E. Stenhouse

“ The study of the skeleton.—The study of the rabbit’s skeleton is not only highly interesting in itself, but necessary for the intelligent appreciation of the animal’s life. And when it is compared with the skeletons of other familiar animals, a common plan of structure is found which illustrates in the most convincing manner the kinship which often exists between very dissimilar creatures. Such a comparison shows that, almost bone for bone, the skeleton of a rabbit corresponds with that of a man or a horse, and even with that of a bird or a frog. ”

“ The work of flowers.—The roots, stem, and leaves of a plant do a great deal of work, but, as it is performed for the benefit of the plant itself, it is all, in a sense, selfish work. Plants, however, like animals, grow old in time, and at last die. If they are not to become extinct it is evident that they must devote part of their energies to producing new individuals, and to sending these forth into the world as well equipped as possible for the battle of life. This unselfish and self-sacrificing part of a plant’s life-work is called reproduction ”

“ The stored food makes its way to the terminal buds; invigorated by the rich sugary sap the young leaves swell and push forward, burst apart the scales, and open out their folds to the light and air, as if eager to get to work at the earliest possible moment. ”

“ About the fourteenth day the chick turns so as to lie lengthwise in the shell, with its head near the broad end. The yolk-sac dwindles in size, and at last, about the twentieth day, it is drawn into the interior of the body. Now the chick becomes restless, and—usually on the twenty-first day—thrusts its beak through the inner shell-membrane into the air-chamber at the broad end of the egg. For the first time it draws refreshing air into its lungs, and is stimulated to break the shell by a knob on its beak, and to creep out into the world. ”

“ A green plant obtains its carbon from the air.—Since the parts of a plant contain much carbon, and the food which a plant obtains from the soil need not contain any carbon; while the air, on the other hand, does contain carbon, it seems likely that a plant obtains its carbonaceous food from the air. This surmise is confirmed by experiments. One of the most easily recognisable of plant products containing carbon is starch, for it yields a very characteristic blue, or purplish-brown, colour when treated with iodine solution. ”

“ The embryo lies to one side and in the lower half of the seed. At its upper end the young stem and at its lower end the young root—each still enclosed in protecting sheaths—are easily seen. The greater part of the seed is quite outside the embryo; it is a mass of food called the endosperm, which has been stored up for the use of the young plant during its earliest stages of germination. This food mass at once turns blue when a drop of iodine solution is placed upon it, showing that it contains a considerable amount of starch. It is the endosperm which is made into flour when corn is ground. ”

“ The breathing of plants is essentially like that of animals, and consists in taking in oxygen and giving out carbon dioxide; though the mechanism of respiration is—except in the lowest plants and animals—entirely different in the two cases. It is in the sources from which they obtain their food that plants and animals are most unlike. An animal must be supplied with food which has already been prepared by some other living thing; and it is obvious that the food even of carnivorous animals can ultimately be traced back to plants, for the flesh-eater preys upon the vegetarian. ”

“ Skylarks rarely sing in the depth of winter; in autumn they form large flocks which patrol the fields until spring in search for food—rendering incalculable services to mankind by the destruction of insect-larvae. ”

“ Autumn colours and the fall of the leaf.—As the summer wanes, the soil becomes colder, and the chilled roots lose much of their power of absorbing moisture. It is plain that if the leaves continued giving off water when no fresh supplies were forthcoming the tree would suffer. How is the danger to be met? Starch and other foods have already been stored up in quantity sufficient to supply the needs of the winter and the early spring. The leaves have finished their work, and one by one they fall off. ”

“ The rabbit cannot move a muscle except at the expense of the living substance of the muscle, and the more active is its life, the more rapidly does its body waste. It is to counteract this continual waste by continual formation of new living substance that food is taken.
But the succulent plants which the rabbit eats are not suddenly transformed into animal muscle and bone, and so forth, when they are swallowed. They have first of all to undergo a process which is called digestion. This takes place in a tube—the digestive canal—which runs from end to end of the body. ”

