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ADVENTURES WITH A HAND LENS
By Richard Headstrom
Dover Publications, Inc.Copyright © 1976 Richard Headstrom
All rights reserved.
We Peer through Our Lens at Somme Familiar Objects
FOR OUR FIRST ADVENTURE we shall examine a few things we can find around the house. And what can we better start with than the paper on which these words are printed? Examine it with your hand lens or pocket magnifier. Next examine a piece of newspaper and then a piece of glossy paper from one of the better magazines, and finally compare all three with a piece of blotting paper. In which paper do you find a network of loose fibers? I think you will agree that in the blotting paper the fibers are more in evidence and that there are larger spaces between them. This is the secret of the blotting paper's action in absorbing ink. It all has to do with capillarity, which we can define simply as the creeping of a liquid into a very narrow space, and that is just about what the ink does when it passes into the blotting paper.
Now look at a piece of fabric and see how it appears under a lens. Hold up to the light a towel, or shirt, or skirt, or handkerchief and examine a section of it with your lens. You will observe threads running crosswise. (Figure 1). The threads running lengthwise are called the warp; those running crosswise the woof. It is said that the number of threads per inch is an indication of quality or strength. Select a square-inch area of any fabric and count the number of threads in the woof. A high thread count indicates good quality or that the fabric is strong and will wear well; a low thread count indicates the opposite. While you are still holding the fabric to the light, note if there is any unevenness in the weave. If there are spots which appear thinner than others or if the fabric is woven unevenly, the material will wear unevenly.
Most of us regard an egg merely as an article of food, and though we all know that a chicken can be hatched from it we give little thought to this miracle. You will learn how an egg is put together and how a plant or animal develops from it. For the present all we are interested in is the shell of our breakfast egg.
A chicken can be hatched from it, but only under certain conditions. First of all the egg has to be a fertile one, and secondly it has to be incubated. That the developing chick may have air, there must be some way for the air to enter the egg. There must also be some way for waste gases to escape, for every living thing gives off waste gases, and if they are allowed to accumulate they have a toxic effect on the organism. Look at the shell of an uncooked egg through your lens or, better still, hold a piece of shell from your breakfast egg up to a light. You will see numerous small openings, or pores. It is these openings, or pores, which provide for the entrance of air and the escape of the poisonous gases.
Speaking of the breakfast egg calls to mind our breakfast cup of coffee. Spread a little ground coffee and a little instant coffee on a piece of white paper and look at them with your lens. You will find that they differ markedly in appearance. The ground coffee will appear as shown in Figure 2. The instant coffee will appear as tiny brown beads or tiny brown bubbles (Figure 3). Instant tea appears much like instant coffee, although the beads appear larger, or at least those I have examined do. Regular tea differs considerably in appearance since it is simply the dried leaves of the tea plant or, if obtained from a tea bag, pieces of the leaves which have been shredded (Figure 4).
In many families breakfast is followed by a cigarette. Here is another very commonplace article which few of us have ever troubled to examine closely. If a member of your family smokes cigarettes, inspect the tobacco. You will find it consists of very small pieces of the tobacco leaf, which you would naturally expect to find (Figure 5). Examine the filter, too, if the cigarette is provided with one. And while we are on the subject of cigarettes and smoking, view the head of a paper match and the ashes of either a cigarette or cigar. You will find that the ashes look like the gray incrustations we often find on rocks and which we will study in a later Adventure.
Dust is an accumulation of all sorts of debris. It frequently figures in mystery stories and also in real-life police investigations. Criminals have been detected and convicted by dust found on their clothing, but we are not interested in criminal detection; rather in the substances we can identify in some sweepings. Sweep up a little dust from the floor or elsewhere onto a piece of white paper. See how many substances you can recognize.
