Fig. 18.Fig. 18. Skeletons of telescopes. A, A one-foot telescope with a three-inch eye-piece. B, A two-foot telescope with a three-inch eye-piece. e, p, Eye-piece. o, g, Object-glass. r, r, Rays which enter the telescopes and crossing at x form an image at i, i, which is magnified by the lens e, p. The angles r, x, r and i, x, i are the same. In A the angle i, o, i is four times greater than that of i, x, i. In B it is eight times greater.Skeletons of telescopes.A, A one-foot telescope with a three-inch eye-piece.B, A two-foot telescope with a three-inch eye-piece.e,p, Eye-piece.o,g, Object-glass.r,r, Rays which enter the telescopes and crossing atxform an image ati,i, which is magnified by the lense,p. The anglesr,x,randi,x,iare the same. In A the anglei,o,iis four times greater than that ofi,x,i. In B it is eight times greater.
A, A one-foot telescope with a three-inch eye-piece.B, A two-foot telescope with a three-inch eye-piece.e,p, Eye-piece.o,g, Object-glass.r,r, Rays which enter the telescopes and crossing atxform an image ati,i, which is magnified by the lense,p. The anglesr,x,randi,x,iare the same. In A the anglei,o,iis four times greater than that ofi,x,i. In B it is eight times greater.
"But by going to the proper end of the telescopeyou can get quite near the image, and can see and magnify it, if you put a strong lens to collect the rays from it to a focus. This is the use of the eye-piece, which in our diagram is placed at a quarter of a foot or three inches from the image in both telescopes. Now that we are close to the images, the divergence of the pointsi,imakes a great difference. In the small telescope, in which the image is onlyone footbehind the object-glass, the eye-piece being a quarter of a foot from it, is four times nearer, so the anglei,o,iis four times the anglei,x,i, and the man looking through it sees the image magnifiedfour times. But in the longer telescope the image istwo feetbehind the lens, while the eye-piece is, as before, a quarter of a foot from it. Thus the eyepiece is now eight times nearer, so the anglei,o,iis eight times the anglei,x,i, and the observer sees the image magnifiedeight times.
"In real telescopes, where the difference between the focal length of the object-glass and that of the eye-glass can be made enormously greater, the magnifying power is quite startling, only the object-glass must be large, so as to collect enough rays to bear spreading widely. Even in your small telescopes, with a focus of eighteen inches, and an object-glass measuring one and a quarter inch across, we can put on a quarter of an inch eye-piece, and so magnify seventy-two times; while in my observatory telescope, eight feet or ninety-six inches long, an eye-piece of half an inch magnifies 192 times, and I can put on a 1/8-inch eye-piece and magnify 768times! And so we can go on lengthening the focus of the object-glass and shortening the focus of the eye-piece, till in Lord Rosse's gigantic fifty-six-foot telescope, in which the image is fifty-four feet (648 inches) behind the object-glass, an eye-piece one-eighth of an inch from the image magnifies 5184 times! These giant telescopes, however, require an enormous object-glass or mirror, for the points of light are so spread out in making the large image that it is very faint unless an enormous number of rays are collected. Lord Rosse's telescope has a reflecting mirror measuring six feet across, and a man can walk upright in the telescope tube. The most powerful telescope yet made is that at the Lick Observatory, on Mount Hamilton, in California. It is fifty-six and a half feet long, the object-lens measures thirty-six inches across. A star seen through this telescope appears 2000 times as bright as when seen with the naked eye.
"You need not, however, wait for an opportunity to look through giant telescopes, for my small student's telescope, only four feet long, which we carry out on to the lawn, will show you endless unseen wonders; while your hand telescopes, and even a common opera-glass, will show many features on the face of the moon, and enable you to see the crescent of Venus, Jupiter's moons, and Saturn's rings, besides hundreds of stars unseen by the naked eye.
"Of course you will understand that Fig. 18 only shows theprincipleof the telescope. In all good instruments the lenses and other parts are morecomplicated; and in a terrestrial telescope, for looking at objects on the earth, another lens has to be put in to turn them right way up again. In looking at the sky it does not matter which way up we see a planet or a star, so the second glass is not needed, and we lose light by using it.
"We have now three magic glasses to work for us—the magnifying-glass, the microscope, and the telescope. Besides these, however, we have two other helpers, if possible even more wonderful. These are the Photographic camera and the Spectroscope."
Fig. 19.Fig. 19. Photographic camera. l, l, Lenses. s, s, Screen cutting off diverging rays. c c, Sliding box. p, p, Picture formed.Photographic camera.l,l, Lenses.s,s, Screen cutting off diverging rays.c,c, Sliding box.p,pPicture formed.
l,l, Lenses.s,s, Screen cutting off diverging rays.c,c, Sliding box.p,pPicture formed.
