plant," as the non-botanist knows it, and the sporophyte is incon- spicuous. There is a general tendency ^ in the evolution of the vegetable kingdom, for the gametophyte to lose its rela- tive importance and for the sporophyte to become larger and more highly developed. In the seed-bearing plants the sporophyte generation is the only one seen by the non- botanist. The gametophyte stage is of short duration and the parts are small ; it is confined to the time of fertiliza- tion. l8o PLANT BIOLOGY The sporophyte of seed plants, or the " plant " as we know it, produces two kinds of spores — one kind becom-- ing pollen grains and the other kind embryo-sacs. The; pollen-spores are borne in sporangia, which are united into what are called anthers. The embryo-sac, which contains the egg-cell, is borne in a sporangium known as an ovule. A gametophytic stage is present in both pollen and embryo sac : fertilization takes place, ajid a sporophyte arises. Soon this sporophyte becomes dormant, and is then known as an embryo. The embryo is packed away within tight-fitting coats, and the entire body is the seed. When the condi- tions are right the seed grows, and the sporophyte grows into herb, bush, or tree. The utility of the alternation of generations is not understood. The spores of ferns are borne on leaves ; the spores of seed-bearing plants are also borne amongst a mass of specially developed conspicuous leaves known as flowers, therefore these plants have been known as the flowering plants. Some of the leaves are developed as envelopes (calyx, corolla), and others as spore-bearing parts, or spo- rophylls (stamens, pistils). But the spores of the lower plants, as of ferns and mosses, may also be borne in spe- cially developed foliage, so that the line of demarcation between flowering plants and flowerless plants is not so. definite as was once supposed. The one definite distinction between these two classes of plants is the fact that one class produces seeds and the other does not. The seed-plants are now often called spermaphytes, but there is no single coordinate term to set off those which do not bear seeds. It is quite as well, for popular purposes, to use the terms phenogams for the seed-bearing plants and cryptogams for the others. These terms have been objected to in recent years because their etymology does not express literal facts PHENOGAMS AND CRYPTOGAMS i8i {pJienogam signifying "showy flowers," and cryptogam "hidden flowers"), but the terms represent distinct ideas in classification. The cryptogams include three great series of plants — the Thallophytes or algae, lichens, and fungi ; the Bryophytes or mosslike plants; the Pteridophytes or fernlike plants. Suggestions. — 186. The parts of a fern leaf. The primary complete divisions of a frond are called pinnae, no matter whether the frond is pinnate or not. In ferns the word "pinna" is used in essentially the same way that leaf- let is in the once-compound leaves of other plants. The secondary leaflets are called pinnules, and in thrice, or more, compound fronds, the last complete parts or leaflets are ultimate pinnules. The dia- gram (Fig. 263) will aid in making the subject clear. If the frond were not divided to the midrib, it would be simple, but this diagram represents a compound frond. The general outline of the frond, as bounded by the dotted line, is ovate. The stipe is very short. The midrib of a compound frond is known as the rachis. In a de- compound frond, this main rachis is called the primary rachis. Seg- ments (not divided to the rachis) are seen at the tip, and down to h on one side and to m on the other. Pinnae are shown at i, k, I, 0, n. The pinna o is entire ; n is crenate-dentate ; / is sinuate or wavy, with an auricle at the base ; k and / are compound. The pinna k has twelve entire pin- nules. (Is there ever an even number of pinnules on any pinna?) Pinna / has nine compound pinnules, each bearing several entire ultimate pinnules. The spores. — 187. Lay a mature fruiting frond of any fern on white paper, top side up, and allow it to remain in a dry, warm place. The spores will discharge on the paper. 188. Lay the full-grown (but not dry) cap of a mushroom or toadstool bottom down on a sheet of clean paper, under a venti- lated box in a warm, dry place. A day later raise the cap. Fig. 263. — Diagram to explain THE Terminology of the Frond. CHAPTER XXIV STUDIES IN CRYPTOGAMS The pupil who has acquired skill in the use of the com- pound microscope may desire to make more extended ex- cursions into the cryptogamous orders. The following plants have been chosen as examples in various groups. Ferns are sufficiently discussed in the preceding chapter. Bacteria If an infusion of ordinary hay is made in water and allowed to stand, it becomes turbid or cloudy after a few days, and a drop under the microscope will show the presence of minute oblong cells swimming in the water perhaps by means of numerous hair- like appendages, that project through the cell wall from the pro- toplasm within. At the surface of the dish containing the infusion the cells are non-motile and are united in long chains. Each of these cells or organisms is a bacterium (plural, bacterid). (Fig. 135.) Bacteria are very minute organisms, — the smallest Known, — consisting either of separate oblong or spherical cells, or of chains, plates, or groups of such cells, depending on the kind. They possess a membrane-like wall which, unlike the cell walls of higher plants, contains nitrogen. The presence of a nucleus has not been definitely demonstrated. Multiplication is by the fission of the vegetative cells ; but under certain conditions of drought, cold, or exhaustion of the nutrient medium, the protoplasm of the ordinary cells may become invested with a thick wall, thus form- ing an endospore which is very resistant to extremes of environ- ment. No sexual reproduction is known. Bacteria are very widely distributed as parasites and sapro- phytes in almost all conceivable places. Decay is largely caused by bacteria, accompanied in animal tissue by the liberation of foul-smelling gases. Certain species grow in the reservoirs and pipes of water supplies, rendering the water brackish and often undrinkable. Some kinds oi fermentatio7i (the breaking down or decomposing of organic compounds, usually accompanied by the 182 STUDIES IN CRYPTOGAMS 1 83 formation of gas) are due to these organisms. Other bacteria oxidize alcohol to acetic acid, and produce lactic acid in milk and butyric acid in butter. Bacteria live in the mouth, stomach, in- testines, and on the surface of the skin of animals. Some secrete gelatinous sheaths around themselves ; others secrete sulfur or iron, giving the substratum a vivid color. Were it not for bacteria, man could not live on the earth, for not only are they agents in the process of decay, but they are concerned in certain healthful processes of plants and animals. We have learned in Chap. VIII how bacteria are related to nitro- gen-gathering. Bacteria are of economic importance not alone because of their effect on materials used by man, but also because of the disease- producing power of certain species. Pus is caused by a spherical form, tetanus or lock-Jaw by a rod-shaped form, diphtheria by short oblong chains, tuberctdosis or " constimption " by more slen- der oblong chains, and typhoid fever, cholera, and other diseases by other forms. Many diseases of animals and plants are caused by bacteria. Disease-producing bacteria are said to be pathogenic. The ability to grow in other nutrient substances than the natu- ral one has greatly facilitated the study of these minute forms of life. By the use of suitable culture media and proper precau- tions, pure cultures of a particular disease-producing bacterium may be obtained with which further experiments may be con- ducted. Milk provides an excellent collecting place for bacteria coming from the air, from the coat of the cow and from the milker. Dis- ease germs are sometimes carried in milk. If a drop of milk is spread on a culture medium (as agar), and provided with proper temperature, the bacteria will multiply, each one forming a colony visible to the naked eye. In this way, the number of bacteria originally contained in the milk may be counted. Bacteria are disseminated in water, as the germ of typhoid fever and cholera ; in milk and other fluids j in the air ; and on the bodies of flies, feet of birds, and otherwise. Bacteria are thought by many to have descended from algae by the loss of chlorophyll and decrease in size due to the more specialized acquired saprophytic and parasitic habit. ALGiE The algae comprise most of the green floating " scum " which covers the surfaces of ponds and other quiet waters. The masses of plants are often called " frog spittle." Others are attached to stones, pieces of wood, and other objects submerged in streams 1 84 PLANT BIOLOGY and lakes, and many are found on moist ground and on dripping rocks. Aside from these, all the plants commonly known as seaweeds belong to this category ; these latter are inhabitants of salt water. The simplest forms of algae consist of a single spherical cell, which multiplies by repeated division or fission. Many of the forms found in fresh water are filamentous, i.e. the plant body consists of long threads, either simple or branched. Such a plant body is termed a thallus. This term applies to the vegetative body of all plants that are not differentiated into stem and leaves. Such plants are known as thallophytes (p. i8i). All algae contain chlorophyll, and are able to assimilate carbon dioxid from the air. This distinguishes them from the fungi. Nostoc. — On wet rocks and damp soil dark, semitransparent irregular or spherical gelatinous masses about the size of a pea are often found. These consist of a colony of contorted filamentous algae embedded in the jelly-like mass. The chain of cells in the filament is necklace-like. Each cell is homogeneous, without apparent nucleus, and blue-green in color, except one cell which is larger and clearer than the rest. The plant therefore belongs to the group of blue-green algce. The jelly probably serves to maintain a more even moisture and to provide mechanical protec- tion. Multiplication is wholly by the breaking up of the threads. Occasionally certain cells of the filament thicken to become resting- spores, but no other spore formation occurs. Oscillatoria. — The blue-green coatings found on damp soil and in water frequently show under the microscope the presence of filamentous algae composed of many short Fig. 264. —Filament of Oscillatoria, showing one dead cell where the strand will break. homogeneous cells (Fig. 264). If watched closely, some filaments will be seen to wave back and forth slowly, showing a peculiar power of movement characteristic of this plant. Multiplication is by the breaking up of the threads. There is no true spore formation. Spirogyra. — One of the most common forms of the green algae is spirogyra (Fig. 265). This Fig. 265. — Strand OF Spirogyra, showing the chlo- rophyll bands. There is a nu- cleus at a. How many cells, or parts of cells, are shown in this fig- ure ? \ STUDIES IN CRYPTOGAMS 185 I plant often forms the greater part of the floating green mass (or " frog spittle ") on ponds. The threadlike character of the thallus can be seen with the naked eye or with a hand lens, but to study it carefully a microscope magnifying two hundred diameters or more must be used. The threadJs divided into long cells by cross__walls_whi£h, according to the species, are either straight or curiously folded (Fig. 266). Thie_chlorophyJl is arranged- in beautiful spiral ^gj>i^L-neatUiL£-waU-of each .cell. From the character of these bands the plant takes its name. Each cell is _proyided_with. a nucleus and other protoplasm^ The nucleus is suspended near the center of the cell {a, Fig. 265) by delicate strands of protoplasm radiat- ing toward the wall and terminating at certain points in the chlorophyll band. The remainder of the protoplasm forms a thin layer lining the wall. The interior ^f_the_celLisL_filled^_with cell-sap. The^rotoplasm and nucleus cannot l5e~easily seen, but if the plant is stained with a dilute alcoholic solution of eosin they become clear. Spirogyra is propagated vegetatively by the breaking ojf of partj^ of the threads, which con- tinue to grow as new plants. Resting-spores, which may remain dormant for a time, are formed by_a^process known as conjugation. Two threads lying side by side send out short projections, usually from all the cells of a long series (Fig. 266). The projections or processes from opposite cells grow toward each other, meet, and fuse, form- ing a connecting tube between the cells. The protoplasm, nucleus, and chlorophyll band of one cell now pass through this tube, and unite with the contents of the other cell. The en- tire mass then becomes surrounded by a thick cellulose wall, thus completing the resting- spore, or zygospore (2, Fig. 266). Zygnema is an alga closely related to spiro- gyra and found in similar places. Its life history is practically the same, but it differs from spirogyra in having two star-shaped chlorophyll bodies (Fig. 267) in each cell, in- stead of a chlorophyll-bearing spiral band. Fig. 266. —Con- jugation OF Spirogyra. Ripe zygospores on the left ; a, connecting tubes. Fig. 267. — STRAND, OR Filament of Zygnema, freed from its gelatinous covering. 1 86 PLANT BIOLOGY Vaucheria is another alga common in shallow water and on damp soil. The thallus is much branched, but the threads are not divided by cross walls as in spirogyra. The plants are attached by means of colorless root-like organs which are much like the root hairs of the higher plants : these are rhizoids. The chloro- phyll is in the form oi grains scattered through the thread. Vaucheria has a special mode of asexual reproduction by means of swimming spores or swarm-spores. These are formed singly in a short enlarged lateral branch known as the sporangium. When the sporangium bursts, the entire contents escape, forming a single large swarm-spore, which swims about by means of numerous lashes or cilia on its surface. The swarm spores are so large that they can be seen with the naked eye. After swimming about for some time they come to rest and germinate, producing a new plant. The formation of resting-spores of vaucheria is acomplished by means of special organs, odgonia (p, Fig. 268) and antheridia (a. Fig. 268). Both of these are specially devel- oped branches from the thallus. The antheridia are nearly cylindrical, and curved toward the oogonia. „ ,„ ^ ,, The upper part of an an- FiG. 268. — TftREAD OF Vaucheria WITH . j-^ • ^ a- u /^•- A.,^.T„„,T.T. theridium is cut off by a Oogonia and Antheridia. „ ,.,.-'. cross wall, and within it numerous ciliated sperm-cells are formed. These escape by the ruptured apex of the antheridium. The oogonia are more en- larged than the antheridia, and have a beak-like projection turned a little to one side of the apex. They are separated from the thallus thread by a cross wall, and contain a single large green cell, the egg-cell. The apex of the oogonium is dissolved, and through the opening the sperm-cells enter. Fertilization is thus accomplished. After fertilization the egg-cell becomes invested with a thick wall and is thus converted into a resting-spore, the oospore. Fucus. — These are rather large specialized algae belonging to the group known as brown seaweeds and found attached by a disk to the rocks of the seashore just below high tide (Fig. 269). They are firm and strong to resist wave action and are so attached as to avoid being washed ashore. They are very abundant algae. In shape the plants are long, branched, and multicellular, with either flat or terete branches. They are olive-brown. Propagation is by the breaking off of the branches. No zoospores are produced, as in many other seaweeds ; and reproduction is wholly sexual. STUDIES IN CRYPTOGAM^ 1^7 The antheridia, bearing sperm-cells, and the odgonia, each bearing eight e^-cells, are sunken in pits or conceptacles. These pits are aggregated in the swollen lighter colored tips of some of the branches {s, s, Fig. 269). The egg-cells and sperm-cells escape from the pits and fertilization takes place in the water. The matured eggs, or spores, reproduce the fucus plant directly. Fio. 269. — Fucus. Fruiting branches at s, s. On the stem are two air-bladders. Fig. 270. — Nitella. Nitella. — This is a large branched and specialized fresh-water alga found in tufts attached to the bottom in shallow ponds (Fig. 270). Between the whorls of branches are long internodes consisting of a single cylindrical cell, which is one of the largest cells known in vegetable tissue. Under the microscope the walls of this cell are found to be lined with a layer of small stationary chloroplastids, within which layer the protoplasm, under favorable circumstances, will be found in motion, moving up one side and down the other (in rotation). Note the clear streak up the side of the cell and its relation to the moving current. Fungi Some forms of fungi are familiar to every one. Mushrooms and toadstools, with their varied forms and colors, are common in fields, woods, and pastures. In every household the common molds are familiar intruders, appearing on old bread, vegetables, and even within tightly sealed fruit jars, where they form a felt- like layer dusted over with blue, yellow, or black powder. The strange occurrence of these plants long mystified people, who i88 PLANT BIOLOGY thought they were productions of the dead matter upon which they grew, but now we know that a mold, as any other plant,^ cannot originate spontaneously ; it must start from something which is analogous to a seed. The "seed " in this case is a spore. A spore may be produced by a vegetative process (growing out from the ordinary plant tissues), or it may be the result of 2i fertilization process. Favorable conditions for the growth of fungi. — Place a piece of bread under a moist bell jar and another in an uncovered place near by. Sow mold on each. Note the result from day to day. Moisten a third piece of bread with weak copper sulfate (blue vitriol) or mercuric chlorid solution, sow mold, cover with bell jar, note results, and explain. Expose pieces of different kinds of food in a damp atmosphere and observe the variety of organisms appearing. Fungi are saprophytes or parasites, and must be provided with organic matter on which to grow. They are usually most abundant in moist places and wet seasons. Fig. 271. — Mucor Mold. — One of these molds (Mucor mu- MUCEDO, showing habit cedo), which is very common on all decay- ing fruits and vegetables, is shown in Fig. 271, somewhat magnified. When fruiting, this mold appears as a dense mass of long white hairs, often over an inch high, standing erect from the fruit or vegetable on which it is growing. The life of this mucor begins with a minute rounded spore {a, Fig. 272), which lodges on the decaying material. When the spore germinates, it sends out a delicate thread that grows rapidly in length and forms very many branches that soon permeate every part* of the substance on which the plant grows {b, Fig. 272). One of these threads is termed a hypha. All the threads together form the mycelitim of the fungus. The mycelium disorganizes the ma- terial in which it grows, and thus the mucor plant (Fig. 271) is nourished. It corresponds physiologically to the roots and stems of other plants. When the mycelium is about two days old, it begins to form the long fruiting stalks which we first noticed. To study them, use a compound microscope magnifying about two hundred diameters. One of the stalks, magnified, is shown in a, Fig. 274. It consists of a rounded head, the sporangium, sp, supported on a long, Fig. 272. — Spores OF Mucor, some germinating. STUDIES IN CRYPTOGAMS 189 Fig. 274. — MucoR. a, sporangium; b, sporangium bursting; c, columella. delicate stalk, the sporangiophore. The stalk is separated from the sporangium by a wall which is formed at the base of the spo- rangium. This wall, however, does not extend straight across the thread, but it arches up into the sporangium like an inverted pear. It is known as the col- umella, c. When the sporangium is placed in water, the wall immediately dissolves and allows hundreds of spores, which were formed in the cavity within the sporangium, to escape, b. All that is left of the fruit is the stalk, with the pear-shaped columella at its summit, c. The spores that have been set free by the breaking of the sporangium wall are now scattered by the wind and other agents. Those that lodge in favorable places be- gin to grow immediately and reproduce the fungus. The others soon perish. The mucor may continue to reproduce itself in this way indefi- nitely, but these spores are very delicate and usually die if they do not fall on favorable ground, so that the fungus is provided with another means of carrying itself over unfavora- ble seasons, as winter. This is accomplished by means of curious thick-walled resting-spores or zygospores. The zygospores are formed on the mycelium buried within the substance on which the plant grows. They originate in the following way : Two threads that lie near to- gether send out short branches, which grow toward each other and finally meet (Fig. 273). The walls at the ends, a, then disappear, allow- ing the contents to flow together. At the same time, however, two other walls are formed at points farther back, b, b, separating the short section, c, from the remainder of the thread. This section now increases in size and becomes covered with a thick, dark brown wall orna- mented with thickened tubercles. The zygo- spore is now mature and, after a period of rest, it germinates, either producing a sporan- gium directly or growing out as mycelium. The zygospores of the mucors form one of the most interesting and instructive objects among the lower plants. They are, how- ever, very difficult to obtain. One of the mucors {Sporodinia Fig. 273. — MucoR, showing formation of zygospore on the right; germi- nating zygospore on the left. 190 PLANT BIOLOGY grandis) may be frequently found in summer growing on toad- stools. This plant usually produces zygospores that are formed on the aerial mycelium. The zygospores are large enough to be recognized with a hand lens. The material may be dried and kept for winter study, or the zygospores may be prepared for permanent microscopic mounts in the ordinary way. Yeast. — This is a very much reduced and simple fungus, con- sisting normally of isolated spherical or elliptical cells (Fig. 275) containing abundant protoplasm and prob- ably a nucleus, although the latter is not easily observed. It propagates rapidly by budding, which consists of the gradual extru- sion of a wart-hke sweUing that is sooner or later cut off at the base by constriction, thus forming a separate organism. Although sim- „^ —Yeast P^^ ^^ structure, the yeast is found to be Pi ants closely related to some of the higher groups of fungi as shown by the method of spore forma- tion. When grown on special substances Hke potato or carrot, the contents of the cell may form spores inside of the sac-like mother cell, thus resembling the sac-fungi to which blue mold and mildews belong. The yeast plant is remarkable on account of its power to induce alcoholic fermentation in the media in which it grows. There are many kinds of yeasts. One of them is found in the common yeast cakes. In the process of manufacture of these cakes, the yeast cells grow to a certain stage, and the material is then dried and fashioned into small cakes, each cake containing great numbers of the yeast cells. When the yeast cake is added to dough, and proper conditions of warmth and moisture are pro- vided, the yeast grows rapidly and breaks up the sugar of the dough into carbon dioxid and alcohol. This is fermentation. The gases escape and puff up the dough, causing the bread to rise. In this loosened condition the dough is baked ; if it is not baked quickly enough, the bread "falls'^ Shake up a bit of yeast cake in slightly sweetened water : the water soon becomes cloudy from the growing yeasts. Parasitic fungi. — Most of the molds are saprophytes. Many other fungi are parasitic on living plants and animals (Fig. 285). Some of them have complicated life histories, undergoing many changes before the original spore is again produced. The willow mildew and the common rust of wheat -^'-^ serve to illustrate the habits of parasitic fungi. The willow mildew ( Uncinula salicis). — This is one of the sac fungi. It forms white downy patches on the leaves of willows STUDIES IN CRYPTOGAMS 191 Fig. 276. — Colonies of Willow Mildew. (Fig. 276). These patches consist of numerous interwoven threads that may be recognized under the microscope as the mycehum of the fungus. The mycehum in this case hves on the surface of the leaf and nour- ishes itself by sending short branches into the cells of the leaf to ab- sorb food materials from them. Numerous summer-spores are formed of short, erect branches all over the white surface. One of these branches is shown in Fig. 277. When it has grown to a cer- tain length, the upper part begins to segment or divide into spores which fall and are scattered by the wind. Those falling on other wil- lows reproduce the fungus there. This process continues all summer, but in the later part of the season provision is made to maintain the mildew through the winter. If some of the white patches are closely ex- amined in July or August, a number of little black bodies will be seen among the threads. These little bodies are cz^g.^ perithecia, shown in Fig. 278. To the naked eye they appear as minute specks, but when seen under a magnifi- cation of 200 diameters they present a very interesting appear- ance. They are hollow spheri- decorated Fig. 277. — Summer-spores of Willow Mildew. Fig. 278. — Perithecium of Wii^ low Mildew. cal bodies the outside with a fringe of crook-like hairs. The resting-spores of the willow mildew are produced in sacs or ax^/ in- closed with- in the leath- around Fig. 279. — Section through Peri- thecium of Wil- low Mildew. ery perithecia. Figure 279 shows a cross-section of a perithecium with the asci arising from the bottom. The spores remain securely 192 PLANT BIOLOGY packed in the perithecia. They do not ripen in the autumn, but fall to the ground with the leaf, and there remain securely pro- tected among the dead foliage. The following spring they mature and are liberated by the decay of the perithecia. They are then ready to attack the unfolding leaves of the willow and repeat the work of the summer before. lu;. 