In many ways soil is as interesting as dust, for you never know what you may find in the way of very small animals, seeds, and the remains of plants and animals. Also an examination of soil will enable you to determine what kind it is and whether it is suitable for a garden. Get an old spoon, go outdoors and dig up a spoonful of soil, bring it indoors, and spread it out on a piece of white paper. Good garden soil should contain a maximum of humus, which is formed by the partial decomposition of dead plants and animals or parts of them, and a minimum amount of sand and clay. Perhaps you may be able to identify some of the plants and animals from their remains (Figure 6). There are people who are experts in such matters.CHAPTER 2
We Listen to Some Music and Discover How It Is Played
THE CHIRPING OF CRICKETS is a familiar sound on a summer's night, especially to those who live in the country. Only the males chirp. Why, I don't know. It was believed at one time that they play their fiddles to attract the females. But it has since been shown that the females pay no attention to the males' serenades. Someday we may know the reason. What we are primarily interested in is how the male crickets play. The best way to find out is to get one or two of them and observe them at close quarters. Incidentally, crickets make excellent pets and may be kept in a large jar or similar container with a little soil on the bottom. They can be fed bits of melon and other fruits, lettuce, and moist bread. A little bone meal should also be supplied to reduce cannibalism. If eggs are laid and you want to hatch them, sprinkle the soil with water as you would for plants. The female, by the way, can be distinguished from the male by the presence of a long, swordlike ovipositor, or egg-laying apparatus, extending from the end of her body.
To return to our question of how a male cricket plays, observe that when he does so he lifts his wing covers at an angle of forty-five degrees and then rubs them together. Actually it isn't quite as simple as that. If you examine one of the wing covers with your lens, you will note that the venation is of a peculiar scroll pattern which probably serves as a framework for the purpose of making a sounding board of the wing membrane by stretching it out as a drumhead is stretched. Also note that near the base of the wing cover there is a heavy cross vein covered with transverse ridges called the file (Figure 7). Next find on the inner edge of the same wing near the base a hardened area. This area is called the scraper (Figure 7). When the cricket sounds his notes, he does so by drawing the scraper of the underwing cover against the file (Figure 8) of the overlapping one. We can produce a similar sound by running a file along the edge of a tin can.
As the wing covers are excellent sounding boards and quiver when the note is made, the surrounding air is set into vibration, thus creating sound waves which can travel a considerable distance. An interesting sidelight in regard to this sounding device is that the cricket can alternate his use of the wing covers, that is, he can use first one wing cover as a scraper and the other as a file and then reverse them. In this way he can reduce the wear and tear and prevent them from being worn out.
Now there doesn't seem to be much sense in a cricket's being able to produce a sound unless he can hear it. If you look on the tibia of the front leg, you will note a small white disklike spot (Figure 9). This is the ear and is visible to the naked eye.CHAPTER 3
We Give Seeds More Than a Passing Glance
WE ACCEPT SEEDS for what they are and give little thought to them. Yet if we were to look at them more closely, especially with our lens, we would be amazed at their infinite diversity. They are as variable as the flowers that produce them and some are equally as beautiful.
Although they are typically more or less globular or oval in shape (Figure 10), there are seeds that are extremely thin and flat (Figure 11) or greatly elongated (Figure 12). Seeds, too, may be smooth or wrinkled or pitted or angled or furrowed (Figure 13). There are seeds that are twisted or coiled (Figure 14) or otherwise irregularly distorted (Figure 15). Then there are seeds that are more or less covered with hairs or supplied with broad and extremely delicate membranous wings to make them wind-borne. In size the variations are equally pronounced. Some seeds are as fine as dust; others several inches in diameter; and, of course, there are seeds that represent all the gradations in between. But it is in the variety of color and color patterns that they show the most conspicuous external differentiation. I daresay we can find them matching every known color, from shining jet black through the gamut of blue, red, yellow, and other bright tints to the less striking and more somber brown and gray, to say nothing of the manifold designs produced by a blending of these colors.
Colors, needless to say, are not without some purpose. Seeds that are scattered by wind and water are, for the most part, inconspicuously or neutrally colored, but the bright and showy ones are designed to appeal to animal agents of dissemination. Although we may find the numberless variations somewhat surprising, what is even more surprising is that such an infinite variety should be produced under conditions that appear to be more or less uniform and constant. What may also seem incongruous is that plants that may appear superficially similar often produce seeds that are strikingly different, or that plants that are wholly unlike often produce seeds that are very much alike. Generally seeds are so characteristic that they serve as useful agents in classification, in some cases being so characteristically differentiated as to be an infallible clue to the identity of the plant that produced them.