“ In a running flock of sheep does any one animal act as leader? Is the leader a ram or a ewe? Is it a lamb or an old animal? Do the rest of the flock imitate the actions of the leader, and, for example, leap over a wall at the same place in single file? Have you ever noticed that if one animal jumps at a certain place, all the following sheep jump at the same place? Have you ever seen sheep fighting? ”

“ The hen’s egg.—A hen’s egg bears a somewhat similar relation to the adult bird that the maize or bean seed (Chapter I.) bears to the adult plant; for the egg contains
(1) a speck of living matter which little by little grows and becomes marked off, by orderly arrangement, to form the various regions and organs of the adult animal; and
(2) a store of food, which enables the young chick to develop in security, without being hampered, whilst still weak and helpless, by the necessity of earning its own living. ”

“ The carbonaceous food of a young seedling.—Just as a bean or pea seedling is for a time independent of an outside supply of mineral food—its roots needing only to be supplied with water—so there is enough carbonaceous food also stored up in the seed to satisfy for some time the needs of the growing plant—the stored starch being gradually changed into sugar and absorbed. For this reason a young seedling will live healthily in the dark. ”

“ Even in the seed they are green, and plainly leaves. How do they escape from the seed-coat? What is their shape? Do they come out before or after the radicle? Do they get any larger as the stem grows? How large can you get a sycamore seedling to grow in damp sawdust? As large as a seedling of pea or bean? Plant some sycamore seeds on earth and compare the shape of the cotyledons with that of the next-formed leaves. How soon do the “true” leaves appear after the cotyledons have escaped from the seed? Do any “true” leaves grow on the plants in sawdust? ”

“ The plant obtains its mineral food from the soil by means of its roots; and its spreading green leaves, or fronds, enable it, with the help of the sunlight, to decompose the carbon dioxide of the air and to build up starch, sugars, and other carbonaceous compounds.
The male-fern.—The common male-fern (which, by the way, has no sex whatever) may be taken as a type of the group. It occurs abundantly in woods and hedgerows. The stem, or rhizome, is short and stumpy; it grows obliquely upwards, and does not branch. It is covered with old leaf-bases, which are clothed with brown, scaly hairs. ”

“ As the bee thrusts its proboscis down between stamens and pistil in search of the sweet liquid in the pouches, its head is pretty certain to come in contact with, and to brush off, some of the pollen dust hanging loose on the inner faces of the anthers. When the bee flies off to another wallflower and continues its search for nectar, it almost invariably leaves some of the pollen, from the first flower, on the hairy and sticky stigma of the second.
In almost all cases when a flower is brightly coloured it depends upon the help of insects for cross fertilisation. ”

“ The production of flowers and fruit is a great strain on a plant, and it is to prepare for the effort that the turnip and radish store so much food in their roots during the first year as to give them a globular and spindle shape respectively. A carrot is not a crucifer, but it also adopts this device.
The cabbage is grown for its leaves. Varieties of the cabbage are Brussels sprouts, broccoli, and cauliflower; it is the very small flower-buds of the last two which are eaten. Cress and white mustard are eaten in the seedling stage. ”

“ That the plant really has taken up some solid matter from the soil can be proved by a few simple experiments. A plant which has been growing in soil for some time after its seed food is used up is dried and burnt, and the ashes are weighed. The weight of ash or mineral matter thus obtained is found to be considerably greater than that of the ash obtained from an ungerminated seed, or from a seedling grown in damp sawdust or sand which has only been supplied with pure water. ”

“ When mature, the knobs burst open, and the fine spores are scattered in the air. The various parts of the mould are best seen in position by scattering some of the spores, or a little dust from a shelf, upon the surface of clear, colourless fruit-juice in a glass vessel, and following the stages of growth with a lens. It then becomes clear that the mould—like the mushroom—consists of (a) a buried tangle or mycelium of hyphal threads which take in the plant’s food, and of (b) an aërial part which scatters the spores. ”

“ Changes take place in nearly all the internal organs, fitting the animal for its life on land; and these changes are so extensive that there is necessarily a short period when the creature is neither tadpole nor frog, and is incapable of feeding. The tail, however, which would be useless to the terrestrial, leaping frog, is gradually absorbed, and forms a store of nutriment during the transformation.
The gills shrivel up, and the slits close; the outer layer of the skin (including the horny jaws) is thrown off, the hind limbs lengthen, and the animal leaves the water—a frog. ”