"Now that we thoroughly understand the use of lenses, I need scarcely explain this photographic camera (Fig. 19), for it is clearly an artificial eye. In place of thecrystalline lens(compare with Fig. 11) the photographer uses one, or generally two lensesl,l, with a black ledge or stopsbetween them, which acts like the iris in cutting off the rays too near the edge of the lens. The dark cameracanswers to thedark chamberof the eyeball, and the platep,pat the back of the chamber, which is made sensitive by chemicals, answers ourretina. The box is formed of two parts, sliding one within the other atc, so as to place the plate at a proper distancefrom the lens, and then a screw adjusts the focus more exactly by bringing the front lens back or forward, instead of altering the curve as theciliary muscledoes in our eye. The difference between the two instruments is that in our eye the message goes to the brain, and the image disappears when we turn our eyes away from the object; but in the camera the waves of light work upon the chemicals, and the image can be fixed and remain for ever.
"But the camera has at least one weak point. The screen at the back is not curved like our retina, but must be flat because of printing off the pictures, and therefore the parts of the photograph near the edge are a little out of proportion.
"In many ways, however, this photographic eye is a more faithful observer than our own, and helps us to make more accurate pictures. For instance, instantaneous photographs have been taken of a galloping horse, and we find that the movements are very different from what we thought we saw with our eye, because our retina does not throw off one impression after another quickly enough to be quite certain we see each curve truly in succession. Again, the photograph of a face gives minute curves and lines, lights and shadows, far more perfectly than even the best artist can see them, and when the picture is magnified we see more and more details which escaped us before.
"But it is especially when attached to the microscope or the telescope that the photographic apparatus tells us such marvellous secrets; givingus, for instance, an accurate picture of the most minute water-animal quite invisible to the naked eye, so that when we enlarge the photograph any one can see the beautiful markings, the finest fibre, or the tiniest granule; or affording us accurate pictures, such as the one at p. 19 of the face of the moon, and bringing stars into view which we cannot otherwise see even with the strongest telescope.
"Our own eye has many weaknesses. For example, when we look through the telescope at the sky we can only fix our attention on one part at once, and afterwards on another; and the picture which we see in this way, bit by bit, we must draw as best we can. But if we put a sensitive photographic plate into the telescope just at the point (i,i, Fig. 18), where theimageof the sky is focused, this plate gives attention, so to speak, to the whole picture at once, and registers every point exactly as it is; and this picture can be kept and enlarged so that every detail can be seen.
"Then, again, if we look at faint stars, they do not grow any brighter as we look. Each ray sends its message to the brain, and that is all; we cannot heap them up in our eye, and, indeed, after a time we see less, because our nerves grow tired. But on a photographic plate in a telescope, each ray in its turn does a little work upon the chemicals, and the longer the plate remains, the stronger the picture becomes. When wet plates were used they could not be left long, but since dry plates have been invented, with a film of chemically prepared gelatine, they can be left for hours in the telescope, which iskept by clockwork accurately opposite to the same objects. In this way thousands of faint stars, which we cannot see with the strongest telescope, creep into view as their feeble rays work over and over again on the same spot; and, as the brighter stars as well as the faint ones are all the time making their impression stronger, when the plate comes out each one appears in its proper strength. On the other hand, very bright objects often become blurred by a long exposure, so that we have sometimes to sacrifice the clearness of a bright object in order to print faint objects clearly.
"We now come to our last magic glass—the Spectroscope; and the hour has slipped by so fast that I have very little time left to speak of it. But this matters less as we have studied it before.[2]I need now only remind you of some of the facts. You will remember that when we passed sunlight through a three-sided piece of glass called a prism, we broke up a ray of white light into a line of beautiful colours gradually passing from red, through orange, yellow, green, blue, and indigo, to violet, and that these follow in the same order as we see them in the rainbow or in the thin film of a soap-bubble. By various experiments we proved that these colours are separated from each other because the many waves which make up white light are of different sizes, so that because the waves, of red light are slow and heavy, they lag behind when bent in the three-sided glass, while the rapid violet waves are bent more out of their road and run to the farther end of the line,the other colours ranging themselves between."
Fig. 20.Fig. 20. Kirchhoff's spectroscope. A, The telescope which receives the ray of light through the slit in O.Kirchhoff's spectroscope.A, The telescope which receives the ray of light through the slit in O.
A, The telescope which receives the ray of light through the slit in O.
Fig. 21.Fig. 21. Passage of rays through the spectroscope. S, S´, Slit through which the light falls on the prisms. 1, 2, 3, 4, Prisms in which the rays are dispersed more and more. a, b, Screen receiving the spectrum, of which the seven principal colours are marked.Passage of rays through the spectroscope.S, S´, Slit through which the light falls on the prisms. 1, 2, 3, 4, Prisms in which the rays are dispersed more and more.a,b, Screen receiving the spectrum, of which the seven principal colours are marked.