280. — SORI CON- TAINING Teleuto- spoRES OF Wheat Rust. The wheat rust. — The development of some of the rusts, as the common wheat rust {Puccinia graminis), is even more interesting and complicated than that of the mildews. Wheat rust is also a true parasite, affecting wheat and a few other grasses. The mycelium here cannot be seen by the unaided eye, for it consists of threads which are present within the host plant, mostly in the intercellular spaces. These threads also send short branches, or haustoria (Fig. 132), into the neigh- boring cells to absorb nutriment. The resting-spores of wheat rust are produced in late summer, when they may be found in black lines breaking through the epidermis of the wheat stalk (black-rust stage). They are formed in masses, called sori (Fig. 280), from the ends of numerous crowded mycelial strands just beneath the epidermis of the host. The individual spores are very small and can be well studied only with a microscope of high power (x about 400). They are brown two-celled bod- ies with a thick wall (Fig. 281). Since they are the resting or winter-spores, they are termed teleu- tospores ("completed spores"). Usually they do not fall, but remain in the sori during winter. The following spring each cell of the teleutospore puts forth a rather stout thread, which does not grow more than several times the length of the spore and terminates in a blunt extremity. This germ tube, promyceliuni, now becomes divided into four cells by cross walls, which are formed from the top downwards. Each cell gives rise to a short, pointed branch whiclr, in the course of a few hours, forms at its summit a single spore called a sporidium. This in turn germinates and produces a mycelium. In Fig. 282 a germinating teleutospore is drawn to show the promycelium, /, divided into four cells, Fig. 281. — Te- leutospore OF Wheat Rust. STUDIES IN CRYPTOGAMS 193 each producing a short branch with a Httle spo- ridiuni, s. A most remarkable circumstance in the Hfe history of the wheat rust is the fact that the my- ceUum produced by the sporidium can live only in barberry leaves, and it follows that if no bar- berry bushes are in the neighborhood the sporidia finally perish. Those which happen to lodge on a barberry bush germinate immediately, produc- ing a mycelium that enters the barberry leaf and grows within its tissues. Very soon the fungus produces a new kind of spores on the barberry leaves. These are called cecidiospores. They are formed in long chains in little fringed cups, or cecidia, which appear in groups on the lower side of the leaf (Fig. 283). These orange or yellow secidia are termed cluster-cups. In Fig. 284 is shown a cross-section of one of the cups, outlin- ing the long chains of spores, and the mycelium in the tissues. The secidiospores are formed in the spring, and after they have been set free, some of them lodge on wheat or other grasses, where they germinate immediately. The germ-tube enters the Fig. 282. — Ger- minating Te- leutospore OF Wheat Rust. ^,- Fig. 283. — Leaf OF Barberry WITH Clus- ter-cups. Fig. 284. —Section through a Cluster-cup on Barberry Leaf. leaf through a stomate, whence it spreads among the cells of the wheat plant. In summer one-celled reddish uredospores ("blight spores," red-rust stage) are produced in a manner similar to the teleutospores. These are capable of germinating immediately, 194 PLANT BIOLOGY and serve to disseminate the fungus during the summer on other wheat plants or grasses. Late in the season, teleutospores are again produced, completing the hfe cycle of the plant. Many rusts besides Puccinia grammis produce different spore forms on different plants. The phenomenon is called heteroecism, and was first shown to exist in the wheat rust. Curiously enough, the peasants of Europe had observed and asserted that barberry bushes cause wheat to blight long before science explained the relation between the cluster-cups on barberry and the rust on wheat. The true relation was actually demonstrated, as has since been done for many other rusts on their respective hosts, by sow- ing the aecidiospores on healthy wheat plants and thus producing Anttiracnose CanKer Seed Coat" Starch Grains Fig. 285. — How A Parasitic Fungus works. Anthracnose on a bean pod entering the bean beneath. (Whetzel.) the rust. The cedar apple is another rust, producing the curious swellings often found on the branches of red cedar trees. In the spring the teleutospores ooze out from the " apple " in brown- ish yellow masses. It has been found that these attack various fruit trees, producing gecidia on their leaves. Fig. 285 explains how a parasitic fungus works. Puffballs, mushrooms, toadstools, and shelf fungi. — These represent what are called the higher fungi, because of the size and complexity of the plant body as well as from the fact that they seem to stand at the end of one line of evolution. The mycelial threads grow together in extensive strands in rotten wood or in the soil, and send out large complex growths of mycelium in con- STUDIES IN CRYPTOGAMS 195 nection with which the spores are borne. These aerial parts are the only ones we ordinarily see, and which constitute the " mush- room " part (Fig. 131). Only asexual spores {ba- sidiospores) are produced, and on short stalks {basidia) (Fig. 286). In the puff- balls the spores are inclosed and constitute a large part of the "smoke." In the mushrooms and toadstools they are borne on gills, and in the shelf fungi (Fig. 134) on the walls of minute pores of the underside. The my- celium of these shelf fungi frequently lives and grows for a long time concealed in the substratum before the visible fruit bodies are sent out. Practically all timber decay is caused by such growth, and the damage is largely done before the fruiting bodies appear, counts of mushrooms, see Chap. XIV. Fig. 286. — Part of Gill of the Cul- tivated Mushroom. tr, trama tissue; sh, hymenium; b, basidium; st, sterigma; sp, spore. (Atkinson.) For other ac- X Lichens Fig. 287. — Lichen on an Oak Trunk. (A species of Physcia.) Lichens are so common everywhere that the attention of the student is sure to be drawn to them. They grow on rocks, trunks of trees (Fig. 287), old fences, and on the earth. They are thin, usually gray ragged objects, ap- parently Ufeless. Their study is too difficult for beginners, but a few words of explanation may be useful. Lichens were formerly supposed to be a distinct or separate division of plants. They are now known to be or- ganisms, each species of which is a con- stant association of a fungus and an alga. The thallus is ordinarily made up of fun- gous mycelium or tissue within which the imprisoned alga is definitely dis- tributed. The result is a growth unlike either component. This association of 196 PLANT BIOLOGY alga and fungus is usually spoken of as symbiosis, or mutually helpful growth, the alga furnishing some things, the fungus others, and both together being able to accomplish work that neither could do independently. By others this union is considered to be a mild form of parasitism, in which the fungus profits at the expense of the alga. As favorable to this view, the facts are cited that each component is able to grow independently, and that under such conditions the algal cells seem to thrive better than when imprisoned by the fungus. Lichens propagate by means of soredia, which are tiny parts separated from the body of the thallus, and consisting of one or more algal cells overgrown with fungus threads. These are readily observed in many lichens. They also produce spores, usually ascospores, which are always the product of the fungus element, and which reproduce the lichen by germinating in the presence of algal cells, to which the hyphae immediately cling. Lichens are found in the most inhospitable places, and, by means of acids which they secrete, they attack and slowly disin- tegrate even the hardest rocks. By making thin sections of the thallus with a sharp razor and examining under the compound microscope, it is easy to distinguish the two components in many lichens. Liverworts The liverworts are peculiar flat green plants usually found on wet cliffs and in other moist, shady places. They frequently occur in greenhouses where the soil is kept constantly wet. Fig. 288. Fig. 289. Plants of Marchantia. One of the commonest liverworts is Marchantia polymorpha, two plants of which are shown in Figs. 288, 289. The plant consists of 'a ribbon-like thallus that creeps along the ground, becoming repeatedly forked as it grows. The end of each branch STUDIES IN CRYPTOGAMS 197 Fig. 290. — Section of Thallus OF Marchantia. Stomate at a. is always conspicuously notched. There is a prominent midrib extending along the center of each branch of the thallus. On the under side of the thallus, especially along the midrib, there are numerous rhizoids which serve the purpose of roots, absorbing nourishment from the earth and holding the plant in its place. The upper surface of the thallus is di- vided into minute rhombic areas that can be seen with the naked eye. Each of these areas is per- forated by a small breathing pore or stomate that leads into a cavity just beneath the epidermis. This space is surrounded by chlorophyll- bearing cells, some of which stand in rows from the bottom of the cavity (Fig. 290). The delicate assimilating tissue is thus brought in close communication with the outer air through the pore in the thick, protecting epidermis. At various points on the midrib are Httle cups containing small green bodies. These bodies are buds or geftwice which are outgrowths from the cells at the bottonroTtHFcup^ They become loosened and are then dispersed by the rain to other places, where they take root and grow into new plants. The most striking organs on the thallus of marchantia are the peculiar stalked bodies shown in Figs. 288, 289. These are termed archegoniophores and antheridiophores or receptacles. Their structure and function are very interesting, but their parts are so minute that they can be studied only with the aid of a microscope magnifying from 100 to 400 times. Enlarged drawings will guide the pupil. Fig. 291. — Section through ANXHERiniopHORE of Marchantia, showing antheridia. One antheridium more magnified. The antheridiophores are fleshy, lobed disks borne on short stalks (Fig. 291). The upper surface of the disk shows openings scarcely visible to the naked eye. However, a section of the disk, such as is drawn in Fig. 291, shows that the pores lead into oblong cavi- 198 PLANT BIOLOGY Fig, 292. — Archego- NIUM OF Marchantia. ties in the receptacle. From the base of each cavity there arises a thick, club-shaped body, the antheridium. Within the anther- idium are formed many sperm -cells which are capa- ble of swimming about in water by means of long lashes or ciha attached to them. When the anther- idium is mature, it bursts and allows the ciliated sperm cells to escape. The archegoniophores are also elevated on stalks (Fig. 289). Instead of a simple disk, the recepta- cle consists of nine or more finger-like rays. Along the under side of the rays, between deHcately fringed curtains, peculiar flask-like bodies, or arche- gonia, are situated. The archegonia are not visible to the naked eye. They can be studied only with the microscope ( X about 400) . One of them much magnified is represented in Fig. 292. Its principal parts are the long neck, a, and the rounded venter, b, inclosing a large free cell — the egg-cell. We have seen that the antheridium at maturity discharges its sperm-cells. These swim about in the water provided by the dew and rain. Some of them finally find their way to the archegonia and egg-cells, the latter being fertilized, as pollen fertilizes the ovules of higher plants. After fertilization the egg-cell develops into the spore capsule or sporogonium. The mature spore capsules may be seen in Fig. 293. They consist of an oval spore-case on a short stalk, the base of which is imbedded in the tissue of the receptacle, from which it derives the neces- sary nourishment for the development of the sporogonium. At maturity the sporogonium is ruptured at the apex, setting free the spheri- cal spores together with numerous filaments having spirally thickened walls (Fig. 294). These filaments are called elaters. When drying, they exhibit rapid movements by means of which the spores are scattered. The spores germinate and again produce the thallus of marchantia. Fig. 293. — Arche- goniophore, WITH SPORO- GONiA, OF Mar- chantia. 294. — Spores and Elaters of Marchantia. ^ STUDIES IN CRYPTOGAMS Mosses (Bryophyta) 199 If we have followed carefully the development of marchantia, the study of one of the mosses will be comparatively easy. The mosses are more familiar plants than the liver- worts. They grow on trees, stones, and on the soil both in wet and dry places. One of the common larger mosses, known as Polytrichum commune, may serve as an example, Fig. 295. This plant grows on rather dry knolls, mostly in the borders of open woods, where it forms large beds. In dry weather these beds have a reddish brown appearance, but when moist they form beautiful green cushions. This color is due, in the first instance, to the color of the old stems and leaves, and, in the second in- stance, to the peculiar action of the green living leaves under the influence of chang- ing moisture-conditions. The inner or upper surface of the leaf is covered with thin, lon- gitudinal ridges of delicate cells which contain chloro- phyll. These cells are shown in cross-section in Fig. 296, as dots or granules. All the other tissue of the leaf consists of thick-walled, corky cells which do Fig. 295. — Polytrichum commune. f,f, fertile plants, one on the left in fruit, nt, antheridial plant. Fig. 296. — Section of Leaf of Polytrichum commune. not allow moisture to penetrate. When the air is moist the green leaves spread out, exposing the chlorophyll cells to the air, but in 200 PLANT BIOLOGY dry weather the margins of the leaves roll inward, and the leaves fold closely against the stem, thus protecting the delicate assimi- lating tissue. The antheridia and archegonia of polytrichura are borne in groups at the ends of the branches on different plants (many mosses bear both organs on the same branch). They are sur- rounded by involucres of characteristic leaves termed perichcetia ox perichcztal leaves. Multicellular hairs known as /^rd'/Ztji-^j are scattered among the archegonia and antheridia. The involucres with the organs borne within them are called receptacles, or, less appropriately, " moss flowers." As in marchantia, the organs are very minute and must be highly magnified to be studied. The antheridia are borne in broad cup-like receptacles on the antheridial plants (Fig. 297). They are much like the antheridia of marchantia, but they stand free among the paraphyses and are not sunk in cavities. At maturity they burst and allow the sperm cells or sper7natozoids to escape. In poly- trichum, when the receptacles have fulfilled their function, the stem con- FiG. 297. -SECTION THROUGH A ^WiM^^ to grow from the center of RECEPTACLE OF PoLVTRi- ^^e cup (w, Fig. 205). Thc arche- CHUM COMMUNE showing gonia are bome in Other rcceptaclcs paraphyses and antheridia. ° j-rr ^ 1 . n^\ i-i •^ on different plants. Ihey are like the archegonia of marchantia except that they stand erect on the end of the branch. The sporogoiiium which develops from the fertilized egg is shown in a, b, Fig. 295. It consists of a long, brown stalk bearing the spore-case at its summit. The base of the stalk is imbedded in the end of the moss stem by which it is nourished. The capsule is entirely inclosed by a hairy cap, the calyptra, b. The calyptra is really the remnant of the archegonium, which, for a time, increases in size to accommodate and protect the young growing capsule. It is finally torn loose and carried up on the spore-case. The mouth of the capsule is closed by a circular lid, the operculum, having a conical projection at the center. The operculum soon drops, or it may be removed, displaying a fringe of sixty-four teeth guarding the mouth of the capsule. This ring of teeth is known as the peristome. In most mosses the teeth exhibit peculiar hygroscopic movements ; i.e. when moist they bend outwards, and upon drying curve in toward the mouth of the capsule. This motion, it will be seen, serves to disperse the spores gradually over a long period of time. Not the entire capsule is filled with spores. There are no elaters, but the center of the capsule is occupied by a columnar STUDIES IN CRYPTOGAMS 20 1 strand of tissue, the colurnella, which expands at the mouth into a thin, membranous disk, closing the entire mouth of the capsule except the narrow annular chink guarded by the teeth. In this moss the points of the teeth are attached to the margin of the membrane, allow- ing the spores to sift out through the spaces be- tween them. When the spores germinate they form a green, branched thread, the protonema. This gives rise directly to moss plants, which appear as little buds on the thread. When the moss plants have sent their litde rhizoids into the earth, the pro- tonema dies, for it is no longer necessary for the support of the little plants, and the moss plants grow independently. Fujiaria is a moss very common on damp, open soil. It forms green patches of small fine leaves from which arise long brown stalks termi- nated by curved capsules (Fig. 298). The struc- ture is similar to that of polytrichum, except the absence of plates on the under side of the leaves, the continuous growth of the stem, the curved capsule, double peristome, monoecious rather than dicecious re- ceptacles, and nearly glabrous unsymmetrical calyptra. Fig. 298. — Fu- NARIA HY- GROSCOPICA. K Equisetums, or Horsetails (Pteridophyta) I There are about twenty-five species of equisetum, constituting the only genus of the unique family Equisetacece. Among these E. arvense (Fig. 299) is common nn rbyey and j^^riHy t^nil>;. In this species the work of nutrition and that nf spnrp production are performed bv separate shoots from an underground r]lipme. The fertile hranrhp^ appear parly in <;pring Thejgtgm, which is % to 6 inches high, consists of a number o^ ryl'"'^"^-^' furrovved internodes. each sheathed at the base by a circle of scale leaves. The shoots are of a pale yellow color. They contain no chtnSiphyll, and are nnnrkhpH Ky th^ fr.r.rl c«-r.r>>rl jn thf. rV.;^7r^r»» (Fig. 299). The spores are formed on specially developed fertile leaves or sporophyUs which are" collected into a spike nr cone at the end n f the_jtalk {a, Fig. 299}. A single sporophyll is shown at b. It consists of a short stalk expanded into a broad, mushroom-like head. Several large sporangia are borne on its under side. The spores formed in the sporangia are very interesting and beautiful 202 PLANT BIOLOGY objects when examined under the microscope (x about 200). They are spherical, green bodies, each surrounded by two spiral bands attached to th€ spore at their intersection, s. These bands exhibit hygroscopic movements by means of which the spores be- come entangled, and are held together. This is of advantage to the plant, as we shall see. All the spores are alike, but some of the/w- thallia grow to a greater size than the others. The large prothallia produce only archegonia while the smaller ones produce antheridia. Both of these organs are much like those of the ferns, and fertili- -® Fig. 299. — Equisetum arvense. si, sterile shoot; y, fertile shoot showing the spike at a; b, sporophyll, with sporangia; zation is accomplished in the same way. Since the prothallia are usually dioecious, the special advantage of the spiral bands, holding the spores together so that both kinds of prothallia may be in close proximity, will be easily understood. As in the fern, the fertilized egg-cell develops into an equisetum plant. The sterile shoots (x/. Fig. 299) appear much later in the season. They give rise to repented whorls of angular or furrowed branches. The leaves are very much reduced scales, situated at the inter- nodes. The stems are provided with chlorophyll and act as assimilating tissue, nourishing the rhizome and the fertile shoots. Nutriment is also stored in special tubers developed on the rhi- zome. I STUDIES IN CRYPTOGAMS 203 Other species of equisetum have only one kind of shoot — a tall, hard, leafless, green shoot with the spike at its summit. Equise- tum stems are full of silex, and they are sometimes used for scour- ing floors and utensils ; hence the common name " scouring rush." IsoETES (Pteridophyta) Iso'etes or quillvvort is usually found in water or damp soil on the edges of ponds and lakes. The general habit of the plant is seen in Fig. 300, a. It consists of a short, perennial stem bear- ing numerous erect, quill-like leaves with broad sheathing bases. The plants are commonly mis- taken for young grasses. Isoetes bears two kinds of spores, large roughened ones, the macrospores, and small ones or microspores. Both kinds are formed in sporafigia borne in an excavation in the expanded base of the leaf. The macrospores are formed on the outer and the microspores on the inner leaves. A sporangium in the base of a leaf is shown at b. It is partially covered by a thin membrane, the velum. The minute triangu- lar appendage at the upper end of the sporangium is called the iiguie. The spores are liberated by the decay of the sporangia. They form rudimentary prothaUia of two kinds. The microspores produce prothaUia with antheridia, while the macrospores produce pro- thaUia with archegojiia. Ferti- lization takes place as^ the mosses or liverworts, and the fertihzed egg-cell, by continiLedgfowth, gives rise again to the isoetes plant. Fig. 300. — IsoKtes, showing habit of plant at a ; b, base of leaf, show- ing sporangium, velum, and liguIe. ^Tv V VClub-Mosses (Pteridophyta) The clnb-mosses are low trailing plants of moss-like looks and habit, although more closely allied to ferns than to true mosses. Except one genus in Florida, all our club mosses belong to the 204 PLANT BIOLOGY genus Lycopodiutn. They grow mostly in woods, having i -nerved evergreen leaves arranged in four or more ranks. Some of them make long strands, as the ground pine, and are much used for Christmas decorations. The spores are all of one kind or form, borne in i-celled sporangia that open on the margin into two valves. The sporangia are borne in some species (Fig. 301) Fig. 301. —A Lycopodium WITH Sporangia in THE Axils of the Fo- liage Leaves. (^Lyco- podium lucidulum.) Fig. 302. — a Club-moss (Lycopodium complanatum) . as small yellow bodies in the axils of the ordinary leaves near the tip of the shoot; in other species (Fig. 302) they are borne in the axils of small scales that form a catkin-like spike. The spores are very numerous, and they contain an oil that makes them inflammable. About 100 species of lycopodium are known. The plants grown by florists under the name of lycopodium are of the genus Selaginella, more closely allied to isoetes, bearing two kinds of spores (microspores and macrospores) . ANIMAL BIOLOGY CHAPTER I THE PRINCIPLES OF BIOLOGY Biology (Greek, bios, life; logos, discourse) means the science of life. It treats of animals and plants. That branch of biology which treats of animals is called zoology (Gr. zoon, animal ; logos, discourse). The biological science of botany (Gr. botane, plant or herb) treats of plants. Living things are distinguished from the not living by a series of processes, or changes (feeding, growth, develop- ment, multiplication, etc.), which together constitute what is called life. These processes are called functions. Both plants and animals have certain parts called organs which have each a definite work, or function; hence animals and plants are said to be organized. For example, men and most animals have a certain organ (the mouth) for taking in nourishment; another (the food tube), for its digestion. Because of its organization, each animal or plant is said to be an organism. Living things constitute the organic kingdom. Things without life and not formed by life constitute the inorganic, or mineral, kingdom. Mark I for inorganic and O for organic after the proper words in this hst : granite, sugar, lumber, gold, shellac, sand, coal, paper, glass, starch, copper, gelatine, cloth, air, potatoes, alcohol, oil, clay. Which of these things are used for food by animals .-" Conclusion } ANIMAL BIOLOGY Energy in the Organic World. — We see animals exerting energy; that is, we see them moving about and doing work. Plants are never seen acting that way; yet they need energy in order to form their tissues, grow, and raise themselves in the air. Source of Plant Energy. — We notice that green plants thrive only in the Ught, while animal growth is largely in- dependent of light. In fact, in the salt mines of Poland there are churches and villages below the ground, and children are born, become adults, and live all their lives below ground, without seeing the sun. (That these people are not very strong is doubtless due more to want of fresh air and other causes than want of sunlight.) The need of plants for sunligJit shows that they must obtain something from the sun. This has been found to be energy. This enables them to lift their stems in growth, and form the various structures called tissues which make up their stems and leaves. (See Part I, Chap. XIII.) It is noticed that they take in food and water from the soil through their roots. Experiments also show that green plants take in through pores (Fig. i), on the surface of their leaves, a gas composed of carbon and oxygen, and called carbon dioxid. The energy in the sunlight enables the plant to separate out the carbon of the carboti dioxid and build mineral and water and carbon Fig. I. — Surfaces of a Leaf, magnified. rbonic^^Acid Gas in the Air going Into the Leaf ■^ater Fig. 2. — a Leaf storing Energy in Sunlight. THE PRINCIPLES OF BIOLOGY into organic substances. The oxygen of the carbon dioxid is set free and returns to the air (Fig. 2). Starch, sugar, oil, and woody fiber are examples of substances thus formed. Can you think of any fuel not due to plants } How Animals obtain Energy. — You have noticed that starch, oil, etc., will burn, or oxidize, that is, unite with the oxygen of the air; thus the sun's energy, stored in these substances, is changed back to heat and motion. The oxidation of oil or sugar may occur in a furnace; it may also occur in the living substance of the active animal. Fig. 3. — Colorless plants, as MuSH- A GREEN LEAF, even after it is cut, gives ROOMS, give off no oxygen. off oxygen (O) if kept in the sun. Fortunately for the animals the plants oxidize very little of the substances built up by them, since they do not move about nor need to keep themselves warm. We notice that animals are constantly using plant substances for food, and constantly drawing the air into their bodies. If the sun- light had not enabled the green plant to store up these substances and set free the oxygen (Fig. 3), animals would have no food to eat nor air to breathe; hence we may say that the sunHght is indirectly the source of the life and energy of animals. Mushrooms and other plants without green matter cannot set oxygen free (Fig. 3). 4 ANIMAL BIOLOGY Experiment to show the Cause of Burning, or Oxidation. — Obtain a large glass bottle (a pickle jar), a short candle, and some matches. Light the candle and put it on a table near the edge, and cover it with the glass jar. The flame slowly smothers and goes out. Why is this ? Is the air now in the jar different from that which was in it before the candle was lighted .'' Some change must have taken place or the candle would continue to burn. To try whether the candle will burn again under the jar without changing the air, slide the jar to the edge of the table and let the candle drop out. Light the candle and slip it up into the jar again, the jar being held with its mouth a little over the edge of the table to receive the candle (Fig. 5). The flame goes out at once. Evidently the air in the jar is not the same as the air outside. Take up the jar and wave it to and fro a few times, so as to remove the old air and admit fresh air. The candle now burns in it with as bright a flame as at first. So we conclude that the candle will not continue to burn unless there is a constant supply of fresh air. The gas formed by the burning is carbon dioxid. It is the gas from which plants extract carbon. (See Plant Biology, Chap. V.) One test for the presence of this gas is that it forms a white, chalky cloud in lime water ; another is that it smothers a fire. Experiment to show that Animals give off Carbon Dioxid. — Place a cardboard over the mouth of a bottle containing pure air. Take a long straw, the hollow stem of a weed, a glass tube, or a sheet of stiff paper rolled into a tube, and pass the tube into the bottle through a hole in the cardboard. Without drawing in a deep breath, send one long breath into the bottle through the tube, emptying the lungs by the breath as nearly as possible (Fig. 4). Next invert the bottle on the table as in the former experiment, THE PRINCIPLES OF BIOLOGY % afterward withdrawing the cardboard. Move the bottle to the edge of the table and pass the lighted candle up into it (Fig. 5). Does the flame go out as quickly as in the former experiment ? If you breathe through a tube into clear lime water, the water turns milky. The effect of the breath on the candle and on the lime water shows that carbon dioxid is continually leaving our bodies in the breath. Fig. 4. — Breathing into a bottle. i Fig. 5. — Testing the air in the bottle.