A seed is botanically a ripened ovule and consists of an embryo plant and its protective covering or coat. The unripened ovule is a small structure in the ovary of a flower and may readily be seen by cutting the ovary open with a razor blade or pocketknife. In most cases you will find many ovules. The ovule contains an egg cell, and when this egg cell has been fertilized by a sperm cell, the ovule undergoes a number of changes and eventually develops into a seed. The sperm cell is contained in the pollen grain and must be transferred to the stigma of the pistil by some agent as the wind or an insect or by water or even by artificial means. Once the sperm cell has come in contact with the stigma, it makes its way down the pistil until it locates the egg, which it enters.
Obviously the embryo, which is a living plant whose growth has been temporarily suspended, is the most important part of the seed. Food, as a source of energy for the embryo plant until it has developed to the stage where it can manufacture its own food, is stored within the seed. Long ago man discovered that he could make use of this reserve food for his own use. The seeds of wheat and rice are today the principal items of diet for millions of human beings, and countless others consume daily large quantities of such seeds as those of corn and barley, oats and rye. Beans and peas, which are also seeds, are eaten extensively. In addition to their value as food, man has found other uses for them. I might mention cottonseed oil, linseed oil, and coconut oil, which are used in the manufacture of substitutes for butter and lard, soap, and a varietv of other oroducts.
Although seeds exhibit a great diversity of surface markings (Figure 16) and configurations (Figure 17), they all agree in showing a minute pore or pit and a scar called the hilum. The pore or pit marks the position of the micropyle, an opening in the ovule through which the sperm cell entered on its way to the egg cell, and the hilum marks the place where the ovule was attached to the ovary. You should be able to find both of these structures with your hand lens (Figure 18).
Although seeds are more readily available during the summer and early fall, when they may be obtained from almost any plant out-doors, you should have no trouble in getting enough of them during the winter to observe the many variations I have mentioned. Your neighborhood hardware store may have some left from the preceding spring, and I would suggest you visit a local nursery. You should even be able to find some on your pantry shelves, for many seeds are used in cooking. As you examine different seeds, you will very likely begin to wonder how nature could design so many—I did when I first became interested in them. Perhaps it may also occur to you to make a seed collection. It is less expensive than collecting coins or postage stamps, and you should have a great deal of fun doing so.CHAPTER 4
We Become Better Acquainted with the Snail
SNAILS BELONG to a group of animals called the Mollusca. The word Mollusca is derived from the Latin mollis, which means "soft." Hence the group includes such soft-bodied animals as the snail, clam, oyster, squid, and octopus. All these animals have one thing in common—a shell. The shell may be a very simple and drab affair, or it may be highly sculptured and beautiful—to wit, some sea shells. It may also be in one piece, as in the snail, or it may consist of two parts, or valves, as in the clam. The shell of the land snail, which we often find in our gardens, is a spiral cone made from a substance secreted by certain cells and that hardens on exposure to the air. The snail's soft body is twisted and coiled like the shell and extends into the apex, but usually does not completely fill the shell to the tip.
A snail may seem such an insignificant sort of animal and its actions may not seem to bear watching, but I think you will be in for a surprise if you find one and observe its behavior through your lens. In this instance a reading glass will prove to be of greater advantage than a pocket magnifier. Place the snail in a tumbler and watch it climb up the glass sides. As you do so you will find that the snail's foot is one of the most wonderful means of locomotion ever devised by nature. Observe how the foot stretches out and holds on then contracts, and then again stretches out. All this is accomplished by muscles. Observe, too, how a slime gland at the anterior end of the foot deposits a film of mucus on which the animal travels. It lays down a sidewalk, as it were, ahead of itself, and this sidewalk is always the same whether the path is rough or smooth, uphill or downhill.
Excerpted from ADVENTURES WITH A HAND LENS by Richard Headstrom. Copyright © 1976 Richard Headstrom. Excerpted by permission of Dover Publications, Inc..
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