S, S´, Slit through which the light falls on the prisms. 1, 2, 3, 4, Prisms in which the rays are dispersed more and more.a,b, Screen receiving the spectrum, of which the seven principal colours are marked.
"Now when the light falls through the open window, or through a round hole orlargeslit, the images of the hole made by each coloured wave overlap each other very much, and the colours in the spectrum or coloured band are crowded together. But when in the spectroscope we pass the ray of light through a very narrow slit, each coloured image of the upright slit overlaps the next upright image only very little. By using several prisms one after the other (see Fig. 21), these upright coloured lines are separated more and more till we get a very long band or spectrum. Yet, as you know from our experiments with the light of a glowing wire or of molten iron, however much you spread out the lightgiven by a solid or liquid, you can never separate these coloured lines from each other. It is only when you throw the light of a glowing gas or vapour into the slit that you get a few bright lines standing out alone. This is becauseallthe rays of white light are present in glowing solids and liquids, and they follow each other too closely to be separated. But a gas, such as glowing hydrogen for example, gives out only a few separate rays, which, pouring through the slit, throw red, greenish-blue, and dark blue lines on the screen. Thus you have seen the double, orange-yellow sodium line (3, Plate I.) which starts out at once when salt is held in a flame and its light thrown into the spectroscope, and the red line of potassium vapour under the same treatment; and we shall observe these again when we study the coloured lights of the sun and stars."
"We see, then, that the work of our magic glass, the spectroscope, is simply to sift the waves of light, and that these waves, from their colour and their position in the long spectrum, actually tell us what glowing gases have started them on theirroad. Is not this like magic? I take a substance made of I know not what; I break it up, and, melting it in the intense heat of an electric spark, throw its light into the spectroscope. Then, as I examine this light after it has been spread out by the prisms, I can actually read by unmistakable lines what metals or non-metals it contains. Nay, more; when I catch the light of a star, or even of a faint nebula, in my telescope, and pass it through these prisms, there, written up on the magic-coloured band, I read off the gases which are glowing in that star-sun or star-dust billions of miles away.
"Now, boys, I have let you into the secrets of my five magic glasses—the magnifying-glass, the microscope, the telescope, the photographic camera, and the spectroscope. With these and the help of chemistry you can learn to work all my spells. You can peep into the mysteries of the life of the tiniest being which moves unseen under your feet; you can peer into that vast universe, which we can never visit so long as our bodies hold us down to our little earth; you can make the unseen stars print their spots of light on the paper you hold in your hand, by means of light-waves, which left them hundreds of years ago; or you can sift this light in your spectroscope, and make it tell you what substances were glowing in that star when they were started on their road. All this you can do on one condition, namely, that you seek patiently to know the truth.
"Stories of days long gone by tell us of true magicians and false magicians, and the good or evil theywrought. Of these I know nothing, but I do know this, that the value of the spells you can work with my magic glasses depends entirely upon whether you work patiently, accurately, and honestly. If you make careless, inaccurate experiments, and draw hasty conclusions, you will only do bad work, which it may take others years to undo; but if you question your instruments honestly and carefully, they will answer truly and faithfully. You may make many mistakes, but one experiment will correct the other; and while you are storing up in your own mind knowledge which lifts you far above this little world, or enables you to look deep below the outward surface of life, you may add your little group of facts to the general store, and help to pave the way to such grand discoveries as those of Newton in astronomy, Bunsen and Kirchhoff in spectrum analysis, and Darwin in the world of life."
[1]In our Fig. 18 the distances are inches instead of feet, but the proportions are the same.
[1]In our Fig. 18 the distances are inches instead of feet, but the proportions are the same.
[2]Fairyland of Science, Lecture II.; andShort History of Natural Science, chapter xxxiv.
[2]Fairyland of Science, Lecture II.; andShort History of Natural Science, chapter xxxiv.
ornate capital i
t was a lovely warm day in September, the golden corn had been cut and carted, and the waggons of the farmers around were free for the use of the college lads in their yearly autumn holiday. There they stood in a long row, one behind the other in the drive round the grounds, each with a pair of sleek, powerful farm-horses, and the waggoners beside them with their long whips ornamented with coloured ribbons; and as each waggon drew up before the door, it filled rapidly with its merry load and went on its way.
They had a long drive of seven miles before them, for they were going to cross the wild moor, and then descend gradually along a fairly good road to the more wooded and fertile country. Their object thatday was to reach a certain fairy dell known to a few only among the party as one of the loveliest spots in Devon. It was a perfect day for a picnic. As they drove over the wide stretches of moorland, with tors to right and tors to the left, the stunted furze bushes growing here and there glistened with spiders' webs from which the dew had not yet disappeared, and mosses in great variety carpeted the ground, from the lovely thread-mosses, with their scarlet caps, to the pale sphagnum of the bogs, where a halt was made for some of the botanists of the party to search for the little Sundew (Drosera rotundifolia). Though this little plant had now almost ceased to flower, it was not difficult to recognise by its rosette of leaves glistening with sticky glands which it spreads out in many of the Dartmoor bogs to catch the tiny flies and suck out their life's blood, and several specimens were uprooted and carefully packed away to plant in moist moss at home.