^ Oxidation and Deoxidation. — The union of oxygen with carbon and other substances, which occurs in fires and in the bodies of animals, is called oxidation. The separa- tion of the oxygen from carbon such as occurs in the leaves of plants is called deoxidation. The first process sets energy free, the other process stores it up. Animals give off carbon dioxid from their lungs or gills, and plants give off oxygen from their leaves. But plants need some energy in growing, so oxidation also occurs in plants, but to a far less extent than in animals. At night, because of the absence of sunlight, no deoxidation is taking place ^ From Coleman's " Physiology for Beginners," Macmillan Co., N.Y. 6 ANIMAL BIOLOGY in the plant, but oxidation and growth continue ; so at night the plant actually breathes out some carbon dioxid. The deepest part of the lungs contains the most carbon dioxid. Why was it necessary to empty the lungs as nearly as possible in the experiment with the candle ? Why would first drawing a deep breath interfere with the experi- ment ? Why does closing the draught of a stove, thus shutting off part of the air, lessen the burning ? Why does a " firefly " shine brighter at each breath ? Why is the pulse and breathing faster in a fever ? Very slow in a trance ? The key for understanding any animal is to find how it gets food and oxygen, and how it uses the energy thus obtained to grow, move, avoid its enemies, and get more food. Because it moves, it needs senses to guide it. The key for understanding a plant is to find how it gets food and sunlight for its growth. It makes little provision against enemies ; its food is in reach, so it needs no senses to guide it. The plant is built on the plan of having the nutritive activities near the surface {e.g. absorption by roots ; gas exchange in leaves). The animal is built on the plan of having its nutritive activities on the inside {e.g. digestion ; breathing). Cell and Protoplasm. — Both plants and animals are composed of small parts called cells. Cells are usually microscopic in size. They have various shapes, as spheri- cal, flat, cylindrical, fiber-like, star-shaped. The living substance of cells is called protoplasm. It is a stiff, gluey fluid, albuminous in its nature. Every cell has a denser spot or kernel called a nucleus, and in the nucleus is a still smaller speck called a nucleolus. Most cells are denser and tougher on the outside, and are said to have a cell wall, but many cells are naked, or without a wall. Hence the indispensable part of a cell is not the wall but the nucleus. THE PRINCIPLES OF BIOLOGY and a cell may be defined as a bit of protoplasm containing a nucleus. This definition includes naked cells as well as cells with walls. One-celled Animals. — There are countless millions of animals and plants the existence of which was not sus- pected until the invention of the micro- scope several centuries ago. They are one-celled, and hence microscopic in size. It is believed that the large animals and plants are descended from one-celled ani- mals and plants. In fact, each individual plant or animal begins life as a single cell, called an Qg% cell, and forms its organs by the subdivision of the egg cell into many cells. An Q,^^ cell is shown in Fig. 6, and the first stages in the development of an ^^g cell are shown in Fig. 7. The animals to be studied in the first chapter are one- celled animals. To understand them we must learn how Fig. 6. — Egg cell of mammal with yolk. Fig. 7. — I .ii; subdivides into many cells forming a sphere (morula) containing a liquid. A dimple forms and deepens to form the next stage (gastrula). they eat, breathe, feel, and move. They are called Pro- tozoans (Greek protos, first; zoon, life). All other animals are composed of many cells and are called Metazoans (Greek meta, beyond or after). The cells composing the mucous membrane in man are shown in Fig. 8. The cellu- lar structure of the leaf of a many-celled plant is illustrated in Fig. 1. (See also Chap. I, Human Biology.) 8 ANIMAL BIOLOGY Method of Classifying Animals. — The various animals display differences more or less marked. The question arises, are not some of them more closely related than others } We conclude that they are, since the differ- ence between some animals is very slight, while the difference between others is quite marked. To show the different steps in classi- fying an animal, we will take an ex- ample,— the cow. Even little children learn to recognize a cow, although indi- vidual cows differ somewhat in form, size, color, etc. The varieties of cows, such as short-horn, Jersey, etc., all form one species of animals, having the scientific name taurus. Let us include in a larger group the animals closest akin to a cow. We see a cat, a bison, and a dog ; rejecting the cat and the dog, we see that the bison has horns, hoofs, and other similarities. We in- FiG. 8. — Mucous Mem- clude it with the cow in a genus called BRANE formed of one Bos, Calling the COW Bos taurus, and layer of cells. A few , , . -r. i ■ ^^-i cells secrete mucus. ^he bison, Bos bison. The sacred cow of India (Bos indicus) is so like the cow and buffalo as also to belong in the genus Bos. Why is not the camel, which, like Bos bison, has a hump, placed in the genus Bos .-• The Old World buffaloes, — most abundant in Africa and India, — the antelopes, sheep, goats, and several other genera are placed with the genus Bos in a family called the Jiollow-liorned animals. This family, because of its even number of toes and the habit of chewing the cud, resembles the camel family. THE PRINCIPLES OF BIOLOGY ' 9 the deer family, and several other families. These are all placed together in the next higher systematic unit called an order, in this case, the order of ruminants. The ruminants, because they are covered with hair and nourish the young with milk, are in every essential respect related to the one-toed horses, the beasts of prey, the apes, etc. Hence they are all placed in a more inclusive division of animals, the class called mammals. All mammals have the skeleton, or support of the body, on the inside, the axis of which is called the verte- bral column. This feature also belongs to the classes of reptiles, amphibians, and fishes. It is therefore consistent to unite these classes by a general idea or conception into a great branch of animals called the vertebrates. Returning from the general to the particular by succes- sive steps, state the branch, class, order, family, genus, and species to which the cow belongs. / The Eight Branches or Sub-kingdoms. — The simplest classification divides the whole animal kingdom into eight branches, named and characterized as follows, be- ginning with the lowest : I. Protozoans. One-celled. II. Sponges. Many openings. III. Polyps. Circular; cup-like ; having only one opening which is both mouth and vent. IV. EcHiNODERMS. Circular; rough-skinned; two openings. V. Mollusks. No skeleton ; usually with ex- ternal shell. VI. Vermes. Elongate body, no jointed legs. VII. Arthropods. External jointed skeleton; jointed legs. VIII. Vertebrates. Internal jointed skeleton with axis or backbone. CHAPTER II PROTOZOA (One-celled Animals) The Ameba Suggestions. — Amebas live in the slime found on submerged stems and leaves in standing water, or in the ooze at the bottom. Water plants may be crowded into a glass dish and allowed to decay, and after about two weeks the ameba may be found in the brown sHme scraped from the plants. An ameba culture sometimes lasts only three days. The most abundant supply ever used by the writer was from a bottle of water where some oats were germinating. Use 3^ or ^ inch objective, and cover with a thin cover glass. Teachers who object to the use of the compound microscope in a first course should require a most careful study of the figures. Fig. 9. — Ameba proteus, much enlarged. 10 i PROTOZOA II Fig. io.— Ameba. cv, contractile vacuole; ec, ectoplasm; en, endoplasm; «, nucleus; ps, pseudopod; ps' , pseudopod forming; ectoplasm pro- trudes and endoplasm flows into it. Form and Structure. — The ameba (also spelled amoeba) looks so much Hke a clear drop of jelly that a beginner cannot be certain that he has found one until it moves. It is a speck of protoplasm (Fig. 9), with a clear outer layer, the ectoplasm ; and a granular, internal part, the endoplasm. Is there a dis- tinct line between them } (Fig. 10.) Note the central portion and the slender prolonga- tions or pseudopods (Greek, false feet). Does the endoplasm extend into the pseudo- pods } (Fig. 10.) Are the pseudopods arranged with any regularity .-* Sometimes it is possible to see a denser appearing por- tion, called the nucleus ; also a clear space, the contractile vacuole (Fig. 10). Movements. — Sometimes while the pseudopods are be- ing extended and contracted, the central portion remains in the same place (this is mo- tio7i). Usually only one pseudo- pod is extended, and the body flows into it ; this is locomotioft (Fig. 11). There is a new foot made for each step. Feeding. — If the ameba crawls near a food particle, the pseudopod is pressed against it, or a depression occurs (Fig. 12), and the particle is soon embedded in the endoplasm. Often a clear space called a. food vacuole is noticed around the food particle. This is the water that is taken in with Fig. II. — The same ameba seen at different times. 12 ANIMAL BIOLOGY the particle (Fig. 12). The water and the particle are soon absorbed and assimilated by the endoplasm. Excretion. — If a particle of sand or other indigestible matter is taken in, it is left behind as the ameba moves on. There is a clear space called the contractile vacuole, which slowly contracts and disappears, then reap- pears and expands (Figs. 9 and 10), This possibly aids in excreting oxidized or useless material. Circulation in the ameba consists of the movement of its protoplasmic particles. It lacks special organs of circulation. Feeling. — Jarring the glass slide seems to be felt, for it causes the activity of the ameba to vary. It does not take in for food every particle that it touches. This may be the beginning of taste, based upon mere chemical affinity. The pseudopods aid in feeling. Reproduction. — Sometimes an ameba is seen dividing into two parts. A narrowing takes place in the middle ; the nucleus also divides, a part going to each portion (Fig. 13). The mother ameba finally divides into two daughter amebas. Sex is wanting. Source of the Ameba' s Energy. — We thus see that the ameba moves without feet, eats without a mouth, digests without a stomach, feels without nerves, and, it should also be stated, breathes without lungs, for oxygen is absorbed from the water by its whole fig. 13. — ameba, dividing. Fig. 12. — The Ameba tak- ing food. PROTOZOA 13 surface. Its movements require energy ; this, as in all ani- mals, is furnished by the uniting of oxygen with the food. Carbon dioxid and other waste products are formed by the union ; these pass off at the surface of the ameba and taint the water with impurities. Questions. — Why will the ameba die in a very small quantity of water, even though the water contains enough food? Why will it die still quicker if air is excluded from contact with the drop of water? The ameba never dies of old age. Can it be said to be immortal? According to the definition of a cell {Chapter I), is the ahieba a unicellular or multicellular animal? Cysts. — If the water inhabited by a protozoan dries up, it encysts, that is, it forms a tough skin called a cyst. Upon return of better conditions it breaks the cyst and comes out. Encysted protozoans may be blown through the air : this explains their appearance in vessels of water containing suitable food but previously free from proto- zoans. The Slipper Animalcule or Paramecium Suggestions. — Stagnant water often contains the Paramecium as well as the ameba ; or they may be found in a dish of water con- taining hay or finely cut clover, after the dish has been allowed to stand in the sun for several days. A white film forming on the surface is a sign of their presence. They may even be seen with the unaided eye as tiny white particles by looking through the side of the dish or jar. Use at first z \ ox \ in. objective. Restrict their movements by placing cotton fibers beneath the cover gjass ; then examine with 3^ or ^ objective. Otherwise, study figures. Shape and Structure. — The Paramecium's whole body, like the ameba's, is only one cell. It resembles a slipper in shape, but the pointed end is the hind end, the front end being rounded (Fig. 14). The paramecium is propelled by the rapid- beating of numerous fine, threadlike append- 14 ANIMAL BIOLOGY ages on its surface, called cilia (Latin, eyelashes) (Figs.). The cilia, like the pseudopods of the ameba, are merely prolongations of the cell protoplasm, but they are permanent. The sepa- ration between the outer ectoplasm. and the interior granular endoplasm is more marked than in the ameba (Fig. 14). Nucleus and Vacuoles. — There is a large nucleus called the macro- nucleus, and beside it a smaller one called the micronucleus. They are hard to see. About one third of the way from each end is a clear, pul- sating space (bb. Fig. 15) called the pulsat- ing vacuole. These spaces contract until they disappear, and then reappear, gradually ex- panding. Tubes lead froln the vacuoles which probably serve to keep the contents of the cell in circulation. Feeding. — A depression, or groove, is seen on one side, this serves as a mouth (Figs.). A tube which serves as a gullet leads from the mouth-groove to the in- terior of the cell. The mouth-groove is lined with cilia which sweep food particles inward. Fig. 14. — Paramecium, showing cilia, c. Two contractile vacuoles, cv, the macronucleus, tng; two micronuclei, mi; the gullet (CE), a food ball forming and ten food balls in their course from gullet to vent, a. Fig. 15, Fig. 16, ■ •Two Paramecia exchanging parts of their nuclei. The particles accumulate PROTOZOA 15 in a mass at the inner end of the gullet, become separated from it as a food ball{Y\%. 14), and sink into the soft pro- toplasm of the body. The food balls follow a circular course through the endoplasm, keeping near the ectoplasm. Reproduction. — This, as in the ameba, is by division, the constriction being in the middle, and part of the nucleus going to each half. Sometimes two individ- uals come together with their mouth-grooves touching and exchange parts of their nuclei (Fig. 16). They then separate and each divides to form two new individuals. We thus see that the Para- mecium, though of only one cell, is a much more complex afid advanced animal than the ameba. The tiny paddles, or cilia, the mouth-groove, etc., have their special duties similar to the specialized organs of the many-celled animals to be studied later. If time and circumstances allow u prolonged study, sev- eral additional facts may be observed by the pupil, e.g. Does the paramecium swim with the same end always foremost, and same side uppermost .-' Can it move backwards .'' Avoid obsta- cles "i Change shape in a narrow passage } Does refuse fig. 19. — shell of a radiolarian. Fig. 17. — VoKTi- cella (or bell animalcule), two extended, one withdrawn. Fig. 18.— Euglena. l6 ANIMAL BIOLOGY matter leave the body at any particular place ? Trace movement of the food particles. Draw the Paramecium. Which has more permanent parts, the ameba or para- meciiim ? Name two anatomical similarities and three dif- ferences ; four functional similarities and three differences. The ameba belongs in the class of protozoans called Rhizopoda "root footed." Other classes of Protozoans are the Infusorians (in the broad sense of the term), which have many waving cilia (Fig. 17) or one whip-Hke fiagellum (Fig. 18), and the Foraminifers , which possess a calcareous shell pierced with holes (Fig. 19). Much chalky limestone has been formed of their shells. To which class does the parameciftm belong } Protozoans furnish a large amount of food to the higher animals. To the Teacher. If plant, animal, and human biology are to be given in one year as planned, and full time allowed for practical work, the portions of the text in small type, as Chapter III, may be omitted or merely read and discussed. Any two of the three parts forming the course may be used for a year's course by using all of the text and spending more time on practical and field work. CHAPTER III SPONGES Suggestions. — In many parts of the United States, fresh-water sponges may, by careful searching, be found growing on rocks and logs in clear water. They are brown, creamy, or greenish in color, and re- semble more a cushion-like plant than an animal. They have a char- acteristic gritty feel. They soon die after removal to an aquarium. A number of common small bath sponges may be bought and kept for use in studying the skeleton of an ocean sponge. These sponges should not have large holes in the bottom ; if so, too much of the sponge has been cut away. A piece of marine sponge preserved in alco- hol or formalin may be used for showing the sponge with its flesh in place. Microscopic slides may be used for showing the spicules. The small fresh-water sponge (Fig. 21) lacks Fig. 21. Fresh-water Sponge. the more or less vase- like form typical of sponges. It is a rounded mass growing upon a rock or log. As indicated by the arrows, where does wafer enfer the sponge? This may be tested by putting color- ing matter in the water near the living sponge. Where does the water come out'i (Fig. 22.) Does it pass through ciliated chambers in its course ? Is the n^k^^^ w- Fig. 22. — Section of fresh-water sponge (enlarged). c 17 i8 ANIMAL BIOLOGY Fig. 23.- ■ Ek5GS and spici^les of fresh-water sponge (enlarged). surface of the sponge rough or smooth ? Do any of the skeletal spicules show on the surface? (Fig. 21.) Does the sponge thin out near its edge? The egg of this sponge is shown in Fig. 23. It escapes from the parent sponge through the osculum, or large outlet. As in most sponges, the first stage after the egg is f- 'I il II (P'^'MBl WH.'-^'-^ IbHUPM W *' ciliated and free-swim- ^' ;-=... tning. Marine Sponges. — The grantia (Fig. 24) is one of the simplest of marine sponges. What is the shape of grantia ? What is its length and diameter? How does the free end differ from the fixed end? Are the spicules projecting from its body few or many? Where is the osculum, or large outlet? With what is this surrounded? The osculum opens from a central cavity called the cloaca. The canals from the pores lead to the cloaca. Buds are sometimes seen growing out from the sponge near its base. These are young sponges formed asexually. Later they become detached from the parent sponge. Commercial " Sponge." — What part of the complete animal remains in the bath sponge? Slow growing spo7iges grow more at the top and form tall, simple, tubular or vase-like animals. Fast growing sponges grow on all sides at once and form a complicated system of canals, pores, and oscula. Which of these habits of growth do you think belonged to the bath sponge ? Is there a large hole in the base of your specimen ? If so, this is because the cloaca was reached in trimming the lower part where it was attached to a rock. Test the elasticity of the sponge when dry and when wet by squeezing it. Is it softer when wet V ^??<2s<5<^<^^ or dry? Is it more elastic when wet or dry? Fig. 21; —Plan of How many oscula does your specimen have? a sponge. How many inhalent pores to a square inch? Fio. 24. - Grantia. SPONGES 19 Using a probe (a wire with knob at end, or small hat pin), try to trace the canals from the pores to the cavities inside. Do the fibers of the sponge appear to interlace, or join, according to any system ? Do you see any fringe-Hke growths on the surface which show that new tubes are be- ginning to form? Was the sponge growing faster at the top, on the sides, or near the bottom ? Burn a bit of the sponge ; from the odor, what would you judge of its composition? Is the inner cavity more conspicuous in a simple sponge or in a compound sponge hke the bath sponge? Is the bath sponge Fig. 26. — Bath Sponge. Fig. 27. — Bath Sponge. Fig. 28. — Bath Sponge. branched or lobed? Compare a number of specimens (Figs. 26, 27, 28) and decide whether the common sponge has a typical shape. What features do their forms possess in common? Sponges are divided into three classes, according as their skeletons are flinty (silicious), limy (calcareous), or horny. Some of the silicious sponges have skeletons that resemble spun glass in their deHcacy. Flint is chemically nearly the same as glass. The skeleton shown in Fig, 29 is that of a glass sponge which lives near the Philippine Islands. The horny sponges do not have spi- cules in their skeletons, as the flinty and FiG.29.-Skeietonofa ^^^^ sponges have, but the skeleton glass sponge. is Composed of interweaving fibers of 20 ANIMAL BIOLOGY ii- •ijiiTgj'',;/>^ Fig. 30. — A horny sponge. spongin, a durable substance of the same chemical nature as silk (Figs. 30 and 31). The limy sponges have skeletons made of numerous spicules of lime. The three-rayed spicule is the commonest form. The commercial sponge, seen as it grows in the ocean, appears as a roundish mass with a. smooth, dark exterior, and having about the consistency of beef liver. Several large openings (oscula), from which the water flows, are visible on the upper surface. Smaller holes (inhalent pores — many of them so small as to be indistinguishable) are on the sides. If the sponge is disturbed, the smaller holes, and perhaps the larger •ones, will close. The outer layer of cells serves as a sort of skin. Since so much of the sponge is in contact with water, most of the cells do their own breathing, or absorp- tion of oxygen, and giving off of carbon dioxid. Nutriment is passed on from the surface cells to nourish the rest of the body. Reproduction. — Egg-cells and sperm-cells are produced by certain cells along the canals. The egg-cell, after it is fertilized by the sperm-cell, begins to divide and form new cells, some of which possess cilia. The embryo sponge passes out at an oscu- lum. By the vibration of the cilia, it swims about for a while. It afterwards settles down with the one end attached to the ocean floor and remains fixed for the rest of its life. The other end de- velops oscula. Some of the cilia continue to vibrate and create currents which bring food and oxygen. The cilia in many species are found only in cavities called ciliated chambers. (Figs. 22, 32.) There are no distinct organs in the sponge and there is very little specialization of cells. The ciliated cells and the reproductive cells are the only specialized cells. The sponges were for a long time considered as colonies of separate one-celled animals classed as protozoans. They are Fig. 31. — Section of horny sponge. SPONGES 21 without doubt, many-celled animals. If a living sponge is cut into pieces, each piece will grow and form a complete sponge. That the sponge is not a colony of one-celled animals, each like an ameba, but is a many-celled animal, will be realized by exam- ining Fig. 32, which shows a bit of sponge highly magnified. A sponge may be conceived as having developed from a one-celled animal as follows : Sev- eral one-celled animals happened to live side by side ; each possessed a thread-like flagellum (E, Fig. 32) or whip-lash for striking the water. By lashing the water, they caused a stronger cur- rent (Fig. 25) than pro- tozoans living singly could cause. Thus they obtained more food and multiplied more rapidly than those living alone. The habit of working together left its impress on the cells and was trans- mitted by inheritance. Cell joined to cell formed a ring ; ring Fig. 32. — Microscopic plan of ciliated chamber. E^ch cell lining the chamber has a nucleus, a whip-lash, and a collar around base of whip-lash. Question : State two uses of whip-lash. joined to ring formed a tube which was still more effective than a ring in lashing the water into a current and bringing fresh food (particles of dead plants and animals) and oxygen. Few animals eat sponges ; possibly because spicules, or fibers, are found throughout the flesh, or because the taste and odor are unpleasant enough to protect them. Small animals sometimes crawl into sponges to hide. One sponge grows upon shells in- habited by hermit crabs. Moving of the shell from place to place is an advantage to the sponge, while the sponge conceals and thus protects the crab. Special Report : Sponge " Fisheries." (Localities; how sponges are taken, cleaned, dried, shipped, and sold.) CHAPTER IV POLYPS (CUPLIKE ANIMALS) Fig. 33. — A Hydra. The Hydra, or Fresh Water Polyp Suggestions. — Except in the drier regions of the United States, the hydra can usually be found by careful search in fresh water ponds not too stagnant. It is found attached to stones, sticks, or leaves, and has a slender, cylindrical body from a quarter to half an inch long, varying in thickness from that of a fine needle to that of a common pin. The green hydra and the brown hydra, both very small, are common species, though hydras are often white or colorless. They should be kept in a large glass dish filled with water. They may be distinguished by the naked eye bUt are not studied satisfactorily without a magnifying glass or microscope. Place a living specimen attached to a bit of wood in a watch crystal filled with water, or on a hol- lowed slip, or on a slip with a bit of weed to support the cover glass, and examine with hand lens or lowest power of microscope. Prepared microscopical sections, both transverse and longitudinal, may be bought ofdealers in mi- croscopic sup- plies. One is shown in Fig. 39. Is the hy- dra's body round or two- sided .? (Fig. 35.) What is its general shape ? shape .? (Fig. 34.) Fig. 34. — Forms assumed by Hydra. Does one individual keep the same How does the length of the thread- POLYPS {CUPLIKE ANIMALS^ 23 like tentacles compare with the length of the hydra's body ? About how many tentacles are on a hydra's body ? Do all have the same number of tentacles ? Are the tentacles knotty or smooth ? (Fig. 35.) The hydra is usually ex- tended and slender ; sometimes it is contracted and rounded. In which of these conditions is the base (the foot) larger around than the rest of the body .-* (Fig. 34.) Smaller 1 How many openings into the body are visible } Is there a depression or an eminence at the base of the tentacles .-• For what is the opening on top of the body probably used ? Why are the tentacles placed at the top of the hydra's body } Does the mouth have the most con- venient location possible ? The conical projection bear- ing the mouth is called hypo- stome (Fig. 34). The mouth opens into the digestive cavity. Is this the same as the general body cavity, or does the stomach have a wall distinct from the body cavity ? How far down does the body cavity extend } Does it extend up into the tentacles .-' (Fig. 39,) If a tentacle is touched, what happens? Is the body ever bent? Which is more sensitive, the columnar body or the tentacles ? In searching for hydras would you be more likely to find the ten- tacles extended or drawn in? Is the hypostome ever extended or drawn in? (Fig. 34.) Locomotion. — The round surface, or disk, by which the hydra is attached, is called its foot. Can you move on one foot without hopping? The hydra moves by alter- FiG. 35. — Hydra (much enlarged) . 24 ANIMAL BIOLOGY Fig. 36. — Nettlinc; Cki.l. II. discharged, and I. not discharged. nately elongating and rounding the foot. Can you dis- cover other ways by which it moves? Does the hydra always stand upon its foot ? Lasso Cells. — Upon the tentacles (Fig. 35) are numer- ous cells provided each with a thread-like process (Fig. 36) which lies coiled within the cell, but which may be thrown out upon a water flea, or other minute animal that comes in reach. The touch of the lasso paralyzes the prey (Fig. 37). These cells are variously called lasso cells, nettling cells, or thread cells. The thread is hollow and is pushed out by the pressure of hquid within. When the pressure is withdrawn the thread goes back as the finger of a glove may be turned back into the glove by turning the finger outside in. When a minute animal, or other particle of food comes in contact with a tentacle, how does the tentacle get the food to the mouth .-' By bending and bringing the end to the mouth, or by shortening and changing its form, or in both ways } (Fig. 34, C^ Do the neighboring tentacles seem to bend over to assist a tentacle in securing prey .? (Fig. 34, C.) Digestion. — The food parti- FiG. 37. — Hydra captunng a cles break up before remaining water flea. POLYPS {^CUPLIKE ANIMALS) 25 long in the stomach, and the nutritive part is absorbed by the lining cells, or endoderm (Fig. 39). The indiges- tible remnants go out through the mouth. The hydra is not provided with a special vent. Why could the vent not be situated at the end opposite the mouth } Circulation and Respiration. — Does water have free access to the body cavity ? Does the hydra have few or nearly all of its cells exposed to the water in which it lives ? From its structure, decide whether it can breathe like a sponge or whether special respiratory cells are necessary to supply it with oxygen and give off carbon dioxid. Blood vessels are unnecessary for transfer- ring oxygen and food from cell to cell. Reproduction. — Do you see any swellings upon the side of the hydra ? (Fig. 34, A.) If the swelling is near the tentacles, it is a spermary ; if near the base it is an ovary. A sperm coalesces with or fertilizes the ovum after the ovum is exposed by the breaking of the ovary wall. Sometimes the sperm from one hydra unites with the ovum of another hydra. This is called cross-fertilization. The same term is applied to the process in plants when the male element, developed in the pollen of the flower, unites with the female element of the ovule of the flower on another plant. The hydra, like most plants and some other animals, is hermaphrodite, that is to say, both sperms and ova are produced by one individual. In the autumn, eggs are produced with hard shells to withstand the cold until spring. Sexual reproduction takes place when food is Fig. 38. — Hydras on pondweed. 26 ANIMAL BIOLOGY OVARY- OVUM scarce. Asexual generation (by budding) is common with the hydra when food supply is abundant. After the bud grows to a cer- tain size, the outer layer of cells at the base of the bud con- stricts and the young hydra is detached. Compare the sponge and the hydra in the fol- lowing respects : — many celled, or one celled ; obtaining food ; breathing; tubes and cavities ; openings ; re- production ; loco- motion. Which ranks higher among the metazoa ,'' The metazoa, or many celled ani- mals, include all animals except which branch ? Figure 39 is a microscopic view of a vertical section of a hydra to show the structure of the body wall. There is an outer layer called the ectoderm, and an inner layer called the endoderm. There is also a thin supporting layer (black in the figure) called the mesoglea. The mesoglea is the thinnest layer. Are the cells larger in the endoderm or the ectoderm ? Do both layers of cells assist in forming the reproductive bud ? The ecto- derm cells end on the inside in contractile tails which form a thin line and have the effect of muscle fibers. They serve the hydra for its remarkable changes of shape. When the bydra is cut in pieces, each piece makes complete hydra, provided it contains both endoderm and ectoderm, j c. Fig. 39. — Longitudinal section of hydra (microscopic and diagrammatic). 