“ Something very similar often takes place in plants. It was seen (p. 33) that the cotyledons of a pea become sweet during germination. Starch is a convenient form of food for storing in the cotyledons of a pea, the endosperm of the maize seed, the short stem of the crocus-corm, and so on; but before the plant can use it as food the starch must be made soluble and diffusible by being changed into sugar. In plants the change is brought about, not by saliva, but by a substance known as diastase. ”

“ A creeping stem.—Examine a plant of the ground ivy. Is the stem strong enough to stand upright? How does it spread out its leaves to the light and air? The stem grows along the ground, and at intervals it gives off a pair of leaves which grow upwards, and a tuft of roots which grow down to the ground.
2. A runner.—Is the “runner” of the strawberry of the same nature, i.e. is it a continuous stem like that of the ground ivy? When the plant is carefully examined, the creeping “stem” is seen to be a branch arising in the axil of a leaf. ”

“ Each flower consists of two stamens, borne on a silky scale which has a tiny honey cup at the base. The female flowers form long, narrow, and silvery catkins; each flower is merely a single pistil with a forked stigma, and, like a male flower, is supported on a small honeyed bract. The flowers appear in March, before the leaves, and the catkins are very conspicuous. They are visited by bees for the sake of the honey and pollen, pollination being thus effected. In June, the female catkins are ripe. Each ovary has now become a fruit, which opens and liberates the silky seeds. ”

“ It ought to be borne in mind, however, that the essence of respiration is the same in all living things, and consists in a replacement of excess carbon dioxide by fresh oxygen (p. 242) ; the difference lies merely in the manner of effecting the exchange. In the rabbit, the blood, carrying the excess of carbon dioxide, is brought to the air (in the lungs) ; in the tadpole it is exposed, in the gills, to the dissolved air of the surrounding water; while in the cockroach the air is carried directly to the tissues needing fresh oxygen. ”

“ The food, which consists chiefly of insects, snails, and worms, must be moving to excite interest; then the frog, whose favourite position is half squatting, half supported by the arms, erects itself and, facing the insect, turns round upon its haunches, adjusts its position anew by a shifting of the legs, and betrays its mental agitation by a few rapid movements of the throat. ”

“ The thrush family.—For many reasons the thrush family forms a convenient starting point in the study of the habits of common British birds. It includes some of our very finest songsters and therefore most popular birds; many of its members are abundant in most parts of the country, so that nearly every student has the opportunity of observing them at first hand; the birds are not specially shy; and, lastly, the family affords excellent material for the method of comparison and contrast, which, be it repeated, is the essence of all sound work in nature-study. ”

“ The life-history of Dytiscus.—In March or April the female Dytiscus lays her eggs in slits which she cuts in the submerged stems of pond-weeds, and the eggs hatch in about three weeks. The creature which emerges from the egg is of active habits, but is not at all like the parent in appearance. A young animal which leads an independent and self-supporting life, and differs markedly in structure from the adult, is called a larva. Thus a tadpole is a larval frog, and a caterpillar is the larva of a butterfly or moth. ”

“ Even in the egg, it may be heard chirping soon after it has taken its first breath of air; and the complex activities of walking, running, jumping over obstacles, and, later, preening the feathers and scratching the ground—each of which involves the nicest adjustment of several muscles—are also instinctive. Certain other powers have to be learnt; the hen, for example, lifts and drops before the chick a particle of food which she wishes it to seize, and it soon learns to peck. ”

“ It is at once plain that the seedlings fall into two classes, according to the number of cotyledons or seed-leaves which they possess. The wheat and maize have only one such seed-leaf, while the mustard, bean, pea, sycamore, and vegetable marrow have two each. We shall see later on that one-seed-leaved plants differ from those with two seed-leaves not only in the number of their cotyledons, but also in the characters of their leaves and flowers and in their method of growth. ”

“ The structure of the martin, like that of the swallow, is admirably adapted to a life in the air, and to a diet of flying insects—the bird having powerful wings, small and weak feet, and a soft and short but widely-opening beak. ”