From this bog onwards the road ran near by one of the lovely streams which feed the rivers below, and, passing across a bridge covered with ivy, led through a small forest of stunted trees round which the woodbine clung, hanging down its crimson berries, and the bracken fern, already putting on its brown and yellow tints, grew tall and thick on either side. Then, as they passed out of the wood, they came upon the dell, a piece of wild moorland lying in a hollow between two granite ridges, with large blocks of granite strewn over it here and there, and furze bushes growing under their shelter, still covered with yellow blossoms together with countless seed-bearing pods,which the youngsters soon gathered for the shiny-black seeds within them.
Here the waggons were unspanned, the horses tethered out, the food unpacked, and preparations for the picnic soon in full swing. Just at this moment, however, a loud shout from one part of the dell called every one's attention. "The fairy rings! the fairy rings! we have found the fairy rings!" and there truly on the brown sward might be seen three delicate green rings, the fresh sprouting grass growing young and tender in perfect circles measuring from six feet to nearly three yards across.
"What are they?" The question came from many voices at once, but it was the Principal who answered.
"Why, do you not know that they are pixie circles, where the 'elves of hills, brooks, standing lakes, and groves' hold their revels, whirling in giddy round, and making the rings, 'whereof the ewe not bites'? Have you forgotten how Mrs. Quickly, in theMerry Wives of Windsor, tells us that
"'nightly, meadow-fairies, look you sing,Like to the Garter's compass, in a ring:The expressure that it bears, green let it be,More fertile-fresh than all the field to see'?
"If we are magicians and work spells under magic glasses, why should not the pixies work spells on the grass? I brought you here to-day on purpose to see them. Which of you now can name the pixie who makes them?"
A deep silence followed. If any knew or guessed the truth of the matter, they were too shy to risk making a mistake.
"Be off with you then," said the Principal, "andkeep well away from these rings all day, that you may not disturb the spell. But come back to me before we return at night, and perhaps I may show you the wonder-working pixie, and we may take him home to examine under the microscope."
The day passed as such happy days do, and the glorious harvest moon had risen over the distant tors before the horses were spanned and the waggons ready. But the Principal was not at the starting place, and looking round they saw him at the farther end of the dell.
"Gently, gently," he cried, as there was one general rush towards him; "look where you tread, for I stand within a ring of fairies!"
And then they saw that just outside the green circle in which he stood, forming here and there a broken ring, were patches of a beautiful tiny mushroom, each of which raised its pale brown umbrella in the bright moonlight.
"Here are our fairies, boys. I am going to take a few home where they can be spared from the ring, and to-morrow we will learn their history."
The following day saw the class-room full, and from the benches eager eyes were turned to the eight windows, in each of which stood one of the elder boys at his microscope ready for work. For under those microscopes the Principal always arranged some object referred to in his lecture and figured in diagrams on the walls, and it was the duty of each boy, after the lecture was over, to show and explainto the class all the points of the specimen under his care. These boys were always specially envied, for though the others could, it is true, follow all the descriptions from the diagrams, yet these had the plant or animal always under their eye. Discussion was at this moment running high, for there was a great uncertainty of opinion as to whether a mushroom could be really called a plant when it had no leaves or flowers. All at once the hush came, as the Principal stepped into his desk and began:—
"Life is hard work, boys, and there is no being in this world which has not to work for its living. You all know that a plant grows by taking in gases and water, and working them up into sap and living tissue by the help of the sunshine and the green matter in their leaves; and you know, too, that the world is so full of green plants that hundreds and thousands of young seedlings can never get a living, but are stifled in their babyhood or destroyed before they can grow up.
"Now there are many dark, dank places in the world where plants cannot get enough sunlight and air to make green colouring matter and manufacture their own food. And so it comes to pass that a certain class of plants have found another way of living, by taking their food ready made from other decaying plants and animals, and so avoiding the necessity of manufacturing it for themselves. These plants can live hidden away in dark cellars and damp cupboards, in drains and pipes where no light ever enters, under a thick covering of dead leaves in the forest, under fallen trunks andmossy stones; in fact, wherever decaying matter, whether of plant or animal, can be found for them to feed upon.