4 \ POLYPS {CUPLIKE ANIMALS') 2/ In what ways does the hydra show '■'■ division of labor " ? Answer this by explaining the classes of cells specialized to serve a different purpose. Which cells of the hydra are least specialized? In what par- ticulars is the plan of the hydra different from that of a simple sponge ? An ingenious naturalist living more than a century ago, asserted that it made no difference to the hydra whether the ectoderm or the endoderm layer were outside or inside, — that it could digest equally well with either layer. He allowed a hydra to swallow a worm attached to a thread, and then by gently pulling in the thread, turned the hydra inside out. More recently a Japanese naturalist showed that the hydra could easily be turned inside out, but he also found that when left to itself it soon reversed matters and returned to its natural condition, that the cells are really specialized and each layer can do its own work and no other. Habits. — The hydra's whole body is a hollow bag, the cavity extending even into the tentacles. The tentacles may increase in number as the hydra grows but seldom exceed eight. The hydra has more active motion than locomotion. It seldom moves from its place, but its ten- tacles are constantly bending, straightening, contracting, and expanding. The body is also usually in motion, bend- ing from one side to another. When the tentacles ap- proach the mouth with captured prey, the mouth (invisible without a hand lens) opens widely, showing five lobes or lips, and the booty is soon tucked within. A hydra can swallow an animal larger in diameter than itself. The endoderm cells have ameboid motion, that is, they extend pseudopods. They also resemble amebas in the power of intra-celliilar digestion ; that is, they absorb the harder particles of food and digest them afterwards, re- jecting the indigestible portions. Some of these cells have flagella (see Fig. 39) which keep the fluid of the cavity in constant motion. Sometimes the hydra moves after the manner of a small caterpillar called a " measuring worm," that is, it takes hold first by the foot, then by the tentacles, looping its 28 ANIMAL BIOLOGY Fig. 40.— Hydroid Colony, with nutritive (P) reproductive (A/) and defensive (S) hydranths. body at each step. Sometimes the body goes end over end in slow somersaults. The length of the extended hydra may reach one half inch. When touched, both tentacles and body contract until it looks to the unaided eye like a round speck of jelly. This shows sensibility, and a few small star-shaped cells are believed to be nerve cells, but the hydra has not a nervous system. Hydras show their liking for light by moving to the side of the vessel or aquarium whence the light comes. The Branch Polyps (sometimes called Coelen- teratd). — The hydra is the only fresh water rep- resentative of this great branch of the animal kingdom. This branch is characterized by its members having only one opening to the body. The polyps also include the salt water animals called hydroids, jelly- fishes, and coral polyps. Hydroids. — Figure 40 shows a hydroid, or group of hydra-like growths, one of which Fig. 41. — " Portuguese Man-o'-war" (compare with Fig. 40). A floating hydroid colony with long, stinging (and sensory) streamers. Troublesome to bathers in Gulf of Mexico. Notice balloon-like float. POLYPS {CUPLIKE ANIMALS) 29 eats and digests for the group, another defends by nettling cells, another produces eggs. Each hydra-Hke part of a hydroid is called a hydranth. Sometimes the buds on the hydra remain attached so long that a bud forms upon the first bud. Thus three generations are represented in one organism. Such growths show us that it is not always easy to tell what consti- tutes an indi- vidual animal. Hydro ids may be con- ceived to have been developed by the failure of budding hy- dras to sepa- rate from the parent, and by the gradual formation of the habit of living together and assisting each other. When each hydranth of the hydroid devoted itself to a special function of digestion, defense, or reproduction, this group lived longer and prospered ; more eggs were formed, and the habits of the group were trans- mitted to a more numerous progeny than were the habits of a group where members worked more independently of each other. As the sponge is a simple example of the devotion of special cells to special purposes, the hydroid is a primitive and simple example of the occurrence of organs, that is of special parts of the body set aside for a special work. Fig. 42. — The formation of many free swimming jelly- fishes from one fixed hydra-like form. The saucer-like parts (A) turn over after they separate and become like Fig. 43 or 44. Letters show sequence of diagrams. 30 ANIMAL BIOLOGY How many mature hydranths are seen in the hydroid shown in Fig. 40? Why are the defensive hydranths on the outside of the colony ? Which hy- dranths have no tenta- cles ? Why not ? Jellyfish. — Alterna- tion of Generations. — Medusa. — With some species of hydroids, a very curious thing hap- pens. — The hydranth that is to produce the eggs falls off and be- comes independent of the colony. More sur- prising still, its appear- ance changes entirely and instead of being hydra-like, it becomes the large and complex creature called jellyfish (Fig. 43). But the egg of the jellyfish pro- duces a small hydra- like ani- mal-^Yi^c^ gives rise by budding to a hydroid, and the cycle is complete. The bud (or reproductive hydranth) of the hydroid Fig. 44. — a jellyfish (medusa). .. Hj— A Jellyfish. POLYPS {CUPLIKE ANIMALS) 3 1 does not produce a hydroid, but a jellyfish ; the egg of the jellyfish does not produce a jellyfish, but a hydroid. This is called by zoologists, alternation of generations. A complete individual is the life from the germination of one Qgg to the production of another. So that an "individual" con- sists of a hydroid colony fixed in one place together with all the jellyfish produced from its buds, and which may now be floating miles away from it in the ocean. Bathers in the surf are sometimes touched and stung by the long, streamer-like tentacles of the jellyfish. These, like the tentacles of the hydra, have nettling cells (Fig. 41). The umbrella-shaped free swimming jellyfish is called a medusa (Fig. 44). Coral Polyps. — Some of the salt water relatives of the hydra produce buds which remain attached to the parent without, p,^, 45.- coral polyps (.enta- however, becoming different cies, a multiple of six). Notice c .-> ^ . hypostome. from the parent in any way. The coral polyps and corallines are examples of colonics of this kind, possessing a common stalk which is formed as the process of multiplication goes on. In the case of coral polyps, the separate animals and the flesh connecting them secrete within themselves a hard, limy, supporting structure known as coral. In some species, the coral, or stony part, is so developed that the polyp seems to be inserted in the coral, into which it withdraws itself for partial protection (Fig- 45). The corallines secrete a smooth stalk which affords no protection, but they also secrete a coating or sheath which incloses both themselves and the stalk. The 32 ANIMAL BIOLOGY coating has apertures through which the polyps pro- trude in order to feed when no danger is near (Fig. 46). Fig. 46. — Red Coral- line with crust and polyps (eight tentacles) . Fig. 47. — Sea Fan (a The red " corals " used for jewelry are bits of stalks of cor- allines. The corallines (Figs. 47, 48) are not so abundant nor so important as the coral polyps (Figs. 45, 49). Colonies of coral polyps grow in countless numbers in the tropical seas. The coral formed by successive colo- nies of polyps accu- mulates and builds up many islands FIG. 48. - ORGAN PIPE '• Coral •• (a coralline) . ^^^ important addi- tions to continents. The Florida " keys," or islands, and the southern part of the mainland of Florida were so formed. POLYPS {CUPLIKE ANIMALS') 33 The Sea Anemone, like the coral polyp, lives in the sea, but like the fresh water hydra, it deposits no limy support for its body. The anemone is much larger than the hydra and most coral polyps, many spe- cies at- taining a height of several inches. It does not form colo- nies. When its arms are drawn in, it looks Hke a large knob of shiny but opaque jelly. Polyps used to be called zoophytes {plant- animals), because of their flower-like appearance (Figs. 50, 51). Fig. 49. — Upright cut through coral polyp X 4. nts, mouth; mr, gullet; k, h, fleshy partitions (mesen- teries) extending from outer body wall to gullet (to in- crease absorbing surface) ; J, s, shorter partitions ; mb, Jb, stony support (of lime, called coral) ; t, tentacles. Fig. 50. — Sea Anemone. Fig. 51. — Sea Anemones, CHAPTER V ECHINODERMS (SPINY ANIMALS) Fig. 52. — Starfish on a rocky shore. The Starfish Suggestions. Since the echinoderms are aberrant though inter- esting forms not in the regular line of development of animals, this chapter may be omitted if it is desired to shorten the course. — The common star- fish occurs along the At- lantic coast. It is captured by wading along the shore when the tide is out. It is killed by immersion in warm, fresh water. Specimens are usually preserved in 4 per cent formalin. Dried starfish and sea urchins are also useful. A living starfish kept in a pail of salt water will be instructive. \. / f \ / External Features. — Starfish are usually brown or yellow. Why? (See Fig. 52.) Has it a head or tail ? Right and left sides ? What is the shape of the disk, or part which bears the five arms or rays ? (Fig. 53.) Does the body as a whole have symmetry on two sides of a line (bilateral symmetry), or around a point (radial symmetry) ? Do the separate rays have 34 Plan of starfish madreporite. ECHINODERMS {SPINY ANIMALS) 35 Fig. 54. — Limy Plates in portion of a ray. Fig. 55. — Starfish (showing Madreporite). bilateral symmetry ? The skeleton consists of limy plates embedded in the tough skin (Fig. 54). Is the skin rough or smooth? Hard or soft? Are the projections (or spines) in the skin long or short? The skin is hardened by the limy plates, ex- cept around the mouth, which is at the center of the lower side and surrounded by a mem- brane. Which is rougher, the mouth side, (tfnz/side) or the opposite {aboral %\dt) ? Which side is more nearly flat ? The vent is at or near the center of the disk on the aboral surface. It is usually very small and sometimes absent. Why a vent is not of much use will be understood after learning how the starfish takes food. An organ peculiar to animals of this branch, and called the madreporic plate, or madreporite, is found on the aboral surface between the bases of two rays (Fig. 55). It is wartlike, and usually white or red. This plate is a sieve ; the small openings keep out sand but allow water to filter through. Movements : the Water-tube System. — The water, which is filtered through the perforated madreporite, is needed to supply a system of canals (Fig. 56). The madreporite opens into a canal called the stone canal, the wall of which is hardened by the same kind of mate- rial as that found in the skin. The stone canal leads to the ring capiat which sur- rounds the mouth (Fig. 56). The ring canal sends radial canals into each ray to supply the double row of tube feet found in the groove at the lower side of each ray (Fig. 57). Because of their arrangement in rows, the feet are 'H Fig. 56. — Water tube System of starfish. vt, madreporite; stc, stone canal; ap, ampulla. 36 ANIMAL BIOLOGY also called ambulacral feet (Latin ambulacra, "forest walks"). There is a water holder {ampulla), or muscular water bulb at the base of each tube foot (Fig. 58). These con- tract and force the water into the tube feet and extend them. The cuplike ends of the tubes cling to the ground by suction. The feet contain delicate muscles by which they contract and shorten. Thus the animal pulls itself slowly along, hundreds of feet acting together. The tube feet, for their own protection, may contract and retire into the groove, the water which extended them being sent back into the ampulla. This system of water vessels (or water- 1 'w vascular system) of the echinodermata is characteristic of them ; /./%tf^t tube feet more or less extended; au, eye spot; ^, gills; da, stomach; nt, madreporite; j/, stone canal; /, ampulla; ei, ovary. ECHINODERMS {SPINY ANIMALS) 37 Respiration. — The system of water vessels serves the additional purpose of bringing water containing oxygen into contact with various parts of the body, and the starfish was formerly thought to have no special respiratory organs. However there are holes in the aboral wall through which the folds of the delicate lining mem- brane protrude. These are now supposed to he gills {k, Fig. 58). The nervous system is so close to the aboral surface that much of it is visible without dissection. Its chief parts are a nenie ring around the mouth, which sends off a branch along each ray. These branches may be seen by separating the rows of tube feet. They end in a pigmented cell at the end of each ray called the eye-spot. The food of starfish consists of such animals as crabs, snails, and oysters. When the prey is too large to be taken into the mouth, the starfish turns its stomach inside out over the prey (Fig. 59). After the shells separate, the stomach is applied to the soft digestible parts. After the animal is eaten, the stomach Fig. 59. — Starfish eat- is retracted. This odd way of eating is very '"^ ^ ^^* ^"^"- 1 . .. J. ,. r 7 3, Stomach everted. economical to its digestive powers, for only that part of the food which can be digested and absorbed is taken into the body. Only the lower part of the stomach is wide and extensible. The upper portion (next to the aboral surface) is not so wide. This portion receives the secretion from five pairs of digestive glands, a pair of which is situated in each ray. Jaws and teeth are absent. (Why?) The vent is sometimes wanting. Why ? Reproduction. — There is a pair of ovaries at the base of each ray of the female starfish (Fig. 58). The spermaries of the male have the same position and form as the ovaries, but they are lighter colored, usually white.^ Regeneration after Mutilation. — If a starfish loses one or more rays, they are replaced by growth. Only a very ignorant oyster- man, angry at the depredations of starfish upon his oyster beds, ^The sperm cells and egg cells are poured out into the water by the adults, and the sperm cell, which, like nearly all sperm cells, has a vibratory, tail- like flagellum to propel it, reaches and fertilizes the egg cell. 38 ANIMAL BIOLOGY would chop starfish to pieces, as this only serves to multiply them. This power simulates multiplication by division in the simplest animals. Steps in Advance of Lower Branches. — The starfish and other echinodermata have a more developed nervous system, sensory organs, and digestion, than forms previously studied ; most dis- tinctive of all, they have a body cavity distinct from the food cavity. The digestive glands, reproductive glands, and the fluid which serves imperfectly for blood, are in the body cavity. There is no heart or blood vessels. The motions of the stomach and the bend- ing of the rays give motion to this fluid in the body cavity. It cannot be called blood, but it contains white blood corpuscles. The starfish when first hatched is an actively swim- ming bilateral animal, but it soon becomes starlike (Fig. 60). The limy plates of the starfish belong neither to the outer nor inner layer (endoderm and ectoderm) of the body wall, but to a third or middle layer (mesoderm) ; for echinoderms, like the polyps, belong to the three-layered animals. In this its skeleton differs from the shell of a crawfish, which is formed by the hardening of the skin itself. Protective Coloration. — Starfish are brown or yellow. This makes them inconspicuous on the brown rocks or yellow sands of the seashore. This is an example of protective coloration. Fig. 60. — Young starfish crawling upon their mother. (Challenger Reports.) The Sea Urchin External Features. — What is the shape of the body? What kind of symtnetry has it? Do you find the oral (or mouth) sur- face ? The aboral surface ? Where is the body flattened ? What is the shape of the spines? What is their use? How are the tube ECHINODERMS {SPINY ANIMALS) 39 feet arranged ? Where do the rows begin and end ? Would you think a sea urchin placed upside down in water, could right itself less or more readily than a star- fish ? What advantage in turn- ing would each have that the other would not have? The name sea urchin has no refer- ence to a mischievous boy, but means sea hedgehog (French oursiti, hedgehog), the name beijig suggested by its spines. Compariscn of Starfish and Sea Urchin. — The water sys- tem of the sea urchin, consist- ing of madreporite, tubes, and water bulbs, or ampullae, is similar to that of the starfish. The tube feet and locomotion are alike. There is no need for well-developed respiratory organs in either animal, as the whole body, inside and out, is bathed in water. The method of repro- duction is the same. The starfish eats soft animal food. The food of the sea urchin is mainly vegetable, and it needs teeth (Fig. 62, 63 ) ; Fig. 61. — A Sea Urchin crawling up the glass front wall of an aquarium (showing mouth spines and tube feet j. ^MylliL^^), / y\J/ Fig. 62. — A Sea Urchin with spines removed, the limy plates showing the knobs on which the spines grew. Fig. 63. — Sechon ok Sea Urchin with soft parts removed, showing the jaws which bear the teeth protruding in Fig. 62. its food tube is longer than that of a starfish, just as the food tube of a sheep, whose food digests slowly, is much longer than that of a dog. 40 ANIMAL BIOLOGY .-^S-^^rK" r\ Fig. 64. —The Sea Ot- ter, an urchin with mouth ((?) and vent (A) on same side of body. The largest species of sea urchins are almost as big as a child's head, but such size is unusual. The spines are mounted on knobs, and the joint resembles a ball-and-socket joint, and allows a wide range of movement. Some sea urchins live on sandy shores, other species live upon the rocks. The sand dollars are lighter colored. (Why?) They are usu- ally flatter and have lighter, thinner walls than the other species. The five- holed sand cake or sand dollar has .its weight still further diminished by the holes, which also allow it to rise more easily through the water. Both starfish and sea urchin rest on the flattened lower surface of the body, while the tube feet are stretching for- ward for another step. Other Echinoderms The sea cucumbers, or holothurians, re- semble the sea urchin in many respects, t iG. 05. — Sea Cucumbers. but their bodies are elon- gated, and the'limy plates are absent or very mi- nute. The mouth is sur- rounded by tentacles (Fig. 65). The brittle stars resem- ble the starfish in form, but their rays are very slender, more distinct from the disk, and the tube feet are on the edges of the rays, not under them (Fig. 66). Fig. 66. — A Brittle Star. ECHINODERMS {SPINY ANIMALS) 41 Fig. 67.— Crinoid, arms closed. The crinoids are the most ancient of the echino- derms. (Figs. 67, 68.) Their fossils are very abundant in the rocks. They inhabited the geological seas, and it is believed that some of the other echinoderms de- scended from them, A few now inhabit the deep seas. Some species are fixed by stems when young, and later break away and become free- swimming, others remain fixed throughout life. The four classes of the branch echinoderms are Starfish {asteroids). Sea urchins {echinoids), Sea cucumbers (holothurians), and Sea lilies (crinoids). Comparative Review Make a table like this as large as the page of the notebook will allow, and fill in without guessing. Fig. 68. — Disk of Cri- noid from above, show- ing mouth in center and vent near it, at right (arms removed). Ameba Sponge Hydra Coral Polyp Starfish Is body round, two- sided, or irregular What organs of sense Openings into body Hard or supporting parts of body How food is taken How move How breathe CHAPTER VI WORMS Suggestions : — Earthworms may be found in the daytime after a heavy rain, or by digging or turning over planks, logs, etc., in damp places. They may be founc^ on the surface at night by searching with a lantern. Live specimens may be kept in the laboratory in a box packed with damp (not wet) loam and dead leaves. They may be fed on bits of fat meat, cabbage, onion, etc., dropped on the surface. When studying Uve worms, they should be allowed to crawl on damp paper or wood. An earth- worm placed in a glass tube with rich, damp soil, may be watched from day to day. External Features. — Is the body bilateral f Is there a dorsal and ventral surface .-' Can you show this by a test with live worm .-' Do you know of an animal with dorsal and ventral surface, but not bilateral .-' Can you make out a head .? A head end .-* A neck } Touch FIG. 69. -AN EARTHWORM. ^^^ ^^^j ^^^ ^gg^. whether it can be made to crawl backwards. Which end is more tapering .? Is the mouth at the tip of the head end or on the upper or lower surface } How is the vent situated .'' Its shape .-' As the worm lies on a horizontal surface, is the body anywhere flattened } Are there any very distinct divisions in the body ? Do you see any eyes ? Experiment to find whether the worm is sensitive (i) to touch, (2) to light, (3) to strong odors, (4) to irritating liquids. Does it show a sense of taste? The experiments should show whether 42 WOJiMS 43 Fig. 70. — Mouth and Set^, it avoids or seeks a bright light, as a window ; also whether any parts of the body are especially sensitive to touch, or all equally sensitive. What effect when a bright light is brought suddenly near it at night ? Is red blood visible through the skin ? Can you notice any pulsations in a vessel along the back ? Do all earth- worms have the same number of divisions or rings ? Com- pare the size of the rings or segments. Can it crawl faster on glass or on paper } A magnifying glass will show on most species tiny bristle- like projections called setcB. How are the setae arranged .'' {d, Fig. 70.) How many on one ring of the worm .-' How do they point } Does the worm feel smoother when it is pulled forward or backward between i| the fingers .'' Why } Are setae on the lower sur- face .'' Upper surface .-' The sides .'* What is the use of the setae } Are they useful below ground } Does the worm move at a uniform rate .-' What change in form occurs as the front part of the body is pushed forward .-' As the hinder part is pulled onward } How far does it go at each movement } At certain seasons a broad band, or ring, appears, covering several segments and making them seem enlarged (Fig. 71). This is the clitelluin, or reproductive girdle. Is this girdle Earth- nearer the mouth or the tail } WORM, TN 1 • r , mouth end Draw the exterior of an earthworm. above. Doisal and Ventral Surfaces. — The earthworm always crawls with the same surface to the ground ; this is called the vejitral surface, the opposite surface is the dorsal surface. This is the first animal studied to which ^>c ANIMAL BIOLOGY these terms are applicable. What are the ventral and dorsal surfaces of a fish, a frog, a bird, a horse, a man ? The name " worm " is often carelessly applied to various crawling things in general. It is prop- erly applied, however, only to segmented animals without jointed appendages. Although a caterpillar crawls, it is not a worm for several reasons. It has six jointed legs, and it is not a developed animal, but only an early stage in the hfe of a moth or but- terfly. A " grubworm " also has jointed legs (Fig. 167). It does not remain a grub, but »u in the adult stage is a bfeetle. A worm never develops into njs another animal in the latter a part of its life; its setae are not jointed. The Food Tube. — The earthworm has no teeth, and the food tube, as might be inferred from the form of the body is simple and straight. Its parts, recognizable because of slight differences in size and structure, are named the pharynx (muscular), gullet, crop, gizzard (muscular), and stomach-intestine. The last ex- tends through three fourths of the length of the body (Fig. 72). The functions of the parts of the food tube are indicated by their names. Circulation. — There is a large dorsal blood Fig. 74. vessel above the food tube (Fig. 73). From the Fig. 72. — Food Tube of earth- worm. (Top view.) Fig. 73. — Food Tube ' and Blood Ves- sels of earth- worm showing the ring-like hearts. (Side view.) WORMS 45 front portion of this tube arise several large tubular rings or "hearts" which are contractile and serve to keep the blood circulating. They lead to a ventral vessel below the food tube (Fig. 74). The blood is red, but the coloring matter is in the Hquid, not in the blood cells. Nervous System. — Between the ventral blood vessels is a nerve cord composed of two strands (see Fig. 75). There is a slight swelling, or gatiglion, on each strand, in each segment (Fig. 75). The strands sepa- rate near the front end of the worm, and a branch goes up each side of the gullet and enters the two pear-shaped cerebral ganglia, or "brain " (Fig. 75). Food. — The earthworm eats earth contain- ing organic matter, the inorganic part passing through the vent in the form of circular casts; these are found in the morning at the top of the earthworm's burrow. The earthworm has no teeth. It excretes through the mouth an alkali?ie fluid which softens and partly digests the food before it is eaten. When this fluid is poured out upon a green leaf, the leaf at once turns brown. The starch in the leaf is also acted upon. The snout aids in pushing the food into the mouth. Kidneys. — Since oxidation is occurring in its tissues, and impurities are forming, there must be some way of removing impurities from the tissues. The earthworm does not possess one-pair organs like the kidneys of higher animals to serve this purpose, but it has numerous pairs of small tubular organs called nephridia which serve the purpose. Each one is simply a tube with several coils. There is a pair on the floor of each segment. Each neph- FiG. 75.- Ganglia NEAR Mouth and part of nerve chain of earthworm. 46 ANIMAL BIOLOGY Fig. 76. — Two pairs OF Nephridia in a worm (diagram). ridiura has an inner open end within the body cavity, and its outer end opens by a pore on the surface between the setae. The nephridia absorb waste from the liquid in the celom, or body cavity surrounding the food tube, and convey it to the outside. Respiration. — The skin of the earthworm is moist, and the blood capillaries approach so near to the surface of the body that the oxygen is constantly passing in from the air, and carbon dioxid passing out ; hence it is constantly breathing through all parts of its skin. // needs no lungs nor special respiratory organs of any kind. Reproduction. — When one individual animal produces both sperm cells and egg cells, it is said to be hermaphrodite. This is true of the earthworm. The egg cell is always fertilized, however, not by the sperm cells of the same worm, but by sperm cells formed by another worm. The openings of these ovaries consist of two pairs of small pores found on the ventral surface of the fourteenth segment in most species (see Fig. 77). There are also two pairs of small receptacles for temporarily holding the foreign sperm cells. One pair of the openings from these receptacles is found (with diffi- culty) in the wrinkle behind the ninth segment (Fig. 77), and the other pair behind the tenth segment. The sperm- aries are in front of the ovaries (Fig. 77), but the sperm ducts are longer than the oviducts, and open behind them on the fifteenth segment (Figs. 77, 78). The worms exchange sperm cells, but not Fig. j-j. — Sperm {sp) and egg glands («) of worm. WOJiMS A7 egg cells. The reproductive girdle, or clitellum, already spoken of, forms the case which is to hold the eggs (see Fig. 71). When the sperm cells have been exchanged, and the ova are ready for fertili- zation, the worm draws itself backward from the collar-like case or clitellum so that this slips over the head. As it passes the four- teenth segment, it collects the ova, and as it passes the ninth and tenth segments, it collects the sperm cells previously received from another worm. The elastic, collar-like clitellum closes at the ends after it has slipped over the worm's head, forming a capsule. The ova axe fertilized in this capsule, and some of them hatch into worms in a few days. These devour the eggs which do not hatch. The eggs develop into complete but very small worms before escaping from the capsule. Habits. — The earthworm is omnivorous. It v^^ill eat bits of meat as well as leaves and other vegetation. It has also the advantage, when digging its hole, of eating the earth which must be excavated. Every one has noticed the fresh " casts " piled up at the holes in the morn- ing. As the holes are partly filled by rains, the ^^^- 78 — casts are most abundant after rains. The chief showing sete, enemies of the earthworm are moles and birds, nephridia The worms work at night and retire so early in reproducUve the morning that the very early bird has the openings, advantage in catching worms. Perhaps the nearest to an intelligent act the earthworm accomplishes is to con- ceal the month of its hole by plugging it with a pebble or bit of leaf. Worms hibernate, going below danger of frost in winter. In dry weather they burrow several feet deep. The muscular coat of the body wall is much thicker than the skin. It consists of two layers : an outer layer of fibers which run around the body just beneath the skin, and an 48 ANIMAL BIOLOGY inner, thicker layer of fibers which run lengthwise. The worm crawls by shortening the longitudinal muscles. As the bristles {setcz) point backward, they prevent the front part of the body from slipping back, so the hinder part is drawn forward. Next, the circular muscles contract, an4 the bristles preventing the hind part from slipping back, the fore portion is pushed forward. Is the worm thicker when the hinder part is being pulled up or when the fore part is being thrust forward } Does the earthworm pull or push itself along, or does it do both ? Occasionally it trav- els backward, e.g. it sometimes goes backward into its hole. Then the bristles are directed forward. The right and left halves of the body are counterparts of each other, hence the earthworm is bilaterally symmetrical. The lungs and gills of animals must always be kept moist. The worm cannot live long in dry air, for respiration in the skin ceases when it cannot be kept moist, and the worm smothers. Long immersion in water is injurious to it, perhaps because there is far less oxygen in water than in the air. Darwin wrote a book called "Vegetable Mold and Earth- worms." He estimated that there were fifty thousand earth- worms to the acre on farm land in England, and that they bring up eighteen tons of soil in an acre each year. As the acids of the food tube act upon the mineral grains that pass through it, the earthworm renders great aid in form- ing soil. By burrowing it makes the soil more porous and brings up the subsoil. Although without eyes, the worm is sensitive to light falling upon its anterior segments. When the light of a lantern suddenly strikes it at night, it crawls quickly to its burrow. Its sense of touch is so keen that it can detect a light puff of breath. Which of the foods kept in a box of WORMS 49 damp earth disappeared first? What is indicated as to a sense of taste ? Why is the bilateral type of structure better adapted for development and higher organization than the radiate type of the starfish ? The earthworm's body is a double tube ; the hydra's body is a single tube ; which plan is more advantageous, and why ? Would any other color do just as well for an earthworm ? Why, or why not ? The sandworm (Nereis) lives in the sand of the seashore, and swims in the sea at night (Fig. 79). It is more advanced in structure than the earth- worm, as it has a distinct head (Fig. 80), eyes, two teeth, two lips, and several pairs of antennae, and two rows of muscular projections which serve as feet. It is much used by fishermen for bait. If more easily obtained, it may be studied instead of the earthworm. There are four classes in the branch Vermes : i) the worms, including sandworms and leeches; 2) the roundworms, including trichina, hairworms, and vinegar eels; i) flatworms, including tapeworm and liver fluke ; 4) rotifers, which are microscopic aquatic forms. The tapeworm is a flatworm which has lost . most of its organs on account of its parasitic life. Its &%% is picked up by an herbivorous animal when grazing. The embryo under- goes only partial development in the body of .the herbivorous animal, e.g. an ox. The next stage will not develop until the beef is eaten by a carnivorous animal, to whose food canal it attaches itself and soon develops a long chain of segments called a "tape." Each segment absorbs fluid food through its Fig. 79. — Sand Worm x | (Nereis). Fig. 80. — Head OF Sandworm (enlarged) . 50 ANIMAL BIOLOGY body wall. As the segments at the older end mature, each becomes full of eggs, and the segments become detached and pass out of the canal, to be dropped and perhaps picked up by an herbivorous animal and repeat the life cycle. The trichina is more dangerous to human life than the tapeworm. It gets into the food canal in uncooked pork (bologna sausage, for example), multiplies there, migrates into the muscles, causing great pain, and encysts there, remaining until the death of the host. It is believed to get into the bodies of hogs again when they eat rats, which in turn have obtained the cysts from carcasses. Summary of the Biological Process. — An earthworm is a living machine which does work (digging and crawling; seizing, swallowing, and digesting food; pumping blood: growing and reproducing). To do the work it must have a continual supply of energy. The energy for its work is set free by the protoplasm (in its microscopic cells) under- going a destructive chemical change {oxidation). The waste products from the breaking down of the protoplasm must be continually removed {excretion). The broken- down protoplasm must be continually replaced if life is to continue (the income must exceed the outgo if the animal is still growing). The microscopic cells construct more protoplasm out of food and oxygen {assimilation) supplied them by the processes of nutrition (eating, digesting, breathing, circulating). This protoplasm in turn oxidizes and releases rnore energy to do work, and thus the cycle of life proceeds. CHAPTER VII CRUSTACEANS Crawfish Suggestions. — In regions where crawfish are not found, a live crab may be used. Locomotion and behavior may be studied by providing a tub of water, or better, a large glass jar such as a broad candy jar. For suggestions on study of internal structure, see p. 58. Habitat. — Do you often see crawfish, or crayfish, mov- ing about, even in water where they are known to be abun- dant? What does your answer suggest as to the time when they are probably most active .' Why do you never see one building its chimney, even where crawfish holes are abundant? Is the chimney always of the same color as the surface soil ? Are the crawfish holes only of use for protection ? In what kind of spots are crawfish holes always dug ? Why ? What becomes of crawfish when the pond or creek dries up ? How deep are the holes? How large are the lumps of mud of which the chimney is built? How does it get them out of the hole ? Why is the mud built into a chim- ney instead of thrown away ? (What would happen to a well with its mouth no higher than the ground ?) Why are crawfish scarce in rocky regions, as New England ? How does the color of the crawfish compare with its surroundings ? Is its color suited to life in clear or muddy water ? Define protective coloration. 5» 52 ANIMAL BIOLOGY Habits. — Does the crawfish walk better in water or out of it ? Why ? Does it use the legs with the large claws to assist in walking? Do the swimmerets (under the ab- domen) move fast or slow ? (Observe it from below in a large jar of clear water.) What propels it backward ? Forward? Does the crawfish move at a more uniform rate when swimming backward or forward? Why? In which way can it swim more rapidly ? Do the big legs with claws offer more resistance to the water while it is swimming backward or forward ? How does it hold the tail after the stroke, while it is darting backward through the water ? Hold a crawfish with its tail submerged and its head up. Can the tail strike the water with much force? Allow it to grasp a pencil: can it sustain its own weight by its grip ? Feeding. — Offer several kinds of food to a crawfish that has not been alarmed or teased. Does it prefer bread, meat, or vegetables ? How does it get the food to its mouth ? Does it eat rapidly or slowly ? Does it tear the food with the big pincers ? Can it gnaw with the small appendages near the mouth ? Breathing. — Does the crawfish breathe with gills or lungs ? Place a few drops of ink near the base of the hind legs of a crawfish resting quietly in shallow water. Where is the ink drawn in ? Where does it come out ? To ex- plain the cause and purpose of this motion, place a craw- fish in a large glass jar containing water, and see the vibratory motion of the parts under the front portion of the body. There is a gill paddle, or gill bailer, under the shell on each side of the body that moves at the same rate. Senses. — Crawfish are best caught with a piece of meat or beef's liver tied to a string. Do they always lose hold as soon as they are lifted above the water ? What do you CRUSTACEANS 53 conclude as to the alertness of their senses ? Does the cov- ering of its body suggest the possession of a delicate or dull sense of touch ? Of what motions are the eyes capable ? Touch one of the eyes. The result? Can a crawfish see in all direc- tions ? To test this, place a crawfish on a table and try whether you can move to a place where you can see the Fig. 8i. — Crawfish (dorsal surface). -w\^ Fig. 82. crawfish without seeing its eyes. What are the advantages and disadvantages of having the eyes on stalks } Touch the body and the several appendages of the crawfish. Where does it seem most sensitive to touch ? Which can reach farther, the antennae or the big claws.? Why are short feelers needed as well as long ones } Make a loud and sudden noise without jarring the craw- fish. Is it affected by sound? External Anatomy (Figs. 81, 82, 83, 84). — Is the body of the crawfish rounded out (convex) everywhere, or is any part of its surface either flat or rounded in (concave) "i 54 ANIMAL BIOLOGY Fig. 83. — Lateral view of Crawfish. is the advantage of such a covering } What color has the crawfish .'' Is this color of any use to the crawfish ? Make out the two distinct regions or divisions of the body (Fig. 81). The anterior (front) region is called the head- chest or cephalothorax, and the posterior (rear) region is called the tail. Which region is larger .-' Why } Which is flex- ible.? Why.? Is the covering of the body hard or soft .? What What are its dis- advantages } How is the covering modified at the joints to permit motion } Tail. — How many joints, or segments, of the tail .? ( Figs. 81, 83.) Does the hard covering of each segment slip under or over the segment behind it when the tail is straight .? Does this lessen friction while swimming forward .? Is there a pair of swimmerets to each segment of the tail.? (Figs. 82, 86.) Notice that each swimmeret has a main stalk (protopod), an outer branch (exopod), and an inner branch (endopod) (Fig. 84). Are the stalk and the branches each in one piece or jointed .? The middle part of the tail fin is called the telson. By finding the position of the vent, decide whether the food tube goes into the telson (Fig. 82). Should it be called an abdominal segment. Are the side pieces of the tail fin attached to the telson or to the sixth segment ? Do these side pieces correspond Fig. 84.— Fourth Abdo- minal Segment of Crawfish with swimmeret. CRUSTACEANS 55 to swimmerets ? Do they* likewise have the Y-shaped structure? (Fig. Z6?) If the swimmerets on the first abdominal segment are large, the specimen is a male. If they are small, it is a female. Which sex is shown in Fig. 82 ? Fig. 86 } Carapace. — The covering of the head chest (cephalothorax) is called the cara- pace. Has it free edges .-' The gills are on the sides of the body and are covered by the carapace (Fig. ^7\ The projection in front is called the rostrum, meaning beak. Does the rostrum project beyond the eyes } There is a transverse groove across the cara- pace which may be said to divide the head from the abdomen. Where does this groove end at the sides } . Legs. — How many legs has the crawfish .-' How many are provided with large claws } Small claws .-• Is the outer claw hinged in each of the large grasping pincers } The inner claw "i Appendages for Taking Food. — If possible to watch a living craw- fish eating, notice whether it places the food directly into the mouth with the large claws. Bend the large claws under and see if they will reach the mouth. Attached just in front of the legs the crawfish has three pairs of finger-Uke appendages, called foot jaws (maxilli- peds), with which it passes the food from the large pincers Fig. 85. — I, mandi- ble; 2, 3, maxillae; 4, 5, 6, maxillipeds. Fig. 86. — Crawfish (ventral surface). 56 ANIMAL BIOLOGY to its mouth (Figs. 85, 86). They are in form and use more like fingers than feet. In front of the foot jaws are two pairs of thin jaws (maxillae) and in front of the thin jaws are a pair of stout jaws (mandi- bles) (Fig. 85). Do the jaws move sidewise or up and down .-' Which of the jaws has a jointed finger (palp) attached to it ? Do all of the appen- dages for taking food have both exopod and endopod branches on a basal stalk or protopod } Which of the appendages have a scalloped edge.'' How would you know from looking at the crawfish that it is not merely a scavenger } Why are there no pincers on the hind feet .-' Sense Organs. — Find the antenncB, or long feelers (Figs. 82, 90). Are the antennae attached above or below the eyes ? (Fig. 87.) Fig. 87. Gill cover removed and gills exposed. Mp, gill bailer. r r Fig. 88. — Lengthwise Section of Male Crawfish. c, heart; Ac, artery to head; Aa, artery to abdomen; Km, stomach; D, intestine; Z, liver; /■, spermary; CPo, opening of sperm duct; CP, brain; A^, nerve chain. Find the pair of antennules, or small feelers. Are their divisions like or unlike each other 1 Compare the length of the antennules and the antennae. Compare the flex- ibility of the antennae with that of the other appendages. i CRUSTACEANS 57 Observe the position of the eyes (Figs. 8i, Z'^\ How long are the eyestalks ? Is the stalk flexible or stiff ? Touch the eye. Where is the joint which enables the stalk to move } Is the outer covering of the eye hard or soft .'' A mounted preparation of the transparent covering (cornea) of the eye, seen with lower power of microscope, reveals that the cornea is made up of many divisions, called facets. Each facet is the front of a very small eye, hundreds of which make up the whole eye, which is therefore called a com- pound eye. The elongated openings to the ear sacs are located each on the upper side of the base of a t^fmall feeler just below the eye. Respiratory System. — The respiratory organs are gills located on each side of the thorax in a space between the carapace and body (Fig. 87). The gills are white, curved,, and feathery. Is the front gill the largest or the smallest 1: The gills overlap each other ; which is the outermost gill "i On the second maxilla is a thin, doubly curved plate called a gill bailer (Fig. 85). The second maxilla is so placed that the gill bailer comes at the front end of the gill chamber. The bailer paddles continually, bringing the water forward out of the gill. The gills are attached below at the base of the legs. Are the gills thick or thin t How far upward do they go } Does the backward motion in swimming aid or hinder the passage of the water through the gills } Does a crawfish, when at rest on the bottom of a stream, have its head up or down stream } Why } Openings. — The slitlike vent is on the under side of the telson (Figs. 82, 88). The mouth is on the under side of the thorax behind the mandibles. At the base of the long antennae are the openings from the green glands^ two glands in the head which serve as kidneys (Fig. 89). The openings of the reproductive organs are on the third 58 ANIMAL BIOLOGY pair of legs in the female, and the fifth pair of legs in the male (Fig. 88). The eggs are carried on the swimmerets. Internal Structure. — Suggestions. If studied by dissection, it will be necessary to have several crawfish for each pupil, one for gaining general knowledge, and others for studying the systems in detail. Specimens should have lain in alcohol for several days. The Food Tube. — Is the stomach in the head portion of the cephalothorax or in the thoracic portion? ( Figs. 88, 89). Is the stomach large or small? What is its general shape? Does the gullet lead upward or backward? Is it long or short? (Fig. 88.) The mid tube, which is the next portion of the food tube, is smaller than the stomach. On each side of it are openings from the bile ducts which bring the secretion from the digestive gland, sometimes called the liver. Does this gland extend the whole length of the thorax? Is it near the floor or the top of the cavity? The third and last portion of the food tube is the intestine. It extends from the thorax to the vent. Is it large „ or small? Straight or curved? The powerful flexor muscles of the tail lie in the abdomen below the intestines. Compare the size of these muscles with the extensor muscle above' the intestine (Fig. 90). Why this difference? Does the food tube ex- tend into the telson ? Lo- pjq 90. — Section of Crawfish showing Gate the vent (Fig. 90) . stomach s, liver /;, and vent a. Fig. 89. — Level length wise section showing h, heart. d, green gland. le, liver. kie, gills. kh, gill cavity. ma, stomach. (After Huxley.) CRUSTACEANS 59 The Circulation. — The blood is a liquid containing white cor- puscles. It lacks red corpuscles and is colorless. The heart is in the upper part of the thorax. It is sur- rounded by a large, thin bag, and thus it is in a chamber (called the pericardial sinus). The blood from the pulmonary veins enters this sinus before it enters the heart. The origin of this pericardial sinus by the fusing of veins is shown in Fig. 1 30. Does one artery, or do several arteries, leave the heart ? There is a larger dorsal artery lying on the intestine and passing back to the telson ; there are three arteries passing forward close to the dorsal surface (Figs. 89, 91). One large artery (the sternal) passes directly downward (Figs. 88, 91), and sends a branch forward and another backward near the ventral surface. The openings into the heart from the sinus have valvular lips which prevent a backward flow of blood into the sinus. Hence, when the heart contracts, the blood is sent out into the sev- '^ eral arteries. The arteries take a supply of fresh blood H \ to the eyes, stomach, muscles, liver, and the various organs. After it has given oxygen to the several organs and taken up carbon dioxid, it returns by veins to pass through the gills on each side, where it gives out the use- less gas and takes up oxygen from the water. It is then led upward by veins into the pericardial sinus again. The central nervous system consists of a double chain of ganglia (Fig. 92). This main nerve chain lies along the ventral surface below the food tube (Fig. 90), except one pair of ganglia which lie above the esophagus or gullet (Fig. 88), and are called the supra-esophageal ganglia, or brain. Fig. 91. — Showing heart and main blood vessels. Crustacea. — The crawfish and its kindred are placed in the class called Crustacea. 6o ANIMAL BIOLOGY Fig. 93.— Crab from BELOW. Fig. 94. — Hermit Crab, using shell of sea snail for a house. Decapods. — All Crustacea which have ten feet belong in the order called decap'oda (ten-footed). This order includes the crabs, lobsters, shrimp, etc. The crabs and lobsters are of considerable importance because of use as food. Small boys sometimes catch crawfish, and in some instances are known to cook and eat them for amusement, the only part cooked being the muscular tail. The crab's tail is small and flat and held under the body (Fig. 93). Since the limy covering to serve the purpose of protection is not soft enough to be alive and growing, it is evident that the Crustacea are hampered in their growth by their crusty covering. Dur- ing the first year the craw- fish sheds its covering, or molts three times, and once each year thereafter. It grows very fast for a few days just after molt- ing, while the Fig. 95. — Development of a Crab, covering is soft a, nauplius just after hatching; b,c,d,z(xa.; «,megalops; _/, adult. orifl PxtPTlsible Question: Which stage is most like a crayfish? Compare . . with metamorphoses of insects. omCC It IS at A CRUSTACEANS 6 1 the mercy of birds, fish, and other enemies while in this soft and defenseless condition, it stays hidden until the covering hardens. Hence it cannot eat much, but probably by the absorption of water the tissues grow ; that is, enlarge. In the intervening periods, when growth is impossible, it develops ; that is, the tissues and organs change in structure and become stronger. " Soft-shelled crab " is a popular dish, but there is no species by that name, this being only a crab just after molting which has been found by fishermen in spite of its hiding. General Questions. — How do crawfish choose their food ? How long can they live out of water? Why do their gills remain moist out of water longer than a fish? How do they breathe out of water ? Are they courageous or cowardly animals ? When they lose appendages in fighting or molting, these are readily reproduced, but an organ molts several times in regaining its size. Have you seen crawfish with one claw smaller than the other? Explain. Compare the crawfish and crab (Figs. 8i, 93, and 95) in the following particulars : shape, body, eyes, legs, abdomen, habitat, movement. KEY TO THE FOUR CLASSES IN BRANCH ARTHROPODS 1 . Insects ... 3 body divisions, 6 legs 2. Arachnids . . 2 body divisions, 8 legs 3. Myriapods . . many body divisions, many legs 4. Crustaceans . gill breathers, skeleton (external) limy By the aid of the key and of figures 96-105, classify the following Arthropods : tick, thousand-leg centipede, king crab, pill bug, spider, scorpion, beetle. 62 ANIMAL BIOLOGY Fig. 96. — Pill Bug. Fig. 97.— Lady Beetle. Fig. 101. — One Seg- ment OF Centipede with one pair of legs. Fig. 102.— One Segment OF Thousand Legs with two pairs of legs. a b Fig. 99. — Tick before and after feeding. Fig. 103. — Thousand Legs. Fig. 104. — a Spider. Fig. 105. — King Crab. niuBtrated Study. Classification of Arthropods. Key on p. 61. CHAPTER VIII INSECTS The Grasshopper Suggestions. — Collect grasshoppers, both young and full- grown, and keep alive in broad bottles or tumblers and feed on fresh grass or lettuce. When handling a live grasshopper, never hold it by its legs, as the joints are weak. To keep them for some time and observe their molts, place sod in the bottom of a box and cover the box with mosquito netting or wire gauze. What is the general shape of its. body.!* (Fig. io6.) Where is the body thickest? Is it bilaterally symmetri- cal, that is, are the two sides of the body alike .-' Is the skeleton, or hard part of the body, internal or external .■' Is the skeleton as stiff and thick as that of a crawfish .-' What is the length of your specimen ? Its color } Why does it have this coloration } In what ways does the grasshopper resemble the crawfish ? Differ from it "i The Three Regions of the Body. — The body of the grass- hopper is divided into three regions, — the Jiead, thorax, and i^jr^ abdomen. Which of these three divisions has no distinct subdivisions ? The body of the grasshopper, like that of the earthworm, is made of ringlike segments. Are the segments most distinct in the head, thorax, or abdomen.? Which region is longest } Shortest ? Strongest .-' Why .? Which region bears the chief sense organs ? The ap- pendages for taking food ? The locomotory appendages .' Which division of the body is most active in breathing .-' 63 Fig. 106. — a Grass- hopper. 64 ANIMAL BIOLOGY The Abdomen. — About how many segments or rings in the abdomen ? Do all grasshoppers have the same num- ber of rings ? (Answer for different species and different individuals of the same species.) The first segment and the last two are incomplete rings. Does the flexibility of the abdomen reside in the rings, or the joints between the rings } Is there merely a thin, soft hne between the rings, or is there a fold of the covering .<• Does one ring slip into the ring before it or behind it when the abdomen is bent } As the grasshopper breathes, does each ring enlarge and diminish in size .'' Each ring is divided into two parts by folds. Does the upper half-ring overlap the lower half-ring, or the 'reverse .-* With magnifying glass, find a small slit, called a spiracle^ or breath- ing hole, on each side of each ring just above the side groove (Fig. io6). A tube leads from each spiracle. While the air is being taken in, do the two portions of the rings move farther apart .-* When they are brought together again, what must be the effect } In pumping the air, the abdomen may be said to work like a bellows. Bellows usually have folds to allow motion. Is the comparison correct .-• How many times in a minute does the grasshopper take in air } If it is made to hop vigorously around the room and the breathing is again timed, is there any change .'' Find the ears on the front wall of the first abdominal ring (Fig. 107). They may be seen by slightly pressing the abdomen so as to widen the chink between it and the thorax. The ears are merely glistening, transparent membranes, oval in form. A nerve leads from the inner Fig. 107. — A Grass- hopper Dissected. INSECTS 65 surface of each membrane. State any advantage or dis- advantage in having the ears located where they are. Ovipositor. — If the specimen is a female, it has an egg- placer or ovipositor, consisting of four blunt projections at the end of the abdomen (Fig. 107). If it is a male, there are two appendages above the end of the abdomen, and smaller than the parts of the ovipositor. Females are larger and more abundant than males. In laying the eggs, the four blunt points are brought tightly to- gether and then forced into the ground and opened (Fig. 108). By repeating this, a pit is made almost as deep as the abdomen is long. The eggs are laid in the bottom of the pit. Draw a side view of the grass- hopper. Thorax. — This, the middle por- fig. 108. — grasshopper tion of the body, consists of three ^^^'^^ ^^^'- ^^^"^-^ segments or rings (Fig. 107). Is the division between the rings most apparent above or below .? Which two of the three rings are more closely united } The front ring of the thorax is called prothorax. Is it larger above or below ? Does it look more Hke a collar or a cape } (Fig. 106.) A spiracle is found on the second ring {mesothorax, or middle thorax) just above the second pair of legs. There is another in the soft skin between the prothorax and mesothorax just under the large cape or collar. The last ring of the thorax is called the metathorax (rear thorax). How many legs are attached to each ring of the tho- rax } Can a grasshopper walk } Run } CUmb } Jump .? Fly .? Do any of the legs set forward } (See Fig. 106.) 66 ANIMAL BIOLOGY Outward ? Backward ? Can you give reasons for the posi- tion of each pair? (Suggestion : What is the use of each pair ?) If an organ is modified so that it is suited to serve some particular purpose or function, it is said to be special- ized. Are any of the legs specialized so that they serve for a different purpose than the other legs ? The leg of a grasshopper (as of all insects) is said to \va.\Qfive parts, all the small parts after the first four parts being counted as one part and called the foot. Are all the legs similar, that is, do the short* and long joints in all come in the same order ? Numbered in order from the Fig. 1C9. — How a Grasshopper Walks. Fig. no. — How a Spider Walks. body, which joint of the leg is the largest, — the first, sec- ond, third, or fourth "i Which joint is the shortest.-' The slenderest? Which joint has a number of sharp points or spines on it ? Find by experiment whether these spines are of use in walking (Fig. 106). Jumping? Climbing? In what order are the legs used in walking ? How many legs support the body at each step ? All animals that have ears have ways of communicating by sounds. Why would it be impossible for the grasshop- per to have a voice, even if it had vocal cords in its throat? The male grasshoppers of many species make a chirping, or stridulation, by rubbing the wing against the leg. Look on the inner side (why not outer side ?) of the INSECTS 67 Fig. z\i. — A, Row of Spines, z, used in chirping. B, the same more enlarged. largest joint of the hind leg for a row of small spines visi- ble with the aid of a hand lens (Fig. in). The sound is produced by the outer wings rubbing against the spines. Have you noticed whether the sound is produced while the insect is still or in motion .