"It is to this class, calledfungi, which includes all mushrooms and moulds, mildews, smuts, and ferments, that the mushroom belongs which we found yesterday making the fairy rings. And, in truth, we were not so far wrong when we called them pixies or imps, for many of them are indeed imps of mischief, which play sorry pranks in our stores at home and in the fields and forest abroad. They grow on our damp bread, or cheese, or pickles; they destroy fruit and corn, hop and vine, and even take the life of insects and other animals. Yet, on the other hand, they are useful in clearing out unhealthy nooks and corners, and purifying the air; and they can be made to do good work by those who know how to use them; for without ferments we could have neither wine, beer, nor vinegar, nor even the yeast which lightens our bread.
"I am going to-day to introduce you to this large vagabond class of plants, that we may see how they live, grow, and spread, what good and bad work they do, and how they do it. And before we come to the mushrooms, which you know so well, we must look at the smaller forms, which do all their work above ground, so that we can observe them. For thefungiare to be found almost everywhere. The film growing over manure-heaps, the yeast plant, the wine fungus, and the vinegar plant; the moulds and mildews covering our cellar-walls and cupboards, or growing on decayed leaves and wood, on stale fruit,bread, or jam, or making black spots on the leaves of the rose, the hop, or the vine; the potato fungus, eating into the potato in the dark ground and producing disease; the smut filling the grains of wheat and oats with disease, the ergot feeding on the rye, the rust which destroys beetroot, the rank toadstools and puffballs, the mushroom we eat, and the truffles which form even their fruit underground,—all these arefungi, or lowly plants which have given up making their own food in the sunlight, and take it ready made from the dung, the decaying mould, the root, the leaf, the fruit, or the germ on which they grow. Lastly, the diseases which kill the silkworm and the common house-fly, and even some of the worst skin diseases in man, are caused by minute plants of this class feeding upon their hosts."
Fig. 22.Fig. 22. Three forms of vegetable mould magnified. 1, Mucor Mucedo. 2, Aspergillus glaucus. 3, Penicillium glaucum.Three forms of vegetable mould magnified.1,Mucor Mucedo. 2,Aspergillus glaucus. 3,Penicillium glaucum.
1,Mucor Mucedo. 2,Aspergillus glaucus. 3,Penicillium glaucum.
"In fact, thefungiare so widely spread over all things living and dead, that there is scarcely anything free from them in one shape or another. The minute spores, now of one kind, now of another, float in the air, and settling down wherever they find suitable food, have nothing more to do thanto feed, fatten, and increase, which they do with wonderful rapidity. Let us take as an example one of the moulds which covers damp leaves, and even the paste and jam in our cupboard. I have some here growing upon a basin of paste, and you see it forms a kind of dense white fur all over the surface, with here and there a bluish-green tinge upon it. This white fur is the common mould,Mucor Mucedo(1, Fig. 22), and the green mould happens in this case to be another mould,Penicillium glaucum(3, Fig. 22); but I must warn you that these minute moulds look very much alike until you examine them under the microscope, and though they are called white, blue, or green moulds, yet any one of them may be coloured at different times of its growth. Another very common and beautiful mould,Aspergillus glaucus(2, Fig. 22), often grows with Mucor on the top of jam.
"All these plants begin with a spore or minute colourless cell of living matter (s, Fig. 23), which spends its energy in sending out tubes in all directions into the leaves, fruit, or paste on which it feeds. The living matter, flowing now this way now that, lays down the walls of its tubes as it flows, and by and by, here and there, a tube, instead of working into the paste, grows upwards into the air and swells at the tip into a colourless ball in which a number of minute seed-like bodies called spores are formed. The ball bursts, the spores fall out, and each one begins to form fresh tubes, and so little by little the mould grows denser and thicker by new plants starting in all directions.
"Under the first microscope you will see a slideshowing the tubes which spread through the paste, and which are called themycelium(m, Fig. 23), and amongst it are three upright tubes, one just startinga, another with the fruit ball formingb, and a thirdc, which is bursting and throwing out the spores. TheAspergillusand thePenicilliumdiffer from theMucorin having their spores naked and not enclosed in a spore-case. InPenicilliumthey grow like the beads of a necklace one above the other on the top of the upright tube, and can very easily be separated (see Fig. 22); whileAspergillus, a most lovely silvery mould, is more complicated in the growth of its spores, for it bears them on many rows branching out from the top of the tube like the rays of a star."
Fig. 23.Fig. 23. Mucor Mucedo, greatly magnified. (After Sachs and Brefeld.) m, Mycelium, or tangle of threads. a, b, c, Upright tubes in different stages. c, Spore-case bursting and sending out spores. s, 1, 2, 3, A growing spore, in different stages, starting a new mycelium.Mucor Mucedo, greatly magnified. (After Sachs and Brefeld.)m, Mycelium, or tangle of threads.a,b,c, Upright tubes in different stages.c, Spore-case bursting and sending out spores.s, 1, 2, 3, A growing spore, in different stages, starting a new mycelium.
m, Mycelium, or tangle of threads.a,b,c, Upright tubes in different stages.c, Spore-case bursting and sending out spores.s, 1, 2, 3, A growing spore, in different stages, starting a new mycelium.