-' Why .-• The male grasshop- pers of some species, instead of having spines, rub the under side of the front wing on the upper side of the hind wing. Wings. — To what is the first pair of wings attached .■' The second pair ? Why are the wings not attached to the prothorax .'' Why are the wings attached so near the dorsal line of the body } Why are the second and third rings of the thorax more solidly joined than the first and second rings .-* Compare the first and second pairs of wings in shape, size, color, thickness, and use (Fig. 112). How are the second wings folded so as to go under the first wings } About how many folds in each .-• Draw a hind wing opened out. Head. — What is the shape of the head viewed from the front, the side, and above } Make sketches. What can you say of a neck .'' Is the head movable in all directions .-' What is the position of the large eyes ^ Like the eyes of the craw- fish, they are compound, with many facets. But the grass- hopper has also three simple eyes, situated one in the middle of the forehead and one just above each antenna. They are too small to be seen without a hand lens. How does Fig. 112. — Grasshopper in Flight. 68 ANIMAL BIOLOGY the grasshopper's range of vision compare with that of the crawfish ? Are the antennae flexible ? What is their shape ? Posi- tion ? Are they segmented ? Touch an antenna, a wing, a leg, and the abdomen in succession. Which seems to be the most sensitive to touch? The antennae are for feeling; in some species of insects they also are organs of hearing and smeUing. The mouth parts of a grasshopper should be compared with the mouth parts of a bee- tle shown in Fig. 113, since they correspond Fig. 113. closely. If the grasshopper is fed with a blade of fresh grass, the function of each organ may be plainly seen. It is almost impossible to understand these functions by studying a dead specimen, but a fresh speci- men is much better than a dry one. The upper lip, or labrum, is seen in front. Is it tapering or expanded ? In what direction is it movable.^ The dark pointed biting jaws {mandibles) are next. Are they curved Fig. 114. — a. Food Tube of Beetle. ^(gizzard; i/, intestine; f, biliary vessels. See Fig. 127. or straight.'' Sharp or blunt pointed .? Notched or smooth .? Do they work up and down, or. sideways .-* The holding jaws {maxillce), each with two jaw fingers {maxillary palpi), are behind the chewing jaws. Why.'' The lower Hp {labium) has a pair of lip fingers {labial palpi) upon it. The brown INSECTS 69 tongue, usually bathed in saliva, is seen in the lower part of the mouth. Since the grasshopper has no Hps, or any way of producing suction, it must lap the dew in drinking. Does it merely break off bits of a grass blade, or does it chew .? The heart, circulation, nervous system, digestive and res- piratory organs of the grasshopper agree mainly with the general description of the organs of insects given in the next section. Microscopic Objects. — These may be bought ready mounted, or may be examined fresh. A portion of the covering of the large eye may be cut off and the dark layer on the inside of the covering scraped off to make it trans- parent. What is the shape of the facets .■* Can you make any estimate of their number } A portion of the transparent hind wing may be used, and the " veins " in it studied. A thin bit of an abdominal segment containing a spiracle will show the structure of these important organs. Growth of the Grasshopper. — Some species hibernate in sheltered places and lay eggs in the spring, but adult species are scarce at that season. Most species lay the eggs in the fall; these withstand the cold and hatch out in the spring. . Those hatched from one set of eggs sometimes stay together for a few days. They eat voraciously, and as they grow, the soft skin becomes hardened by the deposit of horny sub- stance called chitin. This retards further growth until the insect molts, the skin first splitting above the prothorax. After hatching, there are five successive periods of growth. At which molt do the very short wings first appear 1 (Fig. 1 1 5.) Fig. 115. — Ekx; and Molts of a Grasshopper. 70 ANIMAL BIOLOGY After the last molt the animal is complete, and changes no more in size for the rest of its life. There has been an attempt among writers to restrict the term grasshopper to the long-winged, slender species, and to call the shorter winged, stouter species locusts according to old EngUsh usage. Economic Importance of Grasshoppers. — Great injury is often done to vegetation by grasshoppers ; however, the milUons of tiny but ravenous eaters hatched in early spring are usually soon thinned out by the birds. The migra- tory locusts constitute a plague when they appear, and Fig. 117. — Praying Mantis, or devil's horse. Fig. 118. — Cricket. they have done so since ancient times. The Rocky Moun- tain locusts flying eastward have darkened the sky, and where they settled to the earth ate almost every green thing. -^U-j^^^ In 1874-5 they produced almost "S^ \ a famine in Kansas, Nebraska, ^'^- "9- -mole cricket. and other Western states. The young hatched away from the mountains were not healthy, and died prematurely, and their devas- tations came to an end. Of course the migrations may occur again, Packard calculates that the farmers of the leg^of Mole West lost $200,000,000 because of grass- Cricket. X3. hopper ravages in 1874-5. INSECTS 71 The cockroaches (Fig. 1 16), kindred of the grasshoppers, are household pests that have migrated almost everywhere that ships go. The praying mantis (Fig. 117), or devil's horse, also belongs to this order. It is beneficial, since it destroys noxious insects. Which of its legs are specialized ? The walking stick (Fig. 121) and cricket (Fig. 118), like most members of the order, are vegetarian. Are grasshoppers more common in fields and meadows, or in wooded places } How many different colors have you seen on grasshoppers } Which colors are most common } Grasshoppers are very scarce in Europe as they love dry, warm countries. Why do lo- custs migrate .-* Give an in- stance in ancient times. How long do most grass- hoppers live .-* Does a grass- hopper spread its wings before it flies .'' Does it jump and fly together } Can it select the place for alighting } Note to Teacher. — Field work in Zoology should be systematic. Every trip Fig. 121. — Four WALKING Stick has a definite region and definite line of INSECT'S, study in view, but every animal seen should be noted. The habitat, adapta- tion by structure and habits to the environment, relations to other animals, classification of animals seen, should be some of the ideas guiding the study. The excursions may be divided somewhat as follows, according as opportunities offer : Upland woods, lowland woods, upland pastures, fields, swamps, a fresh- water lake, a pond, lower sea beach, higher sea beach, sand hills along shore, roadside, garden, haunts of birds, insect visits to flowers, ground insects, insects in logs. An alphabetical letter file may be used for filing individual field observations. These should be placed before the class orally or in writing. If accepted as reliable (repeated and revised if necessary), the observations should be filed 72 ANIMAL BIOLOGY away and credit given the student on a regular scale. Thus will grading and marks be placed to encourage intelligent study of nature rather than book or laboratory cram. One per cent to be added to the final grade may be cred- ited for every species of pupa, every rare insect (with an observed fact as to its habits) brought in, every bird migration observed, every instance of protective coloration, mimicry (p. 146), outwitting of enemy, instance of injurious insects, and how to combat them, etc. Sharp eyes and clear reasoning will then count as much on school grades as a memory for words or mechanical following of laboratory directions. On scale of lOO, class work = 50, examination = 25, field work = 25. Collecting Insects. — In cities and towns insects, varying with the season, are attracted by electric lights. Beetles and bugs will be found under the lights, moths on posts near the lights, grass- hoppers and crickets and other insects in the grass near by. A lamp placed by a window brings many specimens. In the woods and in rocky places insects are found under logs and stones, and under the bark of dead trees. In open places, prairies, meadows, and old fields with grass and flowers, it will be easy to find grass- hoppers, butterflies, and some beetles. Ponds and streams are usually rich in animal forms, such as bugs and beetles, which swim on or under the surface, and larvae of dragon flies crawling on the bottom. Dragon flies and other insects that lay eggs on the water are found flying in the air above. (In the spring, newly hatched crawfish, tadpoles, and the eggs of frogs and toads should also be collected, if found.) Moths may be caught at night by daubing molasses or sirup made from brown sugar upon the trunks of several trees, and visiting the trees at intervals with a lantern. An insect net for catching butterflies and for dredging ponds may be made by bending a stout wire into a circle one foot in diameter, leaving enough straight wire to fasten with staples on an old broomstick. To the frame is fastened a flour sack, or cone made of a piece of mosquito netting. Butterflies and moths should be promptly killed, or they will beat their wings to pieces. The quickest method is by dropping several drops of gasoline upon the ventral (under) side of the thorax and abdomen. (Caution : Gasoline should never be used near an open fire, or lamp, as explosions and deaths result from INSECTS 73 the flame being led through the gasoline- saturated air to the vessel containing it.) A cigar box and a bottle with a notched cork may be used for holding specimens. Cigar boxes may be used for holding collec- tions of dried insects. Cork or ribbed packing paper may be fixed in the bottom for supporting the insect pins. Moth balls or tobacco may be placed in each box to keep out the insect pests which infest collections. It is pleasant and profitable to take to the fields a small book like this one, or even Comstock's " Manual of Insects," or Kel- logg's "American Insects," and study the insects and their habits where they are found. Captured insects which, in either the larval or perfect stage, are injurious to vegetation, should always be killed after studying their actions and external features, even if the internal structure is not to be studied. Beneficial insects, such as ladybugs, ichneumon flies, bees, mantis (devil's horse), dragon flies, etc., should be set free uninjured. Anatomy and General Characteristics of the Class Insecta The body of an insect is divided by means of two marked narrow^ings into three parts : the head, chest, and ab- domen. The head is a freely movable cap- sule bearing four pairs of append- ages. Hence it is regarded as having been formed by the union of four rings, since the ancestor of the insects is believed to have con- sisted of similar rings, each ring bearing a pair of unspecialized legs. The typical mouth parts of an insect (Fig. 123) named in order from above, are (i) an upper lip (labrum, ol), (2) a pair Fig. 122. —Yellow Fever Mosquito, showing head, thorax, abdomen. 74 ANIMAL BIOLOGY Fig. 123. — Mouth Parts of Beetle. of biting jaws (mandibles, ok), (3) a pair of grasping jaws (maxillae, A, B), and (4) a lower lip (labium, ;;/, a, b). The grasping jaws bear two pairs of jointed jaw fingers (maxillary palpi, D, C), and the lower lip bears a pair of similar lip fingers (labial palpi, £i). The biting jaws move sideways ; they usually have several pointed notches which serve as teeth. Why should the grasping jaws be beneath the chewing jaws ? Why is it better for the lower lip to have fingers than the upper Hp } Why are the fingers (or palpi) jointed .'' (Watch a grasshopper or beetle eating.) Why does an insect need grasping jaws .-' The chest, or thorax, consists of three rings (Fig. 124) called the front thorax (prothorax), middle thorax (mesothorax) and hind thorax (metathorax), or first, second, and third rings. The first ring bears the first pair of legs, the second ring bears the second pair of legs and the upper or front wings, and the third ring bears the third pair of legs and the under or hind wings. The six feet of insects are characteristic of them, since no other adult animals have that number, the spider having eight, the craw- fish and crabs having ten, the centipedes still more, while the birds and beasts have less than six. Hence the insects Fig. 124. — External Parts OF A Beetle. Fig. 125. — Leg OF Insect, INSECTS 75 are sometimes called the Six-Footed class {Hexapodd). The insects are the only animals that have the body in three divisions. Man, beasts, and birds have only two divisions (head and trunk) ; worms are not divided. Define the class insecta by the two facts characteristic of them {i.e. possessed by them alone), viz. : Insects are ani- mals with and . Why would it be ambig- uous to include " hard outer skeleton " in this definition } To include "bilateral symmetry".? " Segmented body " .? The definition of a class must include all the individuals of the class, and exclude all the animals that do not belong to the class. The leg of an insect (Fig. 125) has five joints (two short joints, two long, and the foot). Named in order from above, they are (i) the hip (coxa), (2) thigh ring (trochanter), (3) thigh (femur), (4) the shin (tibia), (5) the foot, which has five parts. Which of the five joints of a wasp's leg (Fig. 122) is thickest? Slenderest? Shortest? One joint (which?) of the foot (Fig. 122) is about as long as the other four pj^ 126— Foot^f joints of the foot combined. Is the relative fly, with climbing length of the joints of the leg the same in v^^^- grasshoppers, beetles, etc., as in the wasp (Figs.)? Figure 125 is a diagram of an insect's leg cut lengthwise. The leg consists of thick-walled tubes {0, n) with their ends held together by thin, easy-wrinkling membranes which serve as joints. Thus motion is provided for at the expense of strength. When handling live insects they should never be held by the legs, as the legs come off very easily. Does the joint motion of insects most resemble the motion of hinge joints or ball-and-socket joints? Answer by tests of living insects. There are no muscles in the foot of an insect. The claw is moved by a muscle (w) in the thigh with which it is connected by the long tendon (2, s, i, ?'). In which part are the breathing muscles? As the wings are developed from folds of the dorsal skin, the wing has two layers, an upper and a lower layer. These inclose the so-called " nerves " or ribs of the wing, each of which consists of a blood tube inclosed in an air tube. 76 ANIMAL BIOLOGY The abdomen in various species consists of from five to eleven overlapping rings with their foldlike joints be- tween them. Does each ring overlap the ring in front or the one behind it ? The food tube (Fig. 127) begins at the mouth, which usually bears salivary glands (4, Fig. 127, which repre- sents internal organs of the grasshopper). The food tube expands first into a croplike enlargement; next to this is an organ (6, Fig. 127), which resembles the gizzard ^ ^'1 Fig. 127. — Viscera op Grasshopper. Key in text. Compare with Fig. 114. Fig. 128. — Air Tubes of Insect. in birds, as its inner wall is furnished with chitinous teeth {b. Fig. 114). These reduce the food fragments that were imperfectly broken up by the biting jaws before swallow- ing. Glands comparable to the liver of higher animals open into the food tube where the stomach joins the small intestine. At the junction of the small and large intestine (9) are a number of fijie tubes (8) which correspond to kidneys and empty their secretion into the large intestine. The breathing organs of the insects are peculiar to them (see Fig. 128). They consist of tubes which are INSECTS 77 ^r^ -Mvy^ ^1-/^ A|t/N? Fig. 130. — Diagrams of Evolution OF Pericardial Sac around in- sect's heart from a number of veins (Lankester) . ■I h» Fig. 129. Insect's Heart (plan). kept open by having in their walls continuous spirals of horny material called chitin. Most noticeable are the two large membranous tubes filled with air and situated on each side of the body. Do these tubes extend through the thorax? (Fig. 128.) The air reaches these two main tubes by a number of pairs of short windpipes, or tracheas, which begin at openings {spiracles). In which division are the spiracles most numerous .-• (Fig. 128.) Which division is without spiracles } Could an insect be drowned, i.e. smothered, by holding its body under water } Could it be drowned by immersing all of it but its head } The motion of the air through the breathing tubes is caused by a bellowslike motion of the abdomen. This is readily observed in grasshoppers, beetles, and wasps. As each ring slips into the ring in front of it, the abdomen is shortened, and the impure air, laden with carbon dioxid, is forced out. As the rings slip out, the abdomen is extended and the fresh air comes in, bringing oxygen. The Circulation. — Near the dorsal surface of the abdomen (Fig. 131) extends the long, slender heart ( Fig. \ 29). The heart has divisions separated by valvelike partitions. The blood comes into each of the heart compartments through a pair of openings. The heart contracts from the rear toward Fig. 131. — Position of Insect's Heart, food tube, and nerve chain. 78 ANIMAL BIOLOGY the front, driving the blood forward. The blood contains bodies corresponding to the white corpuscles of human blood, but lacks the red corpuscles and the red color. The blood is sent even^ to the wings. The veins in the wings consist of horny tubes inclosing air tubes surrounded by blood spaces, and the purification of the blood is taking place throughout the course of the circulation. Hence the im- perfect circulation is no disadvan- tage. The perfect provision for supplying oxygen explains the remarkable activity of which in- sects are capable and their great strength, which, considering their size, is unequaled by any other animals. The Nervous System. — The heart in backboned animals, e.g. man, is ventral and the chief nerve trunk is dorsal. As already stated, the heart of an insect is dorsal ; its chief nerve chain, consisting of a doicble row of ganglia^ is near the ventral surface (Fig. 131). All the ganglia are below the food tube except the first pair in the head, which are above the gullet. This pair may be said to correspond somewhat to the brain of backboned animals ; the nerves from the eyes and feelers lead to it. With social insects, as bees and ants, it is large and complex (Fig. 132). In a typical insect they are the largest ganglia. The Senses. — The sense of smell of most in- sects is believed to be located in the feelers. The organ of hearing is variously located in different in- sects. Where is it in the grasshopper.? The organs of Fig. 132. — Nervous Sys- tem OF Bee. INSECTS 79 Fic;. 134. — Diagram of simple eye of insect. L, lens; TV, optic nerve. sight are highly developed, and consist of two compound eyes on the side of the head and three simple eyes on the top or front of the head between the com- pound eyes. The simple eye has nerve cells, pigments, and a lens resembhng the lens in the eyes of vertebrates (Fig. 134). The compound eye (Fig. 135) has thousands of facets, usually hexagonal, on its surface, the facets being the outer ends of cones which have their inner ends directed toward the center of the eye. It is probable that the large, or compound, eyes of insects only serve to distinguish bright objects from dark objects. The simple eyes afford dis- tinct images of objects within a few inches of the eye. In gen- eral, the sight of insects, contrary to what its complex sight organs would lead us to expect, is not at all keen. Yet an insect can fly through a forest without striking a twig or branch. Is it better for the eyes that are immovable in the head to be large or small ? Which has comparatively larger eyes, an insect or a beast } Inherited Habit, or Instinct. — Insects and other ani- mals inherit from their parents their particular form of body and of organs which perform the different functions. For example, they inherit a nervous system with a struc- ture similar to that of their parents, and hence with a ten- dency to repeat similar impulses and acts. Repeated acts constitute a habit, and afi inherited habit is called an in- Fig. 135. —Compound Eye OF Insect. I, hexagonal facets of crystalline cones. 6, blood vessel in optic nerve 80 ANIMAL BIOLOGY stinct. Moths, for example, are used to finding nectar in the night-blooming flowers, most of which are white. The habit of going to white flowers is transmitted in the struc- ture of the nervous system ; so we say that moths have an instinct to go to white objects; it is sometimes more obscurely expressed by saying they are attracted or drawn thereby. Instincts are not Infallible. — They are trustworthy in only one narrow set of conditions. Now that man makes many fires and lights at night, the instinct just mentioned often causes the death of the moth. The instinct to provide for offspring is necessary to the perpetuation of all but the simplest animals. The dirt dauber, or mud wasp, because of inherited habit, or instinct, makes the cell of the right size, lays the egg, and provides food for offspring that the mother will never see. It seals stung and semiparalyzed spiders in the cell with the tgg. If you try the experiment of removing the food before the cell is closed, the insect will bring more spiders ; if they are removed again, a third supply will be brought; but if taken out the third time, the mud wasp will usually close the cell without food, and when the egg hatches the grub will starve. The Development of Insects. — The growth and molting of the grasshopper from egg to adult has been studied. All insects do not develop exactly by this plan. Some hatch from the egg in a condition markedly different from the adult. The butterfly's Qgg produces a wormlike cater- pillar which has no resemblance to the butterfly. After it grows it forms an inclosing case in which it spends a quiet period of development and comes out a butterfly. This change from caterpillar to butterfly is called the metamorphosis. The life of an insect is divided into four INSECTS 8i Fig. 136. — Measuring worm, the larva of a moth. Stages : (i) egg, (2) larva, (3) pupa, and (4) imaga, or per- fect insect (Figs. 136, 137, 138). The egg stage is one of development, no nourishment being absorbed. The larval stage is one of voracious feed- ing and rapid growth. In the pupa stage no food is taken and there is no growth in size, but rapid devel- opment takes place. In the per- fect stage food is eaten, but no growth in size takes place. In this stage the eggs are produced. When there is very little resemblance between the larva and imago, and no pupal stage, the metamorphosis, or change, is said to be complete. When, as with the grasshopper, no very marked change takes place between the larva and imago, there being no pupal stage, the metamorphosis is said to be in- complete. By studying the illustrations .and specimens, and by thinking of your past observations of insects, determine which of the insects in the following list have a complete metamorphosis: beetle, house fly, grass- hopper, butterfly, cricket, wasp. Fig. 137. — Pupa of a mosquito. Fig. 138. — The Four Stages of a Botfly, all enlarged. *» '88 °n hair of horse (bitten off and swallowed) ; b, larva; c, larva with hooks for holding to lining of stomach; d, pupal stage, passed in the earth; e, adult horse fly. 82 ■ ANIMAL BIOLOGY RECOGNITION-CHARACTERS FOR THE PRINCIPAL ORDERS OF ADULT WINGED INSECTS (All are wingless when young, and wingless adult forms occur in all the orders : order Aptera lacks wing-bearing thoracic structures.) A single pair of wings is characteristic of the order DiPTEiyi.. A jointed beak, that is sheath-like, fnclosing the^btHer riibuth parts, is characteristic of the order Hemiptera. A coiled sucking proboscis and a wing covering of dust-like microscopic scales are characteristic of the order Lepidqpiera. Horny sheath-like fore wings, covering the hind wings and meeting in a straight line down the middle of the back, will dis- tinguish the order Coleopte^a. Hind wings folded like a fan beneath the thickened and over- lapping fore wings, will distinguish most members of the order Orthoptera. The possession of a sting (in females) and of two pairs of thin membranous wings — the small hind wing hooked to the rear mar- gin of the fore wing — will distinguish the common Hymenoptera. Besides these, there remain a number of groups most of which have in the past been included under the order Neuroptera, among which the Mayflies will be readily recognized by the lack of mouth parts and by the possession of two or three long tails j the dragon flies by the two pairs of large wings, enormous eyes, and minute bristle-like antennae ; the scorpion flies, by the possession of a rigid beak, with the mouth parts at its tip ; the caddis flies, by their hairy wings and lack of jaws ; the lace wings, by the exquisite regularity of the series of cross veins about the margin of their wings, etc. INSECTS 83 Fig. 139. — May Fly. What order (see table)? Exercise in the Use of the Table or Key. — Write the name of the order after each of the fol- lowing names of insects : — Wasp (Fig. 122) Weevil (Fig. 163) Squash bug ( Fig. 184) Ant lion (Fig. 170) Dragon fly (Fig. 177) Ichneumon fly (Fig. 159) House fly (Fig. 172) Flea (Fig. 173) Silver scale or earwig (Fig. 140) CodHng moth (Fig. 141) Botfly (Fig. 138) Fig. 140. — Silver Scale. (Order?) Moths and Butterflies. — Order .? Why (p. 82) ? ! The presence of scales on the wings is a iiever-faiHng test of a moth or butterfly. The wings do not fold at all. They are so large and the legs so weak and delicate j that the butterfly keeps its balance with difficulty when / walking in the wind. The maxillae are developed to form the long sucking proboscis. Ylow do they fit together to form a tube ^ (See Fig. 147.) The proboscis varies from a fraction of an inch in the "miller" to five inches in some tropical moths, which use it to extract nectar from long tubular flowers. When not in use, it is held coiled like a watch spring under the head (Fig. 148). The upper lip (labrum), under lip (labium), and hp fingers (labial palpi) are very small, and the mandibles small or wanting (Fig. 146). The metamorphosis is complete, the contrast between the caterpillar or larva of the moth and butterfly and the adult form being very great. The caterpillar has the three pairs of jointed legs typical of insects ; these are 84 ANIMAL BIOLOGY found near the head (Fig. 141). It has also from three to five pairs of fleshy unjoin ted proplegs, one pair of which is always on the last segment. How many pairs of proplegs has the silkworm caterpillar? (Fig. 143.) The measuring worm, or looper? (Fig. 136.) The pupa has a thin shell. Can you see external signs of the antennae, wings, and legs in this stage .<' (Fig. 143.) The pupa is concealed by protective coloration, and is some- times inclosed in a silken cocoon which was spun by the caterpillar before the last molt. Hairy caterpillars are uncomfortable for birds to eat. The naked and brightly marked ones (examples of warning coloration) often con- tain an acrid and distasteful fluid. The injuries from lepidoptera are done in the caterpillar stage. The codling moth (Fig. 141) destroys apples to the estimated value of ;^6,ooo,ooo annually. The. ciolhes moth (Fig. 171) is a household pest. The tent caterpillar denudes trees of their leaves. The only useful caterpillar is the silkworm X Fig. 143). In Italy and Japan many of the country dwellings have silk rooms where thousands of these caterpillars are fed and tended by women and children. Why is the cab- bage butterfly so called .-• Why can it not eat cabbage .■' Why does sealing clothes in a paper bag prevent the ravages of the clothes moth } Flight of Lepidoptera. — Which appears to use more ex- ertion to keep afloat, a bird or a butterfly } Explain why. Of all flying insects which would more probably be found highest up mountains ? How does the butterfly suddenly change direction of flight .>" Does it usually fly in a straight or zigzag course .-' Advantage of this .'' Bright colors are protective, as lepidoptera are in greatest danger when at rest on flowers. Are the brightest colors on upper or under side of wings of butterfly } Why } (Think of the INSECTS 85 colors in a flower.) Why is it better for moths to hold their wings flat out when at rest ? Where are moths dur- ing the day ? How can you test whether the color of the wings is given by the scales ? State how moths and butterflies differ in respect to: body, wings, feelers, habits. ^Insects and Flowers. — Perhaps we are indebted to in- sects for the bright colors and sweet honey of flowers. Flowers need insects to carry their pollen to other flowers, as cross-fertilization produces the best seeds. The insects need the nectar of the flowers for food, and the bright colors and sweet odors are the advertisements of the flowers to attract insects. Flowers of brightest hues are the ones that receive the visits of insects. Moths, butter- flies, and bees carry most pollen (see Plant Biology, Chap. VI). Comparative Study. — Make a table like this, occupying entire page of notebook, leaving no margins, and fill in accurately: — Grass- hopper Butter- fly Fly PP- 92. 