"I want you to look at each of these moulds carefully under the microscope, for few people who hastily scrape a mould away, vexed to find it on food or damp clothing, have any idea what a delicate andbeautiful structure lies under their hand. These moulds live on decaying matter, but many of the mildews, rusts, and other kinds of fungus, prey upon living plants such as thesmutof oats (Ustilago carbo), and thebunt(Tilletia caria) which eats away the inside of the grains of wheat, while another fungus attacks its leaves. There is scarcely a tree or herb which has not one fungus to prey upon it, and many have several, as, for example, the common lime-tree, which is infested by seventy-four different fungi, and the oak by no less than 200.
"So these colourless food-taking plants prey upon their neighbours, while they take their oxygen for breathing from air. The 'ferments,' however, which liveinsideplants or fluids, take even their oxygen for breathing from their hosts.
"If you go into the garden in summer and pluck an overripe gooseberry, which is bursting like this one I have here, you will probably find that the pulp looks unhealthy and rotten near the split, and the gooseberry will taste tart and disagreeable. This is because a small fungus has grown inside, and worked a change in the juice of the fruit. At first this fungus spread its tubes outside and merelyfedupon the fruit, using oxygen from the air in breathing; but by and by the skin gave way, and the fungus crept inside the gooseberry where it could no longer get any fresh air. In this dilemma it was forced to break up the sugar in the fruit and take the oxygen out of it, leaving behind only alcohol and carbonic acid which give the fermented taste to the fruit.
"So the fungus-imp feeds and grows in nature,and when man gets hold of it he forces it to do the same work for a useful purpose, for the grape-fungus grows in the vats in which grapes are crushed and kept away from air, and tearing up the sugar, leaves alcohol behind in the grape-juice, which in this way becomes wine. So, too, the yeast-fungus grows in the malt and hop liquor, turning it into beer; its spores floating in the fluid and increasing at a marvellous rate, as any housewife knows who, getting yeast for her bread, tries to keep it in a corked bottle.
Fig. 24.Fig. 24. Yeast cells growing under the microscope. a, Single cells. b, Two cells forming by division. c, A group of cells where division is going on in all directions.Yeast cells growing under the microscope.a, Single cells.b, Two cells forming by division.c, A group of cells where division is going on in all directions.
a, Single cells.b, Two cells forming by division.c, A group of cells where division is going on in all directions.
"The yeast plant has never been found wild. It is only known as a cultivated plant, growing on prepared liquor. The brewer has to sow it by taking some yeast from other beer, or by leaving the liquor exposed to air in which yeast spores are floating; or it will sow itself in the same way in a mixture of water, hops, sugar, and salt, to which a handful of flour is added. It increases at a marvellous rate, one cell budding out of another, while from time to time the living matter in a cell will break up into four parts instead of two, and so four new cells will start and bud. A drop of yeast will very soon cover a glass slide with this tiny plant, as you will see under the second microscope, where they are now at work (Fig. 24)."
"But perhaps the most curious of all the minute fungi are those which grow inside insects and destroythem. At this time of year you may often see a dead fly sticking to the window-pane with a cloudy white ring round it; this poor fly has been killed by a little fungus calledEmpusa muscæ. A spore from a former plant has fallen perhaps on the window-pane, or some other spot over which the fly has crawled, and being sticky has fixed itself under the fly's body. Once settled on a favourable spot it sends out a tube, and piercing the skin of the fly, begins to grow rapidly inside. There it forms little round cells one after the other, something like the yeast-cells, till it fills the whole body, feeding on its juices; then each cell sends a tube, like the upright tubes of theMucor(Fig. 23) out again through the fly's skin, and this tube bursts at the end, and so new spores are set free. It is these tubes, and the spores thrown from them, which you see forming a kind of halo round the dead fly as it clings to the pane. Other fungi in the same way kill the silkworm and the caterpillars of the cabbage butterfly. Nor is it only the lower animals which suffer. When we once realise that fungus spores are floating everywhere in the air, we can understand how the terrible microscopic fungi calledbacteriawill settle on an open wound and cause it to fester if it is not properly dressed.
"Thus we see that these minute fungi are almost everywhere. The larger ones, on the contrary, are confined to the fields and forests, damp walls and hollow trees; or wherever rotting wood, leaves, or manure provide them with sufficient nourishment. Few people have any clear ideas about the growthof a mushroom, except that the part we pick springs up in a single night. The real fact is, that a whole mushroom plant is nothing more than a gigantic mould or mildew, only that it is formed of many different shaped cells, and spreads its tubesundergroundor through the trunks of trees instead of in paste or jam, as in the case of the mould."
Fig. 25.Fig. 25. Early stages of the mushroom. (After Sachs.) m, Mycelium. b1-3, Mushroom buds of different ages. b4, Button mushroom. g, Gills forming inside before lower attachment of the cap gives way at v.Early stages of the mushroom. (After Sachs.)m, Mycelium.b1-3, Mushroom buds of different ages.b4, Button mushroom.g, Gills forming inside before lower attachment of the cap gives way atv.
m, Mycelium.b1-3, Mushroom buds of different ages.b4, Button mushroom.g, Gills forming inside before lower attachment of the cap gives way atv.
"The part which we gather and call a mushroom, a toadstool, or a puffball is only the fruit, answering to the round balls of the mould. The rest of the plant is a thick network of tubes, which you will see under the third microscope. These tubes spread underground and suck in decayed matter from the earth; they form themycelium(m, Fig. 25) such as we found in the mould. The mushroom-growers call it 'mushroom spawn' because they use it to spread over the ground for new crops. Out of these underground tubes there springs up from time to time a swollen round body no bigger at first than a mustard seed (b1, Fig. 25). As it increases in size it comes above ground and grows into the mushroom orspore-case, answering to the round balls which contain the spores of the mould. At first this swollen body is egg-shaped, the top half being largest and broadest, and the fruit is then called a 'button-mushroom'b4. Inside this ball are now formed a series of folds made of long cells, some of which are soon to bear spores just as the tubes in the mould did, and while these are forming and ripening, a way out is preparing for them. For as the mushroom grows, the skin of the lower part of the ball (v,b4) is stretched more and more, till it can bear the strain no longer and breaks away from the stalk; then the ball expands into an umbrella, leaving a piece of torn skin, called the veil (v, Fig. 26), clinging to the stalk."
Fig. 26.Fig. 26. Later stages of the mushroom. (After Gautier.) 1, Button mushroom stage. c, Cap. v, Veil. g, Gills. 2, Full-grown mushroom, showing veil v after the cap is quite free, and the gills or lamellæ g, of which the structure is shown in Fig. 27.Later stages of the mushroom. (After Gautier.)1, Button mushroom stage.c, Cap.v, Veil.g, Gills.2, Full-grown mushroom, showing veil v after the cap is quite free, and the gills or lamellæg, of which the structure is shown in Fig. 27.
1, Button mushroom stage.c, Cap.v, Veil.g, Gills.
2, Full-grown mushroom, showing veil v after the cap is quite free, and the gills or lamellæg, of which the structure is shown in Fig. 27.
"All this happens in a single night, and the mushroom is complete, with a stem up the centre and abroad cap, under which are the folds which bear the spores. Thus much you can see for yourselves at any time by finding a place where mushrooms grow and looking for them late at night and early in the morning so as to get the different stages. But now we must turn to the microscope, and cutting off one of the folds, which branch out under the cap like the spokes of a wheel, take a slice across it (1, Fig. 27) and examine."
Fig. 27.Fig. 27. 1, One of the gills or lamellæ of the mushroom slightly magnified, showing the cells round the edge. c, Cells which do not bear spores. fc, Fertile cells. 2, A piece of the edge of the same powerfully magnified, showing how the spores s grow out of the tip of the fertile cells fc.1, One of the gills or lamellæ of the mushroom slightly magnified, showing the cells round the edge.c, Cells which do not bear spores.fc, Fertile cells. 2, A piece of the edge of the same powerfully magnified, showing how the sporessgrow out of the tip of the fertile cellsfc.
1, One of the gills or lamellæ of the mushroom slightly magnified, showing the cells round the edge.c, Cells which do not bear spores.fc, Fertile cells. 2, A piece of the edge of the same powerfully magnified, showing how the sporessgrow out of the tip of the fertile cellsfc.
"First, under a moderate power, you will see the cells forming the centre of the fold and the layer of long cells (candfc) which are closely packed all round the edge. Some of these cells project beyond the others, and it is they which bear the spores. We see this plainly under a very strong power when you can distinguish the sterile cellscand the fertile cellsfcprojecting beyond them, and each bearing four spore-cellsson four little horns at its tip.
"These spores fall off very easily, and you can make a pretty experiment by cutting off a large mushroom head in the early morning and putting it flat upon a piece of paper. In a few hours, if you lift it very carefully, you will find a number of dark lines on the paper, radiating from a centre like the spokes of a wheel, each line being composed of the spores which have fallen from a fold as it grew ripe. They are so minute that many thousands would be required to make up the size of the head of an ordinary pin, yet if you gather the spores of the several kinds of mushroom, and examine them under a strong microscope, you will find that even these specks of matter assume different shapes in the various species.