93 Dragon Fly, p. 93 Beetle pp. 90, 91 Bee pp. 88, 89 Number and kind of wings Description of legs Antennae (length, shape, joints) Biting or sucking mouth parts Complete or incom- plete metamor- phosis 86 Illustrated Studies Fig. 142. — Cabbage Butterfly, male and female, larva and pupa. Fig. 141. — Codling Moth, from egg to adult. (See Farmers' Bulletin, p. 95.) ^ (5) f \^ , Fig. 143. — Life History of Silkworm. Fig. 144. — Scales from Butterflies' Wings, as seen under microscope. Illustrated Studies 87 To THE Teacher : These illustrated studies require slower and more careful study than the text. One, or at most hvo, studies will suffice for a lesson. The questions can be answered by studying the figures. Weak observers will often fail and they should not be told, but should try again until they succeed. Figs. 141-148. Illustrated Study of Lepidoptera. — Study the stages in the development of codling moth, silk- worm moth, and cabbage butterfiy. Where does each lay its eggs ? What does the larva of each feed upon ? Describe the pupa of each. Describe the adult forms. Find the spiracles and prolegs on the silkworm. Compare antenna of moth and butterfly. Which has larger body compared to size of wings ? Describe the scales frofn a butterfly's wings as seen under microscope (144). How are the scales arranged on moth's wing (145) ? By what part is scale attached to wing ? Do the scales overlap ? Study butterfly's head and proboscis (Figs. 146-148). What shape is compound eye ? Are the antennae jointed ? Is the proboscis jointed ? Why not call it a tongue ? (See text.) Which mouth parts have almost disappeared ? What is the shape of cut ends of halves of proboscis ? How are the halves joined to form a tube ? If you saw a butterfly on a flower, for what purpose would you think it was there? What, if you saw it on a leaf? How many spots on fore wing of female cabbage butterfly ? (Fig. 124, above.) Does the silkworm chrysalis fill its cocoon ? Eggs may be obtained from U. S. Dept. of Agriculture. Fig. 145.— Scales ON Moth's Wing. Fig. 146. — Head OF Butterfly. Fig. 148. —Head OF Butterfly (side view). Fig. 147. — Section OF Proboscis of butterfly showing lapping joint and dovetail joint. 88 Illustrated Studies :^"' Fig. 155. Fig. 156. Fig. 157. Fig. 158. - - Anatomy of bee. Figs. 149-161. Illustrated Study of Bees and their Kin- dred. — Head of worker (Fig. 149) : o, upper lip ; ok, chew- ing jaws; uk, grasping jaws; kt, jaw finger: It, lip finger; z, tongue. How do heads of drone (150) and queen (151) differ as to mouth, size of the two compound eyes, size and position of the three simple eyes ? Is the head of a worker more like head of drone or head of queen ? Judging by the head, which is the queen, drone, and worker in Figs. 154-156 ? Which of the three is largest ? Smallest ? Broadest ? Figure 152 shows hind leg of worker. What surrounds the hollow, us, which serves as pollen basket ? The point, fh, is a tool for removing wax which is secreted {c. Fig. 157) between rings on abdomen. In Fig. 158, find relative pwDsitions of heart, v, food tube, and nerve chain. Is crop, /, in thorax or abdo- men ? In this nectar is changed to honey, that it may not spoil. Compare aerve chain in Fig. 132. Illustrated Studies 89 Compare the cells of butnble bee (Fig. 153) with those of hive bee. They differ not only in shape but in material, being made of web instead of wax, and they usually contain larvas instead of honey. Only a few of the queens among bumble bees and wasps survive the winter. How do ants and honey bees provide for the workers also to survive the win- ter ? Name all the social insects that you can think of. Do they all belong to the same order ? The ichneumon fly shown enlarged in Fig. 159 lays its eggs under a caterpillar's skin. What becomes of the eggs ? The true size of the insect is shown by the cross lines at a. The eggs are almost microscopic in size. The pupae shown (true size) on caterpillar are sometimes mistaken for eggs. The same mistake is made about the pupa cases of ants. Ichneumon flies also use tree-borers as " hosts " for their eggs and larva. Is this insect a friend of man ? The digging wasp (Figs. 160 and 161) supplies its larva with caterpillars and closes the hole, sometimes using a stone as pounding tool. Among the few other uses of tools among lower animals are the elephant's use of a branch for a fly brush, and the ape's use of a walking stick. This wasp digs with fore feet like a dog and kicks the dirt out of the way with its hind feet. Are the wings of bees and wasps more closely or less closely veined than the wings of dragon flies? (Fig. 177.) For an interesting account of the order " Joined-wings " (bees and their kindred) see Comstock's " Ways of the Six- footed," Ginn & Co. Fig. 161. — Wasp using pebble. From Peckham's " Solitary Wasps," Houghton, Mifflin & Co. 90 Illustrated Studies Illustrated Study of Beetles. Fig. 162. — Diving beetle {Dysticus), with larva, a. FlG. 163. — Weevil. Fig. 169. — Colorado beetle (potato bug). Illustrated Studies 91 Illustrated Study of Beetles (Figs. 162-169). — Write the life history of the Colorado beetle, or potato bug (Fig. 169), stating where the eggs are laid and describ- ing the form and activities of each stage (the pupal stage, b, is passed in the ground). Do the same for the May beetle (Figs. 167-168). (It is a larva — the white grub — for three years; hogs root them up.) Beetles, like moths, maybe trapped with a lantern set above a tub of water. Where does a Scarab (or sacred beetle of the Egyptians, also called tumble Lug (Fig. 164), lay its eggs (Fig. 165)? Why? How does the click beetle, ox jack snapper (Fig, 166), throw itself into the air? For what purpose ? The large proboscis of the weevil (Fig. 163) is used for piercing a hole in which an egg is laid in grain of corn, boll of cotton, acorn, chestnut, plum, etc. How are the legs and body of the diving beetle suited for swimming (Fig. 162) ? Describe its larva. What is the shape of the lady bug (Fig. 97) ? It feeds upon plant lice (Fig. 185) . Is any beetle of benefit to man ? Fig. 170. — Life history of ant lion. Illustrated Study of Ant Lion, or Doodle Bug (Fig. 170). — Find the pitfall (what shape? ) ; the larva (describe it) ; the pupa case (ball covered with web and sand) ; the imago. Compare imago with dragon fly (Fig. 177). How does ant lion prevent ant from climbing out of pitfall (see Fig. 170) ? What is on edge of nearest pitfall ? Explain. Ant lions may be kept in a box half filled with sand and fed on ants. How is the pitfall dug ? What part of ant is eaten ? How is unused food removed ? How long is it in the larval state ? Pupal state? Keep net over box to pre- vent adult from flying away when it emerges. 92 Illustrated Studies Fig. 175. — Bed bug. x 3. Fig. 176. — Life history of mosquito. Illustrated Studies 93 Illustrated Study of Insect Pests (Figs. 171-176). — Why does the clotkes moth (171) lay its eggs upon woolen clothing ? How does the larva conceal itself? The larva can cut through paper and cotton, yet sealing clothes in bags of paper or cotton protects them. Explain. The house fiy eats liquid sweets. It lays its eggs in horse dung. Describe its larval and pupal forms. Banishing horses from city would have what beneficial effect ? Describe the louse and its eggs, which are shown attached to a hair, natural size and enlarged. Describe the bed bug. Benzine poured in cracks kills bed bugs. Do bed bugs bite or suck ? Why are they wingless ? Describe the larva, f, pupa, g, and the adult fiea, all shown enlarged. Its mandibles, b, b, are used for piercing. To kill fleas lather dog or cat completely and let lather remain on five minutes before washing. Eggs are laid and first stages passed in the ground. How does the mosquito lay its eggs in the water without drowning (176) ? Why are the eggs always laid in still water ? Which part of the larva (wiggletail) is held to the surface in breathing ? What part of the pupa (called tumbler, or bull head) is held to the surface in breathing ? Give differences in larva and pupa. Where does pupa change to perfect insect ? Describe mouth parts of male mosquito (at left) and female (at right). Only female mosquitoes suck blood. Males suck juice of plants. Malarial mosquito alights with hind end of body raised at an angle. For figure see Human Biology, Chap. X. Why does killing fish and frogs increase mosquitoes? i oz. of kerosene for 15 ft. of surface of water, renewed monthly, prevents mosquitoes. What is the use to the squash bug (Fig. 184) of having so bad an odor ? Fig. 177. Illustrate- .:,i„„^ ^. u.^^„^ ily. - ^ ^..^..^ .....s^.. fly laying its eggs in water while poised on wing. Describe the larval form (water tiger). The extensible tongs are the maxillae enlarged. The pupa (i) is active and lives in water. Where does transformation to adult take place (5) ? Why are eyes of adult large ? its legs small ? Compare front and hind wings. Do the eyes touch each other ? Why is a long abdomen useful in flight ? Why would long feelers be useless ? What is the time of greatest danger in the development of the dragon fly ? What other appropriate name has this insect ? Why should we never kill a dragon fly ? 94 Illustrated Studies Est* Fig. 178. — The tarantula. Fig. 179. — Trap-door spider. Fig. 182. — Laying egg. Fig. 183. — Foot of spider. Illustrated Study of Spiders (Figs. 178-183).— The tarantula, like most spi- ders, has eight simple eyes (none compound). Find them (Fig. 178). How do spiders and insects differ in body ? Number of legs ? Which have more joints to legs? Does trap-door spider hold the door closed (Fig. 179)? How many pairs of spinnerets for spinning web has a spider {S/>w, 180) ? Foot of spider has how many claws ? How many combs on claws for holding web ? Spiders spin a cocoon for holding eggs. From what part of abdomen are eggs laid {E, 182; 2,181)? Find spider's air sacs, /«, Fig. 181; spinning organs, jr/ ; fang, /J/; poison gland, ^; palpi, /J/; eyes, a« ; nerve ganglia, t?f, «^; sucking tube, jr; stomach, rf; intestine, ma ; liver, /'». "^ A ^T- Fig. 240.— Sea Horse , ( Hippocampus) , with incubat- ing pouch, Br/. Fig. 243. — Laniern Fish {^Linophryne luci/er). (After Collett.) Fig. 244. — Lung Fish of Australia {^Ceratodus mioUpis). Fig. 242, — Torpedo. Elec- trical organs, at right and left of brain. Fig. 246. — Seaweed Fish, x^ {Phyllopteryx eques) . Remarkable Fish. Special Reports. (Encyclopedia, texts, dictionary.) 124 GENERAL CLASSIFICATION 125 RECOGNITION GROUP CHARACTERS The commoner members of the several branches may be recog- nized by the following characters : — 1. The Protozoans are the only one-celled animals. 2. The Sponges are the only animals having pores all over the body for the inflow of water. 3. The Polyps are the only many-celled animals having a single opening into the body, serving for both mouth and vent. They are radiate in structure, and usually possess tentacles. 4. The Echinoderms are marine animals of more or less radiate appearance, having a food tube in the body separate from the body wall. The following groups are plainly bilateral : that is, dorsal and ventral surfaces, front and hind ends are different. 5. The Vermes have usually a segmented body but lack jointed legs. 6. The Arthropods have an external skeleton and jointed legs. 7. The Mollusks have soft bodies, no legs, no skeleton, but usually a limy shell. 8. The Vertebrates have an internal skeleton of bones, and usually two pairs of legs. CHAPTER XI BATRACHIA The theory of evolution teaches that animal life began in a very simple form in the sea, and that afterward the higher sea animals lost their gills and developed lungs and legs and came out to live upon the land ; truly a marvelous procedure, and incredible to many, although the process is repeated every spring in count- less instances in pond and brook. In popular language, every cold-blooded vertebrate breathing with lungs is called a reptile. The name reptile is properly applied only to lizards, snakes, turtles, and alligators. The com- mon mistake of speaking of frogs and salamanders as reptiles arises from considering them only in their adult condition. Rep- tiles hatch from the egg as tiny reptiles resembling the adult forms ; frogs and salamanders, as every one knows, leave the egg in the form of tadpoles (Fig. 248). The fact that frogs and salamanders begin active hfe as fishes, breathing by gills, serves to distinguish them from other cold-blooded animals, and causes naturalists to place them in a separate class, called batrachia (twice breather) or amphibia (double life). Tadpoles Suggestions. — Tadpoles may be studied by placing a number of frog's eggs in a jar of water, care being taken not to place a large number of eggs in a srfjall amount of water. When they hatch, water plants {e.g. green algae) should be added for food. The behavior of frogs may be best studied in a tub of water. A toad in captivity should be given a cool, moist place, and fed well. A piece of meat placed near a toad may attract flies, and the toad may be observed while catching them, but the motion is so swift as to be almost imperceptible. Live flies nay be put into a glass jar with a toad. Toads do not move about until twilight, except 126 BATRACHIA 127 in cloudy, wet weather. They return to ponds and brooks in spring at the time for laying eggs. This time for both frogs and toads is shown by trilling. All frogs, except tree frogs, remain in or near the water all the year. Fig. 248. — Metamorphoses of the Frog, numbered in order. Do eggs hatch and tadpoles grow more rapidly in a jar of water kept in a warm place or in a cold place } In pond water or drinking water } Can the tadpoles be seen to move in the eggs before hatching } When do the external gills show } (Fig. 248.) What parts may be described in a tadpole .? What is the shape of the tail } Compare the tadpole with the fish as to (i) general shape, (2) cover- ing, (3) fins, (4) tail, (5) gills. Do the exter- nal gills disap- pear before or after any rudiments of limbs appear .■* (6, 7, Fig. 248.) Can you locate the gills after they be- come internal .'' (Fig. 249.) Fig. 249. — Tadpole, from below, showing intestine and internal gills. (Enlarged.) 128 ANIMAL BIOLOGY In what state of growth are the legs when the tadpole first goes to the surface to breathe ? Which legs appear first ? What advantage is this ? What becomes of the tail ? Is the tail entirely gone before the frog first leaves the water ? Are tadpoles habitually in motion or at rest ? Is the intestine visible through the skin ? (Fig, 249.) Is it straight or coiled ? Remembering why some fish have larger intestines than others, and that a cow has a long intestine and a cat a short one, state why a tad- pole has a relatively longer intestine than a frog. Compare the mouth, jaws, eyes, skin, body, and habits of tadpole and frog. Frogs Prove that frogs and toads are beneficial to man. Did you ever know of a frog or toad destroying anything useful, or harming any one, or causing warts ? How many pupils in class ever had warts ? Had they handled frogs before the warts came ? Frogs are interesting, gentle, timid animals. Why are they repulsive to some people } Environment. — Where are frogs found in greatest numbers } What occurs when danger threatens them .-• What etiemies do they have .-' What color, or tint, is most prominent on a frog .■* Does the color " mimic " or imi- tate its surroundings ? What is the color of the under side of the body } (Fig. 250.) Why is there greater safety in that color 1 What enemies would see water frogs from below.? Do tree frogs mimic the bark.? The leaves } Can a frog stay under water for an indefinite time ? Why, or why not.? What part of a frog is above the B ATRAC HI A 129 surface when it floats or swims in a tub of water ? Why ? Do frogs croak in the water or on the bank ? Why do they croak after a rain ? Do toads croak ? Are the eggs laid in still or flowing water ? In a clear place or among sticks and stems ? Singly, or in strings or in masses ? (Fig. 248.) Describe an Qgg. Why do frogs dig into the mud in autumn in cold climates ? Why do they not dig in mud at the bottom of a pond ? Why is digging unnecessary in the Gulf states ? 5tl Fig. 250. — Painted Frog {Choropkilus omatus),oi Mexico. Describe the position of the frog when still (Fig. 250). What advantage in this position } Does the frog use its fore legs in swimming or jumping .-^ Its hind legs.'' How is the frog fitted for jumping "i Compare it in this respect with a jumping insect; a jumping mammal. How is it fitted for swimming } Is the general build of its body better fitted for swimming or jumping.? How far can a frog jump .-• External Features. — The frog may be said to have two regions in its body, the head and trunk. A neck hardly I30 ANIMAL BIOLOGY exists, as there is only one vertebra in front of the shoul- ders (Fig. 252), while mammals have seven neck (cervical) vertebrae. There are no tail (caudal) vertebrae, even in the tadpole state of frogs and toads. The head appears triangular in shape when viewed from what direction ? The head of a frog is more pointed than the head of a toad. Is the skull a closed case of broad bones or an open structure of narrow bones .'' (Fig. 252.) Describe the mouth. Observe the extent of the mouth opening (Fig. 251). Atq teeth present in the upper jaw.? The lower jaw } Are the teeth sharp or dull } Does the frog chew its food } Is the tongue slender or thick.'' (Fig. 251.) Is it attached to the front or the back of the mouth .-* In what direction does the free end extend when the tongue lies flat.? Is the end pointed or lobed } How far out will the Fig. 251. — Head of Frog. tongue stretch .-' For what is it used } Why is it better for the teeth to be in the upper jaw rather than in the lower jaw } That the teeth are of little service is shown by the fact that the toad with simi- lar habits of eating has no teeth. Will a toad catch and swallow a bullet or pebble rolled before it.? The toad is accustomed to living food, hence prefers a moving insect to a still one. The Senses. — Compare the eyes with the eyes of a fish in respect to position and parts. Are the eyes pro- truding or deep-set .? Touch the eye of a live frog. Can it be retracted ? What is the shape of the pupil .? The color of the iris .? Is the eye bright or dull .? What probably gave rise to the superstition that a toad had a jewel in its head .? Is there a third eyelid ,? Are the BATRACHIA 131 upper and lower eyelids of the same thickness ? With which lid does it wink ? Close its eye ? Observe the large oval ear drum or tympanum. What is its direction from the eye? (Fig. 251.) The mouth? Is there a projecting ear? Does the frog hear well? What reason for your answer ? As in the human ear, a tube (the Eustachian tube) leads from the mouth to the inner side of the tympanum. How many nostrils? (Fig. 251.) Are they near to- gether or separated ? Large or small ? A bristle passed into the nostril comes into the mouth not far back in the roof. Why must it differ from a fish in this ? How &o Xho. fore and hind legs diiiQv } How many toes on the fore foot or hand ? On the hind foot ? On which foot is one of the toes rudimentary ? Why is the fore limb of no assistance in propelling the body in jumping ? Do the toes turn in or out? (Fig. 250.) How does the frog give direction to the jump ? What would be the disadvantage of always jumping straight forward when fleeing? Which legs are more useful in alighting ? Divisions of the Limbs. — Distinguish the upper arm, fore- arm, and hand in the fore limb (Figs. 252 and 253). Compare with skeleton of man (Fig. 399). Do the arms of a man and a frog both have one bone in the upper arm and two in the forearm ? Both have several closely joined bones in the wrist and Fig. 252. — Skeleton of Frog. 132 ANIMAL BIOLOGY five separate bones in the palm. Do any of the frog's fingers have three joints ? Compare also the leg of man and the hind leg of the frog (Figs. 253 and 399). Does the thigk have one bone in each ? The shank of man has two bones, shin and splint bone. Do you see a groove near the end in the shank bone of a frog (Fig. 252), in- dicating that it was formed by the union of a shin and FIG. .53.-SKELETON OF FROG. gpij^^ ^^^^ p ^^^ first two of the five bones of the ankle are elongated, giv- ing the hind leg the appearance of having an extra joint (Fig. 253). The foot consists of six digits, one of which, like the thumb on the fore limb, is rudimentary. The five developed toes give the five digits of the typical verte- brate foot. Besides the five bones cor- responding to the instep, the toes have two, three, or four bones each. How is the hind foot specialized for swim- ming.? Which joint of the leg con- tains most muscle .!' (Fig. 254.) Find other bones of the frog analogous in position and similar in form to bones in the human skeleton. Fig. 254. — Leg Mus- cles OF Frog. BATRACHIA 133 Is the skin of a frog tight or loose ? Does it have any appendages corresponding to scales, feathers, or hair of other vertebrates ? Is the skin rough or smooth ? The toad is furnished with glands in the skin which are some- times swollen ; they form a bitter secretion, and may be, to some extent, a protection. Yet birds and snakes do not hesitate to swallow toads whole. Show how both upper and under surfaces of frog illustrate protective coloration. All batrachians have large and numerous blood vessels ill the skin by which gases are exchanged with the air, the skin being almost equal to a third lung. That the skin may function in this way, it must not become dry. Using this fact, account for certain habits of toads as well as frogs. If a frog is kept in the dark or on a dark surface, its skin will be- come darker than if kept in the light or on a white dish. Try this experi- ment, comparing two frogs. This power of changing color is believed to be due to the diminution in size of certain pigment cells by contrac- tion, and enlargement from relaxation. This power is possessed to a certain degree not only by batrachians but also by many fishes and reptiles. The chameleon, or green lizard of the Gulf states, surpasses all other animals in this respect (Fig. 280). What advantage from this power .-' Digestive System. — The large mouth cavity is connected by a short throat with the gullet, or esophagus (Fig. 255). FiG. 255. — Digestive Canal of Frog. Mh, mouth; Z, tongue pulled outward; S, opening to larynx; (9^, gullet; M,%Xoxa- ach; D, intestine; P, pan- creas; L, liver; G, gall bladder; R, rectum; Hb, bladder; CI, cloaca; A, vent. 134 ANIMAL BIOLOGY ceives jee ducts^^Lf A slit called the glottis opens from the throat into the lungs (Fig. 255). Is the gullet long or short? Broad or narrow? Is the stomach short or elongated? Is the division distinct between the stomach and gullet, and stomach and intestine ? Is the liver large or small ? Is it simple or lobed ? The pancreas lies between the stomach and the first bend of the intestines (Fig. 255). What is its shape ? A bile duct connects the liver with the small intestine {Dc, Fig. 255), It passes through the pancreas, from which it re- everal pancreatic fter many turns, the estine joins the large intestine. The last part of the large intestine is called the rectum (Latin, straight). The last part of the rectum is called the cloaca (Latin, a drain), and into it the ducts from the kidneys and repro- ductive glands also open. The kidneys are large, elongated, and flat. They lie under the dorsal wall. The urinary bladder is also large. Does the salamander have a similar digestive system ? (Fig. 256.) Why are the liver and lungs (Fig. 256) longer in a sala- mander than in a frog ? Respiration. — How many lungs ? Are they simple or lobed ? (Fig. 256.) A lung cut open is seen to be baglike, with numerous ridges on its inner surface. This increases the surface with which the air may come in contact. In the walls of the lungs are numerous Fig. 256. — Anatomy of Sala- mander. fa, heart; ^, lungs; ^ a, stomach; J ^.in- testine; J c, large intestine; 4, liver; (S, egg masses ; /o, bladder; //, vent. BATRACHIA 1 35 capillaries. Does the frog breathe with 7nouth open or closed? Does the frog have any ribs for expanding the chest ? What part of the head expands and contracts ? Is this motion repeated at a slow or rapid rate ? Regu- larly or irregularly ? There are valves in the nostrils for opening and closing them. Is there any indication of opening and closing as the throat expands and contracts } The mouth and throat (pharynx) are filled with air each time the throat swells, and the exchange of gases (which gases ?) takes place continually through their walls and the walls of the lungs. At intervals the air is forced through the glottis into the lungs. After a short time it is expelled from the lungs by the muscular abdominal walls, which press upon the abdominal organs, and so upon the lungs. Immediately the air is forced back into the lungs, so that they are kept filled. In some species the lungs regularly expand at every second con- traction of the throat. This is shown by a slight out- ward motion at the sides. Does the motion of the throat cease when the frog is under water } Why would the frog be unable to breathe (except through the skin) if its mouth were propped open } Why does the fact that the breathing is so slow as to almost cease when hibernat- ing, aid the frog in going through the winter without starving ? (Chap. I.) Why must frogs and toads keep their skins moist } Which looks more like a clod .'' Why } The Heart and Circulation. — What is the shape of the heart ? (Fig. 257.) Observe the two auricles in front and the conical ventricle behind them. The great arterial trunk from the ventricle passes forward beyond the auricles ; it divides into two branches which turn to the right and left (Fig. 257). Each branch im- mediately subdivides into three arteries (Fig. 257), one going to the head, one to the lungs and skin, and a third, the largest, 136 ANIMAL BIOLOGY passes backward in the trunk, where it is united again to its fellow. (Colored Fig. 2.) Both of the pulmonary veins, returning to the heart with pure blood from the lungs, empty into the left auricle. Veins with the impure blood from the body empty into the right auricle. Both the auricles empty into the ventri- cles, but the pure and impure blood are prevented from thoroughly mix- ing by ridges on the inside of the ventricle. Only in an animal with a four-chambered heart does pure blood from the lungs pass unmixed and pure to all parts of the body. Fig. 257. — Plan of Frog's Circulation. Venous system is black; the arterial, white. A U, auricles ; V, ventricle ; Z., lung; Z./K, liver. Aorta has one FiG. 258. — FrO(,'s 15i ood (magnified 2500 branch to right, another to left, which areas). Red cells oval, nucleated, and reunite below. Right branch only jarger than human blood cells. Nuclei of persists m b.rds. left branch in beasts ^^^ ^^jf^ ^^,,5 ^i^jbie near center. (Pea- and man. , , . body.) and only such animals are warm-blooded. The purer {i.e. the more oxygenated) the blood, the greater the oxidation and warmth. The red corpuscles in a frog's blood are oval and larger than those of man. Are all of them nucleated? (Fig. 258.) The flow of ^/fi'^ in the web of a frog's foot is a striking and interesting sight. It may be easily shown by wrapping a small frog in a wet cloth and laying it with one foot extended upon a glass slip on the stage of a miscroscope. BA TRA CHI A 137 The brain of the frog (Fig. 259) is much like that of a fish (Fig. 224). The olfactory, cerebral, and optic lobes, cerebellum and medulla are in the same relative position, although their rela- tive sizes are not the same. Compared with the other parts, are the olfactory lobes more or less developed than in a fish? The cerebral hemispheres ? The optic lobes? The cerebellum? There is a cavity in the brain. It is readily exposed on the under surface of the medulla by cut- ting the membrane, which is there its only covering (Fig. 259). Fig. 259.— Brain of Frog. Fig. 260. — Nervous System OF Frog. Frogs and toads are beneficial (why } ) and do not the slight- est injury to any interest of man. If toads are encouraged to take up their abode in a garden, they will aid in ridding it of insects. A house may be made in a shady corner with four bricks, or better still, a hole a foot deep may be dug to furnish them protection from the heat of the day. A toad's muzzle is not so tapering as a frog's (why T), its feet are not so fully webbed (why.''), and its skin is not so smooth (why .''). In case of doubt open the mouth and rub the finger along the up- per jaw; a frog has sharp teeth, a toad none at all. The tadpoles of frogs, toads, and sala- manders are much alike. In toad's spawn the eggs lie in strings inclosed in jelly ; frogs spawn is in masses (Fig. 248). ^t"^ -♦^t'^ Fig. 261. — Position of legs in tail- less {A) and tailed (5) amphibian. 138 ANIMAL BIOLOGY Any batrachian may easily be passed around the class after placing it in a tumbler with gauze or net tied over top. It should be kept in a box with two inches of moist earth on the bottom. If no live insects are obtainable for feeding a toad, bits of moist meat may be dangled from the end of a string. If tadpoles are placed in a pool or tub in a garden, the toads hatched will soon make destructive garden insects become a rarity. Does a frog or a salamander have the more primitive form of body .'* Why do you think so ? Salamanders are sometimes called mud puppies. The absurd belief that salamanders are poisonous is to be classed with the belief that toads cause warts. The belief among the ancients that salamanders ate fire arose perhaps from seeing them coming away from fires that had been built over their holes on river banks by travelers. Their moist skin pro- tected them until the fire became very hot. Describe the "mud puppy" shown in Fig. 262. In the West the pouched gopher, or rat (Fig. 371), is sometimes absurdly called a salamander. Fig. 262. — Blind Salamander {Proteus anguinus). x 4. Found in caves and underground streams in Balkans. Gills external, tail finlike, legs small. CHAPTER XII REPTILIA (REPTILES) This class is divided into foiir orders which have such marked differences of external form that there is no diffi- culty in distinguishing them. These orders are represented by Lizards, Snakes, Turtles, and Alligators. Of these, only the forms of lizards and alligators have similar propor- tions, but there is a marked difference in their size, lizards being, in general, the smallest, and alligators the largest of the reptiles. Comparison of Lizards and Salamanders. — To make clear the difference between reptiles and batrachians, it will be well to compare the orders in the two classes which re- semble each other in size and shape ; namely, lizards and I Fig. 263. — A Salamander. Fig. 264. — A Lizard. salamanders (Figs. 263 and 264). State in a tabular form their differences in skin, toe, manner of breathing, develop- ment from egg, shape of tail, habitat, habits. Each has an elongated body, two pairs of limbs, and a long tail, yet they are easily distinguished. Are the differences sug- gested above valid for the other batrachians (frogs) and other reptiles {e.g. turtles) ? Trace the same differences 139 I40 ANIMAL BIOLOGY between the toad or frog (Fig. 250) and the "horned toad," which is a Hzard (Fig. 265). Fig. 265. Horned Toad" Lizard, of the Southwest i^Phrynosoma cornita) . x \. Study of a Turtle or Tortoise Suggestions. — Because of the ease with which a tortoise or turtle may be caught and their movements and habits studied, it is suggested that one of these be studied as an example of reptiles. Besides a live specimen, a skeleton of one species and the shells of several species should be available. Fig. 266. — European Pond Turtle {Etnys lutaria). (After Brehms.) The body (of a turtle or tortoise) is divided distinctly into regions (Fig. 266). Is there a head } Neck .-• Trunk .? Tail .'' The trunk is inclosed by the so-called shell, which REPTILIA 141 consists of an upper portion, the carapace, and a lower portion, the plastron. How are the other regions covered ? What is the shape of the head ? Is the mouth at the front, or on the under side ? Where are the nostrils ? Are the motions of breathing visible ? Is there a beak or snout ? Do the jaws contain teeth f Do the eyes project? Which is thinner and more movable, the upper or lower lid ? Identify the third eye- lid {nictitating membrane). It is translucent and comes from, and is drawn into, the inner corner of the eye. It cleanses the eyeball. Frogs and birds have a similar membrane. The circular ear drum is in a depression back of the angle of the mouth. What other animal studied has an external ear drum .-' The tortoise has a longer, more flexible neck than any other reptile. Why does it have the greatest need for such a neck ? Is the skin over the neck tight or loose ? Why.? Do the legs have the three joints or parts found on the limbs of most vertebrates .-* How is the skin of the legs covered.-* Do the toes have claws? Compare the front and hind feet. Does the tortoise slide its body or lift it when walking on hard ground .'' Lay the animal on its back on a chair or table at one side of the room in view of the class. Watch its attempts to right itself. Are the motions suited to accomplish the object .'' Does the tortoise succeed 1 What are the prevailing colors of turtles .-' How does their coloration correspond to their surroundings .-' What parts of the tortoise extend at times beyond the shell .'' Are any of these parts visible when the shell is closed? What movements of the shell take place as it is closed .'' Is the carapace rigid throughout .'' Is the plastron .-' 142 ANIMAL BIOLOGY The Skeleton (Fig. 267), — The carapace is covered with thin epidermal plates which belong to the skin. The bony nature of the carapace is seen when the plates are removed, or if its inner surface is viewed (Fig. 267). It is seen to con- sist largely of wide ribs (how many ?) much flat- tened and grown together at their edges. The ribs are seen to be rigidly at- tached to the vertebrae. The rear projections of the vertebrae are flattened into a series of bony plates which take the place of the sharp ridge found along the backs of most Fig. 267. — Skeleton of European Tortoise. C, rib plates; M, marginal plates; B, plastron; H, humerus bone; R, radius; U, ulna; Fe, femur. Fig. 268. — Three-cham- bered Heart of a Rep- tile (tortoise). a, veins; b,f, right and left auri- cles; ff', ventricle; rf, arteries to lungs; f, veins from lungs; /, «, two branches of aorta. Compare with Fig. 269 and colored Fig. 2. vertebrates. Show that the shell of a turtle is not homologous with the shells of moUusks. Does the turtle have shoulder blades and collar bones .-* Hip bones .-' Thigh bones } Shin bone (fibia) and splint bone (fibula).? (Fig. 267.) Do the plates formed by the ribs extend to the edge of the cara- pace .'' See Fig. 267. About how many bony plates form the cara- pace .'' The plastron } Do the horny plates outside correspond to the bony plates of the shell } REPTILIA 143 Fig. 269. — Plan of Rep- tilian Circulation. See arrows. How many axial plates .'' How many costal (rib) plates .•* How many border plates.'' Which plates are largest .-' Smallest ? Do the horny plates overlap like shingles, or meet edge to edge .'' Is there any mark where they meet on the bony shell .'' Basing it upon foregoing facts, give a connected and complete de- scription of the structure of the carapace. Compare the skeleton of the turtle with that of the snake, and correlate the differences in structure with differences in habits. Draw the tortoise seen from the side or above, with its shell closed, showing the arrange- ment of the plates. Place soft or tender vegetable food, lettuce, mushroom, roots, ber- ries, and water, also meat, in reach of the turtle. What does it pre- fer .'' How does it eat .-* It has no lips ; how does it drink } Study the movements of its eye- balls and eyelids, and the respira- tory and other movements already mentioned. State a reason for thinking that no species of land animals exists that lacks the sim- ple power of righting itself when turned on its back. Fig. 270. — Reptilian Vis- cera (lizard) . Tortoise, Turtle, Terrapin. — The ^r.windpipe; ,4, heart ;/«, lungs; tUrtlcS bcloUg tO the Ordcr of rcp- Ir, liver; ma, stomach; dd, _ md, intestines; hb, bladder. tllcS Called cheloflianS. No OnC 144 ANIMAL BIOLOGY can have any difficulty in knowing a member of this order. The subdivision of the order into families is not so easy, however, and the popular attempts to classify chelonians as turtles, tortoises, and terrapins have not been entirely successful. Species with a vaulted shell and imperfectly webbed toes and strictly terrestrial habits are called tor- toises. Species with flattened shells and strictly aquatic habits should be called terrapins {e.g. mud terrapin). They have three instead of two joints in the middle toe of each foot. The term turtle may be applied to species which are partly terrestrial and partly aquatic {e.g. snapping turtle (Fig. 271)). Usage, however, is by no means uniform. Fig. 271. — Snapping Turtle {Ckefydra serpentina). Most reptiles eat animal food ; green terrapins and some land tortoises eat vegetable food. Would you judge that carnivorous chelonians catch very active prey ? The fierce snapping turtle, found in ponds and streams, sometimes has a body three feet long. Its head and tail are very large and cannot be withdrawn into the shell. It is carnivorous and has great strength of jaw. It has been known to snap a large stick in two. The box tortoise is yellowish brown with blotches of yellow, and like its close kinsman, the pond turtle of Europe (Fig. 266), with- draws itself and closes its shell completely. Both lids of the plastron are movable, a peculiarity belonging to these two species. The giant tortoise of the Galapagos Islands, ac- REPriUA 145 cording to Lyddeker, can trot cheerfully along with three full-grown men on its back. " Tortoise shell " used for combs and other articles is obtained from the overlapping scales of the Jiawkbill turtle, common in the West Indies. Tht diamond-back terrapin, found along the Atlantic Coast from Massachusetts to Texas, is prized for making soup. Fig. 272. — a Rattlesnake. Venomous snakes of United States named in order of virulence : I. Coral snakes, Elaps, about sev- enteen red bands bordered with yel- low and black (colored figure 6) (fatal). 2, Rattlesnakes (seldom fatal). 3. Copperhead (may kill a small animal size of dog). 4. Water moccasin (never fatal). 5. Ground rattler.— jG^^-^/j-.- Pulse fast, breathing slow, blood tubes dilated, blood becomes stored in ab- dominal blood tubes, stupefaction Fig. 273a. — Head of Viper, showing typical triangular shape of head of venomous snake. Fig. 273^. — Side View, showing poison fangs ; also tongue (forked, harmless) . Fig. 274. — Viper's Head, showing poison sac at base of fangs. Fig. 275.— Skull, showing teeth, fangs, and quadrate bone to which lower jaw is joined. See Fig. 284. 146 ANIMAL BIOLOGY Fig. 276. ■ " Glass Snake," a lizard without legs. and death from blood being withdrawn from brain. Al- ways two punctures, the closer together the smaller the snake. Remedies: Ligature between wmmd and heart, lance wound and suck; inject into wound three drops of i per cent solution of chromic acid or potassium perman- ganate. Give strychnine, hypodermically, until strychnine symptoms (twitchings) appear. If symptoms of collapse recur, repeat dose. Digitalin or caffein acts like strych- nine ; alcohol has opposite effect. Protective Coloration and Mimicry. — When an animal imitates the color or form of its inaniniate surroundings it is said to be protectively col- ored or formed. Give an instance of protective col- oration or form among Hzards ; butterflies ; grass- hoppers; amphibians; echi- noderms. When an animal imitates the color or form of another animal it is said to mimic the animal. Mimicry usually enables an animal to deceive enemies into mistaking it for an ani- mal which for some reason they avoid. The milkweed butterfly has a taste that is repulsive to birds. The vice- roy butterfly is palatable to birds, but it is left untouched because of its close resemblance to the repulsive milkweed butterfly. The harlequin snake {Elaps) of the Gulf states is the only deadly snake of North America (Figs. 277, 278). It is very strikingly colored with rings of scarlet, yellow, and black. This is an example of ivarning coloration. The coral snake {Lampropeltis) has bands of Fig. 277. — Skull of Elaps. See colored Fig. 5. Fig. 278. = Skull of Lampropeltis. COLORED FIGURES I. 2. 3— CIRCULATION IN FiSH, REPTILE, MaMMAL In which is blood from heart all impure? Mixed? Both pure and i-npure ? FIG. 4. -ANATOMY OF Carp. For description see Fig. 220. page 117. Fig. 5. — Harlequin Snake {Elaps) The Harmless Coral Snake mimics the Deadly Harlequi Snake. FKi. 6. — Coral Snake (L ampropeltis). REPTILIA 147 scarlet, yellow, and black (colored Fig. 6) of the same tints, and it is hardly distinguishable from the harlequin. The Fig. 279. — vjii.A '^lo'SSTKK {Heloderma iuspecfum), Kji niii.Kjn '\:v'S.T'LY.{Platystemummegalocephalum). x }. China. This and Fig. 282 suggest descent of turtles from a lizardlike form. Figure 282 shows earlier ancestors to have been gill breathers. CHAPTER XIII BIRDS Suggestions. — The domestic pigeon, th'^ fowl, and the English sparrow are most commonly within the rench of students. The last bird has become a pest and is almost the only bird whose destruction is desirable. The female is somewhat uniformly mot- tled with gray and brown in fine markings. The male has a black throat with the other markings of black, brown, and white, in stronger contrast than the marking of the female. As the different species of birds are essentially alike in structural features, the direc- tions and questions may be used with any bird at hand. When studying feathers, one or more should be provided for each pupil in the class. The feet and bills of birds should be kept for study. Does the body of the bird, like the toad and turtle, have a head, trunk, tail, and two pairs of limbs ? Do the fore and hind limbs differ from each other more or less than the limbs of other backboned animals .-' Does any other vertebrate use purposes as widely different .-' Does the eyeball have parts corresponding to the eyeball of a fish or frog; viz., cornea, iris, pupil? Which is more movable, the upper or lower eyelid? Are there any lashes.? The bird (like what other animal?) has a .third eyelid, or nictitating membrane. Compare its thickness with that of the other lids. Is it drawn over the eyeball from the inner or outer comer of the eye ? Can you see in the human eye any wrinkle or growth which might be regarded as remains, or vestige, of such a membrane ? 150 BIRDS 1 5 1 How many nostrils? In which mandible are they located ? Are they nearer the tip or the base of the mandible ? (Fig. 284.) What is their shape ? Do the nasal passages go directly down through the mandible or do they go backward ? Is the inner nasal opening into the mouth or into the throat ? The beak or bill consists of the upper and lower man- dibles. The outside of the beak seems to be of what kind of material .-' Examine the decapitated head of a fowl or of a dissected bird, and find if there is a covering on the bill which can be cut or scraped off. Is the mass of the bill of bony or horny material .-' With what part of the human head are the mandibles ^^^- 284. -skull of Domestic fowl. , . , /T-- o \ y, quadrate ("four-sided") bone by which lower homologous i (r Ig. 284. ) jaw is attached to skull (wanting in beasts, pres- Ears. — Do birds have '"' *" ''^p"'"^ "^^ ^'^- '"^• external ears .■' Is there an external opening leading to the ear .'' In searching for it, blow or push forward the feath- ers. If found, notice its location, size, shape, and what surrounds the opening. There is an owl spoken of as the long-eared owl. Are its ears long .-' The leg has three divisions: the uppermost is the tJiigh (called the "second joint" in a fowl); the middle division is the shank {or "drumstick"); and the lowest, which is the slender bone covered with scales, is formed by the union of the ankle and instep. (The bones of the three divisions are named the femur, tibiotarsus, and tarsometa- tarsus.) The/> toes, the — joints ; The pigeon has - hind toe having of the three front toes, the inner has joints (count the claw as one joint), the Fig. 285. — Leg Bones OF Bird. the Fig. 286. — Skeleton of Bird. Rk, vertebrae; CI, clavicle; Co, coracoid; Sc, scap- ula; St, sternum; H, humerus; R, radius; U, ulna; /", thumb; /v, femur; 7", tibia. See Fig. 394. Questions : Which is the stiffest portion of the vertebral column ? How are the ribs braced against each other ? Which is longer, thigh bone or shin ? Compare shoulder blade with man's ( Fig. 399) . Which is the extra shoulder bone ? Compare tail vertebrae with those of extinct bird, Fig. 29a middle has joints, and outer toe has joints (Fig. 285). Is the thigh of a bird bare or feathered .? The shin .? The ankle } Where is the ankle joint of a bird } Do you see the remains of another bone (the splint bone, or fibula) on the shin bone of the shank.? (Fig. 285 or 286.) Why would several joints in the ankle be a disadvan tage to a bird } BIRDS 153 The thigh hardly projects beyond the skin of the trunk, as may be noticed in a plucked fowl. The thigh extends forward from the hip joint (Figs. 286, 299) in order to bring the point of support forward under the center of weight. Why are long front toes more necessary than long hind toes } As the bird must often bring its head to the ground, the hip joints are near the dorsal surface and the body swings between the two points of support somewhat like a silver ice pitcher on its two pivots. Hence stooping, which makes a man so unsteady, does not cause a bird to lose steadiness. The wing has three divisions which correspond to the upper arm, forearm, and hand of man (Fig. 286). When the wing is folded, the three divisions lie close alongside each other. Fold your arm in the same manner. The similarity of the bones of the first and second divisions to the bones of our upper arm and forearm is very obvious (Fig. 286). Ex- DG.I MC.r plain. ^\vQ. hand oi a bird is furnished with only three dig- its (Fig. 287). The three palm bones (metacarpals) are firmly united (Fig. 287). This^ gives firmness to, the stroke in flying. That the bird is descended from ani- mals which had the fingers and palm bones less firmly united is shown by comparing the hands of a cJiick and of an adult fowl (Figs. 287, 288). The wrist also solidifies with age, the: Fig. 287. — Hand and Wrist of Fowl (after Parker). DC 1-3, digits; MC. 1-3, metacarpals; CC. 3, wiist. Fig. 288. — Hand, Wrist {c), Forearm, and Elbow of Young Chick (after Parker). 154 ANIMAL BIOLOGY Fig. 289. — Breast- bone AND Shoul- der Bones ok Cassowary. five carpals of the chick being reduced to two in the fowl (Figs. 287, 288). The thumb or first digit has a separate covering of skin from tHe other digits, as may be seen in a plucked bird. The de- generate hand of the fowl is of course useless as a hand (what serves in its place ?) but is well fitted for firm support of the feathers in flying. The two bones of the forearm are also firmly joined. There are eighteen movable joints in our arm and hand ; the bird has only the three joints which enable it to fold its wing. The wrist joint is the joint in the forward angle of the wing. Since the fore limbs are taken up with loco- motion, the grasping function has been as- sumed by the jaws. How does their -" shape adapt them to this use ? For the same reason the neck of a bird ,' ' •. i surpasses the necks of all other ani- mals in what respect? Is the trunk of a bird flexible or inflexible } There is thus a cor- relation between struc- ture of neck and trunk. Explain. The same correlation is found in which of the reptiles ? (Why does rigidity of trunk require flexibility of neck ?) Why does ^^ Fig. 290. — A Fossil Bird {archmopteryx) found in the rocks of a former geological epoch. Question: Find two resemblances to reptiles in this extinct bird absent from skeletons of extant birds. BIRDS 155 the length of neck in birds correlate with the length of legs? Examples? (See Figs. 314, 315, 332.) Exceptions? (Fig. 324.) Why does a swan or a goose have a long neck, though its legs are short ? To make a firm support for the wings the vertebrae of the back are immovably joined, also there are three bones in each shoulder, the collar bone, the shoulder blade, and the coracoid bone (Fig. 286). The collar bones are united (why ?) and form the " wishbone " or " puHing bone." To furnish sur- face for the attachment of the large flying muscles there is a prominent ridge or keel on the breastbone (Fig. 286). It is lacking in most birds which do not fly (Fig. 289). The feathers-are-perhaps the most characteristic feature of birds. The large feathers of the wings and tail are called quill featJiers. A quill feather (Fig. 291) is seen to consist of two parts, the shaft, or supporting axis, and the broad vane or web. What part of the shaft is round ? Hollow ? Solid ? Is the shaft straight ? Are the sides of the vane usually equal in width ? Can you tell by looking at a quill whether it belongs to the wing or tail, and which wing or which side of the tail it comes from ? Do the quills overlap with the wide side of the vane above or beneath the next feather ? Can you cause two parts of the vane to unite again Fig. 291. — Quill Feather. D, downy portion. 156 ANIMAL BIOLOGY by pressing together the two sides of a split in the vane ? Does the web separate at the same place when pulled until it splits again ? The hollow part of the shaft of a quill feather is called the quill. The part of the shaft bearing the vane is called the rachis (ra-kis). The vane consists of slender ^^^^tf-which are branches of the shaft (II, Fig. 292). As the name indicates (see dictionary), a barb resembles a hair. The barbs in turn bear second- ary branches called burz. bules, and these again have shorter branches called bop- FiG. 292. — I, Contour Feather. II, III, Parts of Quill Feather, enlarged. bicels (III, Fig. 292). These are sometimes bent in the form of booklets (Fig. 292, III), and the booklets of neighboring barbules interlock, giv- ing firmness to the vane. When two barbules are split apart, and then re- united by stroking the vane between the thumb and finger, the union may be so strong that a pull upon the vane will cause it to split in a new place next time. There are four kinds of feathers, (i) the, £uill feathers, just studied ; (2) the contour feathers (I, Fig. 292), which form the general surface of the body and give it its outlines ; (3) the down^QdiXhQrs, (Fig. 293), abundant on Fig. 293. — a Down Feather, enlarged. BIRDS 157 nestlings and found among the contour feathers of the adult but not showing on the surface ; (4) the pin feathers, which are hair-like, and which are removed from a plucked bird by singeing. The contour feathers are similar in structure to the quill feathers. They protect the body from_blows, overlap so as to shed the rain, and, with the aid of the downy feathers retain the heat, thus accounting for the high temperature of the bird. The downy feathers are soft and fluffy, as they possess few or no barbicels; sometimes they lack the rachis (Fig. 293). The pin feath- ers are delicate horny shafts, greatly resembling hairs, but they may have a tuft of barbs at the ends. A feather grows from a small projection (or papilla) found at the bottom of a depression of the skin. The quill is formed by being molded around the papilla. Do you see any opening at the tip of the quill for blood vessels to enter and nourish the feather .•• What is in the quill ,-' (Fig. 291.) The rachis .-• A young con- tour or quill feather is in- closed in a delicate sheath which is cast off when the feather has been formed. Have you seen the sheath incasing a young feather in a 'molting bird } There are considerable areas or tracts on a bird's skin without contour feath- ers. Such bare tracts are found along the ridge of the breast and on the sides of the neck. However, the contour feathers lie so as to over- lap and cover the whole body perfectly (Fig. 294). The shedding of the feathers is called molting. Feathers, Fig. 294. — Dorsal and Ventral View of Plucked Bird, showing regions where feathers gp-ow. 158 ANIMAL BIOLOGY like the leaves of trees, are delicate structures and lose perfect condition with age. Hence the annual renewal of the feathers is an advantage. Most birds shed twice a year, and with many the summer plum- age is brighter col- ored than the winter plumage. When a feather is shed on one side, the corre- sponding feather on the other side is always shed with it. (What need for this .-") A large oil gland is easily found on the dorsal side of the tail. How does the bird apply the oil to the ^ _ '"'vK.^:^:^^^ y'as feathers .■' Fig. 295. — Wing of Bird. /, false quills (on thumb) ; 2, primaries; 5, secondaries; tertiaries (dark) are one above another at right; a, b, coverts. Fig. 296. A , point dividing primaries from second- aries; S, coverts. In describing and classifying birds, it is necessary to know the names of the various external regions of the body and plum- age. These may be learned by studying Figs. 295, 296, 297, 298, Fig. 297. — Cedar Waxwing, with regions of body marked. S, forehead; Sc, crown (with crest); H/t, nape; IC, throat; Br, breast; Ba, lower parts; /?, back; i?/, tail; B, tail coverts; P, shoulder feathers (scapulars) ; T, wing coverts; HS, primaries; AS, secondaries; A I, thumb feathers. The quills on the hand BIRDS 159 are called primaries, those on the forearm are the sec- ondaries, those on the upper arm are the tertiaries. Those on the tail are called the tail quills. The feathers at the base of the quills are called the coverts. The thumb bears one or more quills called the spurious quills. Is the wing concave on the lower or upper side ? What advantage is this when the bird is at rest ? When it is flying ? Control of Flight. — Did you ever see a bird sitting on a swinging limb .'' What was its chief means of balancing itself .-' When flying, what does a bird do to direct its course upward } Downward .'' Is the body level when it turns to p,^ 298.-PLAN of bird. either side.'' Birds with long, j, center of gravity, pointed wings excel in what respect ? Examples .-' Birds with great wing surface excel in what kind of flight } Ex- amples. Name a common bird with short wings which has a labored, whirring flight. Is its tail large or small } Does it avoid obstacles and direct its flight well .-* Why or why not .'' When a boat is to be turned to the right, must the rudder be pulled to the right or the left .? (The rudder drags in the water and thus pulls the boat around.) When the bird wishes to Fig. 299. — Position of go upward, must its tail be turned up Limbs of Pigeon. , •> tt 1 ... or down i How when it wishes to go down } When a buzzard soars for an hour without flapping its wings, does it move at a uniform rate .-* For what does it use the momentum gained when going with the wind ? i6o ANIMAL BIOLOGY Flying. — When studying the quill feathers of the wing, you saw that the wider side of the vane is beneath the feather next behind it. During the downward stroke of the wing this side of the vane is pressed by the air against Fig. 300. a, clambering foot of chimney sweep; b, climbing foot of woodpecker; c, perching foot of thrush; d, seizing foot of hawk; e, scratching foot of pheasant; /, stalking foot of king- fisher; g, running foot of ostrich; h, wading foot of heron; i, paddling foot of gull; ^, swimming foot of duck; /, steering foot of cormorant; »«, diving foot of grebe; », skim- ming foot of coot. Question: Does any bird use its foot as a hand? (Fig. 320.) the feather above it and the air cannot pass through the wing. As the wing is raised the vanes separate and the air passes through. The convex upper surface of the wing also prevents the wing from catching air as it is raised. Spread a wing and blow strongly against BIRDS i6i its lower surface ; its upper surface. What effects are noticed ? Study the scales on the leg of a bird (Fig. 300). Why is the leg scaly rather than feathered from the ankle down- ward .<• Which scales are largest ."^ (Fig. 300.) How do the scales on the front and back differ } What can you say of the scales at the bottom of the foot ; at the joints of the toes .-' Explain. How does, the covering of the nails and bill compare in color, texture, hardness and firm- ness of attachment with the scales of the leg .'' Draw an outline of the bird seen from the side. Make drawings of the head and feet more detailed and on a larger scale. Why does a goose have more feathers suitable for making pil- lows than a fowl .? In what country did the domestic fowl originate.'' (Encyclopedia.) Why does a cock crow for day } (Consider animal life in jungle.) Activities of a Bird. — Observe a bird eating. Does it seem to chew or break its food before swallowing.? Does it have to lift its head in order to swallow food } To swallow drink } Why is there a difference 1 After feed- ing the bird, can you feel the food in the crop, or enlargement of the gullet at the base of the neck.? (Fig. 304.) Feel and look for any move- M Fig. 301. — An Altrical Bird, i.e. poorly developed at hatch- ing. Young pigeon, na]