"You will be astonished too at the immense number of spores contained in a single mushroom head, for they are reckoned by millions; and when we remember that each one of these is the starting point of a new plant, it reminds us forcibly of the wholesale destruction of spores and seeds which must go on in nature, otherwise the mushrooms and their companions would soon cover every inch of the whole world.
"As it is, they are spread abroad by the wind, and wherever they escape destruction they lie waiting in every nook and corner till, after the hot summer, showers of rain hasten the decay of plants and leaves, and then the mushrooms, toadstools, and puffballs, grow at an astounding pace. If you go into the woods at this season you may see the enormous deep-red liverfungus (Fistulina hepatica) growing on the oak-trees, in patches which weigh from twenty to thirty pounds; or the glorious orange-coloured fungus (Tremella mesenterica) growing on bare sticks or stumps of furze; or among dead leaves you may easily chance on the little caps of the crimson, scarlet, snowy white, or orange-coloured fungi which grow in almost every wood. From white to yellow, yellow to red, red to crimson and purple black, there is hardly any colour you may not find among this gaily-decked tribe; and who can wonder that the small bright-coloured caps have been supposed to cover tiny imps or elves, who used the large mushrooms to serve for their stools and tables?
"There they work, thrusting their tubes into twigs and dead branches, rotting trunks and decaying leaves, breaking up the hard wood and tough fibres, and building them up into delicate cells, which by and by die and leave their remains as food for the early growing plants in the spring. So we see that in their way the mushrooms and toadstools are good imps after all, for the tender shoot of a young seedling plant could take no food out of a hard tree-trunk, but it finds the work done for it by the fungus, the rich nourishment being spread around its young roots ready to be imbibed.
"To find our fairy-ring mushrooms, however, we must leave the wood and go out into the open country, especially on the downs and moors and rough meadows, where the land is poor and the grass coarse and spare. There grow the nourishing kinds, most of which we can eat, and among these is thedelicate little champignon or 'Scotch-bonnet' mushroom,Marasmius Oreades,[1]which makes the fairy-rings. When a spore of this mushroom begins to grow, it sucks up vegetable food out of the earth and spreads its tubes underground, in all directions from the centre, so that the mycelium forms a round patch like a thick underground circular cobweb. In the summer and autumn, when the weather is suitable, it sends up its delicate pale-brown caps, which we may gather and eat without stopping the growth of the plant.
"This goes on year after year underground, new tubes always travelling outwards till the circle widens and widens like the rings of water on a pond, only that it spreads very slowly, making a new ring each year, which is often composed of a mass of tubes as much as a foot thick in the ground, and the tender tubes in the centre die away as the new ones form a larger hoop outside.
"But all this is below ground; where then are our fairy rings? Here is the secret. The tubes, as we have seen, take up food from the earth and build it up into delicate cells, which decay very soon, and as they die make a rich manure at the roots of the grass. So each season the cells of last year's ring make a rich feeding-ground for the young grass, which springs up fresh and green in a fairy ring, whileoutsidethis emerald circle the mushroom tubes are still growing and increasing underneath the grass, so that next year, when the present ring is no longer richly fed, and has become faded and brown like therest of the moor, another ring will spring up outside it, feeding on the prepared food below."
"In bad seasons, though the tubes go on spreading and growing below, the mushroom fruit does not always appear above ground. The plant will only fruit freely when the ground has been well warmed by the summer sun, followed by damp weather to moisten it. This gives us a rich crop of mushrooms all over the country, and it is then you can best see the ring of fairy mushrooms circling outside the green hoop of fresh grass. In any case the early morning is the time to find them; it is only in very sheltered spots that they sometimes last through the day, or come up towards evening, as I found them last night on the warm damp side of the dell.
"This is the true history of fairy rings, and now go and look for yourselves under the microscopes. Under the first three you will find the three different kinds of mould of our diagram (Fig. 22). Under the fourth the spores of the mould are shown in their first growth putting out the tubes to form the mycelium. The fifth shows the mould itself with its fruit-bearing tubes, one of which is bursting. Under the sixth the yeast plant is growing; the seventh shows a slice of one of the folds of the common mushroom with its spore-bearing horns; and under the eighth I have put some spores from different mushrooms, that you may see what curious shapes they assume.
"Lastly, let me remind you, now that the autumn and winter are coming, that you will find mushrooms, toadstools, puffballs, and moulds in plentywherever you go. Learn to know them, their different shapes and colours, and above all the special nooks each one chooses for its home. Look around in the fields and woods and take note of the decaying plants and trees, leaves and bark, insects and dead remains of all kinds. Upon each of these you will find some fungus growing, breaking up their tissues and devouring the nourishing food they provide. Watch these spots, and note the soft spongy soil which will collect there, and then when the spring comes, notice what tender plants flourish upon these rich feeding grounds. You will thus see for yourselves that the fungi, though they feed upon others, are not entirely mischief-workers, but also perform their